OGLE Study of the Sagittarius Dwarf Spheroidal Galaxy and its M54 Globular Cluster
Abstract
We use the fundamental-mode RR Lyr-type variable stars (RRab) from OGLE-IV survey to draw a 3D picture of the central part of the tidally disrupted Sagittarius Dwarf Spheroidal (Sgr dSph) galaxy. We estimate the line-of-sight thickness of the Sgr dSph stream to be FWHMcen=2.42 kpc. Based on OGLE-IV observations collected in seasons 2011-2014 we conduct a comprehensive study of stellar variability in the field of the globular cluster M54 (NGC 6715) residing in the core of this dwarf galaxy. Among the total number of 268 detected variable stars we report the identification of 174 RR Lyr stars, four Type II Cepheids, 51 semi-regular variable red giants, three SX Phe-type stars, 18 eclipsing binary systems. Eighty-three variable stars are new discoveries. The distance to the cluster determined from RRab stars is dM54=26.7±0.03stat±1.3sys kpc. From the location of RRab stars in the period-amplitude (Bailey) diagram we confirm the presence of two old populations, both in the cluster and the Sgr dSph stream.
- Publication:
-
Acta Astronomica
- Pub Date:
- June 2016
- DOI:
- 10.48550/arXiv.1605.04906
- arXiv:
- arXiv:1605.04906
- Bibcode:
- 2016AcA....66..197H
- Keywords:
-
- Galaxies: individual: Sgr dSph;
- globular clusters: individual: M54 (NGC 6715);
- Stars: variables: RR Lyr;
- Cepheids;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- published version, changed IDs of detected variable stars in comparison to the first version