#galaxies

rhysy@diaspora.glasswings.com

Okay, this is the point where I hit the "unsubscribe" button. I've never been a big fan of Sabine but recent videos just make me think she's really losing it. I was going to do a write-up on the "bullshit research" video ("Science is in trouble and it worries me") but decided not to bother, because I suspect it itself is bullshit... most research is worthless, eh ? Humanity's technological progress has stalled ? That fits the "everyone is wrong except me" vibe I've been getting for a long time.

This video is a typical example of terrible outreach. It amounts to little more than "look at these very complicated graphs and take my word for it that I've explained it correctly". It's nonsense to expect the general public to have a proper understanding of what's being shown in the figures in the space of a few seconds, let alone any kind of background in who the groups making the opposing claims actually are.

Now I've not read the particular papers cited here, though I have read many by the same groups along similar lines. Also, unlike Sabine, I'm an observer, not a theoretical physicist. And though I don't research this particular bit of cosmology myself, I do go to conferences and listen to other observers who do. Lo and behold, the observational errors in this are huge - by some estimates, three orders of magnitude. Claiming anything here has been "falsified" is the worst sort of clickbait, the kind that isn't even remotely accurate, even without adding in the myriad of other factors from other observations. And that's without factoring in the MOND group's relentless tendency to cheerfully ignore an endless number of perfectly legitimate objections and their overwhelming tendency to play the "oh woe is me, I'm ostracised from the scientific community for heresy !" card for all it's worth.

The root of it, if there is one, is a belief from the MOND crew that everything must be dominated by gravity and actually very simple. Everything. The opposing view is that no, gravity is but just one factor and baryons have a lot more complicated physics than that, so our observations are hugely biased because we don't observe gravity directly. A while back I did a write-up saying the two are basically philosophically equally valid; nowadays I'm leaning very much more against MOND. Maybe I'm just bitter.

#Science
#Astronomy
#Galaxies
#DarkMatter

https://youtu.be/AagyRrIm2W0?si=VhPwNvO8msXNu7aF

waynerad@diasp.org

The mystery of the possible Dyson spheres may be solved. First, a quick reminder on what Dyson spheres are:

"In their need for more powerful energy sources, an advanced civilization might harness the entire output of a star. They wrap a star within a sphere to capture every last photon of stellar energy. Such an object would have a strange infrared or radio spectrum. An alien glow that is faint and unique. So astronomers have searched for Dyson spheres in the Milky Way, and have found some interesting candidates."

Next the possible Dyson spheres:

"One major search was known as Project Hephaistos, which used data from Gaia, 2MASS, and WISE to look at five million candidate objects. From this they found seven unusual objects. They appear to be M-type red dwarfs at first glance, but have spectra that don't resemble simple stars. This kind of star-like infrared object is exactly what you'd expect from a Dyson sphere. But of course extraordinary claims require extraordinary evidence, and that's where things get fuzzy."

And how the mystery is solved (probably):

"Almost immediately after the paper was published, other astronomers noted that the seven objects could also be hot Dust-Obscured Galaxies, or hotDOGs. These are quasars, so they appear star-like, but are obscured by such a tremendous amount of dust that they mostly emit in the infrared."

So there you have it. Not Dyson spheres, hotDOGs.

Click through if you want to get the paper with all the details of what spectral bands were analyzed and how they were interpreted.

Those Aren't Dyson Spheres, They're HotDOGs

#astronomy #dysonspheres #gaia #2mass #wise #galaxies

rhysy@diaspora.glasswings.com

And now, my selected science highlights of EAS 2024. Featuring :
- Why Euclid is awesome
- Why results from JWST about giant early galaxies are a concern for cosmology but no more than that
- How there are probably no dark galaxies
- The mystery of why we aren't seeing gas accretion even though we know it happens
- Weird radio halos
- Weird galaxies that might lead to substantial revisions in out theory of dark matter, and maybe even rule out modified gravity models.

#Science
#Astronomy
#Galaxies
#Astrophysics

https://llittlephysicists.blogspot.com/2024/07/eas-2024.html

rhysy@diaspora.glasswings.com

On a population of galaxies that quench backwards. That is, whereas the central regions usually use up all their gas first, in these ones the disc is dead but the bulge lives on. This is not so unusual in clusters, where ram pressure preferentially removes the outer gas first... but these galaxies aren't in clusters. How does this work, them ? Nobody knows, but they've got some ideas.

#Science
#Astronomy
#Astrophysics
#Galaxies

https://llittlephysicists.blogspot.com/2024/06/the-galaxies-that-quenched-backwards.html

rhysy@diaspora.glasswings.com

Apparently, all early-type galaxies are forming stars after all - not many, but some : they're red but not quite dead. This had been suspected rather strongly before but here the confirmation looks quite decisive. Caveats are that there's a whopping great extrapolation in the paper and they don't comment on gas content or environment, but it's still a nice piece of work.

#Science
#Astrophysics
#Galaxies

https://llittlephysicists.blogspot.com/2024/05/red-not-dead-but-who-knows-how-well-fed.html

rhysy@diaspora.glasswings.com

On a weird paper claiming to have found a sample of very red, gas-rich galaxies not forming stars. In the original draft (which I'd downloaded some months ago) they didn't have any images of their sample, but presented a very nice narrative of how these were definitely very strange objects. But when I checked the images manually, which they now include in an appendix in the final version, many of them look like normal spiral galaxies. With great big blue spiral arms, it's very difficult to believe they really have unusual low levels of star formation. You just don't get blue structures like this without forming stars. For sure the central regions may be quenched, but surely not the whole galaxy as they claim.

I should probably try and read the new version but I just don't want to.

#Science
#Space
#Galaxies
#Astrophysics

https://llittlephysicists.blogspot.com/2024/05/red-dead-but-very-well-fed.html

rhysy@diaspora.glasswings.com

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

rhysy@diaspora.glasswings.com

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

rhysy@diaspora.glasswings.com

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