Dust and cosmology

In article ,
David Staup writes:
The dust from red dwarf stars

If "red dwarf stars" means stars less than about one solar mass,
which is what I'd expect, such stars produce relatively little dust.
Was the term intended to mean something different?

must come from non hydrogen/helium
components of the matter that make up the star, where did that come from?

Stars relevant to the current discussion are "asymptotic giant branch
stars," which are evolved stars with cool atmospheres. Their initial
masses can be up to about 8 solar masses. They synthesize heavy
elements in their cores and mix them to the surface. One recent
article on modeling such stars is linked at
http://adsabs.harvard.edu/abs/2014MNRAS.439..977V

By the way, in dense environments, dust mantles can contain ices,
i.e., can include hydrogen. That is probably not relevant to dust in
high redshift galaxies observed at visible and near infrared
wavelengths but may be relevant to ALMA submillimeter observations.

Non- supernova stars do not create anything in the time frame under
discussion here ~ 600 million years

Stars near 8 solar masses will evolve through the AGB phase in about
1.5E8 years so can create dust on time scales relevant at fairly high
redshift.

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On 1/4/2016 7:46 PM, Steve Willner wrote:
In article ,
David Staup writes:
The dust from red dwarf stars

If "red dwarf stars" means stars less than about one solar mass,
which is what I'd expect, such stars produce relatively little dust.
Was the term intended to mean something different?

must come from non hydrogen/helium
components of the matter that make up the star, where did that come from?

Stars relevant to the current discussion are "asymptotic giant branch
stars," which are evolved stars with cool atmospheres. Their initial
masses can be up to about 8 solar masses. They synthesize heavy
elements in their cores and mix them to the surface. One recent
article on modeling such stars is linked at
http://adsabs.harvard.edu/abs/2014MNRAS.439..977V

By the way, in dense environments, dust mantles can contain ices,
i.e., can include hydrogen. That is probably not relevant to dust in
high redshift galaxies observed at visible and near infrared
wavelengths but may be relevant to ALMA submillimeter observations.

Non- supernova stars do not create anything in the time frame under
discussion here ~ 600 million years

Stars near 8 solar masses will evolve through the AGB phase in about
1.5E8 years so can create dust on time scales relevant at fairly high
redshift.

So quasars don't produce and distribute heavy elements?

With a lifespan of millions or even tens of millions of years, even with
a production rate far lower than super nova, the continuous production
of the quasar could account for a considerable percentage of the dust in
question

perhaps another question to ask is: If all the dust seen here is from
super nova over 600 million years, what must have been the rate of super
nova explosions to account for all the dust?

Le 05/01/2016 02:46, Steve Willner a écrit :
Stars relevant to the current discussion are "asymptotic giant branch
stars," which are evolved stars with cool atmospheres. Their initial
masses can be up to about 8 solar masses

Yes, there are many conceivable scenarios that could explain the dust.

There are MANY, yes.

But in galaxies, very massive stars are not the norm, rather less
massive stars are common.

A bang supposes:

Most of the stars in those galaxies were very massive but not quite so
that they would sink into a blackhole. Just the right size.



Yeah, but it was right after the bang, conditions were different, etc.

You can still try to save the old viewpoint by just one epicycle more...

In the article you cite we find:

quote
At Z = 8 ? 10-3 we find that the most massive stars produce dust masses
md ~ 0.01 M0, whereas models of smaller mass produce a dust mass 10
times smaller.
end quote

We need 100 of those rare and very massive stars to make a single solar
mass of dust...

Each time you look, there are problems, special conditions needed, the
theory becomes heavier and heavier with special "ad hoc" circumstances.

But this will not get very far: newer, more powerful scopes will end the
big bang in a few years.

[Mod. note: non-ASCII characters removed. Please do not use these -- mjh]

In article ,
David Staup writes:
So quasars don't produce and distribute heavy elements?

Not so far as is known. Furthermore, if the context is the early
universe, quasars are very rare.

With a lifespan of millions or even tens of millions of years, even with
a production rate far lower than super nova, the continuous production
of the quasar could account for a considerable percentage of the dust in
question

Are you confusing "dust" with "heavy elements?" The two are not
synonymous.

Many but not all quasars -- or more generally "active galactic
nuclei" or AGNs -- show evidence of dust being present, but I don't
think there's any evidence AGNs create dust. I'd expect them to
destroy it.

perhaps another question to ask is: If all the dust seen here is from
super nova over 600 million years, what must have been the rate of super
nova explosions to account for all the dust?

I don't know what "here" you mean, but answers for the early universe
are in papers already cited in this thread. The upshot seems to be
that dust formation in the interstellar medium is the most important
process, but there are substantial uncertainties (not least in the
mass of dust present).

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On 1/8/2016 3:01 AM, jacobnavia wrote:
[Mod. note: entire quoted article trimmed -- mjh]

This debate is tied directly to the mechanics of galaxy formation which
is currently under debate. Mounting evidence indicates formation of the
super massive black holes came first.

If that is the case then it would seem likely that quasar ignition would
follow providing for some dust and metal production and a shock wave to
promote star formation. The metalicity distribution of the bulge stars
would, it seems to me, be an indicator of just such a scenario. The
scarcity of quasars at this era may be a problem but maybe not. The rate
of galaxy formation may have been very low in the beginning and it may
just require an expanded survey.

Like you say, it's just a matter of time before we know.

In article ,
David Staup writes:
This debate is tied directly to the mechanics of galaxy formation which
is currently under debate.

I'm not sure enough is known to have any real debate.

Mounting evidence indicates formation of the
super massive black holes came first.

Could you please summarize that evidence?

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In article ,
jacobnavia writes:
At Z = 8 ? 10-3 we find that the most massive stars produce dust masses
md ~ 0.01 M0, whereas models of smaller mass produce a dust mass 10
times smaller.
end quote

We need 100 of those rare and very massive stars to make a single solar
mass of dust...

The argument needs to be quantitative to have any force. For a
galaxy of typical mass, assume an IMF and star formation history.
Then how many AGB stars have formed, and how much dust did they
create? How does that compare with a typical dust mass?

My quick estimate -- not a careful calculation -- suggests that AGB
stars probably aren't important creators of dust in the early
universe. That's what the papers cited in this thread have said: the
important creators are the interstellar medium and supernovae,
probably in that order.

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Help keep our newsgroup healthy; please don't feed the trolls.
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On 1/11/2016 4:12 PM, Steve Willner wrote:
In article ,
David Staup writes:
This debate is tied directly to the mechanics of galaxy formation which
is currently under debate.

I'm not sure enough is known to have any real debate.

Mounting evidence indicates formation of the
super massive black holes came first.

Could you please summarize that evidence?


Dwarf galaxies with super massive black holes

THE GIST

A Hubble Space Telescope study shows even small dwarf galaxies can have
big black holes.

The discovery challenges currently held theories of galaxy formation and
black hole growth.

Dwarf galaxies with massive black holes may be forerunners of galaxies
like our own Milky Way.

The relationship between a galaxy and its black hole is as mystifying as
any of those found among families on Earth.

Scientists don't even know which came first -- galaxies or their black
holes, those regions of space so dense with matter that even photons of
light fall prey to their gravitational jaws.


I also suspect Hot DOGs, Hot dust-obscured galaxies, probably fit in
this discussion also.