Kaylachisum's List: Elliptical and Irregular Galaxies

  Astronomer Avon Huxor from the University of Heidelberg, with collaborators Steve Phillipps and James Price of  the University of Bristol, have used the ACAM instrument on the William Herschel Telescope (WHT) in the discovery  of a unique, isolated, compact elliptical galaxy.  

 Compact ellipticals (cEs) are a rare type of dwarf galaxy, possessing small effective radii and  high central surface brightnesses. The best example is M32, a companion to the nearby Andromeda Galaxy.  All of those found to date are close to massive galaxies, so many astronomers believe that their  unusual features are the consequence of the tidal stripping of a much larger progenitor galaxy by the  very massive host. Others, however, have argued that cEs are formed in the same manner as all elliptical galaxies,  and are simply the rare low-mass examples.  

 The team identified cE candidates from the SDSS to test these scenarios,  seeking isolated cEs that could not have been formed by stripping. One  candidate was subsequently observed with the WHT/ACAM in good seeing to have an effective radius of 500 pc.  Along with the measured surface brightness, this makes the galaxy a cE.  It is at a projected distance of almost one megaparsec from the nearest galaxy,  and so cannot have been formed by stripping. Although other cEs are the result  of stripping (see, for example, Huxor et al. 2011),  this cE shows that they can also form in a manner similar to the more massive elliptical galaxies.