Puffing up elliptical galaxies October 3, 2009
Posted by sarah in: new astronomy, science . 4comments
Elliptical galaxies are the boring uncles of the galaxy family: they’re amorphous blobby things, ubiquitous in the Universe, that contain a fairly uniform population of old, red stars. Without the interstellar gas and dust that is needed to harbour pretty sites of star formation, they are supremely unphotogenic. But they have far more going on beneath their featureless surface: the complex dynamics inside many ellipticals show evidence of a turbulent past and, with many of the most massive known galaxies in our local Universe being ellipticals, they clearly play an important role in galaxies’ evolution.
Studies seem to suggest that high-redshift elliptical galaxies are more compact than their present-day counterparts (figure from Glazebrook, 2009)
Observational surveys of elliptical galaxies at high redshift have in recent years revealed a further interesting fact: ellipticals at high redshift appear to be much smaller in size than those in our local Universe, but have about the same mass and density of stars. In a recent ApJ paper, Ivana Damjanov of the University of Toronto and collaborators describe how a sample of elliptical galaxies at redshifts 1 to 2 looked 2-3 times smaller than those in the local Universe. The first surprise lies in that they evolve at all between redshift 2 and 0. In our current understanding of galaxy formation and evolution, ellipticals are the “red and dead” endpoints of evolution.
