Nearby galaxy is a “fossil” from the early universe

Nearby galaxy is a “fossil” from the early universe | Astronomy.com
http://www.astronomy.com/news/2014/0...early-universe

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In article ,
Yousuf Khan writes:
Nearby galaxy is a fossil from the early universe | Astronomy.com

Article is by Frebel, Simon, & Kirby, 2014 ApJ 786, 74:
http://iopscience.iop.org/0004-637X/786/1/74/article

There's a preprint at
http://arxiv.org/abs/1403.6116

The galaxy is tiny, apparently having only seven red giant stars in
it altogether. Three of them iron abundances less than 1/3000 solar,
and the pattern of metal abundances seems to indicate enrichment by
massive star SNe but no Type 1a's. Fascinating stuff.

Final sentence of Abstract is "Altogether, the chemical abundances of
Segue 1 indicate no substantial chemical evolution, supporting the
idea that it may be a surviving first galaxy that experienced only
one burst of star formation."

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On 06/05/2014 1:14 PM, Steve Willner wrote:
[Subject line repaired. Please be careful when cutting and pasting
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In article ,
Yousuf Khan writes:
Nearby galaxy is a fossil from the early universe | Astronomy.com

Article is by Frebel, Simon, & Kirby, 2014 ApJ 786, 74:
http://iopscience.iop.org/0004-637X/786/1/74/article

There's a preprint at
http://arxiv.org/abs/1403.6116

The galaxy is tiny, apparently having only seven red giant stars in
it altogether. Three of them iron abundances less than 1/3000 solar,
and the pattern of metal abundances seems to indicate enrichment by
massive star SNe but no Type 1a's. Fascinating stuff.

What sort of unique ingredients do Type Ia's populate rather than any
other type of supernova?

With only a few thousand stars, it's smaller than some star clusters,
isn't it?

Yousuf Khan

On Friday, May 9, 2014 6:18:09 PM UTC-7, Yousuf Khan wrote:

What sort of unique ingredients do Type Ia's populate rather than any

other type of supernova?

Here you go...

http://hyperphysics.phy-astr.gsu.edu...ro/snovcn.html

http://imagine.gsfc.nasa.gov/docs/sc...upernovae.html

On 10/05/2014 12:47 AM, palsing wrote:
On Friday, May 9, 2014 6:18:09 PM UTC-7, Yousuf Khan wrote:

What sort of unique ingredients do Type Ia's populate rather than any

other type of supernova?

Here you go...

http://hyperphysics.phy-astr.gsu.edu...ro/snovcn.html

http://imagine.gsfc.nasa.gov/docs/sc...upernovae.html

Good links, but it really doesn't answer the question of what
ingredients each type of supernova should be expected to populate the
interstellar medium with. Although I guess Type I vs. II means whether
there's plenty of hydrogen or not. But I'm assuming a gas cloud from
which new stars are born, are already filled with plenty of hydrogen, so
I don't see how the hydrogen of a Type II might significantly affect the
composition of gas cloud.

Yousuf Khan

In article ,
Yousuf Khan writes:
What sort of unique ingredients do Type Ia's populate rather than any
other type of supernova?

I'm not an expert on this, but as far as I can gather: supermassive
Pop III stars (no longer present) produce predominantly alpha
elements, massive core collapse SNe are needed to produce r-process
elements
http://en.wikipedia.org/wiki/R-process
and thermal runaway (basically Type Ia) SNe produce predominantly
iron group elements. (The Wikipedia article looks basically
accurate, but I don't vouch for everything in it.) These statements
should be taken as generalities, not exact. Probably all SNe produce
a little bit of everything, but the proportions vary.

With only a few thousand stars, [Segue 1 is] smaller than some star
clusters, isn't it?

Indeed. One article at
http://iopscience.iop.org/1538-3881/144/1/4/article
says the galaxy produces less than 1000 solar luminosities of light,
but the mass to light ratio is probably much greater than 1. The
dynamical mass is a few hundred thousand solar masses. Pinning down
better values would take more work, and the actual mass is probably
highly uncertain.

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On 15/05/2014 5:58 PM, Steve Willner wrote:
I'm not an expert on this, but as far as I can gather: supermassive
Pop III stars (no longer present) produce predominantly alpha
elements, massive core collapse SNe are needed to produce r-process
elements
http://en.wikipedia.org/wiki/R-process

Are you saying the original Pop III stars only produced Alpha particles
(i.e. Helium) when they exploded?

and thermal runaway (basically Type Ia) SNe produce predominantly
iron group elements. (The Wikipedia article looks basically
accurate, but I don't vouch for everything in it.) These statements
should be taken as generalities, not exact. Probably all SNe produce
a little bit of everything, but the proportions vary.

So R-process supernovas would have produced more heavier-than-iron
elements, while Type Ia supernovas would have produced mostly iron?

Yousuf Khan

On 15/05/2014 5:58 PM, Steve Willner wrote:
I'm not an expert on this, but as far as I can gather: supermassive
Pop III stars (no longer present) produce predominantly alpha
elements, massive core collapse SNe are needed to produce r-process
elements
http://en.wikipedia.org/wiki/R-process

In article ,
Yousuf Khan writes:
Are you saying the original Pop III stars only produced Alpha particles
(i.e. Helium) when they exploded?

Alpha _elements_ are those with even atomic numbers and atomic masses
a multiple of four: carbon, oxygen, magnesium, etc.

So R-process supernovas would have produced more heavier-than-iron
elements, while Type Ia supernovas would have produced mostly iron?

As I wrote, I'm not an expert and haven't looked up the proper
numbers. I gather, however, that the Ia fail to produce much of
anything beyond the iron group, whereas the core collapse SNe produce
R-process elements in addition to the iron group. I'd be surprised
if they produce a total amount of R-process elements anywhere near
amount of iron they produce, but the proportion is higher.

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