Stellar Populations in the Andromeda V Dwarf Spheroidal Galaxy

TL;DR

This study uses Hubble Space Telescope data to analyze the stellar populations of the Andromeda V dwarf galaxy, determining its metallicity, distance, and variable star content, revealing it as a metal-poor, ancient system with diverse stellar properties.

Contribution

First detailed analysis of Andromeda V's stellar populations using HST imaging, providing metallicity, distance, and variable star data for this dwarf galaxy.

Findings

Mean metallicity of [Fe/H] = -2.20 ± 0.15

Distance modulus (m-M)0 = 24.57 ± 0.04

Identification of at least 10 RR Lyrae stars

Abstract

Using archival imaging from the Wide Field Planetary Camera 2 aboard the Hubble Space Telescope, we investigate the stellar populations of the Local Group dwarf spheroidal Andromeda V - a companion satellite galaxy of M31. The color-magnitude diagram (CMD) extends from above the first ascent red giant branch (RGB) tip to approximately one magnitude below the horizontal branch (HB). The steep well-defined RGB is indicative of a metal-poor system while the HB is populated predominantly redward of the RR Lyrae instability strip. Utilizing Galactic globular cluster fiducial sequences as a reference, we calculate a mean metallicity of [Fe/H] = -2.20 +/- 0.15 and a distance of (m-M)0 = 24.57 +/- 0.04 after adopting a reddening of E(B-V) = 0.16. This metal abundance places And V squarely in the absolute magnitude - metallicity diagram for dwarf spheroidal galaxies. In addition, if we attribute the entire error-corrected color spread of the RGB stars to an abundance spread, we estimate a range of ~0.5 dex in the metallicities of And V stars. Our analysis of the variable star population of And V reveals the presence of 28 potential variables. Of these, at least 10 are almost certainly RR Lyrae stars based on their time sequence photometry.