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Thread: The Evolution of the Standard Candle....Sn1a's

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    The Evolution of the Standard Candle....Sn1a's

    For distance measurements, you need to know how bright your object would appear if it was local...its intrinsic magnitude. Towards that end, astrophysicists continue to refine models, with these authors showing detonation effects for progenitors of different masses and ages. SEE:https://arxiv.org/abs/1710.09384


    pete

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    I don't see a question mark, nor any other sign of a question. Moved from Q&A to Astronomy
    Quote Originally Posted by ToSeek View Post
    This section of the forum is for astronomy and space exploration questions with straightforward, generally accepted answers.
    At night the stars put on a show for free (Carole King)

    All moderation in purple - The rules

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    Quote Originally Posted by trinitree88 View Post
    For distance measurements, you need to know how bright your object would appear if it was local...its intrinsic magnitude. Towards that end, astrophysicists continue to refine models, with these authors showing detonation effects for progenitors of different masses and ages. SEE:https://arxiv.org/abs/1710.09384


    pete
    I have been looking, for more than a decade now, for an accumulation of data that displays redshift distance, (or time) versus delta m(B)15; which is a standard measurement of how a supernova ages over the first few months of its existence. (Larger delta m(B)15 generally correlate with more rapid decliners and lower overall magnitudes.) It is normalized around how much of the absolute magnitude of the event changes fifteen days after the peak magnitude is reached. If I remember correctly, a M(B)15 of 2 would mean the event loses A LOT of magnitude in fifteen days (2 magnitudes?), which would be a very rapid decliner.
    The graphs on page 6 are rather cryptic, but they seem to indicate a rapid change in the supernova type Ia population luminosity function over distance, whether or not the morphology of the galaxies in which the events occur are changing. A straightforward plot of the m(B)15 function vrs redshift would be clarifying, with a secondary look at morphology.
    “It is a capital mistake to theorize before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts.” ― Arthur Conan Doyle, Sherlock Holmes

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    This paper published in August may have been posted before, but it is quite germane:
    https://arxiv.org/pdf/1303.0580.pdf A Redshift-Dependent Color-Luminosity Relation in Type 1a Supernovae Gopolang M. Mohlabeng⋆ and John P. Ralston

    The authors note that there have been few independent analysis of the fundamental assumption in cosmological studies of supernova that the there is no color evolution over redshift distance. They find much better curve fits when a cosmic color shift (beta 1) is included in the equation, and this color shift is opposite the color change that would emerge if the color change is due to either local or cosmic dust. The authors conclude:

    ...An unidentified bias in the observations or data reduction also cannot be ruled out. If a bias exists, it is an important issue and hardly a flaw of what we report, which can only be based on the data published.
    In summary, straightforward tests using the Union 2.1 data finds that the current model using constant β parameter is ruled out compared to the model β(z) = β0 + β1z. Inasmuch as the fitting of cosmological parameters to Type 1a supernova data hinges on a model called into question, the values and errors of those parameters may be questioned. It seems premature to attempt the last word on the highly significant trend we have found.
    “It is a capital mistake to theorize before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts.” ― Arthur Conan Doyle, Sherlock Holmes

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    Quote Originally Posted by Jerry View Post
    If I remember correctly, a M(B)15 of 2 would mean the event loses A LOT of magnitude in fifteen days (2 magnitudes?), which would be a very rapid decliner.
    Yes, that's right. Large delta-M(B)15 means that the event declines rapidly after peak brightness. In most models of Type Ia, such rapidly-declining explosions take place in low-mass white dwarf progenitors.

    The graphs on page 6 are rather cryptic, but they seem to indicate a rapid change in the supernova type Ia population luminosity function over distance, whether or not the morphology of the galaxies in which the events occur are changing. A straightforward plot of the m(B)15 function vrs redshift would be clarifying, with a secondary look at morphology.
    I agree -- that would be very revealing.

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    Here are two interesting papers on this hot topic: The unique supernova PS1-10AFX

    https://arxiv.org/abs/1302.0009
    PS1-10afx at z=1.388: Pan-STARRS1 Discovery of a New Type of Superluminous Supernova
    Chornock et al.

    And

    https://arxiv.org/abs/1302.2785
    Extraordinary Magnification of the Ordinary Type Ia Supernova PS1-10afx
    Quimby et al.

    In Quimby et al.; they argue that the light curve of the supernova event is so ‘normal’ that the determination of the absolute magnitude must include a factor for lensing because the event is much to bright to explain using well established supernova theory.

    In Chornock et al.; they argue there is no physical evidence whatsoever of a lensing galaxy; or any of the ‘normal’ signatures (multiple images, distortions, chromatic aberrations) found in highly-lensed events. So it must be a new type of supernova, (which seems to happen every time we look in the sky.)

    Quimby argues that it must be a new type of lens – either a perfectly aligned black hole or ‘dark matter halo’.

    So who is right? First, it is a sign of a healthy science when there are dramatic disagreements between two groups of researchers: Holler’n science is good science. Second, there are problems no matter which tack you take on this:

    If you accept the Quimby line of reasoning (that there is a lens with no tale-tale signs of a lens); then how can we assume any distant event is not lensed to some degree or another; totally blowing holes in using supernova as distance indicators beyond the local universe.

    On the other hand, If Chornock is correct and this very distant event is a completely new animal (even though it looks like it isn’t); then our standard candle is not standardizable beyond the local universe.

    There is a third possibility, (and there may be more). Twenty years ago, when ultrabright events first started cropping up, some of us argued that there must be a rouge actor; a supernova event similar to a ‘Ia’; but with longer light curves and a much brighter continence. This turned out to be true; and the theories were modified to accommodate this new player: Supernova type ‘Ic’. But this new event, at the great distance it presents itself, (a Z-shift of 1.4) has much too short of a light curve to be viewed as a type Ic. The third possibility then, it is normal type 1c with little or no magnification; but that the distance modulus used to calculate the light curve length is wrong.

    One event can only raise questions and not provide hard answers. But learning it may be necessary to add a new variable (https://arxiv.org/abs/1710.09384) to the distance modulus in order to normalize distant events; hints to us that the next generation of supernova observations could easily turn the topic on-its-head.
    “It is a capital mistake to theorize before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts.” ― Arthur Conan Doyle, Sherlock Holmes

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    Quote Originally Posted by Jerry View Post
    Twenty years ago, when ultrabright events first started cropping up, some of us argued that there must be a rouge actor; a supernova event similar to a ‘Ia’; but with longer light curves and a much brighter continence. This turned out to be true; and the theories were modified to accommodate this new player: Supernova type ‘Ic’.
    Actually, the name "Type Ic" was first proposed 40 years ago (not 20), and in a different context. Wheeler and Harkness

    http://adsabs.harvard.edu/abs/1986ASIC..180...45W

    noticed that a third class of hydrogen-poor supernovae were being found. The original hydrogen-poor supernovae, called "type Ia", have a strong absorption feature at around 6200 Angstroms, due to silicon ions; these originate in close binary systems, when a white dwarf accretes too much material from a companion star. The second class, "type Ib", show no signs of hydrogen in their spectra, but have strong intermediate-mass element lines and appear only in star-forming regions. We think that they are very massive stars which run out of fuel in the centers and suffer from core collapse, like the familiar "type II" events. The reason that "type Ib" explosions lack signs of hydrogen is that they had such strong mass loss late in their lives that strong stellar winds swept away all that material from their outer layers before the final explosion. The "type Ib" did show signs of helium in their spectra, however.

    The "type Ic" events first described in the late 1980s not only lacked hydrogen, but also helium. It is thought that they, too, arise from massive stars which undergo core collapse; but these stars have even stronger stellar winds, which remove not only the hydrogen-rich outer layers of the star, but also the helium-rich layers beneath them, before the star explodes.

    Some years later, with the very interesting type Ic supernova 1997bw, astronomers noticed a connection between (some) gamma-ray bursts and (some) type Ic supernovae. It is currently thought that some (but not all) type Ic events are brighter than normal due to the extra feature of an exotic collapsar at their centers.

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    Quote Originally Posted by StupendousMan View Post
    Actually, the name "Type Ic" was first proposed 40 years ago (not 20), and in a different context. Wheeler and Harkness

    http://adsabs.harvard.edu/abs/1986ASIC..180...45W

    noticed that a third class of hydrogen-poor supernovae were being found. The original hydrogen-poor supernovae, called "type Ia", have a strong absorption feature at around 6200 Angstroms, due to silicon ions; these originate in close binary systems, when a white dwarf accretes too much material from a companion star. The second class, "type Ib", show no signs of hydrogen in their spectra, but have strong intermediate-mass element lines and appear only in star-forming regions. We think that they are very massive stars which run out of fuel in the centers and suffer from core collapse, like the familiar "type II" events. The reason that "type Ib" explosions lack signs of hydrogen is that they had such strong mass loss late in their lives that strong stellar winds swept away all that material from their outer layers before the final explosion. The "type Ib" did show signs of helium in their spectra, however.

    The "type Ic" events first described in the late 1980s not only lacked hydrogen, but also helium. It is thought that they, too, arise from massive stars which undergo core collapse; but these stars have even stronger stellar winds, which remove not only the hydrogen-rich outer layers of the star, but also the helium-rich layers beneath them, before the star explodes.

    Some years later, with the very interesting type Ic supernova 1997bw, astronomers noticed a connection between (some) gamma-ray bursts and (some) type Ic supernovae. It is currently thought that some (but not all) type Ic events are brighter than normal due to the extra feature of an exotic collapsar at
    their centers.
    My bad - thanks for the historical prospective. I was referring to events originally thrown in with class c supernova, then for a time called hypernova Ic ; 1997bw was one of the first identified. Today they are generally called Super Luminous Super Nova (SLSN); type I if they are hydrogen poor; and type II if they are hydrogen rich.
    “It is a capital mistake to theorize before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts.” ― Arthur Conan Doyle, Sherlock Holmes

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    Cosmic evolution of supernova.

    There are a new series of papers delving deeply into the supernova evolution models. This one takes an approach that I have been begging for decades someone would:

    Redshift evolution of the underlying type Ia supernova stretch distribution

    The "stretch factor" has been used since the 1990's to "tune' the modest variability of supernova type Ia about a common magnitude. It is an intrinsic property, meaning that in otherwise unencumbered light curves, stretch factors are a local property of a supernova event. But as stated by the authors, here is the problem:

    "1. The underlying SN Ia stretch distribution is significantly redshift dependent, as previously suggested by Howell et al.
    (2007), for example, in a way that observational selection effects alone cannot explain. This result is largely independent
    of the details of each age-population model."

    2 "2. Redshift-independent models are quantitatively excluded as
    suitable descriptions of the data relative to our base model...

    "3. Models using survey-based asymmetric Gaussian distributions, for instance, as employed in the current implementation of BBC, are excluded as a good description of the data
    relative to our drifting model."

    In other words, if I understand the author's correctly, for decades now, supernova Ia data analysis pipelines have involved complex calculations to normalize the data and extract estimates of the Hubble variables. But when you strip the observations down to the simplest presentation of the intrinsic data; there appears to be an evolution factor - the light curve width - that varies with increasing distance in a way that is incompatible with the normalizing routines now in use.

    The authors suggest a curve that is a better fit to the data, an equation that is based upon the redshift distance (z factor) of supernova events. Real-world interpretations of why this evolution might be occurring, or how it can be corrected for from our single observation platform are problematic.

    By the way, the stretch factor evolution that they are convinced is real, increases the tension between supernova Ia estimates of the Hubble factor (HO), with PLANCK and other estimates. Even before this paper, some authors have concluded that the supernova Ia universe is incompatible with the PLANCK universe by 5 sigma.



    "Tension" simply means that our current theory of the universe is not working very well.
    “It is a capital mistake to theorize before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts.” ― Arthur Conan Doyle, Sherlock Holmes

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    Evolution of Superluminous Supernova Events


    Redshift evolution of the underlying type Ia supernova stretch distribution
    In the previous preprint, I failed to source the paper:

    N. Nicolas , M. Rigault, Y. Copin, R. Graziani, G. Aldering, M. Briday, Y.-L. Kim, J. Nordin, Saul Perlmutter, and M. Smith
    [astro-ph.CO] 26 Apr 2021



    Magnetar Models of Superluminous Supernovae from the Dark Energy Survey: Exploring Redshift Evolution
    Brian Hsu, Griffin Hosseinzadeh, and Edo Berger

    arXiv:2104.09639v2

    This paper looks at what tracks as a virtual high-redshift cut-off of Superluminous Supernova found in the Dark Energy Survey. A cut-off, or at least a tapering, of the less-luminous of these events is an expected Malmquist Biasing effect. However, events with high ejecta rates should be expected, (as they are characterized in the low redshift universe), to exhibit greater magnitudes and therefore not cut-off quite so rapidly due to Malmquist biasing. So, either the sample size is still too small, or there is evolution in this type of event; or something else is wrong.
    “It is a capital mistake to theorize before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts.” ― Arthur Conan Doyle, Sherlock Holmes

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    A Possible Distance Bias for Type Ia Supernovae with Different Ejecta Velocities

    ArXiv:2002.09490v1 [astro-ph.GA] 21 Feb 2020

    M. R. Siebert, R. J. Foley, D. O. Jones, K. W. Davis

    In this paper, they study the spectral ejecta velocities and observe that there is a correlation between the ejecta velocity and the deviation of the predicted distance of the event within the Hubble flow.

    They propose a tweak, that uses the difference between the nominal Hublle distance and the apparent observed distance to warp the event back into the fold. The problem with this approach, is that it assumes the majority of events predict the correct distance modulus, and hammering these counter-intuitive outliers into line solves the problem. If the outliers are caused by a data reduction tool that is wrong; adding another parameter without an assignable physical can compound the error.

    We need to understand why there is an a possible ejecta velocity parameter that changes with redshift distance before deciding it is a useful tool for tuning a model.
    “It is a capital mistake to theorize before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts.” ― Arthur Conan Doyle, Sherlock Holmes

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    Tension with the flat ΛCDM model from a high redshift

    arXiv:1907.07692 [pdf, other] astro-ph.CO
    10.1051/0004-6361/201936223
    Tension with the flat ΛCDM model from a high redshift Hubble Diagram of supernovae, quasars and gamma-ray bursts

    Authors: E. Lusso, E. Piedipalumbo, G. Risaliti, M. Paolillo, S. Bisogni, E. Nardini, L. Amati

    Summarising, these two complementary (and independent) statistical analyses both confirm a tension with the flat ΛCDM
    model at 4σ emerging at high redshifts. Moreover, as the completely independent high-redshift Hubble diagrams of quasars
    and GRBs are fully consistent with each other, this strongly suggests that the deviation from the standard model is not due to
    unknown systematic effects but to new physics
    This tension has been around for more than a decade; and if there is a feature of (delta)CDM cosmology that has survived the last fifteen years it is that in spite of a Greek alphabet of knobs, dials, steps, regressions and French curve fits, there is still primal tension in the model. Supernova are trying to tell us something; but it might not be what anyone expected to hear.
    “It is a capital mistake to theorize before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts.” ― Arthur Conan Doyle, Sherlock Holmes

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    Redshift evolution of the underlying type Ia supernova stretch distribution

    Redshift evolution of the underlying type Ia supernova stretch distribution

    N. Nicolas , M. Rigault , Y. Copin1 , R. Graziani , G. Aldering , M. Briday , Y.-L. Kim , J. Nordin, Saul Perlmutter , and M. Smith

    I missed this analysis in April or May of this year. It is the type of raw look at the data I was hoping for earlier in this thread:

    Quote Originally Posted by Jerry
    I have been looking, for more than a decade now, for an accumulation of data that displays redshift distance, (or time) versus delta m(B)15; which is a standard measurement of how a supernova ages over the first few months of its existence.
    The Stretch Factor is related to the delta(B)15 in that they both standardize about a midpoint in the length of the light curve. Figure 6 on page seven plots binned sets of the stretch factor verses the log of the redshift. This is a bare bones look, and to me, it is stunning:

    The binned sample around a redshift of ~0.75 has a stretch factor range of about 0.2 to 0.4; while the most local stretch factor bin has a stretch factor -0.28 to -0.04.
    These may look like small differences in these dimensionless units, but they are not: If your average light curve width of the total sample is fifteen days, the high redshifted sample is burning 20% to 40% faster; and the most local bin is burning 3% to 30% slower than the mid-redshift bins; and there is NO overlap between the highest redshift and the lowest redshift light curve stretch factor error bars. There is internal tension in the supernova observational data.

    If you do not have significant overlap in the light curve widths of the more local events (with other tools to help with the calibration) and the light curve widths of the most distant events, you do not have game.
    “It is a capital mistake to theorize before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts.” ― Arthur Conan Doyle, Sherlock Holmes

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    The “Stretch Factor” was used by Perlmutter and others in the late 1990s to normalize light curves of supernova about a common magnitude: Brighter events had small negative stretch factors, while dimmer events were corrected by using small positive stretch factors. The redshift at which the supernova were normalized was the somewhat arbitrary redshift at which the high and low redshift events reached the same average brightness. As I argued at the time, if there was an error in one of the cosmological factors assumed in setting the redshift at which light curve templates were normalized, this error would be self-masking until a much larger sample of light curves were obtained.

    Now look what has happened: The average ‘stretch factor’ correction at low redshift has become negative. This should be expected: If smaller events are more common than brighter events, over time, the local sample, which was originally under-represented by brighter events (due to the short observation period of a couple of decades); so as brighter local events are registered, the local stretch factor has become more negative in order to normalize brighter events. This is reasonable.

    What is not reasonable, is that the high redshift stretch factor has become much larger – a stretch factor of 0.4 means that the high redshift events we observe have much shorter light-curves (and are therefore intrinsically smaller and dimmer) than local events. Remember that the stretch factor was used to normalize distant events under the assumption that the high redshift population distribution is the same as the local sample. The lower apparent magnitude of these events after this careful calibration, is THE Supernova EVIDENCE of accelerating expansion of the universe.

    But since the stretch factors no longer normalize about the same distribution; (and renormalizing would require an accelerated expansion rate that is completely at-odds with every other indices); the supernova IA type event becomes a tarnished standard candle. When you include the fact that the ejection velocity, as measured in careful spectral analysis, appears to increase with cosmic distance; (consistent with normal Malmquist bias); there is undeniable and unresolvable theoretical tension.

    In my opinion, this is not acceptable: All of the work; all of the grueling, careful and painstaking care and tens if not hundreds of thousands of dedicated, educated and conscientious manhours tell us that the supernova type IA must be a reliable tool for measuring cosmic distances. Supernova should provide us with such good cosmic reference points that we can immediately determine if-and-when one of our fundamental assumptions is wrong. And I will argue, as always, that radiation transfer mechanics play a much greater role than they are being assigned in cosmic seeing.
    “It is a capital mistake to theorize before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts.” ― Arthur Conan Doyle, Sherlock Holmes

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