The Milky Way's former AGN? Yep.

[trinitree88]

Recently, the surprise result was found during the first few years of the Fermi Gamma Ray Satellite's data..that giant faint bubbles of gamma ray emission occur in scale approximate to the size of the galaxy....with no probable cause seeming to be found. A good mystery, which means we'll learn something as the pros unravel the possibilities. Here's the first good try....at one time the Milky Way may have harbored an Active Galactic Nucleus. SEE:http://arxiv.org/abs/1103.0055
pete


for the Bubble see video:http://www.youtube.com/watch?v=_wwDXt_K1kY:

[SRH]

Do the gamma ray bubbles have mass? (If E=MC^2, then the gamma ray energy can be thought of as mass and quantified, correct?)
Is this mass equal to the amount of mass theorized in the DM spherical halo?

[trinitree88]

Do the gamma ray bubbles have mass? (If E=MC^2, then the gamma ray energy can be thought of as mass and quantified, correct?)
Is this mass equal to the amount of mass theorized in the DM spherical halo?

TOE. Yep mass and energy are interchangeable in the E=mc² equation, but the huge amount of energy you get out of tiny mass annihilations means in the opposite direction a huge energy annihilation gives you very little mass...so nope, it's not considered in most models of the halo problem. Still most likely candidate is CO-free, dust free,molecular hydrogen. pete

[Cougar]

Thanks for the heads-up. I'm surprised they date the bubbles at only a few million years old.

...it's not considered in most models of the halo problem. Still most likely candidate is CO-free, dust free,molecular hydrogen.

Candidate for what? The "halo problem"? Most likely to whom?

[trinitree88]

Thanks for the heads-up. I'm surprised they date the bubbles at only a few million years old.



Candidate for what? The "halo problem"? Most likely to whom?

Cougar
1.SEE:http://www.astronomynotes.com/ismnotes/s3.html
2. The mass of the molecular hydrogen is inferred from a consistent CO/H₂ ratio. That ratio is not always consistent, which brings at least a little doubt into it's authenticity. The UV absorption, also used to estimate masses of molecular clouds/halos, is thought to be inaccurate and tricky to measure when the dust entrained is large, which happens. So the error bars are uncertain,too.
3. As one who follows the travails of particle physics pretty closely, there has never been AFAIK a detection in a billion dollar accelerator lab, or in any of the high energy cosmic ray facilities, or in any of the large volume neutrino facilities of any of the 34 putative Supersymmetry particles, or of any axions, or of any monopoles, or of any WIMPS, or of any unknown DARK MATTER candidates, or of any DARK ENERGY candidates, or of any particles that don't fit the Standard Model. None.
4.Though I'm typing here, I'm not alone in the world of particle physics in dismissing putative claims of lots of stuff that has never been confirmed....even the most recent resonance bump @ CERN/LHC can fit an interaction between the known W+ or W-, and half of a splitting Z.
5. I understand (not being an astronomer) that the pros in the business use the most advanced instrumentation available, carefully prepare their methodologies, double check and double blind their data processing algorithms, submit their papers for anonymous peer review, refine and resubmit till it passes, and push out new stuff to ArXiv and all the Journals......but some of it always remains edgy, and in need of further work.That's the business. Nobody goes back through the old journals and highlights all the wrong results in [color is yellow]YELLOW[color is yellow]. That'd help.
Years ago, I attended a talk @ MIT's Physics Colloquiem by T.D.K.Lee on the history of the weak interaction...one of my favorite subjects.He slowly paraded through the maze of fits and starts of the dance between theory and experiment over ~ 50 years....keeping the audience in stitches along the way. The evidence from particle physics is that the non-Keplerian curve to galactic rotation is most likely hydrogen molecules (baryonic)


SEE also:http://astrobites.com/2012/03/24/sea...warf-galaxies/
It's an unpleasant fact....most of the molecular gas....is completey undetectable in galaxies.


and SEE:http://www.astr.ua.edu/keel/galaxies/gas.html

6 There's an additional effect from the periphery of the galaxy being subjected to gamma ray bursts, which we know from studies of the Milky Way, are predominantly extragalactic ( not associated in general spatial distribution with the physical morphology of our galactic plane)....and part of my talk at Harvard in 94 (Matt Damon & Ben Affleck in the audience).
The binding energy of a nucleon in the nucleus of any atom runs typically....~ 8-20 Mev. That means if you have some entrained CO in the molecular hydrogen of a spiral like the Milky Way, the passage of a gamma ray burst will not only dissociate the molecular hydrogen, but is sufficiently energetic to photodissociate the nuclei in the carbon and the oxygen atoms too. Without CO as a putative tracer of molecular hydrogen, you'd assume there was none in the halo.
7. In some other thread (I'll hunt) I discussed with NGC 3314...a consummate pro...the possibility that trains of dissociated hydrogen gas ...H11...would result from my putative halos. With a recombination time that is large, time lapsed imaging of them ought to show wavy pencil beams of gas emitting visible light, since the beaming factor for GRB's is about 10,000 to 1, but kinematics would distort them some. He liked the idea. Check with him.
8. The places where CO is entrained in molecular clouds are in the interior of the galaxy, where an equilibrium condition can exist, and more CO formed and ejected into the ISM from standard CNO cycle processing occurs, replacing the GRB photodissociated molecules.
pete


As for the age of the FermiLat bubbles, I think the inference comes from the relatively sharp edges of the imaging, where they expect more distortion over time.

[Cougar]

Just a quick note for now....

6 There's an additional effect from the periphery of the galaxy being subjected to gamma ray bursts...

I don't know about today, but in 2003 the closest GRB was:

"At a distance of about 2.6 billion light-years, GRB 030329 is hardly next door. However, compared to other GRBs at typical distances of 8-10 billion light-years..." -- cite

In most cases, what started out as a gamma ray isn't going to be as energetic when it gets here due to expansion....

[Nereid]

Candidate for what? The "halo problem"? Most likely to whom?

Cougar
1.SEE:http://www.astronomynotes.com/ismnotes/s3.html

Link doesn't work.

2. The mass of the molecular hydrogen is inferred from a consistent CO/H₂ ratio. That ratio is not always consistent, which brings at least a little doubt into it's authenticity.

Or that the error bars need to be a bit bigger.

The UV absorption, also used to estimate masses of molecular clouds/halos, is thought to be inaccurate and tricky to measure when the dust entrained is large, which happens. So the error bars are uncertain,too.

Or perhaps "somewhat uncertain"

3. As one who follows the travails of particle physics pretty closely, there has never been AFAIK a detection in a billion dollar accelerator lab, or in any of the high energy cosmic ray facilities, or in any of the large volume neutrino facilities of any of the 34 putative Supersymmetry particles, or of any axions, or of any monopoles, or of any WIMPS, or of any unknown DARK MATTER candidates, or of any DARK ENERGY candidates, or of any particles that don't fit the Standard Model. None.

So?

AFAIK, there are precious few astronomical results which constrain the nature of CDM (other than that most of it can't be baryonic).

4.Though I'm typing here, I'm not alone in the world of particle physics in dismissing putative claims of lots of stuff that has never been confirmed....even the most recent resonance bump @ CERN/LHC can fit an interaction between the known W+ or W-, and half of a splitting Z.

And this is relevant, how exactly?

5. I understand (not being an astronomer) that the pros in the business use the most advanced instrumentation available, carefully prepare their methodologies, double check and double blind their data processing algorithms, submit their papers for anonymous peer review, refine and resubmit till it passes, and push out new stuff to ArXiv and all the Journals......but some of it always remains edgy, and in need of further work.That's the business. Nobody goes back through the old journals and highlights all the wrong results in [color is yellow]YELLOW[color is yellow]. That'd help.

It would? How?

And how it is relevant anyway?

Years ago, I attended a talk @ MIT's Physics Colloquiem by T.D.K.Lee on the history of the weak interaction...one of my favorite subjects.He slowly paraded through the maze of fits and starts of the dance between theory and experiment over ~ 50 years....keeping the audience in stitches along the way. The evidence from particle physics is that the non-Keplerian curve to galactic rotation is most likely hydrogen molecules (baryonic)

Except for the evidence that it - or most of it - can't be hydrogen molecules.

SEE also:http://astrobites.com/2012/03/24/sea...warf-galaxies/
It's an unpleasant fact....most of the molecular gas....is completey undetectable in galaxies.

Except when it isn't.

Interesting that this astrobites document discusses only one method of detecting molecular hydrogen.

and SEE:http://www.astr.ua.edu/keel/galaxies/gas.html

Maybe we could ask Dr Keel to comment? After all, he's a regular CQuestian ...

6 There's an additional effect from the periphery of the galaxy being subjected to gamma ray bursts, which we know from studies of the Milky Way, are predominantly extragalactic ( not associated in general spatial distribution with the physical morphology of our galactic plane)....and part of my talk at Harvard in 94 (Matt Damon & Ben Affleck in the audience).
The binding energy of a nucleon in the nucleus of any atom runs typically....~ 8-20 Mev. That means if you have some entrained CO in the molecular hydrogen of a spiral like the Milky Way, the passage of a gamma ray burst will not only dissociate the molecular hydrogen, but is sufficiently energetic to photodissociate the nuclei in the carbon and the oxygen atoms too. Without CO as a putative tracer of molecular hydrogen, you'd assume there was none in the halo.

I'm afraid I don't understand your point here, would you mind explaining it a bit please?

In particular, you seem to be saying that some/most/a lot/? of the molecular hydrogen in the halo of the Galaxy will be dissociated by GRBs, which kinda makes your original point moot, doesn't it?

7. In some other thread (I'll hunt) I discussed with NGC 3314...a consummate pro...the possibility that trains of dissociated hydrogen gas ...H11...would result from my putative halos. With a recombination time that is large, time lapsed imaging of them ought to show wavy pencil beams of gas emitting visible light, since the beaming factor for GRB's is about 10,000 to 1, but kinematics would distort them some. He liked the idea. Check with him.

Looking forward to the link.

8. The places where CO is entrained in molecular clouds are in the interior of the galaxy, where an equilibrium condition can exist, and more CO formed and ejected into the ISM from standard CNO cycle processing occurs, replacing the GRB photodissociated molecules.
pete

A separate point? Or an extension of 7.?

[trinitree88]

Link doesn't work.


Or that the error bars need to be a bit bigger.


Or perhaps "somewhat uncertain"


So?

AFAIK, there are precious few astronomical results which constrain the nature of CDM (other than that most of it can't be baryonic).


And this is relevant, how exactly?


It would? How?

And how it is relevant anyway?


Except for the evidence that it - or most of it - can't be hydrogen molecules.


Except when it isn't.

Interesting that this astrobites document discusses only one method of detecting molecular hydrogen.


Maybe we could ask Dr Keel to comment? After all, he's a regular CQuestian ...


I'm afraid I don't understand your point here, would you mind explaining it a bit please?

In particular, you seem to be saying that some/most/a lot/? of the molecular hydrogen in the halo of the Galaxy will be dissociated by GRBs, which kinda makes your original point moot, doesn't it?


Looking forward to the link.


A separate point? Or an extension of 7.?

Nereid. The following link to results from the Fermi-LAT SEE:http://www.scholarpedia.org/article/..._bursts_theory

[Cougar]

Nereid. The following link to results from the Fermi-LAT SEE:http://www.scholarpedia.org/article/..._bursts_theory

That link might have helped me avoid my stupid comment above, but I don't see any "results from the Fermi-LAT"....

[Nereid]

Although it didn't appear in Fun Papers in Arxiv, this recent one is quite germane to this thread: A Universal Neutral Gas Profile for Nearby Disk Galaxies (arXiv:1208.1505):

Based on sensitive CO measurements from HERACLES and HI data from THINGS, we show that the azimuthally averaged radial distribution of the neutral gas surface density (Sigma_HI + Sigma_H2) in 33 nearby spiral galaxies exhibits a well-constrained universal exponential distribution beyond 0.2*r25 (inside of which the scatter is large) with less than a factor of two scatter out to two optical radii r25. Scaling the radius to r25 and the total gas surface density to the surface density at the transition radius, i.e., where Sigma_HI and Sigma_H2 are equal, as well as removing galaxies that are interacting with their environment, yields a tightly constrained exponential fit with average scale length 0.61+-0.06 r25. In this case, the scatter reduces to less than 40% across the optical disks (and remains below a factor of two at larger radii). We show that the tight exponential distribution of neutral gas implies that the total neutral gas mass of nearby disk galaxies depends primarily on the size of the stellar disk (influenced to some degree by the great variability of Sigma_H2 inside 0.2*r25). The derived prescription predicts the total gas mass in our sub-sample of 17 non-interacting disk galaxies to within a factor of two. Given the short timescale over which star formation depletes the H2 content of these galaxies and the large range of r25 in our sample, there appears to be some mechanism leading to these largely self-similar radial gas distributions in nearby disk galaxies.

Yes, they use CO as a tracer for molecular hydrogen, but what's curious, and interesting, is that they find a nice, fairly tight, scaling relation.

More evidence that the mass in spiral galaxy halos is not dominated by undetected molecular hydrogen ...

[trinitree88]

That link might have helped me avoid my stupid comment above, but I don't see any "results from the Fermi-LAT"....

Yep. Had link trouble myself with it. In the following, the red dots are above a Gev (they use the defunct billion electron volts)...see:http://science.nasa.gov/science-news...eb_extremegrb/

[trinitree88]

Nereid. Here's one study that showed that the CO emission was high where H was weak and vice versa. I'd like to see more current instrumentation double check that before I go out on a limb. SEE:http://adsabs.harvard.edu/full/1989PASJ...41..113S

[trinitree88]

Nereid. Here's one study that showed that the CO emission was high where H was weak and vice versa. I'd like to see more current instrumentation double check that before I go out on a limb. SEE:http://adsabs.harvard.edu/full/1989PASJ...41..113S

carbon monoxide to molecular hydrogen (molh) ratios most likely depleted by a factor of ~100 ( unless you would prefere a deuterium.protium ratio off by a factor of ~ 100) in this molecular cloud. If such depletion occurs in the halo...SEE:http://cab.inta-csic.es/users/jrpardo/paper26.pdf .. there's your baryonic dark matter.

[ngc3314]

As always on this issue it also would have to be very highly clumped, more so than components seen in CO emission, to avoid trivial detection through the very strong Lyman and Werner bands of H₂ in the deep UV. Low metallicity strengthens limits on diffuse gas, since you'd have progressively less extinction from associated grains (which normally biases UV spectra to lower-column-density sight lines) at lower metal abundance.

[trinitree88]

As always on this issue it also would have to be very highly clumped, more so than components seen in CO emission, to avoid trivial detection through the very strong Lyman and Werner bands of H₂ in the deep UV. Low metallicity strengthens limits on diffuse gas, since you'd have progressively less extinction from associated grains (which normally biases UV spectra to lower-column-density sight lines) at lower metal abundance.

ngc thanks. i need to study this stuff for a bit...I'll post to myself here a series of reference links (others can ignore if they so choose)
SEE:http://astro.berkeley.edu/~ay216/08/...cture14-08.pdf