The zCOSMOS redshift survey: the three-dimensional classification cube and bimodality in galaxy physical properties

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

1 OABO - INAF - Osservatorio Astronomico di Bologna
2 IASF-MI - Istituto di Astrofisica Spaziale e Fisica Cosmica - Milano
3 UNIBO - Alma Mater Studiorum Università di Bologna = University of Bologna
4 OAA - INAF - Osservatorio Astrofisico di Arcetri
5 Institute of Astronomy [ETH Zürich]
6 LATT - Laboratoire Astrophysique de Toulouse-Tarbes
7 LAM - Laboratoire d'Astrophysique de Marseille
8 ESO - European Southern Observatory
9 Unipd - Università degli Studi di Padova = University of Padua
10 MPE - Max-Planck-Institut für Extraterrestrische Physik
11 OAB - INAF - Osservatorio Astronomico di Brera
12 LATT - Laboratoire d'Astrophysique de l'Observatoire Midi-Pyrénées
13 UMS 831 - Services communs OMP
14 MPIA - Max-Planck-Institut für Astronomie
15 CALTECH - California Institute of Technology
16 CPT - Centre de Physique Théorique - UMR 7332
17 IAP - Institut d'Astrophysique de Paris
18 OAR - INAF - Osservatorio Astronomico di Roma

Aims. We investigate the relationships between three main optical galaxy observables (spectral properties, colours, and morphology), exploiting the data set provided by the COSMOS/zCOSMOS survey. The purpose of this paper is to define a simple galaxy classification cube, using a carefully selected sample of around 1000 galaxies. Methods. Using medium resolution spectra of the first 1k zCOSMOS-bright sample, optical photometry from the Subaru/COSMOS observations, and morphological measurements derived from ACS imaging, we analyze the properties of the galaxy population out to z~1. Applying three straightforward classification schemes (spectral, photometric, and morphological), we identify two main galaxy types, which appear to be linked to the bimodality of galaxy population. The three parametric classifications constitute the axes of a "classification cube". Results. A very good agreement exists between the classification from spectral data (quiescent/star-forming galaxies) and that based on colours (red/blue galaxies). The third parameter (morphology) is less well correlated with the first two: in fact a good correlation between the spectral classification and that based on morphological analysis (early-/late-type galaxies) is achieved only after partially complementing the morphological classification with additional colour information. Finally, analyzing the 3D-distribution of all galaxies in the sample, we find that about 85% of the galaxies show a fully concordant classification, being either quiescent, red, bulge-dominated galaxies (~20%) or star-forming, blue, disk-dominated galaxies (~65%). These results imply that the galaxy bimodality is a consistent behaviour both in morphology, colour and dominant stellar population, at least out to z~1.

Mots clés: galaxies: general; galaxies: evolution; galaxies: fundamental parameters

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

M. Mignoli, G. Zamorani, M. Scodeggio, Alessandro Cimatti, C. Halliday, et al.. The zCOSMOS redshift survey: the three-dimensional classification cube and bimodality in galaxy physical properties. Astronomy and Astrophysics - A&A, 2009, 493 (1), pp.39-49. ⟨10.1051/0004-6361:200810520⟩. ⟨hal-00350512⟩