1 July 2014, 0800 AEST:

Distant ‘cannibal twin’ shows how galaxies grow

The Umbrella Galaxy (NGC 4651, shown below) exhibits a dramatic system of streams and shells formed via the shredding of a tiny galaxy only a 50th of its size!

The image below is a combination of data from the 0.5 m BlackBird Remote Observatory telescope and the Subaru Telescope.

Image copyright © 2014 R. J. GaBany

As a follow-up to a study published in 2010, led by David Martínez-Delgado (University of Heidelberg), we have used the DEIMOS instrument on the Keck Telescope to measure the dynamics of the stream of stars around NGC 4651. Using those information, we were able to model the even that led to the formation of the stream.

Image copyright © 2014 Navtej Singh/UCSC

The animated gif above shows the computer generated 3D rotating model of the Umbrella galaxy.  Blue circles highlight the disk of NGC 4651.  The path of the cannibalised dwarf galaxy's nucleus through space is shown in green.  White points show the shredded stellar stream that once belonged to the dwarf galaxy.

This system shows striking resemblances to both our own Galaxy (the Milky Way) and its nearest massive neighbour (Andromeda).

The study has been published in MNRAS and the scientific paper can be found here and the press release can be found here.