Genesis of a dwarf galaxy from the debris of the antennae

Abstract

We show that a dwarf irregular galaxy has formed out of the tidal remnants that were ejected to intergalactic space during an encounter of the disk galaxies NGC 4038/39 (the Antennae). The tidal dwarf consists of a chain of nebulae ionized by recently formed massive stars, which are embedded in an envelope of HI gas and low surface brightness optical emission. Since this object is at the tip of one of the tidal tails, star formation on a scale similar to star forming galaxies is taking place at ~ 100 kpc from the merging disks.