Short-Period Variable Stars in the M31 Halo

Abstract

We report the findings of a new search for RR Lyraes in an M31 halo field located 40 arcminutes from the nucleus of the galaxy along the minor axis. We detected 37 variable stars, of which 24 are classified as RR Lyraes and the others are ambiguous. Estimating a completeness fraction of ~24%, we calculate that there are approximately 100 RR Lyraes in the field, which is consistent with what is expected from deep HST color-magnitude diagrams. We calculate a mean magnitude of g=25.15+/ 0.03, which we interpret to mean that the mean metallicity of RR Lyraes is significantly lower than that of the M31 halo as a whole. The presence of ancient, metal-poor stars opens the possibility that, initially, the M31 halo appeared much like the Milky Way halo.

arXiv comment43 pages, 9 figures. Accepted for publication in AJ

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Cited by in corpus (12)

• Horizontal Branch Stars: The Interplay between Observations and Theory, and Insights into the Formation of the Galaxy
• Leo P: An Unquenched Very Low-Mass Galaxy
• RR Lyrae Stars in the Andromeda Halo from Deep Imaging with the Advanced Camera for Surveys
• The Hubble Space Telescope Survey of M31 Satellite Galaxies I. RR Lyrae-based Distances and Refined 3D Geometric Structure
• Evidence for an Overluminosity of the Variable Star RR Lyr, and a Revised Distance to the LMC
• RR Lyrae Variables in Two Fields in the Spheroid of M31
• HST/ACS Observations of RR Lyrae Stars in Six Ultra-deep Fields of M31
• The ancient stellar population of M32: RR Lyr Variable stars confirmed
• Physical parameters of the Small Magellanic Cloud RR Lyrae stars and the distance scale
• The Early Chemical Enrichment Histories of Two Sculptor Group Dwarf Galaxies as Revealed by RR Lyrae Variables
• Hide and seek between Andromeda's halo, disk, and giant stream
• Variable Star Candidates in an ACS Field of M31