Leo V: A Companion of a Companion of the Milky Way Galaxy?

Abstract

We report the discovery of a new Milky Way satellite in the constellation Leo, identified in data from the Sloan Digital Sky Survey. It lies at a distance of-180 kpc, and is separated by ≤⊙3° from another recent discovery, Leo IV. We present follow-up imaging from the Isaac Newton Telescope and spectroscopy from the Hectochelle fiber spectrograph at the Multiple Mirror Telescope. Leo V's heliocentric velocity is-173.3 ±3.1 km s-1, offset by-40 km s-1 from that of Leo IV. A simple interpretation of the kinematic data is that both objects may lie on the same stream, although the implied orbit is only modestly eccentric (e-0.2) © 2008. The American Astronomical Society. All rights reserved. Printed in U.S.A.