We present the results of an imaging programme of distant galaxies (z~0.8) at
high spatial resolution (~0.1").We observed 7 fields of 1'*1' with the NACO
Adaptive Optics system (VLT) in Ks (2.16um) band with typical V ~ 14 guide
stars and 3h integration time per field. Observed fields are selected within
the COSMOS survey area. High angular resolution K-band data have the advantage
to probe old stellar populations in the rest-frame, enabling to determine
galaxy morphological types unaffected by recent star formation, better linked
to the underlying mass than classical optical morphology studies (HST).
Adaptive optics on ground based telescopes is the only method today to obtain
such high resolution in the K-band. In this paper we show that reliable results
can be obtained and establish a first basis for larger observing programmes. We
analyze the morphologies by means of B/D (Bulge/Disk) decomposition with GIM2D
and CAS (Concentration-Asymmetry) estimators for 79 galaxies with magnitudes
between Ks = 17-23 and classify them in three main morphological types (Late
Type, Early Type and Irregulars). We obtain for the first time an estimate of
the distribution of galaxy types at redshift z ~ 1 as measured from the near
infrared at high spatial resolution. We show that galactic parameters (disk
scale length, bulge effective radius and bulge fraction) can be estimated with
a random error lower than 20% for the bulge fraction up to Ks = 19 (AB = 21)
and that classification into the three main morphological types can be done up
to Ks = 20 (AB = 22) with at least 70% of correct identifications. We used the
known photometric redshifts to obtain a redshift distribution over 2 redshift
bins (z < 0.8, 0.8 < z < 1.5) for each morphological type.Comment: 19 pages, 19 figures, 5 tables, Accepted for publication in A&A,
typos corrected, referee's suggestions added, figure 3 has been strongly
degrade