A globular cluster in the dwarf galaxy Sextans B

Abstract

We present spectroscopic observations of a massive globular cluster in the dwarf irregular galaxy Sextans B, discovered by us on Hubble Space Telescope Wide Field and Planetary Camera 2 (HST WFPC2) images. Long-slit spectra were obtained with the SCORPIO spectrograph on the the 6-m telescope at the Special Astrophysical observatory of the Russian Academy of Sciences. We determine age, metallicity and alpha-element abundance ratio for the globular cluster to be $ 2 \pm 1$ Gyr, $-1.35 \pm 0.25$ dex, and $ 0.1 \pm 0.1$ dex, respectively. Main photometric and structural parameters of it were determined using our surface photometry on the HST images. The mass ($\sim 10^5 M \sun$), luminosity and structural parameters appear to be typical for the globular clusters in our own Galaxy. Our findings shed a new light on the evolutionary history of Sextans B.