#galaxies
On arXiv today, a very nice paper shows that one of the largest optically dark gas clouds isn't quite optically dark after all : it has at least one small patch of very new star formation. It's optically pathetic but the data is good enough that it's definitely real. This has implications for the formation of the cloud itself, which now looks more likely to be the result of ram pressure stripping from one of the galaxies in the vicinity. Many questions still remain, however, not least as to why only a very small part of the cloud is forming stars and why it's apparently only just started doing so.
#Science
#Astronomy
#Astrophysics
#Galaxies
https://llittlephysicists.blogspot.com/2024/02/taking-galactic-paternity-test.html
#AM1054: #Stars Form as #Galaxies Collide
#Astronomy #Picture of the Day
Another strange isolated dark matter-dominated galaxy. Fun times, but a bit much to reach for new physics here.
#Science
#Astrophysics
#Space
#Galaxies
https://llittlephysicists.blogspot.com/2024/02/another-one-for-collection.html
Do galaxies in the early Universe with declining rotation curves count as evidence against dark matter ? My Master's project supervisor from back in the day thinks so. Haven't seen in him years so it's good to know he's still active, but I don't agree with the speculations here. This latest paper simply doesn't present a fair comparison between simulations and observations; there are anyway too many variables at work to draw any conclusions without trying much harder to disentangle everything.
#Science
#Galaxies
#Astronomy
#Physics
https://llittlephysicists.blogspot.com/2024/01/no-stacks-please-were-simulationists.html
A look at dark galaxies from a theoretical perspective. What keeps dark matter halos from lighting up ? Nothing fancy, say the authors, just a combination of isolation, spin, and low mass. Ho-hum. All well and good, but their lack of any distinct comparison with observations is a mite frustrating.
#Science
#Astronomy
#Astrophysics
#Galaxies
https://llittlephysicists.blogspot.com/2024/01/theoretically-dark.html
Ooh, look I read another paper. Hurrah !
This one is about an incredibly, superlatively faint galaxy discovered back in 2018 that I'd forgotten about completely. Here the authors use Hubble observations to rule out an old stellar population - it only has young stars. This most likely means it's a tidal dwarf, having just recently formed due to tidal interactions but not likely to last long.
#Science
#Astronomy
#Space
#Galaxies
https://llittlephysicists.blogspot.com/2024/01/the-faintest-galaxy-is-getting-even.html
Another interesting result from the AAS. Extended UV discs were a hot topic back in 2008 but haven't had much attention since, so it's nice to see them back again.
The weird thing is that some galaxies, about a third of all spirals if I remember rightly, have young stars found well beyond their main stellar disc. That's strange because there's not much gas out there so not scope for star formation, and if they've migrated from the inner disc then it's weird that there aren't older stars as well.
Now it looks like star formation is indeed happening in these regions, but the molecular clouds are especially small and the conversion from atomic to molecular gas is inefficient. Why ? No idea ! Maybe the final publication will have more answers...
Three #Galaxies and a #Comet
#Astronomy #Picture of the Day
The #Fornax #Cluster of #Galaxies
#Astronomy #Picture of the Day
Too many serious papers of late. Time for something controversial and daft.
https://llittlephysicists.blogspot.com/2023/11/el-gordo-plays-ping-pong.html
On a nice little paper that demonstrates pretty damn unequivocally that galaxies lose their gas in groups as well as clusters. This has been long suspected but this demonstrates that this "pre-processing" happens pretty much ubiquitously. It's really quite satisfying to see a trend as clear as this, most of the time things are a lot messier.
https://llittlephysicists.blogspot.com/2023/10/you-should-have-gone-before-we-came-out.html
Another day, another paper. Still eeking out posts from my recent reading binge. This one is a disappointingly weird one looking at so-called "green pea" galaxies, which are highly compact and... green. And they also have lots of gas and form stars like nobody's business. The authors attempt to figure out exactly how the atomic gas correlates with the star formation rate, but don't.
https://llittlephysicists.blogspot.com/2023/10/do-legumes-give-galaxies-gas.html
A short paper that says while galaxies molecular gas has been declining since the peak of star formation, their atomic mass has actually kept growing. So somehow their star formation activity is becoming ever-less efficient. Annoyingly, they don't bother to speculate as to what might be causing this though.
#Science
#Astronomy
#Galaxies
#Astrophysics
https://llittlephysicists.blogspot.com/2023/10/its-gotta-come-from-somewhere.html
More confirmation that those galaxies without dark matter really don't have any, this time with extreme precision. And though they don't make a big song and dance about it, it seems that this is also incompatible with MOND : the authors made a similar claim previously and got rebuked for not doing this properly, so I trust they've correct that this time. We'll see.
https://llittlephysicists.blogspot.com/2023/10/dotting-is-and-crossing-out-dark-matter.html
Another paper about Ultra Diffuse Galaxies, haven't read one of those in a while. I'm a bit disappointed that an ostensibly HI-based paper is actually all about optical scaling relations, and with only one HI-UDG detection there's really not much they can say about it. Still, the target field itself - a "supergroup" - is a pretty interesting place, with not many galaxies but somehow enough hot X-ray gas to strip the HI. That's not at all typical for groups this small.
#Science
#Astronomy
#Galaxies
#Astrophysics
https://llittlephysicists.blogspot.com/2023/10/is-it-group-is-it-cluster-no-its.html
