Bibcode
Wilhelm, R.; Beers, T. C.; Allende Prieto, C.; Rockosi, C.; Yanny, B.; Newberg, H. J.; Sivarani, T.; Lee, Y.
Referencia bibliográfica
American Astronomical Society Meeting 207, #131.12; Bulletin of the American Astronomical Society, Vol. 37, p.1379
Fecha de publicación:
12
2005
Número de citas
0
Número de citas referidas
0
Descripción
The warm star sample (7000 < Teff < 10,000 K) in SDSS is comprised
of field horizontal branch (FHB) stars and a large number of blue
straggler (BS) stars. Because these stars have a higher intrinsic
luminosity than their cooler, turnoff and main-sequence counterparts,
they are an ideal sample for probing both the global properties of the
thick disk and halo of the Galaxy and the properties of distant halo
structures such as the Sagittarius and Monoceros streams.
We have determined stellar parameters of Teff, log g and [Fe/H] for a
large sample (N = 5060) of SDSS stars using a combination of photometric
color indices and spectroscopic line analysis. In addition we have
identified 1110 stars that have significant deviations between the color
indices and hydrogen line strength, of which a subsample appear to be RR
Lyrae variables with photometry and spectroscopy observations taken out
of phase. We present the results of our stellar parameter analysis along
with a new distance calibration for the FHB and BS samples and report on
metallicity trends as a function of distance out to 60 kiloparsecs from
the Sun. In addition we compare the kinematic properties of the halo and
thick disk populations and present metal abundances for the old
population stars in the Sagittarius and Monoceros streams. Finally, we
present evidence that a surprisingly large fraction of the BS sample
occupy the Hertzsprung Gap, a result that is consistent with recently
published findings for BS stars in globular clusters.
T.C.B., S.T., and Y.L. acknowledge partial support from grant AST
04-06784, as well as from grant PHY 02-16783, Physics Frontier
Center/Joint Institute for Nuclear Astrophysics (JINA), awarded by the
US National Science Foundation. H.J.N acknowledges partial support from
NSF grant AST 03-07571.