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TravisM
2005-Feb-14, 12:26 PM
What could this do to our view beyond our own galaxy if it were proven that the milky way does harbor such a halo?

http://chandra.harvard.edu/photo/2001/1138/index.html

TravisM
2005-Feb-14, 10:34 PM
Alright people, no one's saying you have to post an oppinion! :D

But this couldn't account for the CMB or redshifts could it?

George
2005-Feb-14, 11:04 PM
I was more awed by the WHIM's thread. :o

However, looks like this is "hotter" news, at least in one respect....

Chandra found the diffuse halo of X-ray gas to be radiating at a temperature of almost 3 million degrees and extending some 25,000 light years from the galactic plane. (per press release link)

Could this temperature be due, in part, to the same gravitational collapse found in WHIM's? Or, is the supernova idea more favorable an explanation? [this should get ngc3314 in here, TravisM :) ]

TravisM
2005-Feb-14, 11:48 PM
Thanks george, I begining to think no one liked me :oops: . :wink:

George
2005-Feb-14, 11:51 PM
Thanks george, I begining to think no one liked me :oops: . :wink:

I think they are all out with their sweetheart. That reminds me, I got one at home. See ya. :)

ngc3314
2005-Feb-15, 02:02 AM
I was more awed by the WHIM's thread. :o

However, looks like this is "hotter" news, at least in one respect....

Chandra found the diffuse halo of X-ray gas to be radiating at a temperature of almost 3 million degrees and extending some 25,000 light years from the galactic plane. (per press release link)

Could this temperature be due, in part, to the same gravitational collapse found in WHIM's? Or, is the supernova idea more favorable an explanation? [this should get ngc3314 in here, TravisM :) ]

Oh, all right, give me 'til tomorrow morning to post something coherent, since I wanted to go shake down a webcam on the new campus telescope...

But in the meantime - hint: NGC 4631 has a rather high rate of star formation, and starburst galaxies show vast sprays of escaping gas at temperatures yet an order of magnitude higher. And lots 'n lots of galaxies probably did this early on...

George
2005-Feb-15, 02:49 PM
Could this temperature be due, in part, to the same gravitational collapse found in WHIM's? Or, is the supernova idea more favorable an explanation? [this should get ngc3314 in here, TravisM :) ]

Oh, all right, give me 'til tomorrow morning to post something coherent, since I wanted to go shake down a webcam on the new campus telescope...
You are indirectly stating your marriage status (being V-day :) ). More importantly, what "new campus telescope"? Is this another thin mirror like the one ya'll built first for the Vatican's scope?


But in the meantime - hint: NGC 4631 has a rather high rate of star formation, and starburst galaxies show vast sprays of escaping gas at temperatures yet an order of magnitude higher. And lots 'n lots of galaxies probably did this early on...
Because the Bountiful Big Blues Blew Big Back in the Beginning. Right? :)

ngc3314
2005-Feb-15, 02:52 PM
What could this do to our view beyond our own galaxy if it were proven that the milky way does harbor such a halo?

http://chandra.harvard.edu/photo/2001/1138/index.html

Okay, I'm baaaack. The X-ray halo has been detected before, of course not with this level of structural detail. As I mentioned upthread, plenty of starburst galaxies (starting with M82) show very hot expanding halos, driven mostly by supernova input. What attracted attention to NGC 4631 was (a) it's not all that excessive in star-formation rate, more like the Milky Way, (b) it's seen edge-on, making it possible to sort out disk from halo features, and (c) it's ina direction of low galactic neutral hydrogen and dust, which helps in soft X-rays and really helps in the far-UV. The X-ray structure shows the kinds of arcs and loops that indicate energy input from individual star-forming regions in the disk, and so they have not ballooned enough for their hot gas to merge. This makes the authors (at least in a previous paper) call them fountains, blowing up above the disk plane and falling back as the gas cools, rather than winds (which don't come back). The gas in NGC 4631 is also seen in O VI emission by the FUSE satellite; this ion is a tracer of gas at a few hundred thousand K, in this case seen as the "fountain" cools.

It is very likely that the Milky Way has such a halo, but it's harder to se. he X-ray emission is spread all over the sky, and blends with the (brighter) background of X-rays from faint galaxies and quasars. We do see O VI (i.e. oxygen ionized 5 times) in absorption at low velocity all over the sky in a complicated distribution (there have been major projects using FUSE data for this; it's hard to look out and not see Milky Way O VI absorption cluttering up your spectrum). There's a graphic of the "galactic fountain" idea at http://fuse.pha.jhu.edu/Graphics/scigraph/scigraph.html. Sort of like Kuiper-belt style dust, this kind of halo gas can be easier to see around someone else's system than our own.

George
2005-Feb-15, 09:44 PM
... The X-ray structure shows the kinds of arcs and loops that indicate energy input from individual star-forming regions in the disk, and so they have not ballooned enough for their hot gas to merge. This makes the authors (at least in a previous paper) call them fountains, blowing up above the disk plane and falling back as the gas cools, rather than winds (which don't come back).
Is a solar prominence and filament a solar fountain? 8) :)

Certainly the "wind" idea fits the solar wind. It is impressive to me that all the planets reside in the atmosphere of the Sun. It is also impressive that the atmosphere (heliosphere) is mainly a radial wind (I presume).

The solar wind, is a restless wind,
a restless wind that yearns to wander,
and I was born, the next of kin,
the next of kin, to the solar wind.

Eddie Arnold, I think. Of course, revised :)

Hmmm. Just hit me. Since our elements come from stellar winds, this song just got better. 8)



The gas in NGC 4631 is also seen in O VI emission by the FUSE satellite; this ion is a tracer of gas at a few hundred thousand K, in this case seen as the "fountain" cools.
A green fountain?

ngc3314
2005-Feb-16, 12:48 AM
Could this temperature be due, in part, to the same gravitational collapse found in WHIM's? Or, is the supernova idea more favorable an explanation? [this should get ngc3314 in here, TravisM :) ]

Oh, all right, give me 'til tomorrow morning to post something coherent, since I wanted to go shake down a webcam on the new campus telescope...
You are indirectly stating your marriage status (being V-day :) ). More importantly, what "new campus telescope"? Is this another thin mirror like the one ya'll built first for the Vatican's scope?



Wrong inference - she had already declared it a day after subbing in the local elementary school library the day before they expected an inpection from High-Ups.

And wrong UA, sad to say - we're the one in Tuscaloosa which is only sort of Tucson spelled sideways. Working oni a new 16-inch RC reflector from DFM. Not huge, but we just leaped a century in what we can have students do on campus. Now to figure out which part of the building's air-handling system is giving the worst vibrations, when we're not using an expensive way to detect trains on the tracks a mile away...

ngc3314
2005-Feb-16, 12:58 AM
Certainly the "wind" idea fits the solar wind. It is impressive to me that all the planets reside in the atmosphere of the Sun. It is also impressive that the atmosphere (heliosphere) is mainly a radial wind (I presume).

The solar wind, is a restless wind,
a restless wind that yearns to wander,
and I was born, the next of kin,
the next of kin, to the solar wind.

Eddie Arnold, I think. Of course, revised :)

Hmmm. Just hit me. Since our elements come from stellar winds, this song just got better. 8)



The gas in NGC 4631 is also seen in O VI emission by the FUSE satellite; this ion is a tracer of gas at a few hundred thousand K, in this case seen as the "fountain" cools.
A green fountain?

There's some excellent filk in there somewhere... better than my late-night ballad about dark matter to the tune of the best-known of the Polovtsian Dances.

A green fountain? Only if you're looking at redshift 4 or have very interesting retinal and corneal chemistry, since the O VI lines start life at 103 nm. That's what makes them such a challenge (even for the WHIM: or especially for the WHIM).

George
2005-Feb-16, 01:02 AM
[You are indirectly stating your marriage status (being V-day :) ). More importantly, what "new campus telescope"? Is this another thin mirror like the one ya'll built first for the Vatican's scope?
Wrong inference - she had already declared it a day after subbing in the local elementary school library the day before they expected an inpection from High-Ups.
:oops: . Hope all went well for her.


And wrong UA, sad to say - we're the one in Tuscaloosa which is only sort of Tucson spelled sideways. :)


Working oni a new 16-inch RC reflector from DFM. Not huge, but we just leaped a century in what we can have students do on campus. Now to figure out which part of the building's air-handling system is giving the worst vibrations, when we're not using an expensive way to detect trains on the tracks a mile away...
Sounds like a very nice scope. Good luck.

George
2005-Feb-16, 03:28 PM
There's some excellent filk in there somewhere... better than my late-night ballad about dark matter to the tune of the best-known of the Polovtsian Dances.
"Filk". Gee, now you're adding culture words to my vocabulary. Thanks, I like it. But my filkin' ain't milkin' fiction, mine is sound as the Earth is round. :)


A green fountain? Only if you're looking at redshift 4 or have very interesting retinal and corneal chemistry, since the O VI lines start life at 103 nm. That's what makes them such a challenge (even for the WHIM: or especially for the WHIM).
I follow ya. At z=4, 103nm emission becomes 515nm retina absorption - green.

I was thinkin of O II & OIII I suppose for green (closer clouds). Is there a nice reference list of colors for the various common elements?

ngc3314
2005-Feb-16, 04:24 PM
There's some excellent filk in there somewhere... better than my late-night ballad about dark matter to the tune of the best-known of the Polovtsian Dances.
"Filk". Gee, now you're adding culture words to my vocabulary. Thanks, I like it. But my filkin' ain't milkin' fiction, mine is sound as the Earth is round. :)


A green fountain? Only if you're looking at redshift 4 or have very interesting retinal and corneal chemistry, since the O VI lines start life at 103 nm. That's what makes them such a challenge (even for the WHIM: or especially for the WHIM).
I follow ya. At z=4, 103nm emission becomes 515nm retina absorption - green.

I was thinkin of O II & OIII I suppose for green (closer clouds). Is there a nice reference list of colors for the various common elements?

Your wish, my - something or other. Here goes for common emission lines from UV to near-IR, wavelengths in nm. I use the spectroscopic convention in which the neutral species is I, once-ionized is II (astronomical jargon never makes that much sense anyway).
The [brackets] indicate transitions that are forbidden - that is, that take such a long time for the electron orbit to decay that they don't occur in typical lab vacuums (rather, a collision knocks the atom into some other state).

H 121.6 (Lyman alpha; beta... are never strong in emission)
410 (H-delta)
434 H-gamma
486 H-beta
656 H-alpha
[O II] 373
[O III] 496,507
[S II] 407,672,1032
[N II] 655,658
[O I] 558,630,636 (558 is strong in airglow)
O VI 103 (doublet)
Mg II 280 (doublet, strong in quasars)
C IV 155 (doublet)
[C III 191 (only semi-forbidden)
He II 160,469

(I just noticed that leading spaces are being eaten; so much for my careful tabular alignment).

George
2005-Feb-16, 07:14 PM
Your wish, my - something or other. Here goes for common emission lines from UV to near-IR, wavelengths in nm. I use the spectroscopic convention in which the neutral species is I, once-ionized is II (astronomical jargon never makes that much sense anyway).
Ancient Greek thinking (no zeros). :)


The [brackets] indicate transitions that are forbidden - that is, that take such a long time for the electron orbit to decay that they don't occur in typical lab vacuums (rather, a collision knocks the atom into some other state). Thanks. I wondered if there was some significance to the brackets.

In my quest for the sun's color, I have discovered that no two color charts match one another. Each one assigns a delta wavelength band for each color which will not match another's assignment. This probably does not surprise you. It did me, at first, considering the plethora of web info on color.

Blues and reds vary greatly in nm range. I don't recall even seeing, however, indigo anywhere in nm terms. :) The one color that does align fairly well with other charts, partly due to it's narrow band, is yellow. It is the wimpy one, ironically, that the sun is regarded by the populace.

Are surface brighness magnitudes available for specific ionized elements [edit: in cloud structures]? The BA's article in Astronomy "Alien Skies", I think, still has me wondering if we could see them down here (using a colorscope or georgescope or 3314scope :o ]. [Hmmm... 33" surface brightening aperature might allow 14" class magnification :) ] But, this is gettin off topic. :roll:

ngc3314
2005-Feb-16, 07:28 PM
Your wish, my - something or other. Here goes for common emission lines from UV to near-IR, wavelengths in nm. I use the spectroscopic convention in which the neutral species is I, once-ionized is II (astronomical jargon never makes that much sense anyway).
Ancient Greek thinking (no zeros). :)


Well, doesn't that fit with astrophysicists, the people who felt it necessary to simplify the 2x2 Greek periodic table to the even simpler H-He-"metals"?



Are surface brighness magnitudes available for specific ionized elements [edit: in cloud structures]? The BA's article in Astronomy "Alien Skies", I think, still has me wondering if we could see them down here (using a colorscope or georgescope or 3314scope :o ]. [Hmmm... 33" surface brightening aperature might allow 14" class magnification :) ] But, this is gettin off topic. :roll:

Depends on what you're looking at - surface brightness in a given line depends on temperature (and obviously ionization balance within a given element) as well as column density of that ion. [O III] is really really green - I had the chance to see the bright planetary nebula NGC 7027 at the prime focus of the Lick 3m once, and it was unmistakeable. Unearthly. Almost - forbidden. (Didn't make that up on the spot - that's what my thesis advisor was saying over the intercom when I asked the telescope operator not to stow the telescope just yet while Nebula Appreciation Class was in session). Cue the whole argument about colors in the Orion Nebula, but delete references to color scheme of the Eagle Nebula picture...

For numerical values, there's a catalog of intensities of various emission lines from various pieces of planetary nebulae at http://stsdas.stsci.edu/elcat
while more stuff is widely scattered through the literature. For example, Bob O'Dell and co. were able to derive the 3D structure of the emitting region in Orion from the fact that most of the line emission comes from a thin interface with the surrounding dense cloud, so its surface brightness tells how far each bit is from Theta-whatitsname Orionis (the hottest one).

George
2005-Feb-16, 11:17 PM
I had the chance to see the bright planetary nebula NGC 7027 at the prime focus of the Lick 3m once, and it was unmistakeable. Unearthly. Almost - forbidden.
Wow. Nice, no doubt. I did enjoy my views while at McDonalds Observatory!

[ok, I confess, it was their tourist scope down at the gift shop. :) ]


For numerical values, there's a catalog of intensities of various emission lines from various pieces of planetary nebulae at http://stsdas.stsci.edu/elcat
Thanks.


while more stuff is widely scattered through the literature. For example, Bob O'Dell and co. were able to derive the 3D structure of the emitting region in Orion from the fact that most of the line emission comes from a thin interface with the surrounding dense cloud, so its surface brightness tells how far each bit is from Theta-whatitsname Orionis (the hottest one).
Do you use Rayleigh Scattering principles in determining densities/particle sizes/composition?

George
2005-Feb-17, 02:08 AM
Cue the whole argument about colors in the Orion Nebula, but delete references to color scheme of the Eagle Nebula picture...
Hey. I'm trying to behave. :)

ngc3314
2005-Feb-17, 04:00 AM
I had the chance to see the bright planetary nebula NGC 7027 at the prime focus of the Lick 3m once, and it was unmistakeable. Unearthly. Almost - forbidden.
Wow. Nice, no doubt. I did enjoy my views while at McDonalds Observatory!

[ok, I confess, it was their tourist scope down at the gift shop. :) ]


For numerical values, there's a catalog of intensities of various emission lines from various pieces of planetary nebulae at http://stsdas.stsci.edu/elcat
Thanks.


while more stuff is widely scattered through the literature. For example, Bob O'Dell and co. were able to derive the 3D structure of the emitting region in Orion from the fact that most of the line emission comes from a thin interface with the surrounding dense cloud, so its surface brightness tells how far each bit is from Theta-whatitsname Orionis (the hottest one).
Do you use Rayleigh Scattering principles in determining densities/particle sizes/composition?

Not for emission-line gas (scattering is what enters for the continuum interacting with big solid grains, relevant to reflection nebulae at shortish wavelengths). For emission lines, the physics involves excitation of atomic energy levels and subsequent re-emission; the excitation may be directly from absorption of a photon or via the intermediary of collision with an electron knocked loose by ionization of some other atom. Almost certainly more than you want to know may be found at http://www.astr.ua.edu/keel/galaxies/emission.html which is a very compressed distillation of Don Osterbrock's two books (soon, I hear, to see a new edition done with Brad Peterson). As you'll gather, there is a vast lore on deriving physical conditions from various emission-line ratios; most of the uncertainties can be traced to what kinds of fluctuations within the measurement area we can and cannot measure in some way.

TravisM
2005-Feb-17, 04:57 AM
:o

Leave your thread un-attended for a day or two and sheeeeesh! ;)
Ya'll ran with this one didn't ya?

ngc3314
2005-Feb-17, 01:32 PM
:o

Leave your thread un-attended for a day or two and sheeeeesh! ;)
Ya'll ran with this one didn't ya?

But weren't you the one complaining about how lonely it was in here for a day or two?

And to think I worry about being the BABB Threadslayer...

George
2005-Feb-18, 12:15 AM
Not for emission-line gas (scattering is what enters for the continuum interacting with big solid grains, relevant to reflection nebulae at shortish wavelengths).
You must like your molecules quite small. Is diatomic mid-size? :)


Almost certainly more than you want to know may be found at http://www.astr.ua.edu/keel/galaxies/emission.html which is a very compressed distillation of Don Osterbrock's two books (soon, I hear, to see a new edition done with Brad Peterson).
Somewhat impressive, but I prefer it when I see integrals clear across the page, not just 3/4. :wink:

I have been reading Dr. Pasachofs book T_ C_ I_ G_ T_ The Sun. This is the style book made just for me. :-? (I think I found 2 mistakes :) )

ngc3314
2005-Feb-18, 12:29 AM
Not for emission-line gas (scattering is what enters for the continuum interacting with big solid grains, relevant to reflection nebulae at shortish wavelengths).
You must like your molecules quite small. Is diatomic mid-size? :)


Only to the molecule-rental companies. Always be sure to take the dissociation-liability coverage.

George
2005-Feb-18, 03:30 AM
:o

Leave your thread un-attended for a day or two and sheeeeesh! ;)
Ya'll ran with this one didn't ya?
Yep. I want to learn what I can about gas, since many have considered me as such. :-? :)