2015/10/23 by Antonio J. Ordoñez, Ata Sarajedini, Ordoñez, Antonio J. +1 · 1 citation
Physics and Astronomy · #Astrophysics of Galaxies (astro-ph.GA) #FOS: Physical sciences #Solar and Stellar Astrophysics (astro-ph.SR) #astro-ph.GA #astro-ph.SR
paper · pdf · doi:10.48550/arxiv.1510.07075
Accepted for publication into MNRAS, 17 pages, 13 figures, 4 tables
arxiv created 2015/10/23 · arxiv updated 2015/11/27
We have probed the pulsating variable star content of the isolated Local Group dwarf galaxy, DDO210 (Aquarius), using archival Advanced Camera for Surveys/Hubble Space Telescope imaging in the F475W and F814W passbands. We find a total of 32 RR Lyrae stars (24 ab-type, 8 c-type) and 75 Cepheid variables. The mean periods of the ab-type and c-type RR Lyrae stars are calculated to be ⟨Pab⟩ = 0.609±0.011 and ⟨Pc⟩ = 0.359±0.025 days, respectively. The light curve properties of the fundamental mode RR Lyrae stars yield a mean metallicity of ⟨[Fe/H]⟩ = -1.63±0.11 dex for this ancient population, consistent with a recent synthetic colour-magnitude diagram analysis. We find this galaxy to be Oosterhoff-intermediate and lacking in high-amplitude, short-period ab-type RR Lyrae, consistent with behavior recently observed for many dwarf spheroidals and ultra-faint dwarfs in the Local Group. We find a distance modulus of μ= 25.07± 0.12 as determined by the RR Lyrae stars, slightly larger but agreeing with recent distance estimates from the red giant branch tip. We also find a sizable population of Cepheid variables in this galaxy. We provide evidence in favor of most if not all of these stars being short-period classical Cepheids. Assuming all of these stars to be classical Cepheids, we find that most of these Cepheids are ∼300 Myr old, with the youngest Cepheids being offset from the older Cepheids and the centre of the galaxy. We conclude that this may have resulted from a migration of star formation in DDO210.