Gaia 1 and 2. A pair of new Galactic star clusters
Publication date: 16 May 2017
Authors: Koposov, S.E., Belokurov, V., and Torrealba, G.
Journal: Monthly Notices of the Royal Astronomical Society
Volume: 470
Issue: 3
Page: 2702-2709
Year: 2017
Copyright: © 2017 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society
We present the results of the very first search for faint Milky Way satellites in the Gaia data. Using stellar positions only, we are able to re-discover objects detected in much deeper data as recently as the last couple of years. While we do not identify new prominent ultrafaint dwarf galaxies, we report the discovery of two new star clusters, Gaia 1 and Gaia 2. Gaia 1 is particularly curious, as it is a massive (2.2 × 104 M⊙), large (~9 pc) and nearby (4.6 kpc) cluster, situated 10 arcmin away from the brightest star on the sky, Sirius! Even though this satellite is detected at significance in excess of 10, it was missed by previous sky surveys. We conclude that Gaia possesses powerful and unique capabilities for satellite detection, thanks to its unrivalled angular resolution and highly efficient object classification.
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