2008A&A...484..721C


Query : 2008A&A...484..721C

2008A&A...484..721C - Astronomy and Astrophysics, volume 484, 721-732 (2008/6-4)

The stellar content of the Hamburg/ESO survey. IV. Selection of candidate metal-poor stars.

CHRISTLIEB N., SCHOERCK T., FREBEL A., BEERS T.C., WISOTZKI L. and REIMERS D.

Abstract (from CDS):

We present the quantitative methods used for selecting candidate metal-poor stars in the Hamburg/ESO objective-prism survey (HES). The selection is based on the strength of the CaII K line, B-V colors (both measured directly from the digital HES spectra), as well as J-K colors from the 2 Micron All Sky Survey. The KP index for CaII K can be measured from the HES spectra with an accuracy of 1.0Å, and a calibration of the HES B-V colors, using CCD photometry, yields a 1-σ uncertainty of 0.07mag for stars in the color range 0.3<B-V<1.4. These accuracies make it possible to reliably reject stars with [Fe/H]>-2.0 without sacrificing completeness at the lowest metallicities. A test of the selection using 1121 stars of the HK survey of Beers, Preston, and Shectman present on HES plates suggests that the completeness at [Fe/H]←3.5 is close to 100% and that, at the same time, the contamination of the candidate sample with false positives is low: 50% of all stars with [Fe/H]>-2.5 and 97% of all stars with [Fe/H]>-2.0 are rejected. The selection was applied to 379 HES fields, covering a nominal area of 8853deg2 of the southern high Galactic latitude sky. The candidate sample consists of 20271 stars in the magnitude range 10≲B≲18. A comparison of the magnitude distribution with that of the HK survey shows that the magnitude limit of the HES sample is about 2mag fainter. Taking the overlap of the sky areas covered by both surveys into account, it follows that the survey volume for metal-poor stars has been increased by the HES by about a factor of 10 with respect to the HK survey. We have already identified several very rare objects with the HES, including, e.g., the three most heavy-element deficient stars currently known.

Abstract Copyright:

Journal keyword(s): surveys - Galaxy: halo - Galaxy: stellar content - Galaxy: formation - Galaxy: evolution - stars: population II

VizieR on-line data: <Available at CDS (J/A+A/484/721): hescan.dat crossid.dat>

Status at CDS : All or part of tables of objects will be ingested in SIMBAD with priority 1.

Simbad objects: 5

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Number of rows : 5
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2024
#notes
1 SB 44 SB* 00 07 37.5160264968 -35 31 17.704959708   13.23 12.76 12.76   sdF 80 0
2 2MASS J00224486-1724290 Pe* 00 22 44.8620794952 -17 24 29.140962984   13.824 12.887     CEMP-no 20 0
3 CD-38 245 Pe* 00 46 36.1954514592 -37 39 33.555030480   12.733 11.929 13.39 10.996 KIIvw 223 0
4 HE 0305-5442 Pe* 03 06 29.5014981984 -54 30 32.498486568   14.44 13.70 13.212 12.715 KIIvw 74 0
5 HE 2356-0410 Pe* 23 59 13.1419841280 -03 53 48.220213560   14.39 13.60 13.164 12.713 CEMP-no 85 0

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