On the newly discovered Canes Venatici II dSph galaxy

TL;DR

This paper reports the discovery of variable stars in the Canes Venatici II dwarf galaxy, determining its distance and properties through RR Lyrae stars, and classifies it as Oosterhoff type II based on their periods.

Contribution

It presents the first detection of variable stars in CVn II and provides detailed analysis of its stellar population and distance measurement.

Findings

Identification of two RR Lyrae stars in CVn II

Classification of CVn II as Oosterhoff type II

Distance estimate of approximately 160 kpc

Abstract

We report on the detection of variable stars in the Canes Venatici II (CVn II) dwarf spheroidal galaxy, a new satellite of the Milky Way recently discovered by the Sloan Digital Sky Survey. We also present a V, B-V color-magnitude diagram that reaches V = 25.5 mag, showing the galaxy's main sequence turn off at V = 24.5 mag and revealing several candidate blue straggler stars. Two RR Lyrae stars have been identified within the half-light radius of CVn II,a fundamental-mode variable (RRab) with period P_ab = 0.743 days, and a first-overtone (RRc) RR Lyrae star with P_c = 0.358 days. The rather long periods of these variables along with their position on the period-amplitude diagram support an Oosterhoff type II classification for CVn II. The average apparent magnitude of the RR Lyrae stars, <V> = 21.48 +/- 0.02 mag, is used to obtain a precision distance modulus of mu_0 = 21.02 +/- 0.06 mag and a corresponding distance of 160(+4,-5} kpc, for an adopted reddening E(B-V) = 0.015 mag.