We present NICMOS J(110) (rest-frame 1200-2100 angstrom) observations of the three z = 5.7 Ly alpha emitters discovered in the blind multislit spectroscopic survey by Martin et al. These images confirm the presence of the two sources that were previously only seen in spectroscopic observations. The third source, which is undetected in our J110 observations, has been detected in narrowband imaging of the Cosmic Origins Survey, so our non-detection implies a rest-frame equivalent width > 146 angstrom (3 sigma). The two J(110)-detected sources have more modest rest-frame equivalent widths of 30-40 angstrom, but all three are typical of high-redshift Lya emitters. In addition, the J110-detected sources have UV luminosities that are within a factor of 2 of L-UV*, and sizes that appear compact (r(hl) similar to 0.'' 15) in our NIC2 images-consistent with a redshift of 5.7. We use these UV-continuum and Lya measurements to estimate the i(775)-z(850) colors of these galaxies and show that at least one and possibly all three would be missed by the i-dropout Lyman break galaxy selection. These observations help demonstrate the utility of multislit narrowband spectroscopy as a technique for finding faint emission-line galaxies.

We present the WFC3 Infrared Spectroscopic Parallel (WISP) Survey. WISP is obtaining slitless, near-infrared grism spectroscopy of similar to 90 independent, high-latitude fields by observing in the pure-parallel mode with the Wide Field Camera Three on the Hubble Space Telescope for a total of similar to 250 orbits. Spectra are obtained with the G(102) (lambda = 0.8-1.17 mu m, R similar to 210) and G(141) grisms (lambda = 1.11-1.67 mu m, R similar to 130), together with direct imaging in the J and H bands (F110W and F140W, respectively). In the present paper, we present the first results from 19 WISP fields, covering approximately 63 arcmin(2). For typical exposure times (similar to 6400 s in G(102) and similar to 2700 s in G(141)), we reach 5 sigma detection limits for emission lines of f similar to 5 x 10(-17) erg s(-1) cm(-2) for compact objects. Typical direct imaging 5 sigma limits are 26.3 and 26.1 mag. (AB) in F110W and F140W, respectively. Restricting ourselves to the lines measured with the highest confidence, we present a list of 328 emission lines, in 229 objects, in a redshift range 0.3 < z < 3. The single-line emitters are likely to be a mix of H alpha and [O III]5007,4959 angstrom, with H alpha predominating. The overall surface density of high-confidence emission-line objects in our sample is approximately 4 per arcmin2. These first fields show high equivalent width sources, active galactic nucleus, and post-starburst galaxies. The median observed star formation rate (SFR) of our H alpha-selected sample is 4 M-circle dot yr(-1). At intermediate redshifts, we detect emission lines in galaxies as faint as H-140 similar to 25, or M-R < -19, and are sensitive to SFRs down to less than 1 M-circle dot yr(-1). The slitless grisms on WFC3 provide a unique opportunity to study the spectral properties of galaxies much fainter than L* at the peak of the galaxy assembly epoch.

Context. The WIde-field Nearby Galaxy clusters Survey (wings) is a project whose primary goal is to study the galaxy populations in clusters in the local universe (z < 0.07) and of the influence of environment on their stellar populations. This survey has provided the astronomical community with a high quality set of photometric and spectroscopic data for 77 and 48 nearby galaxy clusters, respectively.

We present the galaxy stellar mass function and its evolution in clusters from z similar to 0.8 to the current epoch, based on the WIde-field Nearby Galaxy-cluster Survey (WINGS) (0.04 < z < 0.07), and the ESO Distant Cluster Survey (EDisCS) (0.4 < z < 0.8). We investigate the total mass function and find that it evolves noticeably with redshift. The shape at M-* > 1011 M-circle dot does not evolve, but below M-* similar to 1010.8 M-circle dot the mass function at high redshift is flat, while in the local Universe it flattens out at lower masses. The population of M-* = 1010.2-1010.8 M-circle dot galaxies must have grown significantly between z = 0.8 and 0. We analyse the mass functions of different morphological types (ellipticals, S0s and late types), and also find that each of them evolves with redshift. All types have proportionally more massive galaxies at high than at low-z, and the strongest evolution occurs among S0 galaxies. Examining the morphology-mass relation (the way the proportion of galaxies of different morphological types changes with galaxy mass), we find it strongly depends on redshift. At both redshifts, similar to 40 per cent of the stellar mass is in elliptical galaxies. Another similar to 43 per cent of the mass is in S0 galaxies in local clusters, while it is in late types in distant clusters. To explain the observed trends, we discuss the importance of those mechanisms that could shape the mass function. We conclude that mass growth due to star formation plays a crucial role in driving the evolution. It has to be accompanied by infall of galaxies on to clusters, and the mass distribution of infalling galaxies might be different from that of cluster galaxies. However, comparing with high-z field samples, we do not find conclusive evidence for such an environmental mass segregation. Our results suggest that star formation and infall change directly the mass function of late-type galaxies in clusters and, indirectly, that of early-type galaxies through subsequent morphological transformations.

We report on the discovery of a relation between the stellar mass M* of early-type galaxies (hereafter ETGs), their shape, as parameterized by the Sersic index n, and their stellar mass-to-light ratio M*/L. In a three-dimensional log space defined by these variables, the ETGs populate a plane surface with small scatter. This relation tells us that galaxy shape and stellar population are not independent physical variables, a result that must be accounted for by theories of galaxy formation and evolution.

We present the deepest optical color-magnitude diagram (CMD) to date of the local elliptical galaxy M32. We have obtained F435W and F555W photometries based on Hubble Space Telescope (HST) Advanced Camera for Surveys/High-Resolution Channel images for a region 110 '' from the center of M32 (F1) and a background field (F2) about 320 '' away from M32 center. Due to the high resolution of our Nyquist-sampled images, the small photometric errors, and the depth of our data (the CMD of M32 goes as deep as F435W similar to 28.5 at 50% completeness level), we obtain the most detailed resolved photometric study of M32 yet. Deconvolution of HST images proves to be superior than other standard methods to derive stellar photometry on extremely crowded HST images, as its photometric errors are similar to 2x smaller than other methods tried. The location of the strong red clump in the CMD suggests a mean age between 8 and 10 Gyr for [Fe/H] = -0.2 dex in M32. We detect for the first time a red giant branch bump and an asymptotic giant branch (AGB) bump in M32 which, together with the red clump, allow us to constrain the age and metallicity of the dominant population in this region of M32. These features indicate that the mean age of M32's population at similar to 2' from its center is between 5 and 10 Gyr. We see evidence of an intermediate-age population in M32 mainly due to the presence of AGB stars rising to M-F555W similar to -2.0. Our detection of a blue component of stars (blue plume) may indicate for the first time the presence of a young stellar population, with ages of the order of 0.5 Gyr, in our M32 field. However, it is likely that the brighter stars of this blue plume belong to the disk of M31 rather than to M32. The fainter stars populating the blue plume indicate the presence of stars not younger than 1 Gyr and/or BSSs in M32. The CMD of M32 displays a wide color distribution of red giant branch stars indicating an intrinsic spread in metallicity with a peak at [Fe/H] similar to -0.2. There is not a noticeable presence of blue horizontal branch stars, suggesting that an ancient population with [Fe/H] < -1.3 does not significantly contribute to the light or mass of M32 in our observed fields. M32's dominant population of 8-10 Gyr implies a formation redshift of 1 less than or similar to z(f) less than or similar to 2, precisely when observations of the specific star formation rates and models of "downsizing" imply galaxies of M32's mass ought to be forming their stars. Our CMD therefore provides a "ground truth" of downsizing scenarios at z = 0. Our background field data represent the deepest optical observations yet of the inner disk and bulge of M31. Its CMD exhibits a broad color spread of red giant stars indicative of its metallicity range with a peak at [Fe/H] similar to -0.4 dex, slightly more metal-poor than M32 in our fields. The observed blue plume consists of stars as young as 0.3 Gyr, in agreement with previous works on the disk of M31. The detection of bright AGB stars reveals the presence of intermediate-age population in M31, which is, however, less significant than that in M32 at our field's location.

We present the ellipticity distribution and its evolution for early-type galaxies in clusters from z similar to 0.8 to the current epoch, based on the WIde-field Nearby Galaxy-cluster Survey (0.04 < z < 0.07) and the ESO Distant Cluster Survey (0.4 < z < 0.8). We first investigate a mass-limited sample and we find that above a fixed mass limit (M-* >= 1010.2 M-circle dot), the ellipticity (epsilon) distribution of early-type galaxies notably evolves with redshift. In the local Universe, there are proportionally more galaxies with higher ellipticity, hence flatter, than in distant clusters. This evolution is due partly to the change in the mass distribution and mainly to the change in the morphological mix with z among the early types, the fraction of ellipticals goes from similar to 70 per cent at high z to similar to 40 per cent at low z). Analysing separately the ellipticity distribution of the different morphological types, we find no evolution both for ellipticals and for S0s. However, for ellipticals a change with redshift in the median value of the distributions is detected. This is due to a larger population of very round (epsilon < 0.05) elliptical galaxies at low z. In order to compare our finding to previous studies, we also assemble a magnitude-'delimited' sample that consists of early-type galaxies on the red sequence with -19.3 > M-B + 1.208z > -21. Analysing this sample, we do not recover exactly the same results as the mass-limited sample. This indicates that the selection criteria are crucial to characterize the galactic properties: the choice of the magnitude-'delimited' sample implies the loss of many less-massive galaxies and so it biases the final conclusions. Moreover, although we are adopting the same selection criteria, our results in the magnitude-'delimited' sample are also not in agreement with those of Holden et al. This is due to the fact that our and their low-zsamples have a different magnitude distribution because the Holden et al. sample suffers from incompleteness at faint magnitudes.

We study the color-magnitude red sequence and blue fraction of 72 X-ray selected galaxy clusters at z = 0.04-0.07 from the WINGS survey, searching for correlations between the characteristics of the red sequence (RS) and the environment. We consider the slope and scatter of the red sequence, the number ratio of red luminous-to-faint galaxies, the blue fraction, and the fractions of ellipticals, S0s, and spirals that compose the RS. None of these quantities correlate with the cluster velocity dispersion, X-ray luminosity, number of cluster substructures, BCG prevalence over next brightest galaxies, and the spatial concentration of ellipticals. The properties of the RS, instead, depend strongly on local galaxy density. Higher density regions have a smaller RS scatter, a higher luminous-to-faint ratio, a lower blue fraction, and a lower spiral fraction on the RS. Our results clearly illustrate the prominent effect of the local density in setting the epoch when galaxies become passive and join the red sequence, as opposed to the mass of the galaxy host structure.

We present the morphological catalogue of galaxies in nearby clusters of the WIde-field Nearby Galaxy-clusters Survey (WINGS). The catalogue contains a total number of 39 923 galaxies, for which we provide the automated estimates of the morphological type, applying the purposely devised tool MORPHOT to the V-band WINGS imaging. For similar to 3000 galaxies we also provide visual estimates of the morphological type. A substantial part of the paper is devoted to the description of the MORPHOT tool, whose application is limited, at least for the moment, to the WINGS imaging only. The approach of the tool to the automation of morphological classification is a non-parametric and fully empirical one. In particular, MORPHOT exploits 21 morphological diagnostics, directly and easily computable from the galaxy image, to provide two independent classifications: one based on a maximum likelihood (ML), semi-analytical technique and the other one on a neural network (NN) machine. A suitably selected sample of similar to 1000 visually classified WINGS galaxies is used to calibrate the diagnostics for the ML estimator and as a training set in the NN machine. The final morphological estimator combines the two techniques and proves to be effective both when applied to an additional test sample of similar to 1000 visually classified WINGS galaxies and when compared with small samples of Sloan Digital Sky Survey (SDSS) galaxies visually classified by Fukugita et al. and Nair et al. Finally, besides the galaxy morphology distribution (corrected for field contamination) in the WINGS clusters, we present the ellipticity (?), colour (B-V) and Sersic index (n) distributions for different morphological types, as well as the morphological fractions as a function of the clustercentric distance (in units of R200).

The WFC3 Infrared Spectroscopic Parallel Survey uses the Hubble Space Telescope (HST) infrared grism capabilities to obtain slitless spectra of thousands of galaxies over a wide redshift range including the peak of star formation history of the universe. We select a population of very strong emission-line galaxies with rest-frame equivalent widths (EWs) higher than 200 angstrom. A total of 176 objects are found over the redshift range 0.35 < z < 2.3 in the 180 arcmin(2) area that we have analyzed so far. This population consists of young and low-mass starbursts with high specific star formation rates (sSFR). After spectroscopic follow-up of one of these galaxies with Keck/Low Resolution Imaging Spectrometer, we report the detection at z = 0.7 of an extremely metal-poor galaxy with 12 + log(O/H) = 7.47 +/- 0.11. After estimating the active galactic nucleus fraction in the sample, we show that the high-EW galaxies have higher sSFR than normal star-forming galaxies at any redshift. We find that the nebular emission lines can substantially affect the total broadband flux density with a median brightening of 0.3 mag, with some examples of line contamination producing brightening of up to 1 mag. We show that the presence of strong emission lines in low-z galaxies can mimic the color-selection criteria used in the z similar to 8 dropout surveys. In order to effectively remove low-redshift interlopers, deep optical imaging is needed, at least 1 mag deeper than the bands in which the objects are detected. Without deep optical data, most of the interlopers cannot be ruled out in the wide shallow HST imaging surveys. Finally, we empirically demonstrate that strong nebular lines can lead to an overestimation of the mass and the age of galaxies derived from fitting of their spectral energy distribution (SED). Without removing emission lines, the age and the stellar mass estimates are overestimated by a factor of 2 on average and up to a factor of 10 for the high-EW galaxies. Therefore, the contribution of emission lines should be systematically taken into account in SED fitting of star-forming galaxies at all redshifts.