High-redshift elliptical galaxies: are they (all) really compact?

Understand

We investigate the properties of 12 ultra-massive passively evolving early type galaxies (ETGs) at z_phot>1.4 in the COSMOS 2 deg^2 field.

• These 12 ETGs were selected as pBzKs, have accurate 1.4<= z_phot <=1.7,high Sersic index profiles typical of ellipticals, no detection at 24 micron, resulting in a complete ETG sample at M*>2.5x10^11 M_sun (Chabrier IMF).
• Contrary to previous claims, the half light radii estimated in very high S/N imaging data from HST+ACS are found to be large for most of the sample, consistent with local ellipticals.
• If the high redshift ETGs with M*<2.5x10^11 M_sun are really small in size and compact as reported in previous studies, our result may suggest a &#34;downsizing&#34; scenario, whereby the most massive ETGs reach their final structure earlier and faster than lower mass ones.