Morphology of z~1 galaxies from deep K-band AO imaging in the COSMOS field

We present the first results of a program of observations of a sample of distant galaxies ($z_{median}=0.8$) at high spatial resolution ($ \sim 0.1"$) aiming at studying their morphological evolution with redshift. We observed 7 fields of $1' \times1'$ with the NAOS/CONICA Adaptive Optics system in Ks ($2.2\mu m$) band with typical $m_v=14$ guide stars, which is the largest near-infrared survey at this resolution. Near infrared observations are particularly important because they probe $z\sim1$ objects in their \emph{optical rest frame} and is consequently much simpler to compare to samples of nearby galaxies observed with HST. Furthermore their populations are less dependent on the recent history of star formation, which peaks in the UV in rest frame, and give thus a more objective view of galaxy evolution. The observed fields are selected within the COSMOS- ACS and VVDS treasury survey area, in which multi-wavelength photometric and spectroscopic observations are on-going. We analyzed the morphologies by means of B/D (Bulge/Disk) decomposition using GIM2D (Simard et.al) and CAS (Concentration-Asymetry) estimators (Abraham et al.) for about 80 galaxies with magnitudes between $Ks=17-21$ and classify them in three main morphological types (Late Type, Early Type and Irregulars). This gives for the first time an estimation of the galactic population in the near infrared, at high resolution and at a redshift next to 1. Simulations and comparisons with CFHT and HST data have been carried out to probe the accuracy of adaptive optics for morphological purposes in future larger observations programs.