zCOSMOS: 40 000 redshifts for COSMOS

The project

The zCOSMOS project is a major treasury redshift survey in the COSMOS field.
This project, in which there is a significant involvement of researchers of the Bologna Observatory,
consists in two parallel surveys:

the bright survey, aiming at observing ~ 20 000 magnitude selected galaxies with I_AB ≤ 22.5 and 0.1≤ z ≤ 1.2 over 1.7 deg²;
the deep survey, with approximately 10 000 galaxies selected through color-selection criteria expected to be at 1.4 < z < 3.0, within the central 1 deg².

Observations and data reduction are currently ongoing, involving, besides the Bologna group, other institutes in Zurich (ETH), Milano (Osservatorio Astronomico di Brera and IASF), Marseille (LAM), Toulouse (OMP) and Garching (MPE).

The scientific goals

The main goal of the spectroscopic survey zCOSMOS is to characterize galactic environments throughout the COSMOS volume out to redshifts of around z ~ 3. Some of the main topics that will be addressed to understand the evolution of galactic systems are

the study of large-scale structures by means of the measure of the density field, the evolution of correlation functions, the selection of a catalogue of groups
the study of diagnostics derived from spectra to determine star-formation rates of galaxies, active galactic nucleus (AGN) classification, reddening by dust, stellar population ages, and metallicities,
the description of the galaxy population by means of various distribution functions, like the Luminosity and Galaxy Stellar Mass Functions, as a function of different galaxy types and environments,
the extension of the previous studies complementing the spectroscopic sample with photometric redshifts, which, at present, are characterized by a σ ~ 0.021, excluding stars, BL AGN and the catastrophic failures.

The Bologna involvement

Bologna is mainly involved in the study of the evolution of galaxy stellar mass and luminosity functions of the bright spectroscopic catalogue divided in photometric and spectroscopic types, morphology and environment, as well as in the classification of galaxy types from the spectral analysis.