Advanced

First stars V - Abundance patterns from C to Zn and supernova yields in the early Galaxy

Cayrel, R.; Depagne, E.; Spite, M.; Hill, V.; Spite, F.; François, P.; Plez, B.; Beers, T.; Primas, F. and Andersen, J., et al. (2004) In Astronomy & Astrophysics 416(3). p.1117-1138
Abstract
In the framework of the ESO Large Programme ``First Stars'', veryhigh-quality spectra of some 70 very metal-poor dwarfs and giants wereobtained with the ESO VLT and UVES spectrograph. These stars are likelyto have descended from the first generation(s) of stars formed after theBig Bang, and their detailed composition provides constraints on issuessuch as the nature of the first supernovae, the efficiency of mixingprocesses in the early Galaxy, the formation and evolution of the haloof the Galaxy, and the possible sources of reionization of the Universe.This paper presents the abundance analysis of an homogeneous sample of35 giants selected from the HK survey of Beers et al. (cite{BPS92},cite{Be99}), emphasizing stars of extremely low... (More)
In the framework of the ESO Large Programme ``First Stars'', veryhigh-quality spectra of some 70 very metal-poor dwarfs and giants wereobtained with the ESO VLT and UVES spectrograph. These stars are likelyto have descended from the first generation(s) of stars formed after theBig Bang, and their detailed composition provides constraints on issuessuch as the nature of the first supernovae, the efficiency of mixingprocesses in the early Galaxy, the formation and evolution of the haloof the Galaxy, and the possible sources of reionization of the Universe.This paper presents the abundance analysis of an homogeneous sample of35 giants selected from the HK survey of Beers et al. (cite{BPS92},cite{Be99}), emphasizing stars of extremely low metallicity: 30 of our35 stars are in the range -4.1 <[Fe/H]< -2.7, and 22 stars have[Fe/H] < -3.0. Our new VLT/UVES spectra, at a resolving power ofR∼45 000 and with signal-to-noise ratios of 100-200 per pixel overthe wavelength range 330-1000 nm, are greatly superior to those of theclassic studies of McWilliam et al. (cite{MPS95}) and Ryan et al.(cite{RNB96}).The immediate objective of the work is to determine precise,comprehensive, and homogeneous element abundances for this large sampleof the most metal-poor giants presently known. In the analysis wecombine the spectral line modeling code ``Turbospectrum'' with OSMARCSmodel atmospheres, which treat continuum scattering correctly and thusallow proper interpretation of the blue regions of the spectra, wherescattering becomes important relative to continuous absorption (λ< 400 nm). We obtain detailed information on the trends of elementalabundance ratios and the star-to-star scatter around those trends,enabling us to separate the relative contributions of cosmic scatter andobservational/analysis errors.Abundances of 17 elements from C to Zn have been measured in all stars,including K and Zn, which have not previously been detected in starswith [Fe/H] < -3.0. Among the key results, we discuss the oxygenabundance (from the forbidden [OI] line), the different and sometimescomplex trends of the abundance ratios with metallicity, the very tightrelationship between the abundances of certain elements (e.g., Fe andCr), and the high [Zn/Fe] ratio in the most metal-poor stars. Within theerror bars, the trends of the abundance ratios with metallicity areconsistent with those found in earlier literature, but in many cases thescatter around the average trends is much smaller than found in earlierstudies, which were limited to lower-quality spectra. We find that thecosmic scatter in several element ratios may be as low as 0.05 dex.The evolution of the abundance trends and scatter with decliningmetallicity provides strong constraints on the yields of the firstsupernovae and their mixing into the early ISM. The abundance ratiosfound in our sample do not match the predicted yields frompair-instability hypernovae, but are consistent with element productionby supernovae with progenitor masses up to 100 M<SUB>⊙</SUB>.Moreover, the composition of the ejecta that have enriched the matterBased on observations obtained in the frame of the ESO programme ID165.N-0276(A).Full Tables 3 and 8 are available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/416/1117 This work hasmade use of the SIMBAD database. (Less)
Please use this url to cite or link to this publication:
author
, et al. (More)
(Less)
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Astronomy & Astrophysics
volume
416
issue
3
pages
1117 - 1138
publisher
EDP Sciences
external identifiers
  • wos:000220661900033
  • scopus:7544220293
ISSN
0004-6361
DOI
10.1051/0004-6361:20034074
language
English
LU publication?
yes
id
707be606-72bd-4d41-b9d0-cad0936c0daa (old id 134181)
date added to LUP
2007-07-12 15:39:40
date last changed
2017-12-10 04:33:19
@article{707be606-72bd-4d41-b9d0-cad0936c0daa,
  abstract     = {In the framework of the ESO Large Programme ``First Stars'', veryhigh-quality spectra of some 70 very metal-poor dwarfs and giants wereobtained with the ESO VLT and UVES spectrograph. These stars are likelyto have descended from the first generation(s) of stars formed after theBig Bang, and their detailed composition provides constraints on issuessuch as the nature of the first supernovae, the efficiency of mixingprocesses in the early Galaxy, the formation and evolution of the haloof the Galaxy, and the possible sources of reionization of the Universe.This paper presents the abundance analysis of an homogeneous sample of35 giants selected from the HK survey of Beers et al. (cite{BPS92},cite{Be99}), emphasizing stars of extremely low metallicity: 30 of our35 stars are in the range -4.1 &lt;[Fe/H]&lt; -2.7, and 22 stars have[Fe/H] &lt; -3.0. Our new VLT/UVES spectra, at a resolving power ofR∼45 000 and with signal-to-noise ratios of 100-200 per pixel overthe wavelength range 330-1000 nm, are greatly superior to those of theclassic studies of McWilliam et al. (cite{MPS95}) and Ryan et al.(cite{RNB96}).The immediate objective of the work is to determine precise,comprehensive, and homogeneous element abundances for this large sampleof the most metal-poor giants presently known. In the analysis wecombine the spectral line modeling code ``Turbospectrum'' with OSMARCSmodel atmospheres, which treat continuum scattering correctly and thusallow proper interpretation of the blue regions of the spectra, wherescattering becomes important relative to continuous absorption (λ&lt; 400 nm). We obtain detailed information on the trends of elementalabundance ratios and the star-to-star scatter around those trends,enabling us to separate the relative contributions of cosmic scatter andobservational/analysis errors.Abundances of 17 elements from C to Zn have been measured in all stars,including K and Zn, which have not previously been detected in starswith [Fe/H] &lt; -3.0. Among the key results, we discuss the oxygenabundance (from the forbidden [OI] line), the different and sometimescomplex trends of the abundance ratios with metallicity, the very tightrelationship between the abundances of certain elements (e.g., Fe andCr), and the high [Zn/Fe] ratio in the most metal-poor stars. Within theerror bars, the trends of the abundance ratios with metallicity areconsistent with those found in earlier literature, but in many cases thescatter around the average trends is much smaller than found in earlierstudies, which were limited to lower-quality spectra. We find that thecosmic scatter in several element ratios may be as low as 0.05 dex.The evolution of the abundance trends and scatter with decliningmetallicity provides strong constraints on the yields of the firstsupernovae and their mixing into the early ISM. The abundance ratiosfound in our sample do not match the predicted yields frompair-instability hypernovae, but are consistent with element productionby supernovae with progenitor masses up to 100 M&lt;SUB&gt;⊙&lt;/SUB&gt;.Moreover, the composition of the ejecta that have enriched the matterBased on observations obtained in the frame of the ESO programme ID165.N-0276(A).Full Tables 3 and 8 are available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/416/1117 This work hasmade use of the SIMBAD database.},
  author       = {Cayrel, R. and Depagne, E. and Spite, M. and Hill, V. and Spite, F. and François, P. and Plez, B. and Beers, T. and Primas, F. and Andersen, J. and Barbuy, B. and Bonifacio, P. and Molaro, P. and Nordström, Birgitta},
  issn         = {0004-6361},
  language     = {eng},
  number       = {3},
  pages        = {1117--1138},
  publisher    = {EDP Sciences},
  series       = {Astronomy & Astrophysics},
  title        = {First stars V - Abundance patterns from C to Zn and supernova yields in the early Galaxy},
  url          = {http://dx.doi.org/10.1051/0004-6361:20034074},
  volume       = {416},
  year         = {2004},
}