Milky Way ransacks nearby dwarf galaxies, stripping all traces of star-forming gas

Milky Way ransacks nearby dwarf galaxies
This is an artist's impression of the Milky Way. Its hot halo appears to be stripping away the star-forming atomic hydrogen from its companion dwarf spheroidal galaxies. Credit: NRAO/AUI/NSF

Astronomers using the National Science Foundation's Green Bank Telescope (GBT) in West Virginia, along with data from other large radio telescopes, have discovered that our nearest galactic neighbors, the dwarf spheroidal galaxies, are devoid of star-forming gas, and that our Milky Way Galaxy is to blame.

These new radio observations, which are the highest sensitivity of their kind ever undertaken, reveal that within a well-defined boundary around our Galaxy, are completely devoid of hydrogen gas; beyond this point, dwarf galaxies are teeming with star-forming material.

The Milky Way Galaxy is actually the largest member of a compact clutch of galaxies that are bound together by gravity. Swarming around our home Galaxy is a menagerie of smaller dwarf galaxies, the smallest of which are the relatively nearby dwarf spheroidals, which may be the leftover building blocks of galaxy formation. Further out are a number of similarly sized and slightly misshaped dwarf irregular galaxies, which are not gravitationally bound to the Milky Way and may be relative newcomers to our galactic neighborhood.

"After billions of years of interaction, astronomers wondered if the nearby dwarf spheroidal galaxies have all the same star-forming 'stuff' that we find in more distant dwarf galaxies," said astronomer Kristine Spekkens, assistant professor at the Royal Military College of Canada and lead author on a paper published in the Astrophysical Journal Letters.

Previous studies have shown that the more distant dwarf irregular galaxies have large reservoirs of neutral hydrogen gas, the fuel for . These past observations, however, were not sensitive enough to rule out the presence of this gas in the smallest dwarf spheroidal galaxies.

By bringing to bear the combined power of the GBT (the world's largest fully steerable radio telescope) and other giant telescopes from around the world, Spekkens and her team were able to probe the dwarf galaxies that have been swarming around the Milky Way for billions of years for tiny amounts of atomic hydrogen.

"What we found is that there is a clear break, a point near our home Galaxy where dwarf galaxies are completely devoid of any traces of neutral atomic hydrogen," noted Spekkens. Beyond this point, which extends approximately 1,000 light-years from the edge of the Milky Way's star-filled disk to a point that is thought to coincide with the edge of its dark matter distribution, dwarf spheroidals become vanishingly rare while their gas-rich, dwarf irregular counterparts flourish.

There are many ways that larger, mature galaxies can lose their star-forming material, but this is mostly tied to furious star formation or powerful jets of material driven by supermassive black holes. The dwarf galaxies that orbit the Milky Way contain neither of these energetic processes. They are, however, susceptible to the broader influences of the Milky Way, which itself resides within an extended, diffuse halo of hot hydrogen plasma.

The researchers believe that, up to a certain distance from the galactic disk, this halo is dense enough to affect the composition of dwarf galaxies. Within this "danger zone," the pressure created by the million-mile-per-hour orbital velocities of the dwarf spheroidals can actually strip away any detectable traces of neutral hydrogen. The Milky Way thus shuts down star formation in its smallest neighbors.

"These observations therefore reveal a great deal about size of the hot halo and about how companions orbit the Milky Way," concludes Spekkens.


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Journal information: Astrophysical Journal Letters

Citation: Milky Way ransacks nearby dwarf galaxies, stripping all traces of star-forming gas (2014, October 15) retrieved 17 September 2019 from https://phys.org/news/2014-10-milky-ransacks-nearby-dwarf-galaxies.html
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Oct 15, 2014
artist impression sans its bar?

http://www.newsci..._425.jpg

Oct 15, 2014
Yay Food!!
I was confused about this statement though guys. Can anyone clarify ?
"Beyond this point, which extends approximately 1,000 light-years from the edge of the Milky Way's star-filled disk to a point that is thought to coincide with the edge of its dark matter distribution,"

I thought the MW dm halo stretched much further than 1,000 LY so what does the author mean by "coincide with the edge of its dark matter distribution"

Oct 16, 2014
@Psilly: Good question!

To know, one must read the paper. But it is pay-walled. :-/

The relevant mechanism seems to be related to halo gas stripping though, not directly the DM halo as such: "They are, however, susceptible to the broader influences of the Milky Way, which itself resides within an extended, diffuse halo of hot hydrogen plasma. The researchers believe that, up to a certain distance from the galactic disk, this halo is dense enough to affect the composition of dwarf galaxies."

Oct 16, 2014
dwarf galaxies that orbit the Milky Way contain neither of these energetic processes


Why is it that I got a PhD level physicist of physforums, who hates my guts, to admit that "Energy" doesn't exist as a "thing", but is an artifact of dimensional analysis: Only momentum exists...?

Yet they still teach "energy" and we still measure everything in terms of "energy"?

"Energy" is a fictitious entity.

Even "Fire" is not energy. It is the release of a "Momentum Potential".

in fact, studying the concept of Fire will reveal why no such thing as "energy" exists, and that only momentum potentials exist.

Studying the concept of a Solar Sail will also reveal why this must be true.

I leave the details up to you, as discovering it for yourself is often the best way to learn.

Oct 16, 2014
All he's saying is the hot hydrogen plasma associated with the Milky Way collides with the gas in the other galaxies and ionizes those gas molecules, thus there is no elemental hydrogen as "H2" to form anything.

In principle, this could change if the system were somehow cooled enough, such as a merger with a cool, primordial gas cloud to help leach away some of the heat...provided accretion doesn't produce more heat than it leaches away. Would depend on the speed of the merger. 1000 light years is a long distance even at galactic relative speeds.

If the hydrogen cooled to elemental hydrogen (H2) then the dwarfs would start sweeping it up and making stars and black holes.

Oct 16, 2014
Ideal conservation laws (mainstream model) produce an absurdity in many hypothetical situations.

Imagine two ideal mirrors of limitless width, but very low mass are exactly parallel.
Imagine a photon being produced which is perpendicular to them, and between them.

Conservation of momentum says this little photon will accelerate both objects indefinitely, until they are black-shifted with respect to one another.

Does anyone really believe the universe works like that?

Oct 16, 2014
Why is it that I got a PhD level physicist of physforums, who hates my guts, to admit that "Energy" doesn't exist as a "thing", but is an artifact of dimensional analysis:


Why? Well it might be because you are the silly couyon. But that is just a guess. Maybe we can do one of Really-Skippy's experiments and see if that is true.

Oct 16, 2014
I seriously doubt Torbjorn hates your guts, sport. I doubt he bothers. I don't.

Oct 16, 2014
Why is it that I got a PhD level physicist of physforums, who hates my guts, to admit that "Energy" doesn't exist as a "thing", but is an artifact of dimensional analysis: Only momentum exists...?
-This must have been before you got banned -?
I leave the details up to you, as discovering it for yourself is often the best way to learn
Ahaahaaaaa says the guy who never bothers to check whether someone else has thought of his ideas first.

Another definition of a psychotic is someone who, when HE gets an idea, thinks that it never could have occurred to anyone else and therefore it is evidence that he is a genius. Simply doing a little research can dispel this egomaniacal delusion.
http://www.thenak...41821.50
http://physics.st...momentum

Oct 16, 2014
Why is it that I got a PhD level physicist of physforums, who hates my guts, to admit that "Energy" doesn't exist as a "thing", but is an artifact of dimensional analysis: Only momentum exists...?


That's just idiotic. Both are simply conserved quantities in classical dynamics, to claim one is real and the other not is stupid. It has nothing to do with dimensional analysis.

Oct 18, 2014
SUB; Science to progress in steps-Dark Modes and Matter
Dark modes may prevail within 720 LY . Then Dynamic Phenomea should set in 720-1440 Lightyears and Uplinks to Flow modes in Nature- 2160 LY
Note agnirmukham-Red Rectangle 2300 LY is a clear Index.
The Science of Cosmology and vedas Interlinks search now for confirmative Space data.
It is nice to see -Scientific thoughts are slowly coming around to fixation limits

Oct 22, 2014
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