We present a detailed determination of the restframe B-band galaxy luminosity function (LF) as a function of redshift and star formation activity from z=0 to z '0.75. The dataset used for this purpose is a combined sample of over 1700 redshifts spanning a wide range in apparent magnitude, 11.5< b J <24.0, which we term the Auto b Redshift Survey. The sample includes various earlier magnitude-limited surveys constructed by our team as well as a new survey of 1026 redshifts measured for galaxies at intermediate magnitudes. Spectral classi cations, essential for estimating the k-corrections and galaxy luminosities, are accomplished via cross-correlation with Kennicutt's library of integrated galaxy spectra. The various overlapping surveys in the sample enable us to assess the e ects of redshift incompleteness. We demonstrate that uncertainties in classi cation and those arising from incompleteness do not seriously a ect our conclusions. The large range in apparent magnitude sampled allows us to investigate both the nature of the LF at low redshift (z <0.1) and possible evolution in its shape to z=0.75. We nd that earlier bright surveys have underestimated the absolute normalisation of the LF. Because the shape of the local LF does not change with the survey apparent magnitude limit, it seems unlikely that the local de ciency arises from an underestimated population of low luminosity galaxies. Furthermore, surface brightness losses cannot be signi cant unless they conspire to retain the LF shape over a variety of detection thresholds. Our data directly demonstrates that the B-band LF evolves with redshift. This evolution is best represented as a steepening of the faint-end slope of the LF, from '-1.1 at low redshift to '-1.5 at z '0.5. Using O II] emission as an indicator of star formation activity, we show that the LF of quiescent galaxies has remained largely unchanged since z '0.5, whereas the luminosity density of star-forming galaxies has declined by nearly a factor of 2. The steepening of the overall LF with lookback time is of the form originally postulated by Broadhurst et al. (1988) and is a direct consequence of the increasing space density of blue star-forming galaxies at moderate redshifts.

We analyse Hubble Space Telescope images of a complete sample of 341 galaxies drawn from both the Canada France and Autofib/Low Dispersion Survey Spectrograph ground-based redshift surveys. In this, the first paper in the series, each galaxy has been morphologically classified according to a scheme similar to that developed for the Medium Deep Survey. We discuss the reproducibility of these classifications and quantify possible biases that may arise from various redshift-dependent effects. We then discuss automated classifications of the sample and conclude, from several tests, that we can expect an apparent migration with redshift to later Hubble types that corresponds to a misclassification in our adopted machine classification system of ∼ 24% ± 11 of the true "spirals" as "peculiars" at a redshift z ≃0.9. After allowing for such biases, the redshift distribution for normal spirals, together with their luminosity function derived as a function of redshift, indicates approximately 1 magnitude of luminosity evolution in B AB by z ≃ 1. The elliptical sample is too small for precise evolutionary constraints. However, we find a substantial increase in the proportion of galaxies with irregular morphology at large redshift from 9% ± 3% for 0.3 ≤ z ≤ 0.5 to 32% ± 12% for 0.7 ≤ z ≤ 0.9. These galaxies also appear to be the dominant cause of the rapid rise with redshift in the blue luminosity density identified in the redshift surveys. Although galaxies with irregular morphology may well comprise a mixture of

Abstract. We present the galaxy rest-frame near-IR Luminosity Function (LF) and its cosmic evolution to z ∼ 1.5 based on a spectroscopic survey of a magnitude limited sample of galaxies with K s < 20 (the K20 survey, Cimatti et al. 2002b). The LFs have been derived in the rest-frame J and K s bands. Their evolution is traced using three different redshift bins (z mean 0.5, 1, 1.5) and comparing them to the Local near-IR Luminosity Function. The luminosity functions at different redshifts are fairly well fitted by Schechter functions at z < 1.3. The faint-end of the LFs (L < L * ) is consistent with the local estimates, with no evidence for a change either in the slope or normalization up to z < 1.3. At higher redshift this part of the luminosity function is not well sampled by our data. Viceversa, the density of luminous galaxies (M Ks − 5 log h 70 < −25.5) is higher than locally at all redshifts and relatively constant or mildly increasing with redshift within our sample. The data are consistent with a mild luminosity evolution both in the J-and K s -band up to z 1.5, with an amplitude of about ∆M J −0.69 ± 0.12 and ∆M K −0.54 ± 0.12 at z ∼ 1. Pure density evolution is not consistent with the observed LF at z ≤ 1. Moreover, we find that red and early-type galaxies dominate the bright-end of the LF, and that their number density shows at most a small decrease (<30%) up to z 1, thus suggesting that massive elliptical galaxies were already in place at z 1 and they should have formed their stars and assembled their mass at higher redshift. There appears to be a correlation of the optical/near-IR colors with near-IR luminosities, the most luminous/massive galaxies being red/old, the low-luminous galaxies being instead dominated by blue young stellar populations. We also investigate the evolution of the near-IR comoving luminosity density to z 1.5, finding a slow evolution with redshift (ρ λ (z) = ρ λ (z = 0)(1+z) β(λ) with β(J) 0.70 and β(K s ) 0.37). Finally, we compare the observed LFs with the predictions of a set of the most updated hierarchical merging models. Such a comparison shows that the current versions of hierarchical models overpredict significantly the density of low luminosity galaxies at z ≤ 1 and underpredict the density of luminous galaxies at z ≥ 1, whereas passive evolution models are more consistent with the data up to z ∼ 1.5. The GIF model (Kaufmann et al. 1999) shows a clear deficiency of red luminous galaxies at z ∼ 1 compared to our observations and predicts a decrease of luminous galaxies with redshift not observed in our sample.Key words. galaxies: elliptical and lenticular, evolution, formation, luminosity function -cosmology: observationsinfrared: galaxies IntroductionOver the past few years, a wealth of observations from deep surveys of optically-selected high-redshift galaxies (e.g. Madau et al. 1996;Steidel et al. 1999), complemented by observations in the far-IR/sub-mm (Hughes et al. 1998; Send offprint requests to: L. Pozzetti, e-mail: lucia@bo.astro.it Based on observations ma...

Several aspects of the evolution of star-forming galaxies are studied using measures of the 2dimensional surface brightness profiles of a sample of 341 faint objects selected from the CFRS and LDSS redshift surveys that have been observed with the Hubble Space Telescope. The size function of disk scale lengths in disk-dominated galaxies (i.e. bulge to total ratios, B/T ≤ 0.5) is found to stay roughly constant to z ~ 1, at least for those larger disks with exponential scale lengths α -1 > 3.2 h 50 -1 kpc, where the sample is most complete and where the disk and bulge decompositions are most reliable. This result, which is strengthened by inclusion of the local de Jong et al (1996) size function, suggests that the scale lengths of typical disks can not have grown substantially with cosmic epoch since z ~ 1, unless a corresponding number of large diskshave been destroyed through merging. In addition to a roughly constant number density, the galaxies with large disks, α -1 ≥ 4 h 50 -1 kpc, have, as a set, properties consistent with the idea that they are similar galaxies observed at different cosmic epochs. However, on average, they show higher B-band disk surface brightnesses, bluer overall (U-V) colors, higher [OII] 3727 equivalent widths and less regular morphologies at high redshift than at low redshift, suggesting an increase in the star-formation rate by a factor of about 3 to z ~ 0.7. This is consistent with the expectations of recent models for the evolution of the disk of the Milky Way and similar galaxies. The evolution of the large disk galaxies with scale lengths α -1 ≥ 4 h 50 -1 kpc, isprobably not sufficient to account for the evolution of the overall luminosity function of galaxies over the interval 0 < z < 1, especially if Ω ~ 1. Analysis of the half-light radii of all the galaxies in the sample and construction of the bivariate size-luminosity function suggests that larger changes in the galaxy population are due to smaller galaxies, those with half-light radii around 5 h 50 -1 kpc (i.e. disk scale lengths of 3 h 50 -1 kpc or less).