Giampaolo Vettolani

The GALEX VIMOS-VLT Deep Survey Measurement of the Evolution of the 1500 Å Luminosity Function

We present the first measurement of the galaxy luminosity function (LF) at 1500 A in the range 0.2 ≤ z ≤ 1.2 based on Galaxy Evolution Explorer VIMOS-VLT Deep Survey observations (~1000 spectroscopic redshifts for galaxies with NUV ≤ 24.5) and at higher z using existing data sets. Our main results are summarized as follows: (1) Luminosity evolution is observed with ΔM* ~ -2.0 mag between z = 0 and z = 1 and ΔM* ~ -1.0 mag between z = 1 and z = 3. This confirms that the star formation activity was significantly higher in the past. (2) The LF slopes vary in the range -1.2 ≥ α ≥ -1.65, with a marginally significant hint of increase at higher z. (3) We split the sample in three rest-frame (B - I) intervals, providing an approximate spectral type classification: Sb-Sd, Sd-Irr, and unobscured starbursts. We find that the bluest class evolves less strongly in luminosity than the two other classes. On the other hand, their number density increases sharply with z (~15% in the local universe to ~55% at z ~ 1), while that of the reddest classes decreases.

All-sky catalogs of superclusters of Abell-ACO clusters

We present the results of a statistical analysis of structures in the Abell and ACO catalogs of clusters of galaxies. For both catalogs we have improved upon distance estimates for clusters without measured radial velocity and we discuss in detail the calibration of the magnitude-redshift relation. Through a percolation analysis we have obtained catalogs of superclusters at various density excesses: we analyze their reality and global properties, focusing in particular on the problem of the possible existence of large peculiar motions of clusters in superclusters

A study of the core of the Shapley Concentration – I. The sample

We report the first results of a spectroscopic survey of galaxies in the core of the Shapley Concentration, the richest nearby supercluster of clusters of galaxies. We have measured 311 new galaxy redshifts in an area of ∼4.5 deg 2 centred on the Abell cluster A3558. When the data already available in the literature are also considered, the total number of galaxy redshifts in this area amounts to more than 500. On the basis of these data, we estimate the mean velocities and the velocity dispersions of the Abell clusters A3556 and A3558 and the poor cluster SC 1329-314

Possible geometric patterns in 0.1c scale structure

The union of Abell and Abell-Corwin-Olowin samples of rich clusters provides a view of the universe up to z∼0.1 and within this domain there are two outstanding concentrations of clusters. The nearer of these, the Shapley concentration 140 h −1 Mpc from us, lies close to the direction of our motion inferred from the microwave dipole, suggesting that coherent streaming may extend over this great scale. In addition, there are two startling geometric results: (1) the previously announced concentration of rich clusters to the supergalactic equator extends across a domain of ∼450 h −1 Mpc, representing a ∼6 σ deviation from a Poissonian distribution and a ∼3 σ deviation when clustering is allowed for with a simple model

A comparison of ACO and Abell catalogs of clusters

The results of a statistical analysis of the ACO and Abell catalog of clusters of galaxies are presented. For both catalogs, new estimates of distances, surface, and radial densities are derived. In particular, for the ACO catalog it is found that the derived radial-density distribution (including R = 0 clusters) is consistent with a uniform density of clusters up to at least 350/h Mpc. Moreover, within this distance the ACO data do not show any significant deficiency of R = 0 clusters. In both catalogs the effects of large angular gradients and derive maximum-likelihood estimates for the interesting parameters (i.e., galactic latitude and zenithal dependencies) are also studied. The ACO catalog appears to be more complete, with a larger volume density of clusters than the Abell catalog. 30 refs.

The ESO Slice Project (ESP) galaxy redshift survey - III. The sample

The ESO Slice Project (ESP) is a galaxy redshift survey we have recently completed as an ESO Key-Project. The ESP covers 23.3 square degrees in a region close to the South Galactic Pole. The survey is nearly complete (85%) to the limiting magnitude b_J=19.4 and consists of 3342 galaxies with reliable redshift determination. In this paper, the first in a series that will present the results of the ESP survey, we describe the main characteristics of the survey and briefly discuss the properties of the galaxy sample. From a preliminary spectral analysis of a large sub-sample of 2550 galaxies we find that the fraction of actively star-forming galaxies increases from a few percent for the brightest galaxies up to about 40% for the galaxies fainter than M= -16.5. The most outstanding feature in the ESP redshift distribution is a very significant peak at z ~ 0.1. The detection of similar peaks, at the same distance, in other surveys in the same region of the sky, suggests the presence of a large bidimensional structure perpendicular to the line of sight. The minimum size of this structure would be of the order of 100 x 50 Mpc, comparable with the size of the Great Wall.The ESO Slice Project (ESP) is a galaxy redshift survey extending over about 23 square degrees, in a region near the South Galactic Pole. The survey is ~85% complete to the limiting magnitude b_J=19.4 and consists of 3342 galaxies with redshift determination. The ESP survey is intermediate between shallow, wide angle samples and very deep, one-dimensional pencil beams; the spanned volume is ~ 5 x 10^4 Mpc^3 at the sensitivity peak (z ~ 0.1). In this paper we present the description of the observations and of the data reduction, the ESP redshift catalogue and the analysis of the quality of the velocity determinations.

The distribution of clusters of galaxies within 300 Mpc/h and the crossover to an isotropic and homogeneous universe

Firm evidence is presented from clusters of galaxies in the Abell and ACO galaxies for the spatial convergence of a cosmological dipole which increases with distance up to about 180/h Mpc, then bends and remains flat within the sample depth, while the monopole continues to grow linearly with distance up to a maximum sample depth of 300/h Mpc. It is at that point more than 5 times above the dipole level; this monopole growth behavior demonstrates that the dipoles convergence is real, rather than due to the depth incompleteness of the sample. An analysis of the behavior of the dipole as a function of distance suggests that a nonnegligible fraction of the peculiar acceleration responsible for the Local Group motion comes from greater depths than concluded from earlier studies. 42 refs.

Spectroscopy and multicolor photometry of the medium redshift southern cluster of galaxies A3639

Spectroscopic observations at 360-700 nm and photometric observations in the Gunn g, r, and i bands are reported for Abell 3639. Data obtained using the EFOSC with CCD detectors at the Cassegrain focus of the 3.6-m telescope at ESO during 1987 and 1988 are presented in extensive tables, graphs, and sample spectra and characterized in detail. Ten of 14 cluster-core galaxies studied are identified as cluster members, giving a mean redshift of 0.1496 + or - 0.0027 and a velocity dispersion of sigma = 538 + 212 or - 128 km/sec. No evidence of an extended envelope is found for the dominant galaxy. Investigation of the luminosity function of cluster galaxies down to M(r) = -18 in an area of radius about 500 kpc and elimination of background galaxies on the basis of their position in the color-color diagram gives a total of 105 galaxies in the sample. 28 refs.

Photometric properties of threee X-ray selected clusters of galaxies

Spectral and photometric analysis of three X-ray selected clusters are presented. Redshifts have been obtained for a limited number of galaxies (from 4 to 8) for each cluster. Photometry in the three Gunn filters g, r, i is presented: objects have been automatically classified as stars or galaxies, and background (or foreground) galaxies have been recognized on the basis of the color-color diagram. Best fit parameters of a Schechter luminosity function have been derived in two cases. The cluster morphological compositions, based on galaxy colors, are discussed as a function of distance and X-ray properties

A view of the sub-mJy populations, modelling and perspectives for future deep surveys

We use deep multi-colour (UBVRIJK) images mostly taken in the framework of the ESO Deep Public Survey (DPS) to optically identify and derive photometric redshifts for a complete sample of 131 radio sources with S>0.4 mJy, observed at both 1.4 and 5 GHz as part of the ATESP radio survey. The availability of multi-wavelength radio and optical information is exploited to infer the physical properties of the faint radio population. In particular we find that, considering both early-type galaxies and quasars as sources with an active nucleus, AGNs largely dominate our sample sub-mJy sample (78%). Further radio/optical analysis of such AGN component has revealed a somewhat unexpected class of flat/inverted-spectrum sources with low radio-to-optical ratios (R<100), which are preferentially identified with early-type galaxies. Such sources are quite compact (d<10-30 kpc), suggesting core-dominated radio emission triggered by low luminosity AGNs. This intriguing class of objects deserves further analysis, and new higher resolution radio observations are currently under way. In parallel we are developing radio source models, for both the AGN and the star-forming components of the sub-mJy radio pupulation. Here we discuss the first results.