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

TL;DR

This paper reports the discovery of Leo V, a new dwarf spheroidal galaxy near Leo IV, including its properties and potential association with a stellar stream, based on survey data and follow-up observations.

Contribution

First identification and characterization of Leo V, including imaging and spectroscopic data, expanding knowledge of Milky Way satellite galaxies.

Findings

Leo V is about 180 kpc away from the Milky Way.

Leo V's heliocentric velocity is 173.4 km/s.

Leo V may be part of a stellar stream with Leo IV.

Abstract

We report the discovery of a new Milky Way dwarf spheroidal galaxy in the constellation of Leo identified in data from the Sloan Digital Sky Survey. Leo V lies at a distance of about 180 kpc, and is separated by about 3 degrees 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 173.4 km/s, which is offset by about 40 km/s from that of Leo IV. A simple interpretation of the kinematic data is that both objects may lie on the same stream, though the implied orbit is only modestly eccentric (e = 0.2)