The stellar content of the Hamburg/ESO survey - V. The metallicity distribution function of the Galactic halo

By T. Schorck, N. Christlieb, J. Cohen, Timothy C. Beers, S. Shectman, I. Thompson, A. McWilliam, M. Bessell, J. Norris, Jorge Meléndez and 15 more. 2008

139 citations recorded by the source corpus.

We determine the metallicity distribution function (MDF) of the Galactic halo by means of a sample of 1638 metal-poor stars selected from the Hamburg/ESO objective-prism survey (HES). The sample was corrected for minor biases introduced by the strategy for spectroscopic follow-up observations of the metal-poor candidates, namely "best and brightest stars first". Comparison of the metallicities [Fe/H] of the stars determined from moderate-resolution (i.e., R similar to 2000) follow-up spectra with results derived from abundance analyses based on high-resolution spectra (i.e., R > 20 000) shows that the [Fe/H] estimates used for the determination of the halo MDF are accurate to within 0.3 dex, once highly C-rich stars are eliminated. We determined the selection function of the HES, which must be taken into account for a proper comparison between the HES MDF with MDFs of other stellar populations or those predicted by models of Galactic chemical evolution. The latter show a reasonable agreement with the overall shape of the HES MDF for [Fe/H] > -3.6, but only a model of Salvadori et al. (2007) with a critical metallicity for low-mass star formation of Z(cr) = 10(-3.4) Z(circle dot) reproduces the sharp drop at [Fe/H] similar to -3.6 present in the HES MDF. Although currently about ten stars at [Fe/H] < -3.6 are known, the evidence for the existence of a tail of the halo MDF extending to [Fe/H] similar to -5.5 is weak from the sample considered in this paper, because it only includes two stars [Fe/H] < -3.6. Therefore, a comparison with theoretical models has to await larger statistically complete and unbiased samples. A comparison of the MDF of Galactic globular clusters and of dSph satellites to the Galaxy shows qualitative agreement with the halo MDF, derived from the HES, once the selection function of the latter is included. However, statistical tests show that the differences between these are still highly significant.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/0a903cdbebaa554ec5735c2af8f2c209f72c75c3

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In Astronomy and Astrophysics

1. Timothy C. Beers
2. A. Frebel
3. J. Norris
4. C. Sneden
5. Martin Asplund
6. Hans-Walter Rix
7. N. Christlieb
8. Jo Bovy

In Instrumentation

1. Timothy C. Beers
2. A. Frebel
3. J. Norris
4. Martin Asplund
5. C. Sneden
6. Y. S. Lee
7. Brian Yanny
8. C. Rockosi

Citations in the corpus

• Stellar Abundances for the Galactic Archeology (SAGA) Database — Compilation of the Characteristics of Known Extremely Metal-Poor Stars (2008, unknown): “…(hereafter VMP, defined by [Fe/H] ≤−2.0 according to the nomenclature of Beers & Christlieb 2005), in particular by the HK survey (Beers et al. 1985; Beers et al. 1992) and by the Hamburg/ESO survey (Christlieb et al. 2008), the number of known VMP stars has increased dramatically since the 1990s.”
• HIGH-RESOLUTION SPECTROSCOPY OF EXTREMELY METAL-POOR STARS FROM SDSS/SEGUE. I. ATMOSPHERIC PARAMETERS AND CHEMICAL COMPOSITIONS (2012, background): “…0107-5240 (Christlieb et al. 2002) and HE 1327-2326 (Frebel et al. 2005; Aoki et al. 2006), based on follow-up observations of candidates from the Hamburg/ESO Survey (HES; Christlieb 2003; Christlieb et al. 2008), which has a fainter limiting magnitude and larger survey volume than the HK survey.”
• THE MOST METAL-POOR STARS. IV. THE TWO POPULATIONS WITH [Fe/H] ≲ −3.0 (2012, background): “Extensive observation of metal-poor candidates in the HK survey (Beers et al. 1985, 1992), the Hamburg/ESO Survey (HES; Wisotzki et al. 1996; Christlieb et al. 2008), the Sloan Digital Sky Survey (SDSS; York et al. 2000) and the SEGUE survey (Yanny et al. 2009) has greatly increased the sample 1…”
• A SEARCH FOR STARS OF VERY LOW METAL ABUNDANCE. VI. DETAILED ABUNDANCES OF 313 METAL-POOR STARS (2014, methodology): “Subsequent Surveys The Hamburg/ESO (HE) Survey (Wisotzki et al. 2000) introduced quantitative methods to identify metal-poor candidates from digitized spectra (Christlieb et al. 2008).”
• LAMOST Experiment for Galactic Understanding and Exploration (LEGUE) — The survey's science plan (2012, methodology): “…metallicity distribution function (MDF) of the Galactic halo towards low metallicities, extensive, wide-field objective-prism surveys such as the HK survey (e.g., Beers et al. 1985,1992) and the Hamburg/ESO Survey (HES; Christlieb et al. 2008) have been used to identify the most metal-poor stars.”
• CARBON-ENHANCED METAL-POOR STARS IN SDSS/SEGUE. I. CARBON ABUNDANCE ESTIMATION AND FREQUENCY OF CEMP STARS (2013, background): “The early HK survey (Beers et al. 1985, 1992) and the 14 [Fe/H]=log10(N(Fe)/N(H))⋆ – log10(N(Fe)/N(H))⊙ Hamburg/ESO Survey (HES; Wisotzki et al. 1996; Christlieb 2003; Christlieb et al. 2001, 2008) collectively identifiedseveral thousand VMP stars (Beers & Christlieb 2005).”
• Near-Field Cosmology with Extremely Metal-Poor Stars (2015, background): “In an earlier review of metal-poor stars (Frebel & Norris 2013) we discussed (Fe)MDFs for the Galactic globular clusters, high-proper-motion samples (Ryan & Norris 1991, Carney et al. 1996), and the medium-resolution abundance samples of the Hamburg/ESO Survey (HES) (Schörck et al. 2009, Li et al. ”