Sagittarius II, Draco II and Laevens 3: three new Milky Way satellites discovered in the Pan-STARRS 1 3pi Survey

Understand

We present the discovery of three new Milky Way satellites from our search for compact stellar overdensities in the photometric catalog of the Panoramic Survey Telescope and Rapid Response System 1 (Pan-STARRS 1, or PS1) 3pi survey.

• The first satellite, Laevens 3, is located at a heliocentric distance of d=67+/-3 kpc.
• With a total magnitude of Mv=-4.4+/-0.3 and a half-light radius rh=7+/-2 pc, its properties resemble those of outer halo globular clusters.
• The second system, Draco II/Laevens 4 (Dra II), is a closer and fainter satellite (d~20 kpc, Mv =-2.9+/-0.8), whose uncertain size (rh = 19 +8/-6 pc) renders its classification difficult without kinematic information; it could either be a faint and extended globular cluster or a faint and compact dwarf galaxy.