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Gigabyte
2010-Apr-13, 02:41 AM
Astronomer Mike Hawkins from the Royal Observatory in Edinburgh came to this conclusion after looking at nearly 900 quasars over periods of up to 28 years. When comparing the light patterns of quasars located about 6 billion light years (http://www.physorg.com/tags/light+years/) from us and those located 10 billion light years away, he was surprised to find that the light signatures of the two samples were exactly the same. If these quasars were like the previously observed supernovae, an observer would expect to see longer, “stretched” timescales for the distant, “stretched” high-redshift quasars. But even though the distant quasars were more strongly redshifted than the closer quasars, there was no difference in the time it took the light to reach Earth.
http://www.physorg.com/news190027752.html

Jens
2010-Apr-13, 02:54 AM
How strange. If redshift is really showing velocity, then it seems logical that time dilation would be seen. Is there any explanation offered of what might cause this strange result, or do people assume it's a measurement error or something? Obviously one explanation would be that redshift for quasars is not indicating velocity.

Jens
2010-Apr-13, 02:58 AM
Also, there seem to be older papers on this subject, so maybe it's not so new. Here (http://arxiv.org/abs/astro-ph/0105073)is one, that has some discussion on the implications.

01101001
2010-Apr-13, 03:46 AM
http://www.physorg.com/news190027752.html


More information: * On time dilation in quasar light curves, M. R. S. Hawkins, DOI:10.1111/j.1365-2966.2010.16581.x
Via: New Scientist

Somehow I think the actual paper will present a different view than the New Scientist's reporting (Time waits for no quasar (http://www.newscientist.com/article/mg20627554.200-time-waits-for-no-quasar--even-though-it-should.html)).

Jerry
2010-Apr-13, 04:20 AM
Nice work, Mike.

As of about a year ago there was/is a slight anti-correlation between ultra high energy gamma ray bursts (UHEGRBs) lightcurve lengths and distances, especially after 'correction' for redshift. It is complicated by two distinct groups; with the line between the groups blurring after correction for redshift - I'll dig around for the reference...

Tensor
2010-Apr-13, 04:20 AM
This is an old problem that has a well known reason. There simply isn't a consistent light curve for quasars. SN1a have a well known light curve, simply because SN1a are the same type of explosion. They are White Dwarfs that are fed by an enlarging companion. When enough material gathers onto the White Dwarf, it can no longer support the mass and it explodes. The limit is called the Chandrasekhar limit (`1.44 time the mass of the sun). These type of explosions have a well know upper limit of brightness (around absolute -19.6) and a well known fading time(the light curve). This allows us to see these supernova to rather far distances across the universe. Studies of local SN1a tell us how long the light curve actually is. The distance of non-local SN1as can be found by finding and comparing the light curves to the local light curves and computing the time dilation of the distant SN1a. When this is done, and compared with other methods of finding distances, there is a rather good match in distance among all the methods of finding distances.

With quasars, the problem is quasars get brighter or dimmer depending on what happens within it's accretion disk. If the quasar is gulping down more matter, the quasar gets brighter. If it gulps down less, it gets dimmer. Since each quasar has a different accretion disk, with different amounts and kinds of material, each quasar will have a different light curve. As a result, there is no way to compare two different quasars light curves, with any kind of accuracy, as each quasar light curve is different, depending on what is happening within the accretion disk.

EDG
2010-Apr-13, 04:28 AM
If it's that well known, why didn't this guy know about it? I suspect there's something more to this story, beyond what you said.

Tensor
2010-Apr-13, 04:43 AM
If it's that well known, why didn't this guy know about it? I suspect there's something more to this story, beyond what you said.

Why people are not aware of it is beyond me. There are several papers out there describing the exact same thing I mentioned in a lot more technical detail out there.

ngc3314
2010-Apr-13, 12:33 PM
Hawkins has been getting this kind of result for many years (longer and longer data series). There are other quasar samples which do show evidence for time dilation (for example, Palomar-Green objects measured photoelectrically with <1% accuracy; I had a student do a thesis on that once). As others have said, this is much slipperier for AGN than for SN because you have to do an ensemble average of variability (often using a structure function, the mean level of variation as a function of time interval), which has no distinct sharp features.

Tensor
2010-Apr-13, 12:50 PM
Hawkins has been getting this kind of result for many years (longer and longer data series). There are other quasar samples which do show evidence for time dilation (for example, Palomar-Green objects measured photoelectrically with <1% accuracy; I had a student do a thesis on that once).

That's new to me, but cool. Thanks for the reference on the Palomar-Green objects. I get to go learn something.

Gigabyte
2010-Apr-13, 04:31 PM
Somewhere, somehow, Halton is laughing.

trinitree88
2010-Apr-13, 09:55 PM
This is an old problem that has a well known reason. There simply isn't a consistent light curve for quasars. SN1a have a well known light curve, simply because SN1a are the same type of explosion. They are White Dwarfs that are fed by an enlarging companion. When enough material gathers onto the White Dwarf, it can no longer support the mass and it explodes. The limit is called the Chandrasekhar limit (`1.44 time the mass of the sun). These type of explosions have a well know upper limit of brightness (around absolute -19.6) and a well known fading time(the light curve). This allows us to see these supernova to rather far distances across the universe. Studies of local SN1a tell us how long the light curve actually is. The distance of non-local SN1as can be found by finding and comparing the light curves to the local light curves and computing the time dilation of the distant SN1a. When this is done, and compared with other methods of finding distances, there is a rather good match in distance among all the methods of finding distances.

Somewhere in my posts I covered this last winter, but the new forum is acting up on me a bit here.

With quasars, the problem is quasars get brighter or dimmer depending on what happens within it's accretion disk. If the quasar is gulping down more matter, the quasar gets brighter. If it gulps down less, it gets dimmer. Since each quasar has a different accretion disk, with different amounts and kinds of material, each quasar will have a different light curve. As a result, there is no way to compare two different quasars light curves, with any kind of accuracy, as each quasar light curve is different, depending on what is happening within the accretion disk.

Tensor. Not quite anymore. Recently Fillipenko et al revealed the merger of a pair of white dwarfs as the likely suspect for a rapid rising and falling "type1a"...sans any red giant white dwarf binary, the favored mechanism. Further research has indicated that with each white dwarf able to be up to ~ 3.2 solar masses from stars of up to 8 solar masses, or down to ~ 0.1, the expected luminosity variation from largest to smallest pairs ought to be about a factor of 20. This casts considerable doubt on some claimed standard candle data in a number of surveys. pete SEE:http://esciencenews.com/articles/2009/11/05/rapid.supernova.could.be.new.class.exploding.star

StupendousMan
2010-Apr-13, 10:18 PM
This casts considerable doubt on some claimed standard candle data in a number of surveys.

Fortunately, astronomers became aware of the large differences in luminosity between individual supernovae back in the 1980s, and have devised several methods for discarding some events, and making corrections to others in order to account for these differences.

See the SN literature for the past 25 years.

Jerry
2010-Apr-14, 01:55 AM
SN1a have a well known light curve, simply because SN1a are the same type of explosion. They are White Dwarfs that are fed by an enlarging companion. When enough material gathers onto the White Dwarf, it can no longer support the mass and it explodes. The limit is called the Chandrasekhar limit (`1.44 time the mass of the sun). These type of explosions have a well know upper limit of brightness (around absolute -19.6) and a well known fading time(the light curve).

An old theory, that is bending somewhat to admit new observations:

http://arxiv.org/abs/astro-ph/0611295v2

The Peculiar SN 2005hk: Do Some Type Ia Supernovae Explode as Deflagrations?


The overwhelming majority of SNe Ia obey the peak luminosity vs. decline-rate relationship and display a remarkably uniform spectral evolution. Objects such as SN 1991T and SN 1991bg, which were originally considered to be peculiar (Filippenko et al. 1992a,b; Phillips et al. 1992; Leibundgut et al. 1993), may simply be examples of the high-luminosity and low-luminosity extremes of the overall sequence of normal SNe Ia (Nugent et al. 1995).
However, a handful of SNe Ia truly stand out as peculiar. Among these is SN 2002cx, which was labeled by Li et al. (2003, hereafter LFC) as “the most peculiar known Type Ia supernova.”

Nearby Supernova Factory Observations of SN 2007if: First Total Mass Measurement of a Super-Chandrasekhar-Mass Progenitor

http://arxiv.org/abs/1003.2217

We calculate the bolometric light curve of the SN and use it and the Si II velocity evolution to constrain the mass of the shell and the underlying SN ejecta, and demonstrate that SN 2007if is strongly inconsistent with a Chandrasekhar-mass scenario. Within the context of a “tamped detonation” model appropriate for double-degenerate mergers, and assuming no host extinction, we estimate the total mass of the system to be 2.4±0.2 M(solar), with 1.6±0.1 M(solar) of 56Ni and with 0.3–0.5 M(solar) in the form of an envelope of unburned carbon/oxygen. Our modeling demonstrates that the kinematics of shell entrainment provide a more efficient mechanism than incomplete nuclear burning for producing the low velocities typical of super-Chandrasekhar-mass SNe Ia...

p15 Chandrasekhar-mass progenitors, and progenitors with no envelopes, are ruled out at high significance. We place a lower limit of 2.05 M(solar) (99% CL) on the total mass of the system, and 0.1 M(solar) at similar confidence on the mass of the envelope...

p21 Our observations of SN 2007if provide detailed observations of the evolution of a candidate super Chandrasekhar mass SN Ia event, allowing new constraints on their progenitors...Better models of the progenitors and explosions of SN 2003fg-like SNe Ia are urgently needed, mainly because of the theoretical limits on the existence of supermassive white dwarfs (Piro 2008; Chen & Li 2009) which provide possible initial conditions for a SN 2003fg-like explosion.

http://arxiv.org/abs/0903.1086


There is consensus that SNe Ia are the result of the explosion of a carbon-oxygen white dwarf that grows to near the Chandrasekhar limit in a binary system (Hoyle & Fowler 1960). But is debate over whether the companion is an evolved or main sequence star (single degenerate system; Whelan & Iben 1973), or whether it is another white dwarf, i.e. a double degenerate system (Iben & Tutukov 1984; Webbink 1984). The two scenarios produce different delay times from the birth of the binary system to explosion, so there is hope of deducing the progenitors of SNe Ia by studying their delay time distribution (DTD)...

All current SN studies are sample-size limited. But in the next 10 years, that will no longer be the case. With thousands of SNe Ia discovered per year (we will need a new naming convention), we are leaving the serendipity-driven era, where we learn what nature wants to tell us, and entering the hypothesis-driven era, where large-N subsamples can be constructed to test ideas.

We have a lot to learn, and a lot to look forward to.

Tensor
2010-Apr-14, 03:03 AM
An old theory, that is bending somewhat to admit new observations:

http://arxiv.org/abs/astro-ph/0611295v2



And so? We can tell the difference between the two. We can also tell the time dilation for both. Something that we can't do for the majority of AGNs, which was the question of this thread.

Kwalish Kid
2010-Apr-14, 03:13 AM
Indeed, Jerry is fond of posting links to articles that say absolutely nothing about the question at hand and simply do not support his position. None of those articles seems to suggest any need to doubt the use of type Ia supernovae in cosmological measurements.

Jerry
2010-Apr-14, 11:59 PM
And so? We can tell the difference between the two. We can also tell the time dilation for both. Something that we can't do for the majority of AGNs, which was the question of this thread.

They are both supernova type Ia. We can tell the difference because one of them is way too bright: So much brighter than most of the rest of the events at the same distance that it has to start with an initial mass of at least 2.4 solar; well over the supposed Chandrasekar limit. It can no longer be supposed that the Chandrasekar limit of 1.4 mass (solar) is absolute - this has been falsified. As the authors suggest, it may involve a dual-white dwarf scenario; but nobody is certain. This limits, but does not eliminate the use of Supernova as cosmic distance indicators. As pointed out in one of the papers that I posted; it is not possible (today) to use supernova to constrain what the expansion rate was like at distances greater than ~Z=1; because we are not certain that, with the limited light curve and spectral information we can obtain for the most distant events; we cannot be sure they are not also overluminous or an evolved species.

http://lanl.arxiv.org/abs/1001.5210v5

There is an interesting challenge here:

SUPERNOVA PHOTOMETRIC CLASSIFICATION CHALLENGE

Richard Kessler,1,2 Alex Conley,3 Saurabh Jha,4 Stephen Kuhlmann5
Challenge Released on Jan 29, 2010. Last update: April 14, 2010

ABSTRACT
We have publicly released a blinded mix of simulated SNe, with types (Ia, Ib, Ic, II) selected in
proportion to their expected rate. The simulation is realized in the griz filters of the Dark Energy
Survey (DES) with realistic observing conditions (sky noise, point spread function and atmospheric
transparency) based on years of recorded conditions at the DES site. Simulations of non-Ia type SNe
are based on spectroscopically confirmed light curves that include unpublished non-Ia samples donated
from the Carnegie Supernova Project (CSP), the Supernova Legacy Survey (SNLS), and the Sloan
Digital Sky Survey-II (SDSS–II). We challenge scientists to run their classification algorithms and
report a type for each SN. A spectroscopically confirmed subset is provided for training. The goals
of this challenge are to (1) learn the relative strengths and weaknesses of the different classification
algorithms, (2) use the results to improve classification algorithms, and (3) understand what spectro-
scopically confirmed sub-sets are needed to properly train these algorithms. The challenge is available
at www.hep.anl.gov/SNchallenge, and the due date for classifications is May 1, 2010.

It will be interesting to see how well the classification algorythms work when there are no other clues about the nature-of-the-beast. These classification schemes must work well for us to have confidence in the unbiased ability of the system to classify very distant events.

There are schemes for classifying AGN; but that is not how Hawkins has approached the data. When you transpose QSOs to the frequency domain, it should be possible to extract information that is redshift dependent, but it isn't. That is just plain weird.

Tensor
2010-Apr-15, 02:23 AM
They are both supernova type Ia. We can tell the difference because one of them is way too bright: So much brighter than most of the rest of the events at the same distance that it [I]has to start with anhey are both supernova type Ia. We can tell the difference because one of them is way too bright: So much brighter than most of the rest of the events at the same distance that it has to start with an initial mass of at least 2.4 solar; well over the supposed Chandrasekar limit. It can no longer be supposed that the Chandrasekar limit of 1.4 mass (solar) is absolute - this has been falsified.

No it hasn't been falsified, quit making wild claims. Care to actually support the claim. Of course your next sentence refutes yourself.


As the authors suggest, it may involve a dual-white dwarf scenario; but nobody is certain.

Yep, no one is certain. The dual white dwarf scenario works rather well, this is a far cry from falsifying it.



This limits, but does not eliminate the use of Supernova as cosmic distance indicators. As pointed out in one of the papers that I posted; it is not possible (today) to use supernova to constrain what the expansion rate was like at distances greater than ~Z=1; because we are not certain that, with the limited light curve and spectral information we can obtain for the most distant events; we cannot be sure they are not also overluminous or an evolved species.

Again, you are the one making the claim. You don't work in the field. Those that work in the field have no problem with it. As Kwalish Kid points out, the papers you linked to don't have any problem using SN1a as distance measurements.


When you transpose QSOs to the frequency domain, it should be possible to extract information that is redshift dependent, but it isn't. That is just plain weird.

Nice claim. Care to show exactly how that is supposed work, for a majority of AGN?

DrRocket
2010-Apr-15, 03:41 AM
http://www.physorg.com/news190027752.html



http://front.math.ucdavis.edu/1004.1824

Kwalish Kid
2010-Apr-15, 02:43 PM
No it hasn't been falsified, quit making wild claims. Care to actually support the claim. Of course your next sentence refutes yourself.
Unfortunately, he cannot, since his ATM thread has been closed.

Jerry
2010-Apr-16, 02:40 PM
No it hasn't been falsified, quit making wild claims. Care to actually support the claim. Of course your next sentence refutes yourself.
This is not the only case, there are many:

arXiv:1003.2217v3


Our observations of SN 2007if provide detailed observations of the evolution of a candidate super-Chandrasekharmass SN Ia event, allowing new constraints on their progenitors. SN 2007if is the brightest SN Ia yet discovered, with an inferred 56Ni mass of 1.6±0.1 M(solar)...we use the SN 2007if bolometric light curve to establish the first constraint on the total mass for a super-Chandrasekhar-mass SN Ia progenitor. Our mass estimate should strictly be construed as a lower bound, since reddening by dust and a low central density will both result in a higher mass;
So which is the 'correct' Chandrasekar mass? First principles says 1.4; but here are LOWER constraints of 1.6 and 2.4.

If you could isolate all the dual-denotation events; you may be able to reclaim the 1.4 number; but the best hope for segregation would likely be polarization; and last I read, virtually all supernova events are polarized.


Yep, no one is certain.

No, they are not.

The problem is not that a few events may be overmassive, or be dual-detonations; but that a large portion of the population may be binary events. Dual source events will result in different apparent magnitude depending upon the viewing angle. This a a parameter we must have a better handle on to express supernova magnitudes with higher degrees of confidence.


Again, you are the one making the claim. You don't work in the field. Those that work in the field have no problem with it. As Kwalish Kid points out, the papers you linked to don't have any problem using SN1a as distance measurements.
I am talking about attempts to nail down the value of w, the amount of change in the expansion rate at high redshift; it is currently unconstrained above ~z=1; and the broading range of known supernova events is making it difficult to clamp down this number.


Nice claim. Care to show exactly how that is supposed work, for a majority of AGN?
AGN are just that: Active. Activity generally introduces degrees of periodic variability. For example, when we analyse the frequency domain of the sun there are clearly both long and short term periodic effects. If the prevailing model for an AGN is any where near correct (an accreting black hole); There should be measureable frequencies associated with the rotating mass; just as you can pick out the root tumbling frequency of a clothes dryer by watching the motion of the clothes. It is a reasonable expectation, and requires no priors, other than modest constraints on the possible range of frequencies. There are broad constraints on a black hole accretion ring behavior (minimal size, maximum velocity); so over decades of observations; there is an observable common range of low frequency elements - evidence supporting the supposition that AGN are accretion rings. Hawkins observations span more than three decades; a period of time that allows him to look at the variation of AGN over a broad, low, frequency range. When you bin these observed frequency domain events by redshift; if there is a time dilation element; the most redshifted events should produce observeably lower frequency behavior that is propotional to the redshift. Hawkin can't find this signature. It would be very good evidence of relativistic effects if he could.

parejkoj
2010-Apr-16, 03:50 PM
I feel like we've been over (http://www.bautforum.com/showthread.php/73365-Supernova-time-dilation-confirmed-(again)?p=1412742#post1412742) this territory before (http://www.bautforum.com/showthread.php/77624-Quasar-T-i-m-e-Dilation).

And Jerry is still making many of the same, previously refuted, points.

Tuxford
2010-Apr-16, 03:52 PM
http://www.physorg.com/news190027752.html

Dr. Paul LaViolette in his 2003 book 'Subquantum Kinectics' predicted in several pages that the earlier conclusion that time dilation effects were observed, was incorrect due to data selection effects. He predicted that when a larger data set was considered at extreme red shifts, that no time dilation would be observed.

Jerry
2010-Apr-16, 10:59 PM
I feel like we've been over (http://www.bautforum.com/showthread.php/73365-Supernova-time-dilation-confirmed-(again)?p=1412742#post1412742) this territory before (http://www.bautforum.com/showthread.php/77624-Quasar-T-i-m-e-Dilation).

And Jerry is still making many of the same, previously refuted, points.

There have been at least a dozen mainstream papers published since the 2008 thread stating that some type Ia supernova exceed the cannonical 1.4M(solar) limit; yet Tensor and others still keep publishing the prior misconception about the limits of supernovae magnitude. Are you still insisting I am wrong when I state the limit is problematic?

Tensor
2010-Apr-17, 01:31 PM
No it hasn't been falsified, quit making wild claims. Care to actually support the claim. Of course your next sentence refutes yourself.

This is not the only case, there are many: arXiv:1003.2217v3

Jerry, did you actually read (why do I feel like a broken record) the paper. The authors have no problem using current SN1a as distance indicators, and the Chandrasekar limit that is behind that indicator. They want to find a way to eliminate possible dual detonation events for "next generation" experiments. Note that "next generation" in there. They are very specific about that and also very supportive about current SN1a distance indicators. This is just another paper that you present as a refutation of someone else's point, that turns out to be a refutation of your point.


So which is the 'correct' Chandrasekar mass? First principles says 1.4; but here are LOWER constraints of 1.6 and 2.4.

LOL This statement makes it obvious that you didn't understand the paper, especially the part you quoted. The reason for the 1.6 and the 2.4 are quite apparent. The 1.6 mass is the amount of nickel in the two progenitors. The 2.4 is the total mass of the two progenitors.


If you could isolate all the dual-denotation events; you may be able to reclaim the 1.4 number; but the best hope for segregation would likely be polarization; and last I read, virtually all supernova events are polarized.

I will let the other readers go through the paper and find where you either didn't read or didn't understand the differences between the two types of events, that recovers the 1.4 mass limit. I'll give a hint: spectral qualities.



No, they are not.

The problem is not that a few events may be overmassive, or be dual-detonations; but that a large portion of the population may be binary events.

A large portion? Really? Your paper notes that dual detonations are marked by over-bright events with specific spectral effects. You know how many they've found? Four. Sounds like a large portion to me.


Dual source events will result in different apparent magnitude depending upon the viewing angle. This a a parameter we must have a better handle on to express supernova magnitudes with higher degrees of confidence.

Again, in the paper you presented, dual events are marked by spectrally. What part of that don't you get? Or, again, did you not read that?


AGN are just that: Active. Activity generally introduces degrees of periodic variability. For example, when we analyse the frequency domain of the sun there are clearly both long and short term periodic effects. If the prevailing model for an AGN is any where near correct (an accreting black hole)

Again, Jerry, you are showing your ignorance of the model you claim is wrong. The problem is that events within the accretion disk can cause variability, and changes the range of low and high frequency events. Even Hawkins admits this in his paper as it has been seen in Seyfert galaxies. Here (http://iopscience.iop.org/0004-637X/510/2/659/pdf/38120.web.pdf) is the paper Hawkins links to.

Jerry
2010-Apr-17, 10:51 PM
One more try:

Spectral identification, for the purpose of discriminating between a dual and a single detonation, is only possible with fairly local events; and even then it is only a possible explanation, not the only possilbe explanation for superluminous events. For the most distant events, it is very difficult to discern spectral signatures of the supernova from the host galaxy, let alone quantify the nickel content of the detonation.

See: http://arxiv.org/abs/0911.5484


For this model, we then explore the effects of different viewing angles and the implications for SNe Ia in general. The model predicts that a variation of the central wavelength, depending on the viewing angle, should be seen in some lines (e.g., [Ni II]7378), while the strongest lines (e.g., [Fe III] blend at 4700A) will not show this effect. By examining optical nebular spectra of 12 SNe Ia, we have found that such a variation indeed exists. We suggest that the global asymmetry in the innermost ejecta, as likely imprint of the deflagration flame propagation, is a generic feature of SNe Ia ...

The first deflagration phase may well proceed in a very asymmetric way (Niemeyer et al. 1996; Garc´ıa-Senz &
Bravo 2005; Livne et al. 2005; Jordan et al. 2008). The deflagration wave propagates under the work of the buoyancy force, and thus a small perturbation in the progenitorstructure could result in a global asymmetry. Rotation and convection in the progenitor WD could provide the seed for this asymmetric deflagration propagation. For example, there is a possibility that the convection in the progenitor WD is dominated by a dipole mode (Woosley et al. 2004), which likely results in highly off-axis ignition and propagation of the deflagration flame (R¨opke et al. 2007c; Kasen et al. 2009).

It is, however, observationally challenging to put constraints on the geometry of the explosion. Measurements of polarization suggest that a large global asymmetry does not exist in SNe Ia (Wang et al. 1996), with only a few exceptions (Howell et al. 2001). However, the polarization probes mainly the outer regions of the expanding SN ejecta, at least with the existing telescopes and instruments. The signature of the possible asymmetry in the deflagration phase, however, can only be probed by looking deeper into the innermost regions. In this respect, late-phase ( 1 year past the explosion) spectroscopy can provide an important diagnostics.

We don't have good constraints on the magnitude of the most distant observations.

Tensor
2010-Apr-18, 02:48 AM
One more try:

Spectral identification, for the purpose of discriminating between a dual and a single detonation, is only possible with fairly local events; and even then it is only a possible explanation, not the only possilbe explanation for superluminous events. For the most distant events, it is very difficult to discern spectral signatures of the supernova from the host galaxy, let alone quantify the nickel content of the detonation.

See: http://arxiv.org/abs/0911.5484

Jerry, I bolded your claim. Another case of, you linking to a paper that doesn't show what he thinks it does. The paper is also more about the energy lighting up the ejecta around the SN1a than the SN1a itself. , that particular paper uses a single progenitor, asymmetric explosion model. Exactly how well does the model used in this paper match a dual detonation event, spectrally, in the rest frame of each? You might notice that that particular paper doesn't even mention dual detonation events, so not quite sure why you linked to it as evidence for a difference between single and dual events.

And, speaking of nickel content....


We don't have good constraints on the magnitude of the most distant observations.

Jerry, you,not me, are the one that brought up the paper arXiv:1003.2217v3. I asked you to provide evidence that the Chandrasekar limit was falsified. You presented that paper as evidence. You are the one that quoted from it. I just pointed out where you misunderstood the paper. Where when the authors talked about the amount of nickel (1.6 times the suns mass) it was not a "lower mass limit" as you claimed. It was just the amount of nickel in a dual detonation event. Are you now saying that you referenced that paper in error?

I also pointed out that the authors had no problem with the Chandrasekar limit. The total mass was 2.4 for two white dwarfs. Where they were able to differentiate between single and dual events by spectral identification. I never mentioned anything about local or distant, that was something you brought in to change the goalposts, when it was shown you were wrong.

I wish you would make up your mind when you reference a paper. Now, it appears that a paper you previously used as support (arXiv:1003.2217v3), you now seem to think is invalid, because it claims to be able to measure the nickel content. Which is it?

Kwalish Kid
2010-Apr-19, 03:09 AM
I am talking about attempts to nail down the value of w, the amount of change in the expansion rate at high redshift; it is currently unconstrained above ~z=1; and the broading range of known supernova events is making it difficult to clamp down this number.


You are neither talking about w nor about the amount of change in the expansion rate at high redshift--and these things are not the same thing. In the contemporary cosmological literature, w is used to discuss the equation of state of the field (or effective field) associated with the cosmological constant term. This can be constrained by measuring the amount of change at high redshift. However, this constraint comes after robust support for some kind of dark energy, mostly from measurements using SNe Ia, something you appear to be denying.

There have been at least a dozen mainstream papers published since the 2008 thread stating that some type Ia supernova exceed the cannonical 1.4M(solar) limit; yet Tensor and others still keep publishing the prior misconception about the limits of supernovae magnitude. Are you still insisting I am wrong when I state the limit is problematic?
You are not simply wrong, you are belligerently wrong. You should know that a measurement of progenitor mass need not have anything to do with a deviation from standard SNe Ia light curve theory. This has been pointed out to you again and again. You have been asked to provide evidence for a link again and again and you have failed every time. You have been repeatedly shown that your citations on this matter have nothing to do with what you claim that they do. Yet you continue to harp on the same demonstrably unsupported claim.

Nereid
2010-Apr-19, 03:29 AM
Somewhere, somehow, Halton is laughing.
Why?

Did you read the Hawkins paper (Dr Rocket provided a link to the preprint, in arXiv)?

Jerry
2010-Apr-21, 02:58 AM
You are neither talking about w nor about the amount of change in the expansion rate at high redshift--and these things are not the same thing. In the contemporary cosmological literature, w is used to discuss the equation of state of the field (or effective field) associated with the cosmological constant term. This can be constrained by measuring the amount of change at high redshift. However, this constraint comes after robust support for some kind of dark energy, mostly from measurements using SNe Ia, something you appear to be denying.

Nancy described 'dark energy' as a term used to describe something we do not understand. Whether 'w' is a constant or variable as a function of distance depends upon what is observed. There is not enough information to constrain this apparent acceleration term to a constant value at very high redshifts - and I have posted references - this is no my supposition, it is a simple limitation in our knowledge.


You are not simply wrong, you are belligerently wrong. You should know that a measurement of progenitor mass need not have anything to do with a deviation from standard SNe Ia light curve theory. This has been pointed out to you again and again. You have been asked to provide evidence for a link again and again and you have failed every time. You have been repeatedly shown that your citations on this matter have nothing to do with what you claim that they do. Yet you continue to harp on the same demonstrably unsupported claim.
That is not what I took exception to. I said that using the Chandrasekar limit as an explanation for why type Ia supernova fall within a fairly narrow range of values is outdated. It is no longer kosher to insist that type Ia supernova are the result of an explosion at 1.4m(solar); or as stated in Sullivan et al:

The Dependence of Type Ia Supernova Luminosities on their Host Galaxies

http://arxiv.org/abs/1003.5119


As calibrate-able standard candles, Type Ia supernovae (SNeIa) provide a direct route to understanding the nature of the dark energy that drives the accelerated expansion of the Universe. Yet, the relationships that allow the calibration of their peak luminosities, and hence permit their cosmological use, remain purely empirical.

Nowhere in this, or other recent papers, will you find anyone using a 'standard mass' as justification for the current supernova luminosity/light curve relationship: It is purely empirical. Sullivan goes on to discuss the topic of this paper, which proves to be yet another limitation on our ability to use supernova type Ia to judge acceleration at very great redshift distances:


Cosmological implications

Differences in mean SN Ia properties when split by host galaxy properties, which are not removed by corrections currently employed in cosmological analyses, could clearly lead to systematic errors in cosmological analyses. Observationally, SNe Ia in massive galaxies appear brighter than those in less massive galaxies – a similar effect is seen when considering sSFR, with SNe Ia in low sSFR galaxies brighter than those in high sSFR galaxies. These differences are significant at >3sigma.

Evidence for two populations of SNe Ia with different photometric properties is not by itself alarming, as the nuisance
variables in any global fit will average to values appropriate for the combination of SNe Ia. However, any change
in the mix of SNe Ia with redshift could introduce a serious effect...

(From Conclusion)

The SN Ia luminosity variation with host (galaxy) properties introduces a systematic error into cosmological analyses, as the mean Mstellar and sSFR of the hosts, and hence the mix of SNe Ia, evolves with redshift. This effect is exacerbated by the biased selection of existing low-redshift SNe Ia, and amounts to a systematic error on w comparable to the statistical errors.

To which Sullivan proposes a galactic type supenova luminosity correction factor.

See also The type Ia supernova SNLS-03D3bb from a super Chandrasekhar-mass white dwarf star

Howell et al


The acceleration of the expansion of the universe, and the need for Dark Energy, were inferred from the observations of Type Ia supernovae (SNe Ia). There is consensus that SNe Ia are thermonuclear explosions that destroy carbon-oxygen white dwarf stars that accrete matter from a companion star3, although the nature of this companion remains uncertain. SNe Ia are thought to be reliable distance indicators because they have a standard amount of fuel and a uniform trigger — they are predicted to explode when the mass of the white dwarf nears the Chandrasekhar mass4 — 1.4 solar masses. Here we show that the high redshift supernova SNLS-03D3bb has an exceptionally high luminosity and low kinetic energy that both imply a super-Chandrasekhar mass progenitor. Super-Chandrasekhar mass SNe Ia should preferentially occur in a young stellar population, so this may provide an explanation for the observed trend that overluminous SNe Ia only occur in young environments. Since this supernova does not obey the relations that allow them to be calibrated as standard candles, and since no counterparts have been found at low redshift, future cosmology studies will have to consider contamination from such events.

Jerry
2010-Apr-23, 08:49 PM
Jerry, I bolded your claim. Another case of, you linking to a paper that doesn't show what he thinks it does. The paper is also more about the energy lighting up the ejecta around the SN1a than the SN1a itself. , that particular paper uses a single progenitor, asymmetric explosion model. Exactly how well does the model used in this paper match a dual detonation event, spectrally, in the rest frame of each? You might notice that that particular paper doesn't even mention dual detonation events, so not quite sure why you linked to it as evidence for a difference between single and dual events.

And, speaking of nickel content....



Jerry, you,not me, are the one that brought up the paper arXiv:1003.2217v3. I asked you to provide evidence that the Chandrasekar limit was falsified. You presented that paper as evidence. You are the one that quoted from it. I just pointed out where you misunderstood the paper. Where when the authors talked about the amount of nickel (1.6 times the suns mass) it was not a "lower mass limit" as you claimed. It was just the amount of nickel in a dual detonation event. Are you now saying that you referenced that paper in error?

I also pointed out that the authors had no problem with the Chandrasekar limit. The total mass was 2.4 for two white dwarfs. Where they were able to differentiate between single and dual events by spectral identification. I never mentioned anything about local or distant, that was something you brought in to change the goalposts, when it was shown you were wrong.

I wish you would make up your mind when you reference a paper. Now, it appears that a paper you previously used as support (arXiv:1003.2217v3), you now seem to think is invalid, because it claims to be able to measure the nickel content. Which is it?

Sorry, it took me a week, but I final found the definitive paper; writtten by Robert P. Kirshner, who has been a principle in supernova research for decades:

Foundations of supernova cosmology

http://arxiv.org/abs/0910.0257v1


Though the simple theoretical idea that SN Ia are white dwarfs that ignite near the Chandrasekhar mass has been repeated many times as evidence that SN Ia must be perfect standard candles, nature disagrees. Observations show that there is a factor of three range in luminosity from the most luminous SN Ia (resembling SN 1991T) to the least luminous (resembling SN 1991-bg). Despite the facts, many popular (and professional!) accounts of SN Ia assert that SN Ia are standard candles because they explode when they reach the Chandrasekhar limit. This is wishful thinking. (my bold)

This is a really good paper for the casual astronomer, it is fairly simple, concise and honest. I hope this puts this argument to rest; but if anyone would like to continue to discuss supernova classification and such; let's open another thread with this paper as a root resource for the topic - I'm not sure everyone is as convinced that the 'Chadrasekhar limit' on supernova magnitudes is 'wishful thinking'.

Tensor
2010-Apr-24, 01:43 AM
Sorry, it took me a week, but I final found the definitive paper; writtten by Robert P. Kirshner, who has been a principle in supernova research for decades:

Foundations of supernova cosmology

http://arxiv.org/abs/0910.0257v1

(my bold)

This is a really good paper for the casual astronomer, it is fairly simple, concise and honest. I hope this puts this argument to rest; but if anyone would like to continue to discuss supernova classification and such; let's open another thread with this paper as a root resource for the topic - I'm not sure everyone is as convinced that the 'Chadrasekhar limit' on supernova magnitudes is 'wishful thinking'.

Actually Jerry, it only puts it to rest if you read the first eight pages of the paper. Those first eight pages describe how the early attempts (prior to 1995) to use supernovas were wishful thinking due to a variety of things which is where your quotes come from. Kirshner goes on, in the rest of the paper to describe how SN1a, with the mass limit, became standard candles by correcting those things. He goes on to explain that in the near infrared, that SN1a supernovas are even more alike, spectrally, than optically. to quote from the paper:

As shown in the pioneering work of Krisciunas, Phillips, and Suntzeff (2004), nearby SN Ia in the Hubble flow behave as very good standard candles when measured in near infrared bands (NIR), typically J, H, and Ks.

And this:
This means that the SN Ia actually do behave like standard candles– but in the NIR!

Not to mention this one:

Supernovae have an important role to play because they have been demonstrated to produce results.

Now, we should accept these quotes, right Jerry? After all, according to you:

Sorry, it took me a week, but I final found the definitive paper; writtten by Robert P. Kirshner, who has been a principle in supernova research for decades:

As far as this:


I'm not sure everyone is as convinced that the 'Chadrasekhar limit' on supernova magnitudes is 'wishful thinking'.

Nahh, well keep it right here. I don't think that Kirshner thinks the 'Chadrasekhar limit'(sic) model of supernovas is wishful thinking. At least not from the rest of the paper, why don't you read the rest of it and get back to us.

I love discussing things with you Jerry, you do most of my searches for me. 90% of the papers in this thread, that you cited, gave me the quotes to refute your assertions.

01101001
2010-Apr-24, 02:16 AM
Actually Jerry, [...] 90% of the papers in this thread, that you cited, gave me the quotes to refute your assertions.

As my big brother used to say: Stop hitting yourself! Why are you hitting yourself? Stop hitting yourself!

Jerry
2010-Apr-24, 05:57 AM
Actually Jerry, it only puts it to rest if you read the first eight pages of the paper. Those first eight pages describe how the early attempts (prior to 1995) to use supernovas were wishful thinking due to a variety of things which is where your quotes come from. Kirshner goes on, in the rest of the paper to describe how SN1a, with the mass limit, became standard candles by correcting those things. He goes on to explain that in the near infrared, that SN1a supernovas are even more alike, spectrally, than optically. to quote from the paper:

As shown in the pioneering work of Krisciunas, Phillips, and Suntzeff (2004), nearby SN Ia in the Hubble flow behave as very good standard candles when measured in near infrared bands (NIR), typically J, H, and Ks.

And this:
This means that the SN Ia actually do behave like standard candles� but in the NIR!
Nice cherry, but the Near IR is useless at great cosmological distances - at distances greater than z=1; the Near IR spectrum is redshifted into oblivion! Kirshker is using irony. What we need is a better understanding of what is happening in the ultraviolet spectrum; and this is where supernova as they are understood today are the most ambiguous.


Nahh, well keep it right here. I don't think that Kirshner thinks the 'Chadrasekhar limit'(sic) model of supernovas is wishful thinking. At least not from the rest of the paper, why don't you read the rest of it and get back to us. Kirshker called the Chandrasekar limit 'wishful thinking' , not me - good grief! did you even read his opinion? According to Kirshker NATURE DISAGREES, with the assertion supernovae Ia are the result of a white dwarf star reaching a 'Chandrasekar limit' "because there is a factor of three range in luminosity". In the paragraph I quoted, he is dissing professionals who still insist the mass limit is a valid assumption. I agree with Kirsker...and so does nature.

Tensor
2010-Apr-24, 06:10 PM
Nice cherry,

From the expert at cherry picking.


but the Near IR is useless at great cosmological distances - at distances greater than z=1; the Near IR spectrum is redshifted into oblivion! Kirshker is using irony.

No he is not using irony Jerry, read the paper. That is why it wasn't cherry picking. He is describing how to use NIR and light curves from local SN1a and compare the light curves from distant SN1a. From the paper:

When combined with optical data, the infrared observations can be used to determine the properties of the dust, and to measure even more accurate luminosity distances.

Also, this has nothing to do with distance. Your original claim was that the Chandrasekar limit was falsified. Kirshner describes early attempts at using SN1a were wrong because of a variety of reasons. How those reasons were overcome and how changes were made in using SN1a to make them pretty good standard candles. How in NIR, they behave as standard candles even better than optically, and how to combine local SN1a in NIR and optically to be able to identify large z SN1a better. No where in that paper does Kirshner invalidate the idea that SN1a are not white dwarfs exceeding (well, getting close to before exploding) the Chandrasekar limit. See below for the two specific sentences.




Kirshker called the Chandrasekar limit 'wishful thinking' , not me - good grief! did you even read his opinion? According to Kirshker NATURE DISAGREES, with the assertion supernovae Ia are the result of a white dwarf star reaching a 'Chandrasekar limit' "because there is a factor of three range in luminosity".

As usual, you have misread two paragraphs to what you want to read. He called their use as standard candles in the 70-90s timeframe wishful thinking. Here are the two paragraphs:


Though the simple theoretical idea that SN Ia are white dwarfs that ignite near the Chandrasekhar mass has been repeated many times as evidence that SN Ia must be perfect standard candles, nature disagrees.

and this:


Despite the facts, many popular (and professional!) accounts of SN Ia assert that SN Ia are standard candles because they explode when they reach the Chandrasekhar limit.

Note that in both those sentences he talks about (and disagrees) that SN1a being perfect standard candles when white dwarfs ignite or explode near the Chandrasekhar mass. He does not disagree with the idea that white dwarfs explode when they exceed the Chandrasekhar limit. Also, those particular paragraphs are describing the use of SN1a in the 70s, 80s, and early 90s. I would agree with him, at those times.

However, he goes into some detail explaining how SN1a were studied, how dust was studied, how host galaxies were studied and how all that was put together to get to the point where SN1a can be used as standard candles. I won't say they are perfect, I haven't seen that in any of the papers. But they are pretty darn good. As Kirshner says, and you seemed to ignore in my last post:

Supernovae have an important role to play because they have been demonstrated to produce results.

Note that after describing the problems of the 70- early 90s timeframe, he then goes on, in the first sentence, of the next section with this:

Nevertheless, the hope that SN Ia might prove to be good standard candles began to replace the idea that brightest cluster galaxies were the standard candles best suited to measuring the deceleration of the universe.

Kirshner then goes on to explain how SN1a supernova were found, exceptions were found and how those exceptions are taken into account and how SN1a are used as standard candles. Behind all of this is the model of the SN1a as an explosion of a white dwarf gathering mass near the Chandrasekhar limit


In the paragraph I quoted, he is dissing professionals who still insist the mass limit is a valid assumption.

No he's not. You've just misread it and are spreading misinformation based on your misreading of the paper. Nothing we haven't seen you do here before.


I agree with Kirsker...and so does nature.

Maybe you do agree with Kirsker, but you don't agree with Kirshner

Cougar
2010-Apr-24, 06:52 PM
SN1a have a well known light curve, simply because SN1a are the same type of explosion.An old theory, that is bending somewhat to admit new observations:

Well, the theory had already "bent" 25 years ago, as StupendousMan initially said. I don't think anyone ever said SnIa were all exactly the same. Light-curve shape analysis was one of the early keys to 'normalizing' the observations and getting good estimates. A few apparent Ia's were just anomalous, not useful, and discarded. I haven't been keeping up on the latest findings in SN research, but it seems reasonable that there would be a continuum of usually slight variation largely determined by the relative masses of the binary system. Knowing the stellar lifecycle that results in a white dwarf, how do you ever get to a situation where two white dwarfs are coalescing, anyway?

Jerry
2010-Apr-25, 08:01 PM
"This means that the SN Ia actually do behave like standard candles– but in the NIR!"

Semantics? The word 'But' implies exception. Is Kircher saying they are only standard candles in the NIR? I agree with Tensor and others that in in the balance of the paper Kircher is talking about using supernova as standard candles in other colors; so the term 'standardizable candles' might be more appropriate.

It is curious that greater precision is found in the NIR band than in other wavelengths. It is reasonable to speculate this is tied to a standard mass; but if this is true, it also means we don't have our hands completly around the effect of dust, k-corrections or other parameters in the higher bandwidths - especially at high redshifts. There are reasons for stressing that the magnitude corrections are empirical for now. In any case, with the Hubble repair and more instruments coming on-line in the near future, we will get better snswers.

Tensor
2010-Apr-25, 09:55 PM
Semantics? The word 'But' implies exception. Is Kircher saying they are only standard candles in the NIR? I agree with Tensor and others that in in the balance of the paper Kircher is talking about using supernova as standard candles in other colors; so the term 'standardizable candles' might be more appropriate.

While I agree 'standardized candles' might be a better term, I don't think it'll replace 'standard candle' anytime soon.


It is curious that greater precision is found in the NIR band than in other wavelengths.

Actually, if you think about it, it makes sense as those wavelengths are not as attenuated by dust, as optical wavelengths are. Peak luminosity will not attenuated and thus the peak luminosity-light curve relationship will be more clear.


It is reasonable to speculate this is tied to a standard mass; but if this is true, it also means we don't have our hands completly around the effect of dust, k-corrections or other parameters in the higher bandwidths - especially at high redshifts.

From the number of papers you cited in this thread, and the number I've looked at for this thread, I'd agree that we don't have a complete handle on several different parameters, however, I would argue that we do have a good enough handle to get a good distance indicator on SN1a. I would also say that a better handle on those parameters would be a good thing. Several of the papers you linked to proposed ways to get a better handle on those parameters.


There are reasons for stressing that the magnitude corrections are empirical for now. In any case, with the Hubble repair and more instruments coming on-line in the near future, we will get better answers.

Like I said, you provided several papers where the authors provided several different ways to get better answers and betters constraints on SN1a light curves, dust, metallicity, host galaxy mass, etc.

Jerry
2010-Apr-30, 08:03 PM
Spectral Classification of Quasars in the Sloan Digital Sky Survey: Eigenspectra; Redshift and Luminosity Effects

http://arxiv.org/abs/astro-ph/0408578v1


We find that the spectral classification of quasars is redshift and luminosity dependent, as such there does not exist a compact set (i.e., less than  10 modes) of eigenspectra (covering 900 °A to 8000 °A) which can describe most variations (i.e., greater than  95 %) of the entire catalog. We therefore construct several sets of eigenspectra in different redshift and luminosity bins. From these eigenspectra we find that quasar spectra can be classified (by the first two eigenspectra) into a sequence that is defined by a simple progression in the steepness of the slope of the continuum. We also find a dependence on redshift and luminosity in the eigencoefficients. The dominant redshift effect is a result of the evolution of the blended Fe II emission (optical) and the Balmer continuum (the “small bump”, λrest  2000−4000 °A). A luminosity dependence is also present in the eigencoefficients and is related to the Baldwin effect — the decrease of the equivalent width of an emission line with luminosity, which is detected in Lyα, Si IV+O IV], C IV, He II, C III] and Mg II, while the effect in N V seems to be redshift dependent.
One would expect both redshift and luminosity to change the spectral signature: As thin as the atmosphere of space is, there are hydrogen and other absorption lines that chop up the spectra, and the more distant and redshifted the sample; the greater the hacking.

They attribute a fair share of the spectral eigenvector signature to the Baldwin effect - the propensity of more luminous spectra to have narrower emission lines. This is so counter-intuitive that I wonder how much the total SED/r^ is effected by emission line coherances.

Cougar
2010-May-03, 03:42 PM
Returning to the topic at hand...

Quasar time dilation? As previously noted, the wide variability of quasars makes them very poor candidates from which to confirm time dilation.

matt.o
2010-May-03, 09:14 PM
Quasar time dilation? As previously noted, the wide variability of quasars makes them very poor candidates from which to confirm time dilation.

But this is taken into account in the method Hawkins uses. The assumption which the Hawkins study relies critically on is that the quasar population as a whole, and therefore the distribution of quasar variabilities, is similar at high and low redshift. This means that any differences in the fourier-transformed variabilities when comparing the low- and high-redshift sample will show up in the power spectra of the two samples, and can be compared with the expected differences due to time dilation. No differences are seen, and I expect this is simply due to quasar evolution, or some subtle selection effects. Future multi-colour and multi-epoch surveys, such as the Southern Sky Survey using Skymapper, will provide significantly more data for this type of study and it will definitely be interesting to follow this up.

Jerry
2010-May-04, 04:33 AM
Quasar time dilation? As previously noted, the wide variability of quasars makes them very poor candidates from which to confirm time dilation.

Generally, when there is an assignable spectral signature, there is also a periodic root to the spectral events we witness. It is possible quasa stellar objects don't follow this rule. As we learn more about them, and the dynamic changes that define them; we should be able to put limits on the the periods and bin the observed periods by redshift. If the Hawkin study is correct; there are no bin-able periodic events, even though the spectral events are clearly defined in each redshift bin. It is a simple sanity check that that shouldn't fail. But it does.

Jerry
2010-May-07, 09:06 PM
http://arxiv.org/abs/1005.0901

Dependence of the optical/UV variability on the emission line properties and Eddington ratio in active galactic nuclei


The previously known dependence of the variability on luminosity is not significant, and that on black hole mass---as claimed in recent papers and also present in our data---fades out when controlling for the Eddington ratio in the correlation analysis, though these may be partly due to the limited ranges of luminosity and black hole mass of our samples. Our result strongly supports that an accretion disk is likely to play a major role in producing the opitcal/UV variability.

Fair enough: the larger the accretion ring, the less variable the the AGN. But in order for this to be consistent with no measurable time dilation in the fundamental frequencies of AGN; there must be a 'conspiracy' between AGN sizes and distants, with the most distant AGN becoming smaller with distance at the ratio necessary to cancel out time dilation.

Cougar
2010-May-08, 05:07 PM
...and I expect this is simply due to quasar evolution, or some subtle selection effects.

Evolution makes sense. All the quasars have evolved into more sedate galaxies? Does the data show that trend?

Jerry
2010-May-15, 05:45 AM
According to the current interpretation of QSOs or active galactic nuclei, they have evolved quite dramatically; peaking in number and luminosity at somewhere near Z =2 and then fading. It seems like the active features should be binable; and it would be strange if whatever is evolving here would be masked; not apparent in redshift binning. It would meant that, even though we can identifiy periodic effects and evidence of evolution; these two features cannot be disentanged by redshift binning.

parejkoj
2010-May-16, 05:40 PM
According to the current interpretation of QSOs or active galactic nuclei, they have evolved quite dramatically...

How is this an interpretation? It's what the data shows. Incidentally, star formation shows a similar peak around z~=2.


It seems like the active features should be binable; and it would be strange if whatever is evolving here would be masked; not apparent in redshift binning.

I have no idea what you mean by this.


It would meant that, even though we can identifiy periodic effects and evidence of evolution; these two features cannot be disentanged by redshift binning.

What do you mean, "periodic effects?" What's periodic about AGN?

matt.o
2010-May-16, 09:30 PM
Evolution makes sense. All the quasars have evolved into more sedate galaxies? Does the data show that trend?

By quasar evolution, I meant that the populations of quasars (that is, the black holes and accretion disks surrounding them) as a whole are different at low and high redshift. I think parejkoj would be better placed to comment on this.

parejkoj
2010-May-16, 11:55 PM
Someone ping this thread in a week or so, if I haven't responded by then (currently dissertating a lot).

RGClark
2010-May-19, 12:50 AM
Astronomer Mike Hawkins from the Royal Observatory in Edinburgh came to this conclusion after looking at nearly 900 quasars over periods of up to 28 years. When comparing the light patterns of quasars located about 6 billion light years from us and those located 10 billion light years away, he was surprised to find that the light signatures of the two samples were exactly the same. If these quasars were like the previously observed supernovae, an observer would expect to see longer, “stretched” timescales for the distant, “stretched” high-redshift quasars. But even though the distant quasars were more strongly redshifted than the closer quasars, there was no difference in the time it took the light to reach Earth. http://www.physorg.com/news190027752.html

Thanks for that. There was a theory that instead of the universe expanding it is actually rotating about some preferred center. The redshifts we observe would be due to different parts of the universe moving at different speeds than us depending on their distance from the preferred center, and frame of reference.
By this theory, two quasars might have different distances from us but their redshifts would not have to be different since their redshifts are determined by how far away they are from the center of rotation.

Bob Clark

Jerry
2010-May-19, 11:09 PM
How is this an interpretation? It's what the data shows. Incidentally, star formation shows a similar peak around z~=2.
Nobody has actually warped out to z=2 and counted galaxies and mesured the SFRs. We can only make assumptions about how the light we see is transmitted and attenuated from so far away. Some of these assumptions, such as the net effect of foreground lensing, may be wrong. The Hershel telescope has just demonstrated that half of the cosmic INFRARED background is from point sources. I think this is a major/minor surprise, and until there is a better understanding of point sources > z=2; we are limited to 'best guesses'.



I have no idea what you mean by this.
What do you mean, "periodic effects?" What's periodic about AGN?

According to the Hawkins data, nothing. We observe changes in the luminosity AGN over very long periods. We think these changes are related to the dimensions of accretion flows into AGN. If AGN were larger at z=2 than they are a in later times, it is reasonable to expect a fundamental relationship between the size of the AGN and observed variations in luminosity - especially when it is known that the spectral signature of the source varies as a function of luminosity.

"Binning" Is simply dividing observations in to redshift windows; say every 0.2 z; and looking at the principle components of the luminosity variation in the frequency domain. Finding no redshift-dependent attributes means either 1) there are no fundamental luminosity/period relationships or 2) Any luminosity/period relations are cancelled by evolution or 3) something is wrong with the test (not enough data or poor analysis) or 4) a fundamental assumption is askew.

Jerry
2010-May-21, 02:30 AM
http://arxiv.org/abs/1005.2859v1


Below z.=~1.5, extrapolations of the total IR luminosity of galaxies based on mid-IR measurements agree with those measured directly with Herschel over three decades in luminosity below the ULIRG regime, with a dispersion of only 40% (0.15 dex), and are therefore similar to the local one. This narrow distribution is puzzling when considering the range of physical processes (gas mass fraction, different geometries, grain size distribution, metallicity) that could have affected the SED of these galaxies which dominated the SFR density of the Universe over 80% of the age of the Universe.

There is much to learn.

Glom
2010-May-21, 03:29 PM
I'm sorry. I knew this at one point I'm sure. What is z?

Jerry
2010-May-21, 05:57 PM
'z' is the redshift factor: A 'z' value of 1 means the spectral lines are very deeply redshifted; the theoretical time dilation factor is 1: Any events we are witnessing at this distance should appear to occur at half-speed.

Before Herschel, it has always been necessary to make rather iffy assumptions about how redshifted spectra should be corrected from bandwidth to bandwidth. For the first time, Herschel gives us very broad spectral results, so it is easier to compare the SED (spectral Energy Distribution) of redshifted data with local data.

Also, Herschel has much higher resolution, again giving us the ability to isolate background point sources of noise and remove them up to a redshift of z=1.5. When I pointed out to parejkoj that their may be problems with some of the basic assumptions; I did not know Herschel was already demonstrating this is likely the case. Because at least to me; it seems likely that if there is no evolution in the SED at z=1.5 (with respect to the local distribution); the prior conclusions than the Star Formation rate and AGN magnitudes peak at z=2 are also skewed by background/band correction/selection effects. We really need the James Webb telescope!

Nereid
2010-May-23, 05:09 AM
http://arxiv.org/abs/1005.2859v1



There is much to learn.
And this is related to "Discovery that quasars don't show time dilation mystifies astronomers" how, exactly? :question:

Jerry
2010-May-23, 11:36 PM
There are hundreds of papers out there that use the Spectral Energy Distrubution and/or luminosity evolution to track changes in the universe. What is clear from the latest Herschel data, is that contrary to virtually all model predictions and expectations, as deep as we can reliably track the IR bandwidths, there is no change in the AGN spectral energy distribution.

That means that at least to a distance of z=1.5; AGN, on average, kick out the same spectral signature. If the signature of these beast is tied to an accretion ring; this means that the ring size, composition and luminosity are nearly the same. So it is not surprising that Hawkins can't detect any change in the frequency domain either...except...according to the principles of relativistic time dilation; when we look at a AGN with a redshift of one, all period effects should be time dilated by a factor of 1: twice as slow. No spectral evolution and no evidence of time dilation. Something is very queer.

All evolutionary theories of QSOs should be on hold now, while we wait for good explanations of how luminosity evolves as a power function while the SED doesn't change; and there is measurable periodicity that is consistent with an accretion ring but inconsistent with time dilation.

Nereid
2010-May-24, 02:11 AM
There are hundreds of papers out there that use the Spectral Energy Distrubution and/or luminosity evolution to track changes in the universe. What is clear from the latest Herschel data, is that contrary to virtually all model predictions and expectations, as deep as we can reliably track the IR bandwidths, there is no change in the AGN spectral energy distribution.
Um, and you concluded this from the paper (preprint) you cited?



That means that at least to a distance of z=1.5; AGN, on average, kick out the same spectral signature. If the signature of these beast is tied to an accretion ring; this means that the ring size, composition and luminosity are nearly the same. So it is not surprising that Hawkins can't detect any change in the frequency domain either...except...according to the principles of relativistic time dilation; when we look at a AGN with a redshift of one, all period effects should be time dilated by a factor of 1: twice as slow. No spectral evolution and no evidence of time dilation.
That's a pretty remarkable, er, string of, um, inferences.

You don't think, perchance, that you're being a little, er, loose with the logic?


Something is very queer.
Perhaps ... but is it the astrophysics? or something else?



All evolutionary theories of QSOs should be on hold now, while we wait for good explanations of how luminosity evolves as a power function while the SED doesn't change; and there is measurable periodicity that is consistent with an accretion ring but inconsistent with time dilation.
That's, what's the word, right on the tip of my tongue, um, a remarkable conclusion.

Jerry
2010-May-25, 02:22 PM
Then let’s slow down, and take them one-at-a-time:

“That means that at least to a distance of z=1.5; AGN, on average, kick out the same spectral signature.”

This is a conclusion drawn by the authors bases upon the observed IR and near-IR signatures. The paper points out that prior models estimating the peaks and curvature in these spectral ranges were wrong: Hershel gives us our first depthy look that is not atmosphere impeded; and it tells us that the sed – the spectral energy distribution in the GOODs surveys is flat to at least a z shift of 1.5. – a conclusion drawn by a team of astrophysicists studying Herschel data, not me.

“If the signature of these beast is tied to an accretion ring; this means that the ring size, composition and luminosity are nearly the same.”

Again, the broad band emissions characteristic of AGN are thought to be related to accretion rings. If the composition of material dumped into accretion rings varied considerably, so wouild the SED. Size does matter. if the size of accretion rings evolved; the spectral energies should be different; just as the peak thermal emissions of a larger or smaller wattage of light bulb shift. Likewise, the fundemental (very low) frequencies should change with size.

“So it is not surprising that Hawkins can't detect any change in the frequency domain either”.

If the SED is the same, the frequency domain should be the same, and visa versa. This is also a no-brainer inference.

“...except...according to the principles of relativistic time dilation; when we look at a AGN with a redshift of one, all period effects should be time dilated by a factor of 1: twice as slow. No spectral evolution and no evidence of time dilation.”

The lack of evidence of Time Dilation in the frequency domain of AGN is the conclusion of the Hawkins paper, not me. Others have speculated that this may be due to evolutionary trends off-setting the time signature; but the Herschel data are inconsistent with evolution. The paradox is obvious: To fit the observational data, a model must hold the SED constant while ramping the fundamental frequencies associated with QSOs.

It is damned difficult to accelerate a lorry without either changing the RPMs or shifting gears. And in any case; as a lorry accelerates away from us, there should be a doppler drop in the engine frequency with increasing distance. We don't observe this in QSO; even though the tail lights are getting redder.

Nereid
2010-May-25, 07:50 PM
Then let’s slow down, and take them one-at-a-time:

“That means that at least to a distance of z=1.5; AGN, on average, kick out the same spectral signature.”

This is a conclusion drawn by the authors bases upon the observed IR and near-IR signatures. The paper points out that prior models estimating the peaks and curvature in these spectral ranges were wrong: Hershel gives us our first depthy look that is not atmosphere impeded; and it tells us that the sed – the spectral energy distribution in the GOODs surveys is flat to at least a z shift of 1.5. – a conclusion drawn by a team of astrophysicists studying Herschel data, not me.
Are we reading the same paper?

I don't think so ... even the abstract of the Herschel preprint ("Herschel unveils a puzzling uniformity of distant dusty galaxies") doesn't come close to the radical claim you've just made (that I quoted).



“If the signature of these beast is tied to an accretion ring; this means that the ring size, composition and luminosity are nearly the same.”

Again, the broad band emissions characteristic of AGN are thought to be related to accretion rings. If the composition of material dumped into accretion rings varied considerably, so wouild the SED. Size does matter. if the size of accretion rings evolved; the spectral energies should be different; just as the peak thermal emissions of a larger or smaller wattage of light bulb shift. Likewise, the fundemental (very low) frequencies should change with size.
Well, even if we assume your premise (the previous paras), this claim contains some more, pretty speculative (or wild, YMMV) leaps of logic.



“So it is not surprising that Hawkins can't detect any change in the frequency domain either”.

If the SED is the same, the frequency domain should be the same, and visa versa. This is also a no-brainer inference.
If two animals are black, they must both be cats (because I have seen a black animal, and it was a cat).

No, the logic of your claim, and my statement, is not the same ... except that it is equally spurious.



“...except...according to the principles of relativistic time dilation; when we look at a AGN with a redshift of one, all period effects should be time dilated by a factor of 1: twice as slow. No spectral evolution and no evidence of time dilation.”

The lack of evidence of Time Dilation in the frequency domain of AGN is the conclusion of the Hawkins paper, not me. Others have speculated that this may be due to evolutionary trends off-setting the time signature; but the Herschel data are inconsistent with evolution.
Again, we must be reading two completely different papers (presenting the Herschel data) - how on Earth (or even on an AGN of your choice) did you conclude this from what you read?!?!? :question: :think:


The paradox is obvious: To fit the observational data, a model must hold the SED constant while ramping the fundamental frequencies associated with QSOs.
Sorry to be so blunt, but nonsense.

Time to move this thread to the ATM section?

Jerry
2010-May-26, 09:42 PM
No, It is time for you to try to explain why the Authors consider an observation that the SED of AGN is static to z=1.5 is puzzling. (They seem to think it is self-evident to the communtiy). I say it is paradoxical; especially so when bumped up against the equally queer lack of evidence of time dilation. In this thread, Cougar ventured a evolutional solution to the time dilation problem; but how does a AGN evolve without any measurable change in the SED?

A better explanation for the lack of time dilation observed by Hawkins might be that the contribution of accretion rings to the overall period of AGN is minimal; and the period (variation over time) is totally chaotic.

Also, I have not offered any alternative solutions; only pointed out possible reasons that the authors find the results puzzling. (Unless you consider speculation that a AGN is chaotic ATM, I don't think it is.) If you are not puzzled, are you asking the right questions?

Nereid
2010-May-27, 01:02 AM
No, It is time for you to try to explain why the Authors consider an observation that the SED of AGN is static to z=1.5 is puzzling. (They seem to think it is self-evident to the communtiy). I say it is paradoxical; especially so when bumped up against the equally queer lack of evidence of time dilation. In this thread, Cougar ventured a evolutional solution to the time dilation problem; but how does a AGN evolve without any measurable change in the SED?

A better explanation for the lack of time dilation observed by Hawkins might be that the contribution of accretion rings to the overall period of AGN is minimal; and the period (variation over time) is totally chaotic.

Also, I have not offered any alternative solutions; only pointed out possible reasons that the authors find the results puzzling. (Unless you consider speculation that a AGN is chaotic ATM, I don't think it is.) If you are not puzzled, are you asking the right questions?
No problemo.

Let's start with the title of the paper (preprint actually): "Herschel unveils a puzzling uniformity of distant dusty galaxies"

Is that equivalent to "the SED of AGN is static to z=1.5"?

No.

OK, what about the abstract?

"Here we examine whether the spectral energy distribution (SED) and dust temperature of galaxies have strongly evolved since z~2.5."

Is that equivalent to "the SED of AGN is static to z=1.5"?

No.

OK, what about (some of) the rest of the abstract?

We use Herschel deep extragalactic surveys from 100 to 500um to compute total IR luminosities in galaxies down to the faintest levels, using PACS and SPIRE in the GOODS-North field (PEP and HerMES key programs). We show that measurements in the SPIRE bands can be used below the statistical confusion limit if information at higher spatial resolution is used to identify isolated galaxies whose flux is not boosted by bright neighbors. Below z~1.5, mid-IR extrapolations are correct for star-forming galaxies with a dispersion of only 40% (0.15dex), therefore similar to z~0 galaxies. This narrow distribution is puzzling when considering the range of physical processes that could have affected the SED of these galaxies.

Is that equivalent to "the SED of AGN is static to z=1.5 is puzzling"?

No.

OK, what is there in the abstract that does refer to AGNs?

Above z=1.5, distant galaxies are found to exhibit a substantially larger mid- over far-IR ratio, which could either result from stronger broad emission lines or warm dust continuum heated by a hidden AGN. Two thirds of the AGNs identified in the field with a measured redshift exhibit the same behavior as purely star-forming galaxies. Hence a large fraction of AGNs harbor star formation at very high SFR and in conditions similar to purely star-forming galaxies.

Is that equivalent to "the SED of AGN is static to z=1.5 is puzzling"?

No.

So, how did you conclude "the Authors consider an observation that the SED of AGN is static to z=1.5 is puzzling"?!? :question: Was it, perhaps, in the body of the paper?

ETA: HINT: no it's not in the body of the paper either.

Jerry
2010-May-27, 03:47 AM
Page 3 Elbaz

The tight correlation between L tot IR as derived from 24 μm and Herschel below z=1.5, which extends over three decades in luminosity, is puzzling because galaxies have strongly evolved over the last 9 billion years (70% of the Universe age) during which most present-day stars formed (gas mass fraction, metallicity, compactness, dynamical status, e.g. mergers). It is as puzzling to see that AGNs follow a similar trend as star-forming
galaxies (open triangles in lower panel of Fig. 1)

...AGNs could have been associated to more compact geometries, e.g. due to a merger, and presented different IR signatures. But whether IR galaxies harbor an AGN or not, their star-formation activity produces a similar radiation pattern suggesting no major differences in the coeval activity of star formation with respect to purely star-forming galaxies.

Are the authors just being confusing when they call AGNs puzzling for following "a similar trend as star-forming galaxies"? What trend is it that AGN are following if it is not the same puzzling trend as the topic of the paper?

Nereid
2010-May-27, 06:57 AM
Page 3 Elbaz


Are the authors just being confusing when they call AGNs puzzling for following "a similar trend as star-forming galaxies"? What trend is it that AGN are following if it is not the same puzzling trend as the topic of the paper?
I thought you'd pick on that.

And after all these years here was I thinking you'd learned something about extra-galactic astronomy.

Here's a suggestion for you: start a thread, in the Q&A section, on AGN SEDs, and ask questions about what part of the AGN (in the unified model - accretion disk, jet, dusty torus, NLR, BLR, ...) dominates the SED in different regions (gamma, x-ray, UV, optical, NIR, FIR, ...), and for different viewing geometries. You can also ask about what physical processes are thought to dominate the emission in each region.

Now unless you are familiar with these things, it is all too easy to draw conclusions like yours (which is totally wrong) ... but, and this is important Jerry, you of all BAUT members should know how easy it is to make this kind of mistake (and so, forewarned, ask questions first, before making what, in hindsight, is obviously a wild conclusion). IOW, be aware of confirmation bias.

I'll close with a quote from the paper, which should have given you, Jerry, a hint as to what the authors are on about:

This again shows that in the regime where star formation dominates the IR emission of AGNs, this activity does not differ from normal star-forming galaxies (see also Shao et al 2010, Hatziminaoglou et al. 2010).

loglo
2010-May-27, 07:59 AM
Would a fair conclusion from the above quote from Nereid be that the presence of an AGN in a galaxy does not significantly disrupt (or enhance) new star formation? I would find that puzzling.

Nereid
2010-May-27, 02:31 PM
Let's continue here (http://www.bautforum.com/showthread.php/104354-AGN-SEDs-(the-spectral-energy-distribution-of-active-galactic-nuclei)).

parejkoj
2010-May-27, 03:34 PM
I was going to (eventually) post something along the lines of "Jerry needs to study up on where the different parts of an AGN's spectral energy distribution come from, and which parts are time variable on what timescales." But Nereid beat me to it, so I'm just going to back her up and say:

Jerry, you need to do some very basic reading on this topic before you go off making claims like "All evolutionary theories of QSOs should be on hold now..." which just showcase your lack of knowledge.

parejkoj
2010-May-27, 03:40 PM
Would a fair conclusion from the above quote from Nereid be that the presence of an AGN in a galaxy does not significantly disrupt (or enhance) new star formation? I would find that puzzling.

Not a bad guess, and that's a related problem. What's actually going on in the Herschel paper (note: haven't read the whole thing yet) is that, for galaxies hosting an strongly accreting supermassive black hole (an AGN), the part of their spectrum dominated by star formation looks just like same part of the spectrum in galaxies that are forming a lot of stars but don't have an AGN. I.e., the star forming aspects of an AGN host galaxy look just like any other star forming galaxy (at that redshift). Similar things have been seen in previous studies, but Herschel can get at a portion of the spectrum that's particularly adept at distinguishing star formation processes.

As to your guess about how this relates to AGN shutting down star formation (also referred to as AGN feedback), one important point is the timescale for the AGN's energy to interact with the cold gas that has not yet formed into stars. Any stars that formed before the AGN turns on will be unaffected. And it takes time for an ionization front or wind-driven shockwave to disrupt cold gas reservoirs. So exactly how and when the AGN's presence affects star formation is still rather unclear.

loglo
2010-May-28, 01:19 PM
Thanks parejkoj
I did a bit more reading and just got more confused :) Will follow up in Nereid's new thread.

Gigabyte
2010-May-31, 03:08 PM
One of Hawkins’ possible explanations for quasars’ lack of time dilation is that light from the quasars is being bent by black holes scattered throughout the universe. These black holes, which may have formed shortly after the big bang, would have a gravitational distortion that affects the time dilation of distant quasars. However, this idea of “gravitational microlensing” is a controversial suggestion, as it requires that there be enough black holes to account for all of the universe’s dark matter. As Hawkins explains, most physicists predict that dark matter consists of undiscovered subatomic particles rather than primordial black holes.

There’s also a possibility that the explanation could be even more far-reaching, such as that the universe is not expanding and that the big bang theory is wrong. Or, quasars may not be located at the distances indicated by their redshifts, although this suggestion has previously been discredited. Although these explanations are controversial, Hawkins plans to continue investigating the quasar mystery, and maybe solve a few other problems along the way.
http://www.physorg.com/news190027752.html

It's a good thing he doesn't post on astronomy forums.

Nereid
2010-May-31, 09:02 PM
http://www.physorg.com/news190027752.html

It's a good thing he doesn't post on astronomy forums.
:question: :question:

Why do you say that, Robinson (I'm genuinely puzzled)?

jlhredshift
2010-May-31, 09:19 PM
http://www.physorg.com/news190027752.html

It's a good thing he doesn't post on astronomy forums.

Yeah, because he'd get jumped on and banned.

Gigabyte
2010-May-31, 11:10 PM
Only banned if he refused to answer any and all questions from anyone.

OK now it really makes sense why astronomers don't post here.

01101001
2010-May-31, 11:26 PM
OK now it really makes sense why astronomers don't post here.

It doesn't seem to stop some out-there non-astronomers -- and they've often got absolutely nothing to answer back with.

Nereid
2010-Jun-01, 01:30 AM
Only banned if he refused to answer any and all questions from anyone.
That's a rule which applies to only two sections of BAUT, ATM and CT (AFAIK).

Where did you get the idea that astronomers (and no one else) must "answer any and all questions from anyone"?!?


OK now it really makes sense why astronomers don't post here.
Strange, then, that so many astronomers have, pace Robinson, posted here.

Were you not aware that many astronomers, have in fact, posted here, Robinson?

William
2010-Jun-01, 01:52 AM
There is a set of connected anomalies that point in the same direction. Have you looked at blue stragglers? The Holmberg effect? The Paradox of youth stars? Bell's papers. The MECO papers.

Anomalous redshift evolution of quasar properties. Luminosity and space density evolution of quasars with redshift. Lack of quasar metallicity evolution with redshift. Super metallicity quasars at high redshift.

Curious cluster structural anomalies? (The curious part is the observations are not random.)

Time dilation is one of many.


http://arxiv.org/PS_cache/arxiv/pdf/1004/1004.1824v1.pdf


On time dilation in quasar light curves

In this paper we have used Fourier power spectrum analysis of over 800 quasar light curves to measure timescales of variation at different redshifts. The expected effects of time dilation are absent, the SEDs at high and low redshift being essentially identical. There seems to be no explanation for this within the conventional cosmological framework, and so various other possibilities are considered.


In the right hand panel of Fig. 2 the only difference between the three SEDs is the quasar luminosity, and yet a clear progression in slope of the power law index at short timescales is evident, implying a real and measurable change in the nature of the variability, and not an artefact of the analysis procedure. This provides sound support for believing that the close similarity of the high and low redshift SEDs in Fig. 5 represents indistinguishable patterns of variability, unaffected by any time dilation effect, and not a
spurious agreement.

If it is accepted that time dilation is not seen in quasar light curves, then some departure from conventional cosmology is necessary to explain it. Of the possibilities listed in Section 5, there seems to be overwhelming evidence that quasars are at the cosmological distances indicated by their redshifts, and the challenge to the time dilation found in supernovae light curves has yet to be convincingly established. If we therefore assume that we live in an expanding universe, we have two possibilities. If the variations are due to microlensing then the conclusions of the MACHO project would have to be modified, presumably by a reassessment of the shape of the Galactic halo, and the expected dark matter content. If the effects of time dilation are offset by an increase of timescale of variation with cosmological time, then a mechanism must be found which does not alter the shape of the SED, or involve a correlation of black hole mass with luminosity.

http://arxiv.org/ftp/arxiv/papers/0811/0811.1554.pdf

This is interesting. And you have no idea why the two topics are related.


Galaxies appear simpler than expected

Here we report that a sample of galaxies that were first detected through their neutral hydrogen radio-frequency emission, and are thus free of optical selection effects5, shows five independent correlations among six independent observables, despite having a wide range of properties. This implies that the structure of these galaxies must be controlled by a single parameter, although we cannot identify this parameter from our dataset. Such a degree of organisation appears to be at odds with hierarchical galaxy formation, a central tenet of the cold dark matter paradigm in cosmology.

What could that single parameter be? Something that could affect an entire galaxy. What could that be.

I guess it would be necessary to think about the observations as opposed to keep pushing the same round peg in the square hole.

The starting point is thinking beyond a toy model of what happens to very massive objects when they collapse. Detailed modern observations do not support the toy model.

Incorrect assumptions makes it very difficult to solve the problem. What are the fundamental assumptions? Which one is not correct? (Hint there is more than one. The observations are thoughtfully organized and labeled as anomalies.)

What is a blue straggler? Star burst galaxy?

BH mass downsizing? Have you looked at the mass of the M31 and MW BH? Largest galaxies in a 35 galaxy cluster. (Clue think about the Holmberg affect. There is a morphological pattern of the satellite galaxies.) What happened there? Luminosity is 10000 to 100,000 less than the classic accretion disk model predicts based on absolute minimum estimates of inflow gas.

Looked at magtars? Magnetic fields in pulsars? What could be happening to massive objects?

Nereid
2010-Jun-01, 02:08 AM
There is a set of connected anomalies that point in the same direction. Have you looked at blue stragglers? The Holmberg effect? The Paradox of youth stars?
I have no clue what "anomalies" you are referring to.

Perhaps you could explain?

For example, blue stragglers are not - AFAIK - anomalies (why do you think they are?)


Bell's papers.
Please tell me you're not referring to some 'quasar anomalous redshift' papers, please ...


The MECO papers.
Huh?!?!?


Anomalous redshift evolution of quasar properties. Luminosity and space density evolution of quasars with redshift. Lack of quasar metallicity evolution with redshift. Super metallicity quasars at high redshift.

Curious cluster structural anomalies? (The curious part is the observations are not random.)

Time dilation is one of many.


http://arxiv.org/PS_cache/arxiv/pdf/1004/1004.1824v1.pdf



http://arxiv.org/ftp/arxiv/papers/0811/0811.1554.pdf

This is interesting. And you have no idea why the two topics are related.



What could that single parameter be? Something that could affect an entire galaxy. What could that be.

I guess it would be necessary to think about the observations as opposed to keep pushing the same round peg in the square hole.

The starting point is thinking beyond a toy model of what happens to very massive objects when they collapse. Detailed modern observations do not support the toy model.

Incorrect assumptions makes it very difficult to solve the problem. What are the fundamental assumptions? Which one is not correct? (Hint there is more than one. The observations are thoughtfully organized and labeled as anomalies.)

What is a blue straggler? Star burst galaxy?

BH mass downsizing? Have you looked at the mass of the M31 and MW BH? Largest galaxies in a 35 galaxy cluster. (Clue think about the Holmberg affect. There is a morphological pattern of the satellite galaxies.) What happened there? Luminosity is 10000 to 100,000 less than the classic accretion disk model predicts based on absolute minimum estimates of inflow gas.

Looked at magtars? Magnetic fields in pulsars? What could be happening to massive objects?
William, I have no clue what you're trying to say ... it seems like a random collection with nothing in the least coherent to connect it.

Is this, perhaps, some sort of ATM idea?

Swift
2010-Jun-01, 03:24 PM
Only banned if he refused to answer any and all questions from anyone.

OK now it really makes sense why astronomers don't post here.
OK, enough meta-discussion from everyone. Please stick to the thread topic and don't debate the merits or not of astronomers posting on BAUT or debate about rules (though Nereid is correct and the rule about having to answer questions only strictly applies to ATM and CT).

Jerry
2010-Jun-06, 10:06 PM
Are we reading the same paper?

I don't think so ... even the abstract of the Herschel preprint ("Herschel unveils a puzzling uniformity of distant dusty galaxies") doesn't come close to the radical claim you've just made (that I quoted).


Well, even if we assume your premise (the previous paras), this claim contains some more, pretty speculative (or wild, YMMV) leaps of logic.


If two animals are black, they must both be cats (because I have seen a black animal, and it was a cat).
...

Again, we must be reading two completely different papers (presenting the Herschel data) - how on Earth (or even on an AGN of your choice) did you conclude this from what you read?!?!? :question: :think:
To understand my prospective, try a different analogy: Suppose you are a car manufacturer, and you want to evaluate a new type of paint coating. You take an automobile with the new type of paint coating out for a spin: To the desert and to the ocean, through smoggy cities and salt mountain roads - every worse-case scenario you can image. What you are hoping is that your data will be applicable to all driving situations.

In http://arxiv.org/abs/1005.2859v1 Elbaz is examining " whether the spectral energy distribution (SED) and dust temperature of galaxies have strongly evolved since z~2.5"; as expected by current theories. To do this, they are looking at worst case scenarios: starburst galaxies and especially starburst galaxies with active galactic nuclei.

They are using the expanded range of the Herschel telescope to see if prior models using narrow IR windows are correct. They are not! The first point of the study is that the prior assumptions were wrong. They find "Extrapolations from only one of the 160um, 250um or 350um bands alone tend to overestimate the total IR luminosity". This is a serious error in prior studies: These overestimates overestimate evolution.

The second point is that the Herschel data show little, if any, evidence of evolution in starburst galaxies up to a distance of at least z=1.5 because, according to the observational data, the new "mid-IR extrapolations are correct for star-forming galaxies with a dispersion of only 40% (0.15dex), therefore similar to z~0 galaxies." Elbas finds this puzzling, and so should you: Evolution should be expected to be greatest in starburst galaxies, especially in starburst galaxies with AGN. Their assestment certainly does have implications for many, many prior evolution estimates where limited IR data were available.

It is not a matter of whether or not all animals are black cats, but whether or not the limited bandwidth with which we have been using to make judgements about the evolutionary processes are suspect. In this respect, your analogy is backwards: The most distant animals only looked like black cats because we couldn't see them glowing in the IR; and we were making judgements about the color based only upon the two red dots in their eyes. We see more colour now, and the colour does not change with distance in these most active galaxies. That's contrary to expectations.

I may be extrapolating too much when I imply this new finding impacts every other evolutionary study; but it is time to go back to the blackboard.

More Herschel results:

http://lanl.arxiv.org/abs/1006.0120v1


We find that while many galaxies (~ 56%) are well fitted with the templates used to fit IRAS, ISO and Spitzer sources, for about half the galaxies two new templates are required

New templates. New models.

http://lanl.arxiv.org/abs/1005.5678v1

Herschel unveils a puzzling uniformity of distant dusty galaxies


In short, the metalicity inferred from the dust mass is much higher (by more than an order of magnitude) than that inferred from the optical nebular lines. We discuss the possible explanations of this discrepancy and the possible implications for the investigation of the metalicity evolution at high-z....

The orange and cyan tracks in Fig. 3 show the expected evolution of the dust content and metalicity as predicted by Calura et al. (2008) for ellipticals and spirals, where it is evident that the large discrepancy observed in Submillimeter galaxies cannot be accounted for by models.

So while they identify more dusty galaxies at very great distances; paradoxically the metallicity is much greater than expected in distant submillimeter galaxies.

Another red flag: another model that fails. Something is wrong. I don't even have to know what a submillimeter galaxy is to know that when the models don't work well with the latest-and-greatest data set, it is time to revisited the blackboard and come up with some new ones.

Nereid
2010-Jun-07, 01:35 AM
To understand my prospective, try a different analogy: Suppose you are a car manufacturer, and you want to evaluate a new type of paint coating. You take an automobile with the new type of paint coating out for a spin: To the desert and to the ocean, through smoggy cities and salt mountain roads - every worse-case scenario you can image. What you are hoping is that your data will be applicable to all driving situations.

In http://arxiv.org/abs/1005.2859v1 Elbaz is examining " whether the spectral energy distribution (SED) and dust temperature of galaxies have strongly evolved since z~2.5"; as expected by current theories. To do this, they are looking at worst case scenarios: starburst galaxies and especially starburst galaxies with active galactic nuclei.

They are using the expanded range of the Herschel telescope to see if prior models using narrow IR windows are correct. They are not! The first point of the study is that the prior assumptions were wrong. They find "Extrapolations from only one of the 160um, 250um or 350um bands alone tend to overestimate the total IR luminosity". This is a serious error in prior studies: These overestimates overestimate evolution.

The second point is that the Herschel data show little, if any, evidence of evolution in starburst galaxies up to a distance of at least z=1.5 because, according to the observational data, the new "mid-IR extrapolations are correct for star-forming galaxies with a dispersion of only 40% (0.15dex), therefore similar to z~0 galaxies." Elbas finds this puzzling, and so should you: Evolution should be expected to be greatest in starburst galaxies, especially in starburst galaxies with AGN.
But Jerry, you are making all kinds of wild leaps of logic!

First, where did "Evolution should be expected to be greatest in starburst galaxies, especially in starburst galaxies with AGN" come from?

Second, don't you need to constrain, or at least quantify, the redshift range over which you expect evolution to be greatest? Why should it be greatest in the range that the Herschel data sampled?

Third, in what ways should starburst galaxies with AGN be different from ones without AGNs? Surely for this kind of logic to apply, you need to know things like the duty cycle of AGNs, the time lags (if any) between starbursting and an AGN turning on (and how the two are correlated, if at all), how these vary by class of galaxy/metalicity/galaxy mass/galaxy environment/etc, and so on. As I think you know, none of these questions have good answers yet!

There's more, but that's enough for now.


Their assestment certainly does have implications for many, many prior evolution estimates where limited IR data were available.
No one would disagree with you there, Jerry.


It is not a matter of whether or not all animals are black cats, but whether or not the limited bandwidth with which we have been using to make judgements about the evolutionary processes are suspect. In this respect, your analogy is backwards: The most distant animals only looked like black cats because we couldn't see them glowing in the IR; and we were making judgements about the color based only upon the two red dots in their eyes. We see more colour now, and the colour does not change with distance in these most active galaxies. That's contrary to expectations.

I may be extrapolating too much when I imply this new finding impacts every other evolutionary study; but it is time to go back to the blackboard.
Jerry, every astronomer (and astrophysicist) is at the blackboard, every day (well, except when they're going outside, opening horses' mouths, and counting teeth)!

However, the point remains that the relevance of this Herschel paper to time dilation in quasars is, um, apparent only to you (and you seem to be having a very hard time explaining it, in a meaningful way, to anyone else).

Jerry
2010-Jun-07, 05:05 AM
But Jerry, you are making all kinds of wild leaps of logic!

First, where did "Evolution should be expected to be greatest in starburst galaxies, especially in starburst galaxies with AGN" come from? If not in starburst galaxies - where?
??? Check the Wiki on starburst galaxies: http://en.wikipedia.org/wiki/Starburst_galaxy


The rate of star formation is so great for a galaxy undergoing a starburst that, if the rate was sustained, the gas reservoirs from which stars are formed would be used up on timescales much shorter than that of the galaxy. For this reason, it is presumed that starbursts are temporary...

Studying nearby starburst galaxies can help us determine the history of galaxy formation and evolution. Large numbers of the very distant galaxies seen, for example, in the Hubble Deep Field are known to be starbursts, but they are too far away to be studied in any detail. Observing nearby examples and exploring their characteristics can give us an idea of what was happening in the early universe as the light we see from these distant galaxies left them when the universe was much younger (see redshift).
If SED evolution is not most obvious in rapidly burning systems, where will it be most evident? These are the galaxies that are on the shakedown cruise. Notice in the Wiki that starburst galaxies are not limited to a single morphology; so there is a large range of galaxy types that are included in a starburst survey.


Second, don't you need to constrain, or at least quantify, the redshift range over which you expect evolution to be greatest? Why should it be greatest in the range that the Herschel data sampled?

The constraints are the limit at which the authors feel they can confidently separate galaxies from background galaxies; as they point out that it is the errors caused by background light sources that have led to prior assertions that there is considerable evolution in the SED of starburst galaxies.

If there is no evolution in the SED of starburst galaxies over 80% of the age of the universe - the range of Herschel, how much is the universe changing? True, the universe may have evolved much more rapidly during the initial 20%; but no observable SED change over 80% of the lifespan is indeed puzzling.


Until the launch of the Herschel Space Observatory, these analyses relied strongly on substantial extrapolation from the mid-IR or sub-mm or on even more uncertain corrections of the UV luminosity...Our aim is to determine how accurate these extrapolations are and search for evidence of a major change in the IR properties of galaxies with increasing redshift...

The direct comparison of the 8–1000 μm luminosities derived fromthe 24 μm band alone (Ltot IR[from24 μm]) and from Herschel above 30 μm ...shows a remarkable consistency over a redshift range of z=0–1.5 and over three
decades in luminosity up to ULIRGs...

Above z=1.5, Herschel confirms that the mid-IR overestimates Ltot IR by factors of about 2–3 for the detected ULIRGs, but up to 5–7 when stacking is combined to detections


Third, in what ways should starburst galaxies with AGN be different from ones without AGNs? Surely for this kind of logic to apply, you need to know things like the duty cycle of AGNs, the time lags (if any) between starbursting and an AGN turning on (and how the two are correlated, if at all), how these vary by class of galaxy/metalicity/galaxy mass/galaxy environment/etc, and so on. As I think you know, none of these questions have good answers yet!

Good point! But I think I have a good answer. AGN are thought to have peaked in both luminosity and occurances at about a redshift of z=2; with the number of AGN decreasing on both sides of this peak and practically disappearing today. If the luminosity and count are both evolving; it is reasonable to expect the SED (spectal energy distribution) to evolve as well - or at the very least 'puzzling' if it does not.


However, the point remains that the relevance of this Herschel paper to time dilation in quasars is, um, apparent only to you (and you seem to be having a very hard time explaining it, in a meaningful way, to anyone else).
The Elbaz and other Hershel papers provide somewhat painful evidence that prior studies of SED evolution are tainted by poor assumptions - and when the errors are stripped from the data; the SED evolution disappears.

If we can't find evidence of either time dilation or an evolving spectral energy distribution in AGN clear out to a redshift of z=1.5; how far down this evidentuary trail do we have to go before we can say what is 'puzzling' is in fact revealing?

Nereid
2010-Jun-07, 07:05 AM
But Jerry, you are making all kinds of wild leaps of logic!

First, where did "Evolution should be expected to be greatest in starburst galaxies, especially in starburst galaxies with AGN" come from?If not in starburst galaxies - where?
??? Check the Wiki on starburst galaxies: http://en.wikipedia.org/wiki/Starburst_galaxy

If SED evolution is not most obvious in rapidly burning systems, where will it be most evident? These are the galaxies that are on the shakedown cruise. Notice in the Wiki that starburst galaxies are not limited to a single morphology; so there is a large range of galaxy types that are included in a starburst survey.
You and I have exchanged posts for long enough that I should have expected something like this.

I think you have a quite different idea of "evolution" in this context, certainly than mine, and very likely than what astronomers usually mean.

To estimate what the change in the SEDs of starburst galaxies should be (not is observed to be), don't you first need to understand what causes a galaxy to go starburst?

And if, indeed, starbursts seem to come in many different flavours, why should their evolution (once we agree on the meaning of that word) be simple?

How many starbursts did our own galaxy, the Milky Way, undergo (since the first stars in it formed, well over 10 Gyr ago)?



Second, don't you need to constrain, or at least quantify, the redshift range over which you expect evolution to be greatest? Why should it be greatest in the range that the Herschel data sampled?
The constraints are the limit at which the authors feel they can confidently separate galaxies from background galaxies; as they point out that it is the errors caused by background light sources that have led to prior assertions that there is considerable evolution in the SED of starburst galaxies.

If there is no evolution in the SED of starburst galaxies over 80% of the age of the universe - the range of Herschel, how much is the universe changing? True, the universe may have evolved much more rapidly during the initial 20%; but no observable SED change over 80% of the lifespan is indeed puzzling.
Puzzling, yes.

Obviously tied to Hawkins' observations on time delays in quasars? No.



Third, in what ways should starburst galaxies with AGN be different from ones without AGNs? Surely for this kind of logic to apply, you need to know things like the duty cycle of AGNs, the time lags (if any) between starbursting and an AGN turning on (and how the two are correlated, if at all), how these vary by class of galaxy/metalicity/galaxy mass/galaxy environment/etc, and so on. As I think you know, none of these questions have good answers yet!

Good point! But I think I have a good answer. AGN are thought to have peaked in both luminosity and occurances at about a redshift of z=2; with the number of AGN decreasing on both sides of this peak and practically disappearing today. If the luminosity and count are both evolving; it is reasonable to expect the SED (spectal energy distribution) to evolve as well - or at the very least 'puzzling' if it does not.
That may, or may not, be so.

However, it is irrelevant.

What was observed, by Herschel, is the SED of *galaxies*, not the SED of AGNs.

How did you conclude otherwise?



However, the point remains that the relevance of this Herschel paper to time dilation in quasars is, um, apparent only to you (and you seem to be having a very hard time explaining it, in a meaningful way, to anyone else).
The Elbaz and other Hershel papers provide somewhat painful evidence that prior studies of SED evolution are tainted by poor assumptions - and when the errors are stripped from the data; the SED evolution disappears.

If we can't find evidence of either time dilation or an evolving spectral energy distribution in AGN clear out to a redshift of z=1.5; how far down this evidentuary trail do we have to go before we can say what is 'puzzling' is in fact revealing?
Who knows?

But when you make the amazingly simple mistake of conflating the SEDs of the *galaxies* in which some AGNs reside with the SEDs of the *AGNs themselves*, and build all sorts of wild inferences on that erroneous base, who cares?

RussT
2010-Jun-07, 08:50 AM
http://www.physorg.com/news190027752.html



So, when Mike says...

Astronomer Mike Hawkins from the Royal Observatory in Edinburgh came to this conclusion after looking at nearly 900 quasars over periods of up to 28 years. When comparing the light patterns of quasars located about 6 billion light years from us and those located 10 billion light years away, he was surprised to find that the light signatures of the two samples were exactly the same

That IS the "Observation"



And here is another...

http://www.space.com/scienceastronomy/gemini_survey_040105.html

"Theyre already very old," explained Patrick McCarthy, a co-principal investigator on the study from the Observatories of the Carnegie Institution. "In fact, they're ancient."

"Its probably not at the point where we have to reevaluate our theories of galaxy formation, but its getting there."

These are NOT press releases written by some 'science writer' interpreting the work...These are the Professional Astronomers themselves!!!

The first quote by Patrick McCarthy is telling it like it is, and even emphasizing it..... "In fact, they're ancient."

And the second quote is appeasement with suggestion

And, Mike Hawkins also says...


There’s also a possibility that the explanation could be even more far-reaching, such as that the universe is not expanding and that the big bang theory is wrong.

Now, I believe that the Quasars are at the distances mainstream says they are, mainly because the two "Bright Objects" in Arps 7603 'bridge' are either Quasars in the far background OR they are "Globular Clusters" in the bridge, because IF they are actually physically part of that bridge, they are wayyyyyy to small to be AGN.

And...
Quasars are AGN with their Jets ON, and are Mostly Elliptical galaxies just like M87...
http://blackholes.stardate.org/directory/factsheet.php?p=M87

But, some of them can be like this...

http://antwrp.gsfc.nasa.gov/apod/ap030114.html

Now, can this galaxy still be making new stars? Sure...

In the caption, they make a reference that this galaxy could be compared to the Milky Way....BUT that is NOT right, as the "Bulge" extends almost to th edge of the galaxy...the one that most fits the Milky Way is the face on galaxy they reference in the upper right of the AGN galaxy.

SO, if these type galaxies have their "jets" more orientated toward us, then it would be very difficult to determine if it was an Elliptical galaxy, pretty much done with new star making OR one of these, that are still making new stars to get different kinds of SEDs from.

BUT, the real key is the mass of the Quasar SMBH's...the real dilema comes from how these can be both Ancient and New, and how New Galaxies can even remotely have a chance of starting off with SMBH's in the Billions of Sol Masses.

Was the Milky Way once a Quasar, as many Astronomers have posited???

Nereid
2010-Jun-07, 12:50 PM
http://www.physorg.com/news190027752.html



That IS the "Observation"



These are NOT press releases written by some 'science writer' interpreting the work...These are the Professional Astronomers themselves!!!

The first quote by Patrick McCarthy is telling it like it is, and even emphasizing it..... "In fact, they're ancient."

And the second quote is appeasement with suggestion
Um, the McCarthy quote is from a PR.

The paper which reports the work (http://fr.arxiv.org/abs/astro-ph/0401037) was published in Nature, in 2004 (link is to the arXiv preprint):

Hierarchical galaxy formation is the model whereby massive galaxies form from an assembly of smaller units. The most massive objects therefore form last. The model succeeds in describing the clustering of galaxies, but the evolutionary history of massive galaxies, as revealed by their visible stars and gas, is not accurately predicted. Near-infrared observations (which allow us to measure the stellar masses of high-redshift galaxies) and deep multi-colour images indicate that a large fraction of the stars in massive galaxies form in the first 5 Gyr, but uncertainties remain owing to the lack of spectra to confirm the redshifts (which are estimated from the colours) and the role of obscuration by dust. Here we report the results of a spectroscopic redshift survey that probes the most massive and quiescent galaxies back to an era only 3 Gyr after the Big Bang. We find that at least two-thirds of massive galaxies have appeared since this era, but also that a significant fraction of them are already in place in the early Universe.
Now it is certainly an important paper, having been cited >200 times since!

Did Glazebrook et al.'s conclusions stand up, in the light of many, many, many more observations done subsequently?

Well, why not read some of the 200 or so papers which cite them, and find out for yourself?



And, Mike Hawkins also says...


Now, I believe that the Quasars are at the distances mainstream says they are, mainly because the two "Bright Objects" in Arps 7603 'bridge' are either Quasars in the far background OR they are "Globular Clusters" in the bridge, because IF they are actually physically part of that bridge, they are wayyyyyy to small to be AGN.

And...
Quasars are AGN with their Jets ON, and are Mostly Elliptical galaxies just like M87...
http://blackholes.stardate.org/directory/factsheet.php?p=M87

But, some of them can be like this...

http://antwrp.gsfc.nasa.gov/apod/ap030114.html

Now, can this galaxy still be making new stars? Sure...

In the caption, they make a reference that this galaxy could be compared to the Milky Way....BUT that is NOT right, as the "Bulge" extends almost to th edge of the galaxy...the one that most fits the Milky Way is the face on galaxy they reference in the upper right of the AGN galaxy.

SO, if these type galaxies have their "jets" more orientated toward us, then it would be very difficult to determine if it was an Elliptical galaxy, pretty much done with new star making OR one of these, that are still making new stars to get different kinds of SEDs from.

BUT, the real key is the mass of the Quasar SMBH's...the real dilema comes from how these can be both Ancient and New, and how New Galaxies can even remotely have a chance of starting off with SMBH's in the Billions of Sol Masses.

Was the Milky Way once a Quasar, as many Astronomers have posited???
I think you've been reading far too much into PRs and popular accounts, such as APOD, and far too little of the actual papers, RussT.

For starters, "quasar" is now a term used for a particularly luminous (in the optical waveband) AGN whose accretion disk we can see directly.

As in my earlier comment, one of the interesting topics in research on AGNs today is their duty cycle ... you can think of this as 'how often, over a sufficiently long period of time, does the SMBH have an accretion disk with a luminosity above {threshold}?" Another topic is the extent to which galaxies other than massive ellipticals, near the centre of rich clusters, have very noticeable jets.

As for the formation of SMBH, well, there are essentially no observational constraints, because we can, so far, only see back to about z ~10. The growth of SMBH, since about z ~ 5, is better constrained.