Galaxy and star formation up to z ~ 1.pdf

a r X i v : a s t r o - p h / 0 1 0 9 3 8 4 v 1 2 1 S e p 2 0 0 1 SF2A 2001- Lyon, May 28- June 1st Socie?te? Franc?aise d’Astronomie et d’Astrophysique (eds) EDPS Conference Series in Astronomy Astrophysics GALAXY AND STAR FORMATION UP TO Z～ 1 F. Hammer and H. Flores1 Abstract Star formation history shows a gradual decline since the last 8-9 Gyr (z=1). The bulk of present-day stellar mass and metal content was formed at red- shifts lower than 2-3, which is consistent with a hierarchical scenario of galaxy formation. Observations of galaxy evolution during the last 2/3 of the Universe age could be done in great details, and provide numerous in- sights on the origin of the Hubble diagram. To some extent, the evolution and formation of present-day elliptical and spiral galaxies could be related to the most rapidly evolving galaxy populations at z～ 1, namely the luminous IR galaxies and the luminous compact galaxies. 1 Introduction Analysis of the age-metallicity relation in the solar neigborhood by Twarog (1980) indicated higher star formation rates in the past by factor 2-3, when the disk was from 1/3 to 1/2 of its present age. Hubble Space Telescope studies of Local Group dwarves have revealed a surprisingly large variety of evolutionary histories (see e.g. Grebel, 2000). Rapid technological developments in the last decade have opened a new era for galaxy evolution studies: galaxies can be detected at the earliest epochs of the Universe and their evolution can be directly compared in different redshift slices. Combination of nearby and distant Universe studies, is likely the best way to understand how (and when) stars and metal content were formed in the Universe. The Canada France Redshift Survey (CFRS, Lilly et al, 1995) have probed the evolution of luminous (L?) galaxies up to z= 1. The fraction of star form- ing galaxies rapidly increases with the redshift: more than 50% at z0.5 have W0(OII) 15A? (Hammer et al, 1997), which should be compared to 13% locally