Astronomers investigate an unusual massive gas-rich galaxy

Astronomers investigate an unusual massive gas-rich galaxy
Composite r, g, z-band image of UGC 1378. North is up, east is left, the image size is 7.2×10.1 arcmin. Credit: Saburova et al., 2019.

Russian astronomers have observed UGC 1378—an unusual, massive gas-rich galaxy with extended gaseous and low-surface brightness stellar discs. Results of the new research, presented in a paper published August 29, provide more insights into the nature of this rare type of galaxy.

Giant low-surface brightness (gLSB) galaxies with giant gaseous and stellar discs are very rare. Given that the formation and evolution of these discs in such galaxies is not well understood, astronomers are still searching for new objects of this type to investigate them in detail.

Located some 126 million away, UGC 1378 is a barred spiral galaxy of type SBa (with tightly bound arms of the spiral). Observations have shown that it is an unusual massive gas-rich gLSB system hosting gaseous and low-surface brightness stellar discs.

What puzzles astronomers is UGC 1378's neutral hydrogen (HI) gas content, which is higher than expected relative to its stellar mass. Moreover, the formation scenario of this galaxy is also uncertain. It is assumed that this gLSB system is most likely a result of a major merger in which an extended disc formed from an ample supply of gas cooled down at the late stage of a merger.

In order to resolve these uncertainties, a team of researchers led by Anna Saburova of the Lomonosov State University in Moscow, Russia, decided to conduct deep spectroscopic and multi-band imaging observations of UGC 1378. For this purpose they employed 6-m Russian telescope of the Special Astrophysical Observatory in southern Russia and the 6.5-m telescope of the MMT Observatory at Mt.Hopkins, Arizona.

"We describe observations of UGC 1378, including deep spectroscopy with the Russian 6-m telescope and multi-band imaging with Binospec at the MMT," the astronomers wrote in the paper.

The observations unveiled the complex structure of UGC 1378, including high-surface brightness (HSB) pseudo-bulge and HSB disc with a bar, rings and spiral arms. Moreover, the observational campaign clearly reveal the presence of a gas-rich gLSB disc with spiral arms and a radius of about 163,000 light years.

The global star formation rate (SFR) for UGC 1378 is estimated to be between 1.2 and 2.3 solar masses per year, which is close to that of the Milky Way galaxy. However, the LSB disc was found to have lower SFR surface density than expected from its gas density as for most gLSB galaxies. This, according to the authors of the paper, suggests recent gas accretion.

The study found that the dark matter halo dominates the mass inside the giant LSB disc radius of UGC 1378. Moreover, the ratio of dark to luminous mass is close to 2.0 within the HSB part of the galaxy, which is typical for normal spiral galaxies.

Most importantly, the research found that the stellar velocity dispersion of the HSB disc is close to that expected for its marginal gravitational stability. This, according to the astronomers excludes the possibility that UGC 1378 is a result of recent major mergers. Hence, taking into account the new results, they propose some other explanation.

"We suggest that the formation of UGC 1378 occurred in two stages. The first stage, in common with Milky Way-type , included several episodes of merging during which the HSB part formed and likely most satellites were accreted. In the second stage gLSB stellar and gaseous discs were formed by accretion of metal-poor gas from a cosmic filament," the researchers concluded.


Explore further

Research provides insights into molecular gas in the massive spiral galaxy NGC 5908

More information: Anna Saburova, et al. UGC 1378—a Milky Way-sized galaxy embedded in a giant low-surface brightness disc. arXiv:1908.11383v1 [astro-ph.GA]: arxiv.org/abs/1908.11383

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Sep 10, 2019
"The study found that the dark matter halo dominates the mass inside the giant LSB disc radius of UGC 1378. Moreover, the ratio of dark to luminous mass is close to 2.0 within the HSB part of the galaxy"

......if it's so "gas rich" how do they know this?

"We describe observations of UGC 1378, including deep spectroscopy with the Russian 6-m telescope and multi-band imaging with Binospec at the MMT," the astronomers wrote in the paper."

.......spectroscopy cannot reveal the presence of non- kinetic energy mass, that's right, it's the "gas" that the spectroscopy reveals to exist:

".... including high-surface brightness (HSB) pseudo-bulge and HSB disc with a bar, rings and spiral arms. Moreover, the observational campaign clearly reveal the presence of a gas-rich gLSB"

"the ratio of dark to luminous mass is close to 2.0 within the HSB part of the galaxy,"

......chuckle, chuckle, and how did they do a measurement on this ratio? They didn't, it was simply an insertion.

Sep 10, 2019
^^^^^^ Oh dear! Time to take your meds, janitor boy!

Sep 10, 2019
Features resemble two concentric coplanar rings, at radius r1 and at twice r1. It's a lot like Andromeda, at ~163 light-years across, the two ring sizes here are apparently also close to those seen in IR for Andromeda, the big difference seems to be Andromeda is brighter. It looks like the bar is having some trouble collapsing the inner ring at r1 but a faint "S"-shaped collapse-form there with the bar and inner ring seems to be developing. The outer ring seems to be gradually feeding into the inner ring.

Sep 10, 2019
"~163 light-years across"

I mean 163K light years. It's a pretty galaxy, but nothing particularly unusual, in my opinion.

Sep 10, 2019
^^^^^^ Oh dear! Time to take your meds, janitor boy!

Oh dear!
Janitor boy missed a turd.

Sep 10, 2019
"The study found that the dark matter halo dominates the mass inside the giant LSB disc radius of UGC 1378."

Oh dear! Even the Russian scientists have become contaminated by the Dark Matter aficionados who swear that Dark Matter exists when they STILL cannot find it, but ascribe its existence to an innocent "halo" that is more than likely just GAS PLASMA that is emitted by exploding Stars.

Sep 10, 2019
This comment has been removed by a moderator.

Sep 10, 2019
"The study found that the dark matter halo dominates the mass inside the giant LSB disc radius of UGC 1378."

Oh dear! Even the Russian scientists have become contaminated by the Dark Matter aficionados who swear that Dark Matter exists when they STILL cannot find it, but ascribe its existence to an innocent "halo" that is more than likely just GAS PLASMA that is emitted by exploding Stars.


And why are you commenting on things that you plainly don't understand?

Sep 10, 2019
And why are you commenting on things that you plainly don't understand?


Pop-Cosmology cosmic fairy dust fantasy cannot be understood, understand?

Sep 10, 2019
@Benni
I quote Benni "Pop-Cosmology cosmic fairy dust fantasy cannot be understood, understand? "

Not once have you ever given us a link to some research to support any of your claims. Not even your own research!

One link please or shut up please for the love of mankind.

Even CantDrive links his Thunderbolt EU crap. You never link anything.

Sep 10, 2019
@Benni
I'm surprised you even show yourself on these forums. You continually lose arguments on other threads and abandon them and then keep showing up on new threads. A great example is a recent thread on Solar Sails.

Sep 10, 2019
"The study found that the dark matter halo dominates the mass inside the giant LSB disc radius of UGC 1378."

Oh dear! Even the Russian scientists have become contaminated by the Dark Matter aficionados who swear that Dark Matter exists when they STILL cannot find it, but ascribe its existence to an innocent "halo" that is more than likely just GAS PLASMA that is emitted by exploding Stars.


And why are you commenting on things that you plainly don't understand?
says Castrovagina

I understand it far more than you think you do. I am here to disseminate any (but not all) information to help others understand the Universe and its workings better. You would do well to pay attention and stop griping.

Sep 10, 2019
@Benni
I quote Benni "Pop-Cosmology cosmic fairy dust fantasy cannot be understood, understand? "

Not once have you ever given us a link to some research to support any of your claims. Not even your own research!

One link please or shut up please for the love of mankind.

Even CantDrive links his Thunderbolt EU crap. You never link anything.
says jimmybobo

There are certain things that scientists haven't even begun to research, and yet are the things that make the Universe run well. Humans are relatively new around here, and only started hunting for the answers as to why, how, where, what, when and who. It will take them a very long time to find out all these answers. In the meantime, really GOOD scientists will welcome all reasonable alternatives to what they are in the process of looking into.
If you don't like reasonable alternatives that haven't made it into Physics textbooks yet, then you may be better off reading all the textbooks you can find instead.

Sep 11, 2019
"The study found that the dark matter halo dominates the mass inside the giant LSB disc radius of UGC 1378. Moreover, the ratio of dark to luminous mass is close to 2.0 within the HSB part of the galaxy"

......if it's so "gas rich" how do they know this?
Benni

What do you think how "gas rich" it is has to do with them able to estimate the dark to luminous mass ratio or whether dark matter halo dominates the mass? Explain your reasoning...

.......spectroscopy cannot reveal the presence of non-kinetic energy mass,
"non-kinetic energy mass"? What's that? Some made up crap you just made up? Please study and make sure you understand REAL physics, NOT your made-up hallucinate physics, before commenting on it. DON'T MAKE CRAP UP.

Sep 11, 2019
really GOOD scientists will welcome all reasonable alternatives to what they are in the process of looking into.
Surveillance_Egg_Unit

The problem here you don't recognize when there are NO reasonable alternative explinations (to something) when the scientific facts aren't to your liking, and you also present NO reasonable alternative explinations yourself, only idiotic ones.
I guess what you define as a "really GOOD scientists" are only those that support your ignorant opinions, which are unsupported by few if any scientists let alone the "really GOOD" ones.

Sep 11, 2019
Benni

The term "non-kinetic energy mass" might make sense in the narrow context of special relativity providing what you mean by that is simply "rest-mass". But that's not the context you used it in and you didn't say the correct term of "rest-mass" and thus that's not what you meant and its clear that, in the context you use it in, you obviously have no idea what you are talking about.

Sep 11, 2019
Surveillance_Egg_Unit

.... which are unsupported by few if any scientists let alone the "really GOOD" ones.

My above misedit;
"unsupported" should have been "supported"

Sep 11, 2019
If you don't like reasonable alternatives that haven't made it into Physics textbooks yet, then you may be better off reading all the textbooks you can find instead.


Alternatives that are not in textbooks will still be in scientific papers, conference abstracts (ever look at those?), etc. Your 'alternatives' are just the unscientific ramblings of an unbalanced mind. Of no interest, nor relevance.

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