K+a galaxies in the zCOSMOS Survey: Physical properties of systems in their post-starburst phase

D. Vergani (1) , G. Zamorani (2) , S. J. Lilly (2) , F. Lamareille (3) , C. Halliday , M. Scodeggio (4) , C. Vignali (5) , P. Ciliegi (6) , M. Bolzonella (5) , M. Bondi (6) , K. Kovac (2) , C. Knobel (2) , E. Zucca (7) , K. Caputi (2) , L. Pozzetti (6) , S. Bardelli (6) , M. Mignoli (2) , A. Iovino (2) , C. M. Carollo (8) , T. Contini (3) , J. -P. Kneib (3) , O. Le Fevre (9) , V. Mainieri (2) , A. Renzini (2) , A. Bongiorno (5) , G. Coppa (2) , O. Cucciati (10) , S. de La Torre (2) , L. de Ravel (2) , P. Franzetti (2) , B. Garilli (2) , P. Kampczyk (2) , J. -F. Le Borgne (11) , V. Le Brun (9) , C. Maier (2) , R. Pello (3) , Y. Peng (12) , E. Perez Montero (13) , E. Ricciardelli (2) , J. D. Silverman (2) , M. Tanaka (14) , L. Tasca (9) , L. Tresse (9) , U. Abbas (2) , D. Bottini (2) , A. Cappi (15) , P. Cassata (2) , Alessandro Cimatti (2) , L. Guzzo (2) , A. M. Koekemoer (16) , A. Leauthaud D. Maccagni , Christian Marinoni (17, 18) , H. J. Mccracken (19) , P. Memeo (2) , B. Meneux (9) , P. Oesch (2) , C. Porciani (2) , R. Scaramella (2) , P. Capak (20) , D. Sanders (21) , N. Scoville (22) , Y. Taniguchi (2)

1 OAA - INAF - Osservatorio Astrofisico di Arcetri
2 AUTRES
3 LATT - Laboratoire Astrophysique de Toulouse-Tarbes
4 INAF- Milano
5 UNIBO - Alma Mater Studiorum Università di Bologna = University of Bologna
6 OABO - INAF - Osservatorio Astronomico di Bologna
7 OAB - INAF - Osservatorio Astronomico di Brera
8 University of Chicago
9 LAM - Laboratoire d'Astrophysique de Marseille
10 Dipartimento di Fisica
11 LATT - Laboratoire d'Astrophysique de l'Observatoire Midi-Pyrénées
12 Dipartimento di Fisica e Astronomia [Bologna]
13 Glycosciences Laboratory
14 Tokai University
15 IASF-Bo - Istituto di Astrofisica Spaziale e Fisica cosmica - Bologna
16 STSci - Space Telescope Science Institute
17 CPT - Centre de Physique Théorique - UMR 6207
18 CPT - Centre de Physique Théorique - UMR 7332
19 IAP - Institut d'Astrophysique de Paris
20 MPIA - Max-Planck-Institut für Astronomie
21 Materials & Process technology
22 CALTECH - California Institute of Technology

The identities of the main processes triggering and quenching star-formation in galaxies remain unclear. A key stage in evolution, however, appears to be represented by post-starburst galaxies. To investigate their impact on galaxy evolution, we initiated a multiwavelength study of galaxies with k+a spectral features in the COSMOS field. We examine a mass-selected sample of k+a galaxies at z=0.48-1.2 using the spectroscopic zCOSMOS sample. K+a galaxies occupy the brightest tail of the luminosity distribution. They are as massive as quiescent galaxies and populate the green valley in the colour versus luminosity (or stellar mass) distribution. A small percentage (<8%) of these galaxies have radio and/or X-ray counterparts (implying an upper limit to the SFR of ~8Msun/yr). Over the entire redshift range explored, the class of k+a galaxies is morphologically a heterogeneous population with a similar incidence of bulge-dominated and disky galaxies. This distribution does not vary with the strength of the Hdelta absorption line but instead with stellar mass in a way reminiscent of the well-known mass-morphology relation. Although k+a galaxies are also found in underdense regions, they appear to reside typically in a similarly rich environment as quiescent galaxies on a physical scale of ~2-8Mpc, and in groups they show a morphological early-to-late type ratio similar to the quiescent galaxy class. With the current data set, we do not find evidence of statistical significant evolution in either the number/mass density of k+a galaxies at intermediate redshift with respect to the local values, or the spectral properties. Those galaxies, which are affected by a sudden quenching of their star-formation activity, may increase the stellar mass of the red-sequence by up to a non-negligible level of ~10%.

Domaines: Cosmologie et astrophysique extra-galactique [astro-ph.CO]

D. Vergani, G. Zamorani, S. J. Lilly, F. Lamareille, C. Halliday, et al.. K+a galaxies in the zCOSMOS Survey: Physical properties of systems in their post-starburst phase. Astronomy and Astrophysics - A&A, 2010, 509, pp.A42. ⟨10.1051/0004-6361/200912802⟩. ⟨hal-00421831⟩