Discovery of RR Lyrae in the Ultra-Faint Dwarf Galaxy Virgo III

TL;DR

This study identified three RR Lyrae stars in the ultra-faint dwarf galaxy Virgo III, providing a new distance estimate and insights into the relation between RR Lyrae populations and galaxy luminosity.

Contribution

The paper reports the discovery of RR Lyrae stars in Virgo III and refines the $M_V$-$N_{RRL}$ relation using specific RR Lyrae frequency.

Findings

Distance to Virgo III estimated as 154±25 kpc.

Three RR Lyrae stars identified in Virgo III.

The $M_V$-$N_{RRL}$ relation is better described with specific RR Lyrae frequency.

Abstract

Virgo III is a newly discovered ultra-faint dwarf (UFD) candidate, and finding RR Lyrae associated with this galaxy is important to constrain its distance. In this work, we present a search of RR Lyrae in the vicinity of Virgo III based on the time-series $r$-band images taken from the Lulin One-meter Telescope (LOT). We have identified three RR Lyrae from our LOT data, including two fundamental mode (ab-type) and a first-overtone (c-type) RR Lyrae. Assuming these three RR Lyrae are members of Virgo III, we derived the distance to this UFD as $154\pm25$ kpc, fully consistent with the independent measurements given in the literature. We have also revisited the relation between absolute $V$-band magnitude ($M_V$) and the number of RR Lyrae (of all types, $N_{RRL}$) found in local galaxies, demonstrating that the $M_V$-$N_{RRL}$ relation is better described with the specific RR Lyrae frequency.