The Milky Way's central molecular zone

February 29, 2016
An infrared and multi-wavelength image of the Central Molecular Zone in the Milky Way. Dense gas is shown in red, and warm and cold dust in green and blue respectively. Several key objects in the region are labeled, along with a set of embedded young stellar clusters seen at 24 microns. Credit: C. Battersby

The center of our Milky Way galaxy lies about 27,000 light-years away in the direction of the constellation of Sagittarius. At its core is a black hole about four million solar masses in size. Around the black hole is a donut-shaped structure about eight light-years across that rings the inner volume of neutral gas and thousands of individual stars. Around that, stretching out to about 700 light-years, is a dense zone of activity called the Central Molecular Zone (CMZ). It contains almost eighty percent of all the dense gas in the galaxy - a reservoir of tens of millions of solar masses of material - and hosts giant molecular clouds and massive star forming clusters of luminous stars, among other regions many of which are poorly understood.

For example, the CMZ contains many dense molecular clouds that would normally be expected to produce new stars, but which are instead eerily desolate. It also contains moving at highly supersonic velocities - hundreds of kilometers per second (hundreds of thousands of miles per hours).

Where did the CMZ come from? No place else in the Milky Way is remotely like it (although there may be analogues in other galaxies). How does it retain its structure as its molecular gas moves, and how do those rapid motions determine its evolution? One difficulty facing astronomers is that there is so much obscuring dust between us and the CMZ that visible light is extinguished by factors of over a trillion. Infrared, radio, and some X-ray radiation can penetrate the veil, however, and they have allowed astronomers to develop the picture just outlined.

CfA astronomers Cara Battersby, Dan Walker, and Qizhou Zhang, with their team of colleagues, used the Australian Mopra radio telescope to study the three molecules HNCO, N2H+, and HNC in the CMZ. These particular molecules were selected because they do a good job of tracing the wide range of conditions thought to be present in the CMZ, from shocked gas to quiescent material, and also because they suffer only minimally from cluttering and extinction effects that complicate more abundant species like carbon monoxide. The scientists developed a new computer code to analyze efficiently the large amounts of data they had.

The astronomers find, consistent with previous results, that the CMZ is not centered on the black hole, but (for reasons that are not understood) is offset; they also confirm that the gas motions throughout are supersonic. They identify two large-scale flows across the region, and suggest they represent one coherent (or at most two independent) streams of material, perhaps even spiral-like arms. They also analyze the gas in several previously identified zones of the CMZ, finding that one shell-like region thought to be the result of supernova explosions may instead be several regions that are physically unrelated, and that a giant cloud thought to be independent is actually an extension of the large-scale flows. The scientists note that this work is a first step in unraveling an intrinsically complex galactic environment, and that pending research will trace the gas motions to larger distances and try to model the CMZ gas motions with computer simulations.

Explore further: Massive Stars Near the Galactic Center

More information: J. D. Henshaw et al. Molecular gas kinematics within the central 250 pc of the Milky Way, Monthly Notices of the Royal Astronomical Society (2016). DOI: 10.1093/mnras/stw121

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19 comments

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wduckss
1 / 5 (5) Feb 29, 2016
"One difficulty facing astronomers is that there is so much obscuring dust between us and the CMZ that visible light is extinguished by factors of over a trillion."

Or, more precisely 15,000 light years! If the data can be read krz so thick and dense layer, congratulations.

http://www.svemir...tml#ring seventh article.
Tuxford
1 / 5 (6) Feb 29, 2016
Where did the CMZ come from?


From periodic ejections of new matter formed within the grey core itself. Where else? Why from elsewhere? Most likely the CMZ lies close to the actual source?

Certainly troubling for the merger maniacs. Merger, merger, merger, merger.....
wduckss
1 / 5 (3) Feb 29, 2016
CMZ is an ally of the black hole because a black hole sucks up the body of 15,000 light-years a far objects and matter while CMZ undisturbed dance by a black hole!
Graeme
5 / 5 (1) Feb 29, 2016
MOPRA was threatened with close-down due to lack of funding. Lets hope it can keep working.
Psilly_T
5 / 5 (3) Feb 29, 2016
ughhh guys help this article was confusing and the trolls are @*!&ing confusinger did anyone read the paper and understand it? Why is there so much dense not cold gas on seemingly half of our spiral side?
Captain Stumpy
3 / 5 (8) Feb 29, 2016
did anyone read the paper and understand it?
paywalled, but i will see if there is another copy... if anyone else gets it first, please post it
THANKS
Psilly_T
5 / 5 (5) Feb 29, 2016
thanks anyways capin'
Captain Stumpy
3.5 / 5 (8) Feb 29, 2016
thanks anyways capin'
@psilly
I may have found the preprint... http://arxiv.org/...3732.pdf

haven't read it yet, though...

RealScience
5 / 5 (5) Mar 01, 2016
Yes, that's the right paper, Captain - thanks!

That's quite the paper - ~30 pages, very detailed, and nicely illustrated...
Captain Stumpy
4.3 / 5 (6) Mar 01, 2016
Yes, that's the right paper, Captain - thanks!

That's quite the paper - ~30 pages, very detailed, and nicely illustrated...
@Real
you are welcome... i am still going through it

would love to hear your feedback on it... Thanks

.

.

apparently full-of-bs, benni-kam and duck*ss didn't like it though....
LMFAO
RealScience
5 / 5 (4) Mar 02, 2016
would love to hear your feedback on it...


Basically they got so much spectral data from Mopra that they needed to develop software (Scouse) to automatically analyze it, which then allowed them to analyze each 'pixel' to the extent of teasing out multiple clouds that line up from our perspective. They used rarer HNCO rather than CO spectral lines to allow seeing clouds behind clouds, and teased the clouds apart with line fitting (Scouse) since they found that moment analysis only worked well when there was just one cloud in a line of sight.

This didn't tell which cloud (PPV-structure) is in front, so it didn't provide a 3D picture. They therefore compared the structure to three previous models of gas clouds around the core, and were able to say that one model did NOT agree with the data, and to suggest where to look at masers within the structures to distinguish between the other two models.

A nice paper, with good visuals.
Phys1
4 / 5 (4) Mar 02, 2016
@tf
Merger, merger, merger, merger.....

Consult a psychiatrist.
The merger maniac is you.
cantdrive85
1.8 / 5 (5) Mar 04, 2016
among other regions many of which are poorly understood.

It's plasma, not surprising it's poorly understood by astrophysicists.

the CMZ contains many dense molecular clouds that would normally be expected to produce new stars, but which are instead eerily desolate.

Due to erroneous hypotheses of star formation.

It also contains gas moving at highly supersonic velocities - hundreds of kilometers per second

Actually, it's plasma and that is what you call an electric Birkeland current. It's all just part of the much larger galactic circuit.

How does it retain its structure as its molecular gas moves

EM fields, same way laboratory (all) plasmas retain structure.

They identify two large-scale flows across the region, and suggest they represent one coherent (or at most two independent) streams of material, perhaps even spiral-like arms.

They can't see the obvious due to the fact they're blinded by ignorance of the real plasma physics.
Old_C_Code
1 / 5 (2) Mar 05, 2016

and hosts giant molecular clouds and massive star forming clusters of luminous stars, among other regions many of which are poorly understood.


Most sensible words in the article, "poorly understood". A gas kinematics only model is insane, but sure makes pretty graphs! I'm truly amazed that the effects of electrically conductive plasma (1% or > ionized gas, in effect gaseous metal) and the massive magnetic fields in the region are ignored by the gravity priests, it's getting comical.
Captain Stumpy
4.2 / 5 (5) Mar 05, 2016
not surprising it's poorly understood by astrophysicists
http://ocw.mit.ed...ophysics

astrophysicists understand plasma physics
why you perpetuate this LIE?
... because it is the education system: something you and the eu are unfamiliar with and can't actually get into, so it is poorly understood by the eu cult!
Due to erroneous hypotheses of star formation...electric Birkeland current...blah blah blah
right, because the eu magic 8Ball said so, right?
your links to evidence are overwhelming...(snicker)

of course, your track record sucks, what with the fail on the grand canyon, Shoemaker-Levy 9, moon craters, dust devils, comets, Cassini, plasma discharges killing probes and all that...

strike 42 hundred!
LOL
Whydening Gyre
5 / 5 (3) Mar 05, 2016

and hosts giant molecular clouds and massive star forming clusters of luminous stars, among other regions many of which are poorly understood.


Most sensible words in the article, "poorly understood". A gas kinematics only model is insane, but sure makes pretty graphs! I'm truly amazed that the effects of electrically conductive plasma (1% or > ionized gas, in effect gaseous metal) and the massive magnetic fields in the region are ignored by the gravity priests, it's getting comical.

Not ignored. Just generally considered not to have sufficient effect over gravity to make a difference.
That consideration might be misplaced. But until future evidence (or a radical reassessment of current evidence) suggests that, it stands.
Phys1
4.4 / 5 (7) Mar 06, 2016
@cd
EM fields, same way laboratory (all) plasmas retain structure.

But they don't retain structure.
This is why it is so hard to build a fusion reactor.
How come you, the self appointed fount of knowledge on plasma physics, do not know this ?
Phys1
4.2 / 5 (5) Mar 06, 2016
@wduckss
a black hole sucks up the body of 15,000 light-years a far objects and matter

How did you get this absolutely wrong idea?
Whydening Gyre
not rated yet Mar 06, 2016
It also contains gas moving at highly supersonic velocities - hundreds of kilometers per second

Actually, it's plasma and that is what you call an electric Birkeland current...

Initiated by gravitational effect. Maintained via magnetic effect.

How does it retain its structure as its molecular gas moves

EM fields, same way laboratory (all) plasmas retain structure.

Really? You mean... like a lab with containment field coils and everything? In a building located on a planetary size gravity well and everything?
You thought of this all by yourself, CD? You must be SOoo smart...

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