The rprocess: OK to go on to other things

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The First Stars and the GMT Chris
Sneden University of Texas at Austin
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Focus on the chemical compositions of low
metallicity starsFrom the GMT Science
Documents
?
?
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No problem on targets Sloan data for halo stars
Carollo et al. 2007
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Sloan data (and others) shows structured halo
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Halo birth simulations are now producing
spectroscopic simulations
Halo formation and chemical evolution
concentrating on the influence of Very massive
pair instability SNe Karlsson et al. 2007
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Checking these predictions is difficult without
high-res spectroscopy
Upper panel total evolution in Fe/Ca
Lower panel Fe/Ca if pair instability SNe
dominate in early Galaxy
Karlsson et al. 2007 points are literature
observations
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Fe-peak abundances mainly/only come from high-res
at lowest Fe/H
Aoki et al. 2006
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IF first remaining stars are outer halo, then
must push fainter than current V15ish limit
V15? Informal survey of low metallicity high
res papers
About 2 mag gain at most, if I understand this?
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Huge low-res data sets coming
Lee et al. 2008
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And they can say some things about low
metallicity chemical compositions
Lee et al. 2008
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But high resolution is essential for some issues
CS 22892-052 C-rich AND r-process-rich
R 2,000
R 2,000
R 45,000
Sneden, Cowan, Gallino 2008
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Low metallicity stars provide information about
neutron-capture processes
Sneden, Cowan, Gallino 2008
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The r-process OK to go on to other things?
Sneden, Cowan, Gallino 2008
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Must keep pursuing Th and U
Frebel et al. 2007
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s-rich lead stars global abundance solutions
Sneden, Cowan, Gallino 2008
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General n-capture trends well defined for stars
with Fe/H lt -2
But what are these stars?
Sneden, Cowan, Gallino 2008
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Intriguing new targets low metallicity
spectroscopic binaries example 1
CS 22964-161
Thompson et al. 2008
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BOTH stars have s-process enhancements
(and lithium)
Thompson et al. 2008
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Low metallicity binaries,example 2
Gonzalez Hernandez et al. 2008
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Careful switch in observable features as
metallicity declines oxygen
Gonzalez Hernandez et al. 2008
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More generally of interest to halo chemical
evolution significant scatter in the ? elements?
Sneden Lawler 2008
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One recent update on a elements
Cohen et al. 2007
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Sometimes radical ? element differences
Sneden Lawler 2008
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Sometimes however a worry
Sneden Lawler 2008
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Beware of simple analyses of simple atomic
structures need contributions from all!
Nearly all of these abundances are from the 3905A
line
Sneden Lawler 2008
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New approaches to high resolution chemical
composition studies integrated light
McWilliam et al 2008
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Tests on nearby globular clusters
Figuring out where the light comes from
Evolutionary bin definitions
McWilliam et al 2008
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New approaches to high resolution chemical
composition studies moderately high R, weak S/N,
multi-star
(and here, red wavelengths only)
Kirby et al. 2008
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Works generally well
(Spectral lines become too weak)
Kirby et al. 2008
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And generally recovers the known ? abundances
New abundances compared to literature high-res
results
Kirby et al. 2008
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In short
The future successes in abundance work at lowest
metallicities depends on high resolution
spectrographs for the next generation telescopes,
and clever applications of the received data
some visual l high-res (Q-Spec) should be among
the first-light instruments for the GMT
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