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On the Newly Discovered Canes Venatici II dSph Galaxy

2008; IOP Publishing; Volume: 675; Issue: 2 Linguagem: Inglês

10.1086/533585

1538-4357

Claudia Greco, M. Dall’Ora, G. Clementini, V. Ripepi, Luca Di Fabrizio, Karen Kinemuchi, M. Marconi, I. Musella, H. A. Smith, Christopher T. Rodgers, Charles A. Kuehn, Timothy C. Beers, M. Catelan, B. J. Pritzl,

Gamma-ray bursts and supernovae

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, = 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.