C. Rite

Cluster versus Field Elliptical Galaxies and Clues on Their Formation

Using new observations for a sample of 931 early-type galaxies, we investigate whether the Mg2-σ0 relation shows any dependence on the local environment. The galaxies have been assigned to three different environments depending on the local overdensity (clusters, groups, and field); we used our complete redshift database to guide the assignment of galaxies. It is found that cluster, group, and field early-type galaxies follow almost identical Mg2-σ0 relations, with the largest Mg2 zero-point difference (clusters minus field) being only 0.007±0.002 mag. No correlation of the residuals is found with the morphological type or the bulge-to-disk ratio. Using stellar population models in a differential fashion, this small zero-point difference implies a luminosity-weighted age difference of only ~1 Gyr between the corresponding stellar populations, with field galaxies being younger. The mass-weighted age difference could be significantly smaller if minor events of late star formation took place preferentially in field galaxies. We combine these results with the existing evidence for the bulk of stars in cluster early-type galaxies having formed at very high redshift and conclude that the bulk of stars in galactic spheroids had to form at high redshifts (z3), no matter whether such spheroids now reside in low- or high-density regions. The cosmological implications of these findings are briefly discussed.

The Great Observatories Origins Deep Survey - VLT/ISAAC near-infrared imaging of the GOODS-South field

Aims. We present the final public data release of the VLT /ISAAC near-infrared imaging survey in the GOODS-South field . The survey covers an area of 172.5, 159.6 and 173.1 arcmin 2 in the J, H, and Ks bands, respectively. For point sources total limiting magnitudes of J = 25: 0, H = 24: 5, and Ks = 24: 4 (5� , AB) are reached within 75% of the survey area. Thus these observations are significantly deeper than the previous EIS Deep Public Surve y which covers the same region. The image quality is characterized by a point spread function ranging between 0.34 00 and 0.65 00 FWHM. The images are registered to a common astrometric grid defined by the GSC 2 with an accuracy of�0: 06 00 RMS over the whole field. The overall photometric accuracy, i ncluding all systematic effects, adds up to 0.05 mag. The data are publicly available from the ESO science archive facility. Methods. We describe the data reduction, the calibration, and the quality control process. The final data set is characterized in t erms of astrometric and photometric properties, including the PSF and the curve of growth. We establish an empirical model for the sky background noise in order to quantify the variation of limiting depth and statistical photometric errors over the surve y area. We define a catalog of Ks-selected sources which contains JHKs photometry for 7079 objects. Differential aperture corrections were applied to the color measurements in order to avoid possible biases as a result of the variation of the PSF. We briefly discuss the resu lting color distributions in the context of available redshift data. Fu rthermore, we estimate the completeness fraction and relative contamination due to spurious detections for source catalogs extracted fr om the survey data. For this purpose, an empirical study based on a deep Ks image of the Hubble Ultra Deep Field is combined with extensive image simulations. Results. With respect to previous deep near-infrared surveys, the surface density of faint galaxies has been established with unprecedented accuracy by virtue of the unique combination of depth and area of this survey. We derived galaxy number counts over eight magnitudes in flux up to J = 25: 25, H = 25: 0, Ks = 25: 25 (in the AB system). Very similar faint-end logarithmic slopes between 0.24 and 0.27 mag −1 were measured in the three bands. We found no evidence for a significant change in the slope of the logarithmic galaxy number counts at the faint end.

Redshift-Distance Survey of Early-Type Galaxies: Spectroscopic Data

We present central velocity dispersions and Mg2 line indices for an all-sky sample of ~1178 elliptical and S0 galaxies, of which 984 had no previous measures. This sample contains the largest set of homogeneous spectroscopic data for a uniform sample of elliptical galaxies in the nearby universe. These galaxies were observed as part of the ENEAR project, designed to study the peculiar motions and internal properties of the local early-type galaxies. Using 523 repeated observations of 317 galaxies obtained during different runs, the data are brought to a common zero point. These multiple observations, taken during the many runs and different instrumental setups employed for this project, are used to derive statistical corrections to the data and are found to be relatively small, typically 5% of the velocity dispersion and 0.01 mag in the Mg2 line strength. Typical errors are about 8% in velocity dispersion and 0.01 mag in Mg2, in good agreement with values published elsewhere.

Redshift-Distance Survey of Early-Type Galaxies. I. Sample Selection, Properties, and Completeness*

This is the first in a series of papers describing the recently completed all-sky redshift-distance survey of nearby early-type galaxies (ENEAR) carried out for peculiar velocity analysis. The sample is divided into two parts and consists of 1607 elliptical and lenticular galaxies with cz < 7000 km/s and with blue magnitudes brighter than m_B=14.5 (ENEARm), and of galaxies in clusters (ENEARc). Galaxy distances based on the Dn-sigma and Fundamental Plane (FP) relations are now available for 1359 and 1107 ENEARm galaxies, respectively, with roughly 80% based on new data gathered by our group. The Dn-sigma and FP template distance relations are derived by combining 569 and 431 galaxies in 28 clusters, respectively, of which about 60% are based on our new measurements. The ENEARm redshift-distance survey extends the earlier work of the 7S and the recent Tully-Fisher surveys sampling a comparable volume. In subsequent papers of this series we intend to use the ENEAR sample by itself or in combination with the SFI Tully-Fisher survey to analyze the properties of the local peculiar velocity field and to test how sensitive the results are to different sampling and to the distance indicators. We also anticipate that the homogeneous database assembled will be used for a variety of other applications and serve as a benchmark for similar studies at high-redshift.

Multiwavelength observations of a rich galaxy cluster at z ∼ 1: The HST/ACS colour - Magnitude diagram

Context. XMMU J1229+0151 is a rich galaxy cluster with redshift z = 0.975 that was serendipitously detected in X-rays within the scope of the XMM-Newton Distant Cluster Project. Both HST/ACS observations in the i775 and z850 passbands and VLT/FORS2 spectroscopy were obtained, in addition to follow-up Near-Infrared (NIR) imaging in the J -a ndKs-bands with NTT/SOFI. Aims. We investigate the photometric, structural, and spectral properties of the early-type galaxies in the high-redshift cluster XMMU J1229+0151. Methods. Source detection and aperture photometry are performed in the optical and NIR imaging. Galaxy morphology is inspected visually and by means of Sersic profile fitting to the 21 spectroscopically confirmed cluster members in the ACS field of view. The i775 − z850 colour−magnitude relation (CMR) is derived with a method based on galaxy magnitudes obtained by fitting the surface brightness of the galaxies with Sersic models. Stellar masses and formation ages of the cluster galaxies are derived by fitting the observed spectral energy distributions (SED) with models developed by Bruzual & Charlot. Star-formation histories of the early-type galaxies are constrained by analysing the stacked spectrophotometric data. Results. The structural Sersic index n obtained by model fitting agrees with the visual morphological classification of the confirmed members, indicating a clear predominance of elliptical galaxies (15/21). The i775 −z850 colour−magnitude relation of the spectroscopic members shows a very tight red-sequence with a zero point of 0.86 ± 0.04 mag, and intrinsic scatter equal to 0.039 mag. The CMR obtained with the galaxy models has similar parameters. By fitting both the spectra and SED of the early-type population, we obtain a star-formation-weighted age of 4.3 Gyr for a median galaxy stellar-mass of 7.4 × 10 10 M� . Instead of identifying a brightest cluster galaxy (BCG) unambiguously, we find three bright galaxies with a similar z850 magnitude, which are, in addition, the most massive cluster members, with ∼2 × 10 11 M� . Our results strengthen the current evidence of a lack of significant evolution in both the scatter and slope of the red-sequence out to z ∼ 1.

New southern galaxies with active nuclei

A list of AGN candidates, identified from optical spectra taken as part of an ongoing redshift survey of southern galaxies, is presented. The identification, coordinates, morphological type, measured heliocentric radial velocity, and proposed emission type are given for the galaxies showing evidence of nonstellar nuclear activity. Using standard diagnostics, several new Seyferts and low-ionization nuclear-emission regions (LINERs) are identified among the emission-line galaxies observed. 14 references.

Redshift-Distance Survey of Early-Type Galaxies. II. The Dn-σ Relation*

R-band photometric and velocity dispersion measurements for a sample of 452 elliptical and S0 galaxies in 28 clusters are used to construct a template Dn-� relation. This template relation is constructed by combining the data from the 28 clusters, under the assumption that galaxies in different clusters have similar properties. The photometric and spectroscopic data used consist of new as well as published measurements, converted to a common system, as presented in an accompanying paper. The resulting direct relation, corrected for incompleteness bias, is logDn ¼ 1:203 log � þ 1:406; the zero point has been defined by requiring distant clusters to be at rest relative to the cosmic microwave background. This zero point is consistent with the value obtained by using the distance to Virgo as determined by the Cepheid period-luminosity relation. This new Dn-�relation leads to a peculiar velocity of � 72 � 189 km s � 1 for the Coma Cluster. The scatter in the distance relation corresponds to a distance error of about 20%, comparable to the values obtained for the fundamental plane relation. Correlations between the scatter and residuals of the Dn-� relation with other parameters that characterize the cluster and/or the galaxy stellar population are also analyzed. The direct and inverse relations presented here have been used in recent studies of the peculiar velocity field mapped by the ENEAR all-sky sample.

Redshift-distance Survey of Early-type Galaxies: The D_n-sigma Relation

R-band photometric and velocity dispersion measurements for a sample of 452 elliptical and S0 galaxies in 28 clusters are used to construct a template Dn-� relation. This template relation is constructed by combining the data from the 28 clusters, under the assumption that galaxies in different clusters have similar properties. The photometric and spectroscopic data used consist of new as well as published measurements, converted to a common system, as presented in an accompanying paper. The resulting direct relation, corrected for incompleteness bias, is logDn ¼ 1:203 log � þ 1:406; the zero point has been defined by requiring distant clusters to be at rest relative to the cosmic microwave background. This zero point is consistent with the value obtained by using the distance to Virgo as determined by the Cepheid period-luminosity relation. This new Dn-�relation leads to a peculiar velocity of � 72 � 189 km s � 1 for the Coma Cluster. The scatter in the distance relation corresponds to a distance error of about 20%, comparable to the values obtained for the fundamental plane relation. Correlations between the scatter and residuals of the Dn-� relation with other parameters that characterize the cluster and/or the galaxy stellar population are also analyzed. The direct and inverse relations presented here have been used in recent studies of the peculiar velocity field mapped by the ENEAR all-sky sample.

Redshift-Distance Survey of Early-Type Galaxies. I. The ENEAR[CLC]c[/CLC] Cluster Sample

This paper presents data on the ENEARc subsample of the larger ENEAR survey of the nearby early-type galaxies. The ENEARc galaxies belong to clusters and were specifically chosen to be used for the construction of a D_n-sigma template. The ENEARc sample includes new measurements of spectroscopic and photometric parameters (redshift, velocity dispersion, line index Mg_2, and the angular diameter d_n) as well as data from the literature. New spectroscopic data are given for 229 cluster early-type galaxies and new photometry is presented for 348 objects. Repeat and overlap observations with external data sets are used to construct a final merged catalog consisting of 640 early-type galaxies in 28 clusters. Objective criteria, based on catalogs of groups of galaxies derived from complete redshift surveys of the nearby universe, are used to assign galaxies to clusters. In a companion paper these data are used to construct the template D_n-sigma distance relation for early-type galaxies which has been used to estimate galaxy distances and derive peculiar velocities for the ENEAR all-sky sample.

ESO Imaging Survey - Exploring the optical/infrared imaging data of CDF-S: Point sources

This paper describes the methodology currently being implemented in the EIS pipeline for analysing optical/infrared multi-colour data. The aim is to identify different classes of objects as well as possible undesirable features associated with the construction of colour catalogues. The classification method used is based on the