VizieR Online Data Catalog: Giant Galactic dwarf satellite in Gaia DR2 (Torrealba+, 2019)

We have presented the discovery of a new dwarf satellite galaxy of the Milky Way, Antlia 2. Originally detected in Gaia DR2 data using a combination of RRL (Holl et al. 2018A&A...618A..30H), proper motions, parallaxes and shallow broad-band photometry, this new satellite is also confirmed using deeper archival DECam imaging as well as AAT2dF+ AAOmega follow-up spectroscopy. The CMD of the Antlia 2 dwarf boasts a broad and well-populated RGB as well as a prominent BHB sequence, which we use as a standard candle. The resulting dwarf's distance modulus is m-M=20.6, which is consistent with the location of the RGB, giving an independent confirmation of the BHB distance. In addition, there are possibly three associated RRL stars, lying in front of the dwarf along the line of sight. These likely represent the near side of an extended cloud of tidal debris originating from Antlia 2. The angular half-light radius of the new dwarf is ~1.3°, which translates into a gigantic physical size of ~2.8kpc, on par with the measurements of the largest satellite of the MW, the LMC, but with a luminosity some ~4000 times fainter.

(2 data files).