Gaia 1 and 2. A pair of new Galactic star clusters

Abstract

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 ultra-faint 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$\times$10${}^4$ M${}_{\odot }$), large ($\sim$9 pc) and nearby (4.6 kpc) cluster, situated 10' 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.

9 pages, accepted to MNRAS

References in corpus (18)

• The Gaia mission
• Gaia Data Release 1. Summary of the astrometric, photometric, and survey properties
• HyperLEDA. III. The catalogue of extragalactic distances
• Cats and Dogs, Hair and A Hero: A Quintet of New Milky Way Companions
• The Pan-STARRS1 Surveys
• Gaia Data Release 1: Astrometry - one billion positions, two million proper motions and parallaxes
• Beasts of the Southern Wild: Discovery of nine Ultra Faint satellites in the vicinity of the Magellanic Clouds
• The Luminosity Function of the Milky Way Satellites
• unWISE: unblurred coadds of the WISE imaging
• The Invisibles: A Detection Algorithm to Trace the Faintest Milky Way Satellites
• The Pan-STARRS Data Processing System
• Pan-STARRS Pixel Analysis : Source Detection and Characterization
• Clouds, Streams and Bridges. Redrawing the blueprint of the Magellanic System with Gaia DR1
• Gaia Data Release 1, Pre-processing and source list creation
• A New Catalog of Globular Clusters in the Milky Way
• Automated search for galactic star clusters in large multiband surveys: I. Discovery of 15 new open clusters in the Galactic anticenter region
• Gaia data release 1, the photometric data
• An Observational Limit on the Dwarf Galaxy Population of the Local Group

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