Astrophys. J., 712, 226-237 (2010/March-3)
Superdense massive galaxies in WINGS local clusters.
VALENTINUZZI T., FRITZ J., POGGIANTI B.M., CAVA A., BETTONI D., FASANO G., D'ONOFRIO M., COUCH W.J., DRESSLER A., MOLES M., MORETTI A., OMIZZOLO A., KJAERGAARD P., VANZELLA E. and VARELA J.
Abstract (from CDS):
Massive quiescent galaxies at z > 1 have been found to have small physical sizes, and hence to be superdense. Several mechanisms, including minor mergers, have been proposed for increasing galaxy sizes from high- to low-z. We search for superdense massive galaxies in the WIde-field Nearby Galaxy-cluster Survey (WINGS) of X-ray selected galaxy clusters at 0.04 < z < 0.07. We discover a significant population of superdense massive galaxies with masses and sizes comparable to those observed at high redshift. They approximately represent 22% of all cluster galaxies more massive than 3x1010 M☉, are mostly S0 galaxies, have a median effective radius 〈Re〉 = 1.61±0.29 kpc, a median Sersic index 〈n〉 = 3.0±0.6, and very old stellar populations with a median mass-weighted age of 12.1±1.3 Gyr. We calculate a number density of 2.9x10–2/Mpc3 for superdense galaxies in local clusters, and a hard lower limit of 1.3x10–5/Mpc3 in the whole comoving volume between z = 0.04 and z = 0.07. We find a relation between mass, effective radius, and luminosity-weighted age in our cluster galaxies, which can mimic the claimed evolution of the radius with redshift, if not properly taken into account. We compare our data with spectroscopic high-z surveys and find that–when stellar masses are considered–there is consistency with the local WINGS galaxy sizes out to z ∼ 2, while a discrepancy of a factor of 3 exists with the only spectroscopic z > 2 study. In contrast, there is strong evidence for a large evolution in radius for the most massive galaxies with M* > 4x1011 M☉ compared to similarly massive galaxies in WINGS, i.e., the brightest cluster galaxies.
galaxies: clusters: general - galaxies: evolution - galaxies: fundamental parameters - galaxies: structure
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