Astronomy and Astrophysics – Astrophysics
Scientific paper
2004-02-18
Astronomy and Astrophysics
Astrophysics
15 pages, latex. Accepted for publication in The Astronomical Journal
Scientific paper
10.1086/386355
We present a complete census of RR Lyrae stars in a halo field of the Andromeda galaxy. These deep observations, taken as part of a program to measure the star formation history in the halo, spanned a period of 41 days with sampling on a variety of time scales, enabling the identification of short and long period variables. Although the long period variables cannot be fully characterized within the time span of this program, the enormous advance in sensitivity provided by the Advanced Camera for Surveys on the Hubble Space Telescope allows accurate characterization of the RR Lyrae population in this field. We find 29 RRab stars with a mean period of 0.594 days, 25 RRc stars with a mean period of 0.316 days, and 1 RRd star with a fundamental period of 0.473 days and a first overtone period of 0.353 days. These 55 RR Lyrae stars imply a specific frequency S_RR=5.6, which is large given the high mean metallicity of the halo, but not surprising given that these stars arise from the old, metal-poor tail of the distribution. This old population in the Andromeda halo cannot be clearly placed into one of the Oosterhoff types: the ratio of RRc/RRabc stars is within the range seen in Oosterhoff II globular clusters, the mean RRab period is in the gap between Oosterhoff types, and the mean RRc period is in the range seen in Oosterhoff I globular clusters. The periods of these RR Lyraes suggest a mean metallicity of [Fe/H]=-1.6, while their brightness implies a distance modulus to Andromeda of 24.5+/-0.1, in good agreement with the Cepheid distance.
Brown Thomas M.
Ferguson Henry C.
Kimble Randy A.
Renzini Alvio
Rich Robert Michael
No associations
LandOfFree
RR Lyrae Stars in the Andromeda Halo from Deep Imaging with the Advanced Camera for Surveys does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with RR Lyrae Stars in the Andromeda Halo from Deep Imaging with the Advanced Camera for Surveys, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and RR Lyrae Stars in the Andromeda Halo from Deep Imaging with the Advanced Camera for Surveys will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-180518