arXiv subjects

M. Scodeggio

Publications and source records attributed to M. Scodeggio.

At least 271 records · Page 15Linked to original sources

arXiv2002

1.65 micron (H-band) surface photometry of galaxies. IX: photometric and structural properties of galaxies

As a result of a systematic NIR H-band (1.65 micron) imaging survey of normal galaxies in the local universe, we are able to measure in a highly homogeneous way photometric and structural properties for a sample of 1143 galaxies. We base our analysis on a quantitative structural parameter, the concentration index C_31, instead of relying on the galaxies' morphological classification. The C_31 parameter provides a model independent, quantitative and continuous characterization of the light distribution within galaxies, and it is thus to be preferred to either the Hubble type or a parameter like the bulge-to-disk or bulge-to-total light ratio. We find that galaxies can be completely described by three parameters, namely: a scale parameter (the H-band luminosity), a shape parameter (the concentration index C_31) and a colour parameter (e.g. the B-H colour). At low luminosity dEs and dIs, having similar C_31, are colour-discriminated, while at very high luminosity different C_31 discriminate S0s from Scs, otherwise undistinguishable on the basis of their colour. A single, monotonic relation exists between luminosity and mu_e in the H-band, as opposed to the two separate regimes that are generally observed in the B-band. As NIR luminosity traces quite accurately the galaxy mass distribution, this relation re-enforces the indication in favour of a scale-dependent mass collapse mechanism which produces higher surface-brightness and more centrally peaked galaxies with increasing mass. However, the presence of high-luminosity low-C_31 galaxies hints at other machanisms and physical properties (such as angular momentum) playing an important role in galaxy formation. (abridged)

astro-ph↗

arXiv2002

1.65 micron (H-band) surface photometry of galaxies. VIII: the near-IR k-space at z=0

We present the distribution of a statistical sample of nearby galaxies in the k-space (k1 ~ log M, k2 ~ log Ie, k3 ~ log M/L). Our study is based on near-IR (H-band: lambda = 1.65 micron) observations, for the first time comprising early- and late-type systems. Our data confirm that the mean effective dynamical mass-to-light ratio M/L of the E+S0+S0a galaxies increases with increasing effective dynamical mass M, as expected from the existence of the Fundamental Plane relation. Conversely, spiral and Im/BCD galaxies show a broad distribution in M/L with no detected trend of M/L with M, the former galaxies having M/L values about twice larger than the latter, on average. For all the late-type galaxies, the M/L increases with decreasing effective surface intensity Ie, consistent with the existence of the Tully--Fisher relation. These results are discussed on the basis of the assumptions behind the construction of the k-space and their limitations. Our study is complementary to a previous investigation in the optical (B-band: lambda = 0.44 micron) and allows us to study wavelength-dependences of the galaxy distribution in the k-space. As a first result, we find that the galaxy distribution in the k1--k2 plane reproduces the transition from bulge-less to bulge-dominated systems in galaxies of increasing dynamical mass. Conversely, it appears that the M/L of late-types is higher (lower) than that of early-types with the same M in the near-IR (optical). The origins of this behaviour are discussed in terms of dust attenuation and star formation history.

astro-ph↗

arXiv2001

On the Nature of the EIS Candidate Clusters: Confirmation of z<0.6 candidates

We use public V-band imaging data from the wide-angle surveys conducted by the ESO Imaging Survey project (EIS) to further investigate the nature of the EIS galaxy cluster candidates. These were originally identified by applying a matched-filter algorithm which used positional and photometric data of the galaxy sample extracted from the I-band survey images. In this paper, we apply the same technique to the galaxy sample extracted from V-band data and compare the new cluster detections with the original ones. We find that ~75% of the low-redshift cluster candidates (z<0.6) are detected in both passbands and their estimated redshifts show good agreement with the scatter in the redshift differences being consistent with the estimated errors of the method. For the ``robust'' I-band detections the matching frequency approaches ~85%. We also use the available (V-I) color to search for the red sequence of early-type galaxies observed in rich clusters over a broad range of redshifts. This is done by searching for a simultaneous overdensity in the three-dimensional color-projected distance space. We find significant overdensities for ~75% of the ``robust'' candidates with z_I<0.6. We find good agreement between the characteristic color associated to the detected "red sequence" and that predicted by passive evolution galaxy models for ellipticals at the redshift estimated by the matched-filter. The results presented in this paper show the usefulness of color data, even of two-band data, to both tentatively confirm cluster candidates and to select possible cluster members for spectroscopic observations. Based on the present results, we estimate that ~150 EIS clusters with z_I<0.6 are real, making it one of the largest samples of galaxy clusters in this redshift range currently available in the southern hemisphere.

astro-ph↗

arXiv2001

1.65 micron (H-band) surface photometry of galaxies. VII: dwarf galaxies in the Virgo cluster

We present near-infrared H-band (1.65micron) observations and surface brightness profile decompositions for 75 faint (13.5 < m_p < 18.5) galaxies, primarily taken among dwarf Ellipticals members of the Virgo cluster. We model their surface brightness profiles with a de Vaucouleurs (D), exponential (E), mixed (bulge+disk or M) or truncated (T) law, and we derive for each galaxy the H band effective surface brightness (mu_e) and effective radius (r_e), the asymptotic total magnitude H_T and the light concentration index C_31. Combining the present data with those previously obtained by our group (1157 objects) we analyze the NIR properties of a nearly complete sample, representative of galaxies of all morphological types, spanning 4 decades in luminosity. We confirm our earlier claim that the presence of cusps and extended haloes in the light profiles (C_31>5) is a strong, non-linear function of the total luminosity. We also find that: i) among dEs and dS0s galaxies D profiles are absent; 50% of the decompositions are of type M, the remaining being of type E or T. ii) Less than 50% of the giant elliptical galaxies have pure D profiles, the majority being represented by M profiles. iii) Most giant galaxies (from elliptical to Sb) have M profiles. iv) Most of late type spirals (Scd to BCD) have either E or T profiles. v) The type of decomposition is a strong function of the total H band luminosity, independent of the Hubble classification: the fraction of type E decompositions decreases with increasing luminosity, while those of type M increase with luminosity. Pure D profiles are absent in the low luminosity range L_H<10^10 solar and become dominant above 10^11 solar, while T profiles are present only among low luminosity galaxies.

astro-ph↗

arXiv2001

Automated spectral extraction for high multiplexing MOS and IFU observations

VIMOS main distinguishing characteristic is its very high multiplex capability: in MOS mode up to 800 spectra can be acquired simultaneously, while the Integral Field Unit produces 6400 spectra to obtain integral field spectroscopy of an area approximately 1x1 arcmin in size. To successfully exploit the capabilities of such an instrument it is necessary to expedite as much as possible the analysis of the very large volume of data that it will produce, automating almost completely the basic data reduction and the related bookkeeping process. The VIMOS Data Reduction Software (DRS) has been designed specifically to satisfy these two requirements. A complete automation is achieved using a series of auxiliary tables that store all the input information needed by the data reduction procedures, and all the output information that they produce. We expect to achieve a satisfactory data reduction for more than 90% of the input spectra, while some level of human intervention might be required for a small fraction of them to complete the data reduction. The DRS procedures can be used as a stand-alone package, but are also being incorporated within the VIMOS pipeline under development at the European Southern Observatory.

astro-ph↗

arXiv2001

The VIRMOS-VLT Deep Survey

The aim of the VIRMOS VLT Deep Survey (VVDS) is to study of the evolution of galaxies, large scale structures and AGNs from a sample of more than 150,000 galaxies with measured redshifts in the range 0<z<5+. The VVDS will rely on the VIMOS and NIRMOS wide field multi-object spectrographs, which the VIRMOS consortium is delivering to ESO. Together, they offer unprecedented multiplex capability in the wavelength range 0.37-1.8microns, allowing for large surveys to be carried out. The VVDS has several main aspects: (1) a deep multi-color imaging survey over 18deg^2 of more than one million galaxies, (2) a "wide" spectroscopic survey with more than 130,000 redshifts measured for objects brighter than IAB=22.5 over 18deg^2, (3) a "deep" survey with 50,000 redshifts measured to IAB=24, (4) ultra-deep" surveys with several thousand redshifts measured to IAB=25, (5) multi-wavelength observations with the VLA and XMM.

astro-ph↗

arXiv2000

Optical/Infrared Survey of Galaxy Clusters

In this contribution the ongoing effort to build a statistical sample of clusters of galaxies over a wide range of redshifts to study the evolution of clusters and member galaxies is reviewed. The starting point for this project has been the list of candidate clusters identified from the I-band EIS-WIDE survey data. Since the completion of this survey, new optical/infrared observations have become available and have been used to confirm some of these candidates using the photometric data alone or in combination with the results of follow-up spectroscopic observations. Our preliminary results show that the yield of real physical associations from the original catalog is conservatively >60% and that a large sample of clusters in the southern hemisphere, extending to high-redshifts, is within reach.

astro-ph↗

arXiv2000

1.65 micron (H-band) surface photometry of galaxies. V: Profile decomposition of 1157 galaxies

We present near-infrared H-band (1.65 micron) surface brightness profile decomposition for 1157 galaxies in five nearby clusters of galaxies: Coma, A1367, Virgo, A262 and Cancer, and in the bridge between Coma and A1367 in the "Great Wall". The optically selected (m_p<=16.0) sample is representative of all Hubble types, from E to Irr+BCD, except dE and of significantly different environments, spanning from isolated regions to rich clusters of galaxies. We model the surface brightness profiles with a de Vaucouleurs r^(1/4) law (dV), with an exponential disk law (E), or with a combination of the two (B+D). From the fitted quantities we derive the H band effective surface brightness (mu_e) and radius (r_e) of each component, the asymptotic magnitude H_T and the light concentration index C_31. We find that: i) Less than 50% of the Elliptical galaxies have pure dV profiles. The majority of E to Sb galaxies is best represented by a B+D profile. All Scd to BCD galaxies have pure exponential profiles. ii) The type of decomposition is a strong function of the total H band luminosity (mass), independent of the Hubble classification: the fraction of pure exponential decompositions decreases with increasing luminosity, that of B+D increases with luminosity. Pure dV profiles are absent in the low luminosity range L_H<10^(10) L_solar and become dominant above 10^(11) L_solar.

astro-ph↗

arXiv2000

Spectroscopic confirmation of clusters from the ESO imaging survey

We measure redshifts for 67 galaxies in the field of six cluster candidates from the ESO Imaging Survey (EIS). The cluster candidates are selected in the EIS patches C and D among those with estimated mean redshifts between 0.5 and 0.7. The observations were made with EFOSC2 at the 3.6m ESO telescope. In the six candidate cluster fields, we identify 19 possible sets of 2 to 7 galaxies in redshift space. In order to establish which of the 19 sets are likely to correspond to real dense systems we compare our counts with those expected from a uniform distribution of galaxies with given luminosity function. In order to take into account the effect of the Large Scale Structure, we modulate the probability computed from the luminosity function with random samplings of the Canada-France Redshift Survey. We find that four out of six candidate EIS clusters are likely to correspond to real systems in redshift space (> 95 % confidence level). Two of these systems have mean redshift in agreement with the redshift estimate given by the matched filter algorithm. The other two systems have significantly lower redshifts. We discuss the implications of our results in the context of our ongoing research projects aimed at defining high-redshift optically-selected cluster samples.

astro-ph↗

arXiv2000

EROs in the EIS Fields. I: The AXAF (Chandra) Deep Field

The publicly available EIS-DEEP optical-NIR data for the AXAF (Chandra) Deep Field have been used to construct samples of Extremely Red Objects (EROs) using various single-band and multi-band color criteria. In this work we define as EROs objects with colors consistent with passively evolving elliptical galaxies at z $\geq$ 1. The EROs surface densities we derive are intermediate between previous published values, emphasizing again the need for larger survey areas to constrain the effects of possible large-scale structure. Although various single-color selected samples can be derived, the EROs sample selected using R-Ks > 5, I-Ks > 4, J-Ks > 1.8 jointly is likely to contain the highest fraction of passively evolving luminous field elliptical galaxies at z >= 1, or conversely, the lowest fraction of lower redshift interlopers. The surface density of this multi-band selected EROs sample is consistent with the conclusion that little or no field elliptical volume density evolution has occurred in the redshift range 0 > z > 1.5. However, extensive spectroscopic followup is necessary to confirm this conclusion.

astro-ph↗

arXiv1999

Building a Sample of Distant Clusters of Galaxies

Candidate clusters of galaxies drawn from the sample identified from the moderately deep I-band data of the ESO Imaging Survey (EIS), have been used for follow-up optical/infrared imaging and spectroscopic observations. The observations were conducted to assess the nature of these candidates over a large range of redshifts. Currently, 163 EIS candidates have (V-I) colors, 15 have (I-K) and 65 cluster fields have been observed spectroscopically. From a preliminary analysis of these data, we find that > 65% of the candidates studied show strong evidence of being real physical associations, over the redshift range 0.2 0.6, and six candidates in the interval 0.45<z<0.81 have either been identified directly from measured redshifts or have been confirmed by the measurement of at least one redshift for galaxies located along a red-sequence typical of cluster early-type galaxies. Lastly, five candidates among those already observed in the infrared have (I-Ks) colors consistent with them being in the redshift interval 0.8<z<1.1. The sample of "confirmed" clusters, already the largest of its kind in the southern hemisphere, will be further enlarged by ongoing observations.

astro-ph↗

arXiv1999

1.65 micrometers (H-band) surface photometry of galaxies. IV:observations of 170 galaxies with the Calar Alto 2.2m telescope

We present near-infrared (H band) surface photometry of 170 galaxies, obtained in 1997 using the Calar Alto 2.2m telescope equipped with the NICMOS3 camera MAGIC. The majority of our targets are selected among bright members of the Virgo cluster, however galaxies in the A262 and Cancer clusters and in the Coma/A1367 supercluster are also included. This data set is aimed at complementing the NIR survey in the Virgo cluster discussed in Boselli et al. (1997) and in the Coma Supercluster, presented in Papers I, II and III of this series. Magnitudes at the optical radius, total magnitudes, isophotal radii and light concentration indices are derived. (Tables 1 and 2 are only available in electronic form upon request to gavazzi@uni.mi.astro.it)

astro-ph↗

arXiv1999

1.65 micrometers (H-band) surface photometry of galaxies. III: observations of 558 galaxies with the TIRGO 1.5m telescope

We present near-infrared H-band (1.65 micron) surface photometry of 558 galaxies in the Coma Supercluster and in the Virgo cluster. This data set, obtained with the Arcetri NICMOS3 camera ARNICA mounted on the Gornergrat Infrared Telescope, is aimed at complementing, with observations of mostly early-type objects, our NIR survey of spiral galaxies in these regions, presented in previous papers of this series. Magnitudes at the optical radius, total magnitudes, isophotal radii and light concentration indices are derived. We confirm the existence of a positive correlation between the near-infrared concentration index and the galaxy H-band luminosity. (Tables 1 and 2 are only available in electronic form upon request to gavazzi@uni.mi.astro.it)

astro-ph↗

arXiv1999

Confirming EIS Clusters. Multi-object Spectroscopy

Using EFOSC2 at the 3.6m ESO telescope, we obtained redshifts for 68 galaxies in the field of six cluster candidates from the ESO Imaging Survey (EIS). The cluster candidates were selected in the EIS patches C and D and have estimated mean redshifts between z=0.5 and z=0.7. In the six candidate cluster fields, we identify possible systems of galaxies in the redshift space. The likelihoods of these systems are established by comparison with random resamplings of the Canada-France Redshift Surveys, and using the redshift distribution expected from Postman et al.'s luminosity function, with Poggianti's K- and evolutionary-corrections. Four of the six candidate EIS clusters are found to correspond to a real system in the redshift space, with > 95 % probability. Two of them have a mean redshift in agreement with the estimate from the matched filter algorithm, while the other two have a significantly smaller redshift. The independent analysis of the V-I vs. I color-magnitude diagrams for five of our six cluster fields, supports our conclusions based on the spectroscopic data.

astro-ph↗

arXiv1999

Confirming EIS Clusters. Optical and Infrared Imaging

Clusters of galaxies are important targets in observationally cosmology, as they can be used both to study the evolution of the galaxies themselves and to constrain cosmological parameters. Here we report on the first results of a major effort to build up a sample of distant galaxy clusters to form the basis for further studies within those fields. We search for simultaneous overdensities in color and space to obtain supporting evidence for the reality of the clusters. We find a confirmation rate for EIS clusters of 66%, suggesting that a total of about 80 clusters with z>=0.6 are within reach using the EIS cluster candidates.

astro-ph↗

arXiv1999

VLT and NTT Observations of Two EIS Cluster Candidates. Detection of the Early-Type Galaxies Sequence at z~1

Optical data from the ESO VLT-UT1 Science Verification observations are combined with near-infrared data from SOFI at the NTT to obtain optical-infrared color-magnitude diagrams for the objects in the fields of two EIS cluster candidates. In both cases, evidence is found for a well-defined sequence of red galaxies that appear to be significantly more clustered than the background population. These results suggest that the two systems are real physical associations. The (R-Ks), (I-Ks) and (J-Ks) colors of the red sequences are used, in conjunction with similar data for spectroscopically confirmed clusters, to obtain redshift estimates of z ~ 0.9 and z ~ 1.0 for these two systems. These results make these EIS cluster candidates prime targets for follow-up spectroscopic observations to confirm their reality and to measure more accurately their redshift.

astro-ph↗

arXiv1998

The 3-D structure of the Virgo cluster from H band Fundamental Plane and Tully-Fisher distance determinations

We undertook a surface photometry survey of 200 galaxies in the Virgo cluster (complete to B<14.0 mag) carried out in the near-Infrared (NIR) H band. Combining velocity dispersion measurements from the literature with new spectroscopic data for 11 galaxies we derive distances of 59 early type galaxies using the Fundamental Plane (FP) method. The distance of another 75 late-type galaxies is determined using the Tully-Fisher (TF) method. For this purpose we use the maximum rotational velocity, as derived from HI spectra from the literature, complemented with new H_alpha rotation curves of 8 highly HI deficient galaxies. The zero-point of the FP and TF template relations are calibrated assuming the distance modulus of Virgo mu_o=31.0, as determined with the Cepheids method. Using these 134 distance determinations (with individual uncertainties of 0.35 (TF), 0.45 (FP) mag) we find that the distance of cluster A, associated with M87, is mu_o=30.84+-0.06. Cluster B, off-set to the south, is found at mu_o=31.84+-0.10$. This subcluster is falling onto A at about 750 km/sec. Clouds W and M are at twice the distance of A. Galaxies on the North-West and South-East of the main cluster A belong to two clouds composed almost exclusively of spiral galaxies with distances consistent with A, but with significantly different velocity distributions, suggesting that they are falling onto cluster A at approximately 770 km/sec from the far-side and at 200 km/sec from the near-side respectively. The mass of Virgo inferred from the peculiar motions induced on its vicinity is consistent with the virial expectation.

astro-ph↗

arXiv1998

ESO Imaging Survey. AXAF Field: Deep Optical-Infrared Observations, Data Reduction and Photometry

This paper presents ground-based data obtained from deep optical and infrared observations carried out at the ESO 3.5 New Technology Telescope (NTT) of a field selected for its low HI content for deep observations with AXAF. These data were taken as part of the ESO Imaging Survey (EIS) program, a public survey conducted in preparation for the first year of operation of the VLT. Deep CCD images are available for five optical passbands, reaching 2 sigma limiting magnitudes of U_AB~27.0, B_AB~27, V_AB~26.5, R_AB~26.5 and I_AB~26. An area of ~56 square arcmin is covered by UBVR observations, and ~30 square arcmin also in I. The infrared observations cover a total area of ~83 square arcmin, reaching J_AB~24.5 and K_AB~23.5. This paper describes the observations and data reduction. It also presents images of the surveyed region and lists the optical and infrared photometric parameters of the objects detected on the co-added images of each passband, as well as multicolor optical and infrared catalogs. These catalogs together with the astrometrically and photometrically calibrated co-added images are public and can be retrieved from the URL http://www.eso.org/eis/ . This data set completes the ESO Imaging Survey program sixteen months after it began in July 1997.

astro-ph↗