Andromeda XXVIII: A Dwarf Galaxy More Than 350 kpc from Andromeda

TL;DR

The paper reports the discovery of Andromeda XXVIII, a distant dwarf galaxy satellite of Andromeda, with detailed measurements of its distance, luminosity, and size, expanding knowledge of the Local Group's faint satellites.

Contribution

It presents the discovery and characterization of a new dwarf galaxy, Andromeda XXVIII, including its distance, luminosity, and structural properties, using SDSS DR8 data.

Findings

Andromeda XXVIII is over 350 kpc from Andromeda.

It has an absolute magnitude of -8.5.

Half-light radius is approximately 210 pc.

Abstract

We report the discovery of a new dwarf galaxy, Andromeda XXVIII, using data from the recently-released SDSS DR8. The galaxy is a likely satellite of Andromeda, and, at a separation of $365^{+17}_{-1}$ kpc, would be one of the most distant of Andromeda's satellites. Its heliocentric distance is $650^{+150}_{-80}$ kpc, and analysis of its structure and luminosity show that it has an absolute magnitude of $M_V = -8.5^{+0.4}_{-1.0}$ and half-light radius of $r_h = 210^{+60}_{-50}$ pc, similar to many other faint Local Group dwarfs. With presently-available imaging we are unable to determine if there is ongoing or recent star formation, which prevents us from classifying it as a dwarf spheroidal or dwarf irregular.