Astronomers discover new quiescent galaxy | Hacker News Reader

Astronomers discover new quiescent galaxy

phys.org

58 pointswglb20 comments

If, like me, you’re wondering what quiescent means in the context of a galaxy, it means it isn’t making any new stars:

The observations found that COSMOS-1047519 has a mass of about 60 billion solar masses and a star-formation rate (SFR) at a level of only 10 solar masses per year. The galaxy's stellar age is estimated to be 180 million years.

Trying to find the physical processes responsible for the suppression of star formation in COSMOS-1047519, the authors of the paper propose the most plausible hypothesis.

"These findings suggest that gas depletion due to the starburst and/or AGN feedback triggered by galaxy-galaxy interactions or mergers may be responsible for quenching,"

Thank you for the explanation

Amazing how at a certain distance, a galaxy starts looking a lot like a living organism

Same for planets, or at least what astronauts say about Earth after seeing it from space

That's probably because they all share the same quality of being a large system whose behavior results from the emergent correlated behavior of much smaller parts.

True, and maybe we could say this about almost anything in the Universe

Even just a single cell is made up of millions of smaller particles, all moving around

Everything is always either forming/growing or decaying

TIL how cosmologists tactfully say "murder." Another galaxy murdered this one.

Yowza.

I've been spelunking in this area recently and have been surprised to find there's still a lot unknown in star formation

Most surprisingly, it seems there's a formal paradox in the thermodynamics of self-gravitating systems. As Piet Hut (of Barnes-Hut fame) at the IAS says:

"A thermodynamic treatment of self-gravitating systems is fraught with peril: from a formal point of view, it cannot even be defined, because there is no thermodynamic limit." - Hut, Gravitational Thermodynamics [1]

Also surprising, thanks to JWST, we can now see clearly into the center of the Milky Way, and there's CO ice![2] Probably more types, but JSWT doesn't have the instrument for this.

This is related because that means it's colder than expected, but also quite full of gas (that was obscuring our view until JWST and near microwave). But cold dense gas should collapse to form stars, and we're not seeing nearly what we should.

Both suggest we're missing something about the grav/thermo relationship, and what's called the Jeans Mass[3]. If you go digging, you'll find our Sun should have taken a planetary nebula about 20x larger than what we have. This in turns suggests that simple static models are maybe misleading, as there's usually dynamics almost everywhere we see large gas clouds. And then this in turn begs the question of why gravitational collapse is needed if there's already large kinetic flows involved, slamming mass together.

Anyways, I'm a total amateur and quite possibly have all this wrong. Just dropping in case anyone's interested!

[1] https://www.ias.edu/ids/~piet/act/phys/thermo

[2] https://www.youtube.com/watch?v=rKG9PIrQnnM

[3] https://en.wikipedia.org/wiki/Jeans_instability

Just a quick note to say that JWST is not the first telescope to give us these kinds of views! There are numerous others, SOFIA, IRAS, IRTF, and Alma to name a just a few.

Ah thanks! They mention Alma in the interview.

Maybe the specific claim was that wavelength at a resolution good enough to resolve individual stars, or a star per pixel often enough

Yeah it can be easy to forget but thermodynamics technically only aplies to whole systems at equilibrium. Which a star which constantly produces energy through fission is not.

In most circumstances we get away with it, allowing us to assign temperatures to small objects or even locations in space but it's not surprising that these laws stop working at the extremes.

I feel like Lynden-Bell did a lot of work on this.

Thanks for the reference

I wonder how such galaxies will look like in few billion years (or actually look like now) when current gen stars will burn out - everything circling quasar in the center are mostly red dwarves, with some rare neutron stars and black holes sprinkled here and there.

Not much to see on visible spectrum compared to usual galaxies, other spectra will look better (but still probably quite faint).

And are there such invisible former galaxies out there now?

The observable universe probably isn’t old enough for that. If you don’t restrict “out there” to our past light cone, and/or assume the cosmological multiverse, then there certainly may be.

Why won't they see another generation of star formation when supernovae push gases into dense regions again? It seems like the stage you're talking about is more than a few billion years away (more like 10s of billions).

"Massive galaxies that stopped forming stars (known as massive quiescent galaxies) are plausible progenitors of giant elliptical galaxies."

Could someone explain a bit more what this means? Is it that those galaxies were "born" out of the quiet galaxies, or shaped into ellipses because of them?

Not an expert, but here is my understanding: Elliptical galaxies are typically quiescent (and spiral galaxies aren’t). The “massive” quiescent galaxies observed in the early universe are however smaller than the “giant” elliptical galaxies observed in the more recent universe. It is assumed that the latter evolved from the former, most likely by merging with other galaxies. This question of how exactly they evolve(d) is the subject of continued research.

More generally, see also https://en.wikipedia.org/wiki/Galaxy_formation_and_evolution.

A "progenitor" is an ancestor; it means that the quiescent galaxy "plausibly" turns into an elliptical galaxy.

In this case precursor might be more precise than ancestor.

Agreed; I knew there was something wrong with "ancestor" when I typed it.

[Edit] A progenitor is literally an ancestor; I answered GP's question. It's "progenitor" that should instead be "precursor", in the featured article.

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