Bibcode
DOI
Allende Prieto, Carlos; Rebolo, Rafael; García López, R. J.; Serra-Ricart, Miquel; Beers, Timothy C.; Rossi, Silvia; Bonifacio, Piercarlo; Molaro, Paolo
Bibliographical reference
The Astronomical Journal, Volume 120, Issue 3, pp. 1516-1531.
Advertised on:
9
2000
Citations
30
Refereed citations
25
Description
With the dual aims of enlarging the list of extremely metal-poor stars
identified in the Galaxy and boosting the numbers of moderately
metal-deficient stars in directions that sample the rotational
properties of the thick disk, we have used the 2.5 m Isaac Newton
Telescope and the Intermediate Dispersion Spectrograph to carry out a
survey of brighter (primarily northern hemisphere) metal-poor candidates
selected from the HK objective-prism-interference-filter survey of Beers
and collaborators. Over the course of only three observing runs (15
nights) we have obtained medium-resolution
(λ/δλ~=2000) spectra for 1203 objects (V~=11-15).
Spectral absorption-line indices and radial velocities have been
measured for all the candidates. Metallicities, quantified by [Fe/H],
and intrinsic (B-V)0 colors have been estimated for 731 stars
with effective temperatures cooler than roughly 6500 K by using
artificial neural networks (ANNs) trained with spectral indices. We show
that this method performs as well as a previously explored Ca II K
calibration technique, yet it presents some practical advantages. Among
the candidates in our sample we identify 195 stars with [Fe/H]<=-1.0,
67 stars with [Fe/H]<=-2.0, and 12 new stars with [Fe/H]<=-3.0.
Although the effective yield of metal-poor stars in our sample is not as
large as that in previous HK survey follow-up programs, the rate of
discovery per unit of telescope time is quite high. Further development
of the ANN technique, with the networks being fed the entire spectrum,
rather than just the spectral indices, holds the promise to produce
fast, accurate, multidimensional spectral classifications (with the
associated physical parameter estimates), as is required to process the
large data flow provided by present and future instrumentation. Based on
observations made with the Isaac Newton Telescope operated on the island
of La Palma by the Isaac Newton Group in the Spanish Observatorio del
Roque de los Muchachos of the Instituto de Astrofisica de Canarias.