Poster Contributions

First results from the ELAIS/SCUBA deep X-ray survey
O. Almaini

Abstract: We present the first results from a deep Chandra survey centred on a new wide-area SCUBA submillimetre map. The potential link between the X-ray and infrared/submillimetre backgrounds has wide ranging implications for our understanding of AGN and star-formation processes and the AGN/starburst connection. So far we have analysed 150ks of Chandra data. A further 150ks of XMM time will arrive shortly. We have also accumulated deep near-infrared coverage (K=22), deep VLA radio data and ISO observations at 7, 15, 90 & 175 mm (from the European Large Area ISO Survey, ELAIS). A unique aspect of this survey, however, is the wide area submillimetre survey with SCUBA. Covering ~200 arcmin2 to a depth of 8mJy (850mm), this provides an an ideal match with the depth and coverage of Chandra. Here we present the first results on the link between the infrared, submillimetre and X-ray populations.


On the evolution of nearby star-forming systems and their connection to primeval galaxies
A. Aloisi, L. Greggio, C. Leitherer & M. Tosi

Abstract: We present the state of the art of a project finalized to infer the spectro-photometric and chemical evolution history of some benchmark nearby (d = 2-10 Mpc) star-forming galaxies (I Zw 18, NGC 1569 and NGC 1705). A study of this type is of fundamental importance to extrapolate the local properties of these stellar systems to high redshift, and to better understand galaxy evolution in the early Universe. The project is carried out with HST proprietary and archival data in different spectral ranges. Imaging in the optical U, B, V, I bands (WFPC2) and in the NIR J, H bands (NICMOS) allows us to resolve the stellar populations of these galaxies. Their star formation history over the last 0.2-1 Gyr (optical bands) and over a Hubble time (NIR) are inferred by comparing the observed color-magnitude diagrams with synthetic ones. Spectroscopy in the UV band (FOS, GHRS, STIS) of HII regions/Super Star Clusters and, in some cases, of a few individual stars, allows to deduce chemical abundances in both the gas and stars, gas kinematics, and its interaction with the stellar population. All the information converge into the chemical evolution models, and permit us to reconstruct the photometric-stellar and spectro-chemical properties of starbursting systems as a function of time. These results can be finally compared to the spectro-photometric features of the unresolved stellar populations in all the systems detected at high redshift, as faint blue galaxies and absorbing systems.


Hunting for field LSB galaxies in deep CCD surveys
D.J. Bomans, L. Haberzettl, E. Krusch, R.-J. Dettmar

Abstract: During the last 15 years it became more and more apparent that the commonly used galaxy catalogs are affected by severe selection biases. Galaxies with small size and high surface brightness, as well as galaxies with low central surface brightness (LSB galaxies) are heavily under-represented. With the availability of large format CCDs and now even CCD mosaics conditions improved dramatically for observers to find and study LSB galaxies. While several studies of galaxy clusters have already been conducted or are currently going on, the potential of CCD mosaic surveys for the study of LSB galaxies in the general field is harder to unlock. We are currently undertaking a large program to search for and characterize the field LSB galaxy population using CCD mosaic data.
We will present first results from our analysis of very deep, multicolor CCD mosaic images centered on the Hubble Deep Field South and some other southern fields. Our resulting sample of LSB galaxies extends to smaller scale length, smaller total magnitude, and surface brightness than earlier CCD and photographic surveys and implies a very high surface density of these galaxies. The presence of this population has immediate implications e.g. for the faint end of the local galaxy luminosity function. We will also discuss our search technique and present a new method to select the local LSB galaxies against the background of cosmologically dimmed normal galaxies.


Galaxies near distant damped Ly-alpha clouds
N. Bouché, J.D. Lowenthal

Abstract: The identification and detailed study of galaxies at high redshift remains the most direct path to understanding galaxy formation and evolution. We will present deep, broad-band images in UgriKis with MOSAIC and IRIM at the Kitt Peak 4-m of 2 fields containing QSO damped Ly-alpha clouds at 2<z<4 to search for and study companion galaxies using photometric redshift techniques. Both fields have existing deep HST imaging. The questions we address are:
(1) Are the damped Ly-alpha clouds embedded in much larger systems of galaxies?
(2) What are the underlying stellar populations of galaxies associated with DLAs?
(3) What are the star formation rates of companion galaxies as close as 10kpc to the DLAs as measured via broad-band fluxes?
(4) How does DLA metallicity relate to incidence of emitters?
(5) How does the distribution of emitters in 3D (space & redshift) correlate with the observed velocity structure of absorbers?
These deep continuum data are an important complement both to existing absorption-line spectroscopy of damped clouds and to Lyman break galaxy field surveys.


Morphological number counts and redshift distributions to I=26 from the Hubble Deep Fields
P.D. Bristow and S. Phillipps

Abstract: We revisit our recent results concerning comparisons of magnitude and photometric redshift data from the Hubble Deep Fields to statistical predictions from galaxy population models. Morphological classification enabled us to separate out the distributions for early type galaxies which could be used to constrain cosmological models assuming realistic galaxy populations. Of the various models considered, we found that an Einstein-de Sitter universe with simple passive evolution reproduced the data best. Here we improve the modeling by adding a stage in which a simulated CCD observation of the model population is generated and the predicted counts and redshift distribution are actually derived from this using standard object detection software. In this way isophotal selection effects can be more rigorously modeled and moreover effects such as crowding and pixelisation are better accounted for. We find that the appearance of deep fields can be closely matched by simulted images giving our previous conclusions a more solid basis.


Searching for blazars in the EIS wide
I. Cagnoni, A. Celotti and P. Davide

Abstract: We present the BLEIS project: a search for blazars from the deep optical images of the ESO Imaging Survey (EIS) wide. The goal of the project is to select a faint blazar sample from optical and radio information only; this sample would be an important test for beaming and evolutive models. We discuss the first results compared to model predictions and present the future development of the project.


SPOrt and the microwave polarised sky
E. Carretti on behalf of the SPOrt collaboration

Abstract: The Sky Polarisation Observatory (SPOrt) is an experiment designed to survey the polarised emission in the 22-90 GHz band. This frequency window is unexplored from the polarisation point of view but promises to contain fundamental information about the cosmological parameters. The polarised CMB emission is at most 10% of the anisotropy signal and specially designed instruments are needed to detect it. SPOrt will be the first radio-polarimeter specifically designed for in space Q and U Stokes parameter measurements and will be placed on board the International Space Station in early 2004. SPOrt's main scientific goal is two-fold: first, to make a tentative detection of the CMB polarisation; second, to construct polarised maps of our Galaxy, which will give information about the Galaxy structure and the foreground noise for the CMB. The SPOrt capabilities as well as its main scientific goals will be presented.


On the nature of the sources of the hard X-ray background
A. Comastri

Abstract: Optical and multiwavelengths follow-up observations of hard X-ray selected objects suggest that the sources of the X-ray background (XRB) are characterized by a range of X-ray and optical properties wider than previously thought. More specifically there is increasing evidence (from BeppoSAX, ASCA and recent Chandra observations) of a decoupling between X-ray and optical absorption properties which seems to increase with redshift and luminosity and of the presence of obscured active nuclei hosted by optically passive normal galaxies. The implications for the XRB synthesis models will be discussed.


A multivariate analysis of galaxies in the Hubble Deep Field North
M.R. Corbin, A. Urban, E. Stobie, R.I. Thompson, G. Schneider & M. Rieke

Abstract: We use the combined WFPC2 and NICMOS observations of the Hubble Deep Field North to measure and compare an array of parameters for 210 galaxies. These parameters include measurements of the rest-frame ultraviolet and visible morphological asymmetry and concentration, photometric redshift, star formation rate, and the fraction of the object bolometric luminosity radiated in the rest-frame mid-infrared. We find one strong correlation, between star formation rate and bolometric luminosity. Several weak/suggestive correlations are also found, including between redshift and rest-frame visible asymmetry, and an inverse relation between redshift and the fraction of object luminosity radiated in the mid-infrared. The redshift/asymmetry trend is consistent with qualitative evidence of galaxy morphological evolution, and confirms that such evolution is not an effect of viewing high-redshift galaxies in the rest-frame ultraviolet. The range of these asymmetry values becomes comparable to that measured for galaxies in the local universe at z ~ 0.5. The trend between redshift and the fractional luminosity in the mid-infrared may represent the evolution in galaxy dust content and/or a selection against dusty galaxies above z ~ 2.


Analysis of breaks occuring in UBVRI galaxy counts
S.M. Crawford, M.A. Bershady, and S.M. Majewski

Abstract: We present counts of galaxies to a 50% completeness limit of B~26 from two 0.023deg2 areas of sky, one at the South Galactic Pole and the other in a field at (l,b)= (21,-38)¼ (refered to as BES). The aim of this research is to establish the existence and cause of breaks in the count slopes at faint magnitudes. A suprious source of count-slope breaks is due to systematic errors in observations, detections, and photometry. Great effort was made to correct for these errors, and to eliminate field-to-field variations. The fields were observed during the same nights using the same telescope and detector (the LCO Du Pont 2.5m and a Tektronix 20482 CCD). Images were obtain in the UBVRI bands of the Johnson-Cousins system, and calibrated using the same Landolt standards. Detection and photometry procedures were identical for both fields. Simulations were run in order to verify the reliability of the techniques used, and determine corrections for systematic photometric errors, completeness, and spurious detections. The two fields have nearly identical values for seeing and depth in all bands, but have different Galactic latitudes. Consequently we combined FOCAS and DAOPHOT image classifiers to cross-check our star/galaxy separation procedures. The slope of the galaxy number counts for both fields is within the range of values established for this magnitude regime, but slopes and normalizations vary substantially between fields. In the B band, the slopes are 0.40ʱÊ0.04 and 0.52ʱÊ0.05 for BES and SGP fields, respectively, as averaged over all magnitudes. Recent studies have found values of the B band number counts to range from .31 (Arnouts et al., 1999) to .51 (Brunner et al., 1999). The shape of the counts vary between our two fields: The SGP has a break at B=24 where the slope changes from 0.56 to 0.47ʱÊ0.04, whereas the BES has no noticeable break. A similar break was found by Brunner et al. in a third field. Part of the fluctuation between our two fields can be understood after comparing color-color diagrams that separate galaxies by spectral-type and redshift. Density variations in flux-space exist between the two fields brighter than B~24, and this appears to reflect different redshift distributions between the fields. At this time, it cannot be determined if the density variation is caused by an excess in one field (BES) or a void in the other (SGP). Hence the break observed at B=24 cannot be considered as ÒcharacteristicÓ of the field population at this time.


EROs and the large scale structure of high-z ellipticals
E. Daddi

Abstract: With a 701 arcmin2 survey in the Ks and R band the first quantitative measurement of the clustering of EROs was achieved (Daddi et al. 2000), finding that it is characterized by a very large amplitude A(1o) ~0.02. I will show how this can be regarded as the first detection of the large scale structure traced by field ellipticals at z ~ 1. The implications for the cosmic evolution of the clustering of elliptical galaxies will be discussed together with a comparison with theoretical models.


The population of the galaxy cluster C11601+42 at z=0.54
T. Dahlén, C. Fransson & M. Näslund

Abstract: We use photometric redshifts to determine cluster membership for galaxies in the cluster Cl1601+42 at z = 0.54. With this information we calculate the rest-frame cluster luminosity function (LF) to MB ~ -17. We find a faint end slope alpha ~ -1.4, indicating the existence of a numerous population of faint galaxies. With the information from the photometric redshifts we also calculate the LFs for early and late type galaxies separately. We find that the bright galaxies are mostly red early types. The LF for this population is best fitted by as Gaussian. The faint galaxies are predominantly blue late type galaxies. The LF for this population alone is best fitted by a Schechter function with a steep faint end slope alpha ~ -1.7. The up-turn of the faint end seems to begin at brighter magnitudes for Cl1601+42, compared to clusters at lower redshift. If this is true, then a possible explanation is a general brightening of the blue population at increasing redshifts.
Calculating the radial distribution within the cluster we find that bright galaxies are highly concentrated to the center. The fainter cluster members are more evenly distributed, with an indication of a depletion at the center of the cluster. The radial distribution of early and late type galaxies also show considerably differences. Bright blue late type galaxies are almost absent in the center of the cluster, indicating a decrease in star formation as galaxies are accreated in the core. The faint blue galaxies are more evenly distributed across the cluster with only a small decrease towards the center.


Identification of Mambo MM sources
H. Dannerbauer, F. Bertoldi, M. Lehnert, D. Lutz

Abstract: Using the Max-Planck Millimeter-Bolometer Array - MAMBO - at the IRAM 30 m telescope, MPIfR and MPE are conducting a deep (rms ~ 0.5 mJ), wide (each field more than 100 arcmin2) area survey in order todetect a significant number of the brightest (sub)mm background sourcesat 1.2 mm (effective frequency 250 GHz, bandwith = 80 GHz). Since the 11" beam of the 30 m telescope at IRAM is too large to allow out follow-up optical/IR observations to identify the mm detected sources. While the detected sources are likely to be dusty high redshift objects with high star formation rates, their exact nature is currently unclear. In order to understand the relation of (sub)mm galaxies to other classes of high redshift objects (like Lyman break galaxies, QSOs, or extremely red objects) will ultimately require us to establish their redshift distribution, bolometric luminosities, and spectral characteristics. Obtaining this information is the goal of this project.

We present the general properties of the MAMBO surveyand show first results of our follow-up optical and near-infrared imaging program carried out in two fields, one at the northern hemisphere, the z=0.24 cluster Abell 2125, and the other one, at the southern hemisphere, centered on, but larger than, the NTT Deep Field. For Abell 2125, we present possible R- and K-band identifications andfor the NTT Deep Field and its flanking fields possible optical counterparts found in the multi-color imaging (ESO public archive) on the NTT deep field itself in B, V, r, i, zGUNN, zspecial, J, and Ks, and deep B-, R-, and I-Band images of a 30' field centered on the NTT deep field taken at the 2.2 MPG/ESO telescope using the Wide Field Imager.


The LSB extent of the Fornax Cluster
A. Kambas, J.I Davies, R.M Smith, S. Bianchi and J.A Haynes

Abstract: We have used a large format CCD camera to survey the nearby Fornax cluster and its immediate environment for low luminosity low surface brightness galaxies. Recent observations indicate that these are the most dark matter dominated galaxies known and so they are likely to be a good tracer of the dark matter in clusters. We have identified large numbers of these galaxies consistent with a steep faint end slope of the luminosity function (alpha = -2) down to MB = -12. These galaxies contribute almost the same amount to the total cluster light as the brighter galaxies and they have a spatial extent that is some four times larger. They satisfy two of the important predictions of N-body hierarchical simulations of structure formation using dark halos. The luminosity (mass ?) function is steep and the mass distribution is more extended than that defined by the brighter galaxies. We also find a large concentration of low surface brightness galaxies around the nearby galaxy NGC1291.

By the time of the conference we will also report results for the Virgo cluster.


The most distant damped Ly-a system at zabs=4.466 towards the quasar APM BR J0307-4945
M. Dessauges-Zavadsky, S. D'Odorico, R.G. McMahon, P. Molaro and C. Ledoux

Abstract: We present the abundance analysis of a metal-rich damped Ly-a (hereafter DLA) system at zabs=4.466 towards the quasar APM BR J0307-4945 with a neutral hydrogen column density N(HI) = (4.68±0.97).1020 cm-2. It is the most redshifted DLA system known to the present date. It shows complex low- and high-ion line profiles spanning = 240 and 300 km s-1 in velocity space respectively. We derive accurate abundances for N, O, Al, Si and Fe, and place lower and upper limits on the abundances of C and Ni respectively: [N/H] = -3.07±0.21, [O/H] = -1.63±0.26, [Al/H] = -1.79±0.15, [Si/H] = -1.54±0.16, [Fe/H] = -1.94± 0.28, [C/H] > -1.63 and [Ni/H] < -2.35. The high metallicity found at this redshift, ~1/90 solar, indicates even that at a look-back time of ~12 Gyr this absorber has already experienced a significant metal enrichment. The abundance ratios [Si,O/Fe] are enhanced compared to solar, the [O/Si] ratio is nearly solar suggesting a limited amount of dust, and the [N/O] and [N/Si] ratios are low indicating a secondary production of N. All these results point to an enrichment pattern dominated by Type II supernovae as in the early phases of the evolution of our own Galaxy.


Advantages of NIR multi-object spectroscopy of z~1 galaxies
C. Dominguez-Tagle, F. Prada, A. Manchado

Abstract: Galaxy redshift surveys from z ~ 1 to z > 4 providing thousands of identified objects are already available. However only for a small and selected sample of those galaxies, NIR spectroscopy and emission line studies exist. This is mainly due to the time-consuming work of observing one object at a time. This applies to observing programs such as z ~ 1 galaxies where the object density sets an important observing-efficiency difference between using multiobject or single slit spectrographs. This work presents a study of the efficiency of observing z ~ 1 galaxies using LIRIS, the NIR multi-slit spectrograph that is being built at the IAC for the 4.2m William Herschel Telescope at La Palma.


Deep surveys with SIRTF's Infrared Array Camera
P. Eisenhardt

Abstract: The Infrared Array Camera (IRAC) on NASA’s Space Infrared Telescope Facility (SIRTF) will provide imaging at 3.6, 4.6, 5.8 and 8 microns. The four bands are imaged simultaneously in two adjacent 5 arcminute fields with 1.2 arcsecond pixels. The expected point source sensitivities in the four bands are 3, 4, 17, and 24 microJanskies (5 sigma in 200 seconds) for objects well away from the ecliptic. SIRTF Guaranteed Time Observers have specified field surveys to be carried out with IRAC with integration times per position ranging from 90 to over 10,000 seconds. I will describe the plans for these surveys and their application to the study of galaxy formation and evolution.
This work was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under contract to the National Aeronautics and Space Administration.


VLT imaging of quasar host galaxies at z~1.5
R. Falomo, J. Kotilainen, N. Carangelo, and A. Treves

Abstract: We present high spatial resolution near--infrared images, taken with ISAAC on UT1 of ESO VLT, of three radio-loud quasars (RLQ) at z ~ 1.5. The observations constitute a pilot study aimed at investigating the QSO-galaxy connection for a sample of RLQ and radio-quiet quasars (RQQ) in the redshift range 1 < z < 2. We were able to clearly detect the host galaxy in two quasars (PKS 0000-177 and PKS 0348-120) and marginally in the third one (PKS 0402-362). The host galaxies appear compact (average scale-length ~ 4 kpc) and luminous (average M(H) = -27.6 ± 0.1). They are ~2.5 mag more luminous than the typical galaxy luminosity (M*(H) = -25.0 ± 0.2), and are comparable to the hosts of low redshift RLQ (M(H) ~ -26), taking into account passive stellar evolution and to those of high redshift radio galaxies. Compared with recent results on RQQ at similar z we find that the difference of host galaxies luminosity is more apparent than at low redshift. All three quasars have at least one close companion galaxy at a projected distance < 50 kpc, assuming they are at the same redshift. The issue of close companions is critically discussed.


Measurements and inferences from the high-redshift star formation density and its evolution
A. Fernandez-Soto

Abstract: Using observations of faint galaxies in the Hubble Deep Fields we have examined the distribution of unobscured ultraviolet intensities versus redshift, from which we assess the evolution of the star formation density. We find that
(1) previous measurements have missed a dominant fraction of the UV luminosity density at high redshifts by neglecting cosmological surface brightness dimming effects, which are important at redshifts larger than z~2,
(2) the incidence of the highest intensity star forming regions increases monotonically with redshift, and
(3) the UV luminosity density plausibly increases monotonically with redshift through the highest redshifts observed (z~10). By comparing with observations of high-redshift gas detected toward background QSOs, we further find that
(4) the distribution of star formation intensities matches the distribution of neutral hydrogen column densities at redshifts z~2 to z~5, which establishes a connection between high-redshift galaxies and high column density QSO absorption systems.


Galaxy evolution in the Hubble Deep Field South and North
A. Gabasch & R. Bender

Abstract: Using our own photometric redshift technique (a Basian method using empirical template spectra) we derive the redshifts of the galaxies in the HDFN and HDFS. We find very good agreement between our redshift estimates and the known spectroscopic redshifts. We compare the galaxy number densities N(z) of the HDFN and HDFS and calculate the luminosity densities at different wavelengths. The luminosity densities are in good agreement with CDM predictions for redshifts of z < 2. At higher redshifts the models underestimate the measured luminosity densities. >From the luminosity density in the UV we derive the star formation rate (SFR) as a function of redshift. Our SFR(z) agrees well with other published results.


European VLBI Network 1.6 GHz Observations of the Hubble Deep Field
M.A. Garrett, T.W.B. Muxlow & S.T. Garrington et al., K. Kellermann

Abstract: We present deep, wide-field EVN 1.6 GHz observations of the Hubble Deep Field (HDF-N) region. Above the 5s level, the EVN clearly detects 2 radio sources in a field that encompasses the HDF and part of the Hubble flanking fields (HFF). One of the sources (VLAÊJ123644+621133) is located within the HDF itself, and the other is a dust enshrouded, optically faint, z=4.424 Starburst/AGN system, VLAÊJ123642+621331. In both cases the compact radio emission detected by the EVN most likely arises from the central engine of a low luminosity AGN. VLAÊJ123642+621331 seems to be a system in which both starburst and AGN activity co-exist. We consider the short-term prospects for routine, high resolution VLBI imaging of sub-mJy radio sources, with sensitivity levels comparable to those curently enjoyed by connected element arrays.


Deep optical and near-IR survey in the ELAIS areas
E. González-Solares, I. Pérez-Fournon, F. Cabrera-Guerra, A. Cabrera-Lavers, R. McMahon, M. Rowan-Robinson, S. Oliver, A. Verma, S. Serjeant, C. Willott, P. Ciliegi, O. Almaini, A. Lawrence, B. Mann and ELAIS collaboration

Abstract: The ELAIS (European Large Area ISO Survey; Oliver et al, 2000) is a project that has surveyed about 13 square degrees of high latitude sky in the north and south hemispheres using the ISOCAM and ISOPHOT cameras on board of the ISO satellite. Observations at 6.7, 15, 90 and 175 mm have been obtained. These observations together with the extensive followup programs carried out in these regions have made the ELAIS fields excellent areas for deep surveys. These include radio observations using VLA, optical and near-IR, sub-mm and in the near-future X-rays using Chandra and XMM. We report here the results of our deep optical and near-IR observations on the centers of the northern areas N1 and N2, regions that will be covered also by deep Chandra and XMM observations. We have obtained g', r', i' and H deep images with limiting magnitudes of g' 26.4, r' 26.0, i' 25.4 and H 19.5 (AB magnitudes; 5s detection limit) covering an area of 30' x 30' arcmin using the Wide Field Camera (WFC) and the Cambridge Infrared Survey Instrument (CIRSI) both on the Isaac Newton Telescope (INT) in the Observatorio del Roque de los Muchachos, Canary Islands. These data are extremely useful to identify the faint optical counterparts of the ISO, radio and X-ray sources.


The BMW distant cluster survey
L. Guzzo

Abstract: We have constructed a new X-ray selected sample of candidate distant clusters of galaxies from the recently completed BMW survey of serendipitous X-ray sources over the whole ROSAT HRI archival data. The current master sample includes now ~300 high-quality candidates, with a significantly large sky coverage (about 2 times that of the CfA-PSPC survey of Vikhlinin et al.), down to a flux limit of ~3 x 10-14 erg s-1 cm-2. These somewhat surprising results have been made possible by the clever selection of the HRI energy channels during the BMW catalogue construction, which overcomes the notorious higher-background limitations of this detector for selecting extended sources. These features make it an excellent data set for finding rare, massive clusters at z ~ 0.6-1. In fact, 80% of the candidates show no counterpart on the DSS plates, and we are conducting a multi-site imaging campaing to fully identify the cluster sample. First results at ESO and TNG are extremely encouraging, with 13 clusters out of 19 clearly confirmed and estimated red-sequence redshifts in the range 0.4-0.8. We will present these early results and discuss how this sample can represent for serendipitous X-ray searches of distant clusters an important bridge between the ROSAT-PSPC and XMM eras.


The galaxy environment of quasars in large quasar groups
C.P. Haines, R. G. Clowes, L.E. Campusano

Abstract: Quasars have been used as efficient probes of high-redshift clustering on the basis that they are known to favour rich environments. Quasars may also trace the large-scale structure of the early universe (0.4 < z < 2) in the form of Large Quasar Groups (LQGs), which have comparable sizes (~100-200 h-1 Mpc) to the largest structures seen at the present epoch.
We have conducted an ultra-deep optical (to V~27,I~26) study of a 30' x 30' field containing three quasars from the largest known LQG, the Clowes & Campusano LQG of 18 quasars at z~1.3 (MNRAS 249, 218 [1991]). K imaging h2as been obtained for subfields around two of the LQG quasars, and their galaxy environments have been examined using a combination of photometric redshift and density estimation methods.
The first quasar (J1046.9+0541 with z=1.226) resides in a rich environment, with 15–18 galaxies having the colours and magnitudes expected for massive ellipticals at the quasar redshift, forming colour-magnitude relations at I-K~4.3 and V-K~6.9 (Haines et al., MNRAS submitted [2000]). These galaxies are concentrated in two compact groups 90'' apart, which are bisected by a band of blue galaxies where the quasar is located. This spatial distribution suggests that the two groups are merging and that the interaction of galaxies with shocks in the ICM has triggered the band of enhanced star-formation and also the quasar. A similar distribution of elliptical and star-forming galaxies has been observed for a quasar in another LQG at z=1.1 (Tanaka et al., ApJ 528, 123 [2000]), suggesting that this is a common phenomenon. In contrast the second quasar lies in a much poorer environment, with only 2--3 galaxies having the colours of z~1.3 ellipticals.


Numerical study of the cosmic shear statistics as a probe of the large scale structure formation in the Universe
T. Hamana

Abstract: I will present results from the numerically study of the cosmic shear which uses ray-tracing experiments combined with large N-body simulations. This study aims to make a precious prediction of the variance of the cosmic shear as well as higher order moments of it with fully taking the nonlinear growth of the structure formation into account. I will also discuss how the evolution of the bias affects the cosmic shear measurements.


The low surface brightness extent of the Fornax Cluster
A. Kambas

Abstract: We have imaged the Fornax cluster out to a distance of 8 degrees in the search for low surface brightness (LSB) cluster members. Such LSB objects are believed to be totally dark matter dominated and may trace the mass distribution of the cluster in a different way to their bright giant counterparts. In our survey we have selected galaxies with central surface brightness Rmo fainter than 23 R mag arcsec-2 and exponential scalelength a greater than 3". Simulations indicate that these selection criteria preferentialy select cluster galaxies rather than those in the background. We have identified large numbers of galaxies following an exponential decrease in surface density from the cluster centre, but with a scalelength four times greater than that of the brighter galaxies. At the distance of Fornax these galaxies are as faint as MB = -12. This is consistent with a faint end slope of the luminosity function a=-2 found for other elliptical rich clusters. Such findings support hierarchical models that predict a steep mass function. With half the light of the cluster being attributed to these galaxies and with mass to light ratios believed to be 10 times higher than bright giant members, these galaxies may represent a large fraction of the total cluster mass.


A search for X-ray flares from nearby 'normal' and active galaxies: comparison of ROSAT all-sky survey data with deep PSPC/HRI fields
S. Komossa

Abstract: In the last few years, several giant-amplitude, non-recurrent X-ray flares from galaxies (active and 'normal' ones; e.g., Zwicky 159.034, NGC 5905, RXJ1242-1119) have been discovered. The favored interpretation of these events is the tidal disruption of a star by a supermassive black hole (see astro-ph/0001264 for a review).
The X-ray flares are all very soft (kT ~ 0.06 keV). The ROSAT all-sky survey (RASS) in comparison with the later period of pointed observations, provides an excellent database to search for further of these events, as well as other kinds of variability, on the time scale of months to years (between RASS and pointed observations) and minutes to days (in deep pointings). We have used the catalog of galaxies of Ho et al. (1995) which contains nearby 'normal' and active galaxies with accurate optical spectral information, to search for X-ray variability from >100 galaxies.


Number counts and angular correlation functions in the FORS Deep Field
M.W. Kümmel, J. Heidt, S.J. Wagner, I. Appenzeller, R. Bender, K. Fricke, and the FDF-team

Abstract: The FORS Deep Field (FDF) is a project to obtain a deep field from ground based observations with the VLT. While the FDF is similar to the HDFs in terms of depth, its area is 8 times larger. The main items to be investigated in the FDF are the evolution of field galaxies to a redshift of z=5, the environment around high-redshift QSOs and galaxy-galaxy lensing. As by summer 2000 the imaging observations in the UBgRI by FORS as well as NIR-observations on the NTT in J and Ks have been completed and reduced. In our contribution we show results based on imaging. We present the galaxy number counts in the different filters and analyze galaxy clustering by investigating the angular correlation function. We compare our data with results found in other deep-field studies, e.g. the Hubble Deep Fields, the NTT Deep Fields and the William Herschel Deep Field and discuss the reasons for the differences found at the faint end in both, galaxy densities as well as galaxy correlations.


A study of the contribution of the Damped Lyman-alpha Systems and Lyman Break Galaxies to the metal content of the high-redshift Universe
G. Lanfranchi

Abstract: We investigate the evolutionary history of the metal content of the Universe through chemical abundances, taken from the literature, and predictions from chemical evolution models. The estimated abundances of several elements (C, N, O, S, Si, Fe, Cr and Zn) were taken from observations of QSOs absorption line systems over a wide range of redshifts (z = 0.5-4.5). We estimate the metallicities in representative systems of the early Universe, sampling a variety of environments. First, the observational data, which also includes HI column densities and absorption redshifts, is analysed with robust statistical methods. This analysis reveals us important features: the metallicity of the QSO absorption line systems increases with N(HI) until it reaches a peak at log(N(HI)) = 20 -- 20.5, and then declines suggesting a selection efect; there is an underabundance of Fe and Cr with respect to Zn in Damped Lyman alpha Systems (DLAs); the [alpha/Fe] ratio in DLAs is suprasolar; there is a trend of decreasing abundance with increasing N(HI) for Fe, Cr, Zn, Si and S in DLAs. After the statistical analysis, the observational data is compared with predictions of chemical evolution models. We apply different models to these systems due to the uncertainties about the nature of the QSOs absorption line systems. The DLAs are investigated with one zone models describing: a) dwarf galaxies with galactic wind and b) disk galaxies with infall. A chemodynamical model for spheroids is used to study the Lyman Break Galaxies (LBGs). In order to compare the observational data with the models, we use the ratios [N/alpha] and [alpha/Fe]. These ratios in DLAs are well reproduced by the disk and dwarf galaxy models suggesting that the DLAs come from a variety of morfological types of galaxies. They also imply a typically long timescale for star formation in these systems. In contrast, the observational constraints for LBGs are met by models of spheroid formation with typically short timescales for star formation (= 1 Gyr-1), giving support to a scenario for galaxy formation in wich there is a dicothomy between the formation modes for DLAs (long star formation timescales) and LBGs (short star formation timescales).


Distant galaxy clusters: new detections and follow-up observations in the optical. I. Photometric results
C. Lobo & A. Iovino

Abstract: We have applied a new cluster detection algorithm to the ESO Imaging Survey, thus producing a new catalogue of cluster candidates up to redshift 1. Such a catalogue enables one to perform statistically significant studies as well as detailed research on some of these systems individually and on their member galaxies. The ongoing follow-up of the candidates, in multi-waveband photometry and VLT spectroscopy, is now starting to produce its first results and shall be used later to study the role of environment in the evolution of galaxy populations. We present photometric results for three cluster candidates that enabled us to select them as interesting spectroscopic targets, as discussed in a companion poster. We shall present the new findings on this project and give future prospects.


XMM-Newton Deep Field Observations: the HDF North and serendipitous fields from the in-flight calibration programme
D. Lumb

Abstract: The XMM-Newton Observatory was launched in December 1999. The Calibration/Performance Verification phase was conducted between March and July 2000. Based on preliminary analysis of in-orbit background we report on the sensitivity limits expected, and note that for the relatively unexplored 5-10keV energy band, XMM-Newton will reach a factor 20 deeper than Beppo-SAX, exploring a range not readily accessible with CHANDRA. Sensitivity of a few 10-16 ergs cm-2 s-1 will be achieveable in deep fields in the 0.5-2keV bands, and a few 10-15 ergs cm-2 s- in the >1keV bands. We describe the outlook for the XMMSOC Guaranteed Time 200ksec programme on the Hubble Deep Field North. During the In-Flight Calibration period a number of fields were observed several times, and we report on the preliminary analysis of these serendipitously observed fields, whose combined exposure times each became typically deeper than normal deep Guest Observer pointings.


Cosmological evolution of radio sources: what can theory tell us?
M. Magliocchetti

Abstract: We present a simple, analytical model able to describe the cosmological evolution of radio sources as a function of cosmology and AGN lifetime. Working within Press-Schecther formalism, we obtain a sensible way to relate radio luminosity to the mass of the halo hosting the source under the assumption that more powerful objects radiate with greater efficiency. Model predictions are then compared with data coming from the FIRST 1.4 GHz survey, including sources down to S=1 mJy, and we find that this approach can correctly reproduce the observations. Better fits are obtained for a Lambda-CDM (Omega_0=0.4, Lambda_0=0.6) cosmology with a value for the duty-cycle t_q~ 10^7 yr, in excellent agreement with previous results.


Photometric redshifts: a critical comparison of different templates
M. Massarotti, A. Iovino, A. Buzzoni

Abstract: We discuss the stability of photometric redshift estimate with respect to the choice of templates, and compare results obtained with the different templates usually adopted in the literature. We analyze the redshift estimates obtained in the Hubble Deep Field North modelling the galaxy SEDs with the synthetic spectra compiled according the codes of Bruzual and Charlot (1993), Buzzoni (1999), Fioc and Rocca-Volmerange (1997) and Leitherer et al. (1999) and with the empirical template set of Coleman et al. (1980). The differences in the template libraries between different synthetic codes and between synthetic and empirical model spectra have a minor effect on the redshift stability than the statistical uncertainty due to the photometric errors. Moreover, our study suggests that, especially at high redshift, the description of effects related to interstellar and intergalactic medium is more important than the specific choice of templates, as long as they describe both normal and starburst galaxies.


Photometric redshifts: a comparison with the spectroscopic observations
M. Massarotti, A. Iovino, A. Buzzoni

Abstract: We compare photometric redshift estimates with the available spectroscopic observations, to gain insight on the physical properties of the interstellar (ISM) and intergalactic medium (IGM).
We obtain the best available to date agreement with the spectroscopic data (d z/(1+z) ~0.05) by introducing some improvement in the description of the IGM and ISM. In our modelling we reproduce the amplitude of UV photons scattering and absorption in the Ly-a forest clouds and Lyman-limit systems recently observed in quasar spectra at 1.5 < z < 5. We also introduce a parameter to describe the amplitude of the 2175 Å bump in the differential dust reddening law.
Consequences on the estimate of quantities such as the UV luminosity density as a function of redshift are explored.


The FORS-Deep-Field: first spectroscopic results
D. Mehlert, S. Noll, I. Appenzeller, R. Bender, A. Böhm, N. Drory, K. Fricke, R. Häfner, J. Heidt, K. Jäger, M. Kümmel, C. Möllenhoff, A. Moorwood, H. Nicklas, R. Saglia, W. Seifert, S. Seitz, O. Stahl, E. Sutorius, T. Szeifert, S. Wagner, B. Ziegler

Abstract: We obtained MOS spectra with FORS and UT1 of the VLT centered on the FORS Deep Field. Our Sample contains 58 identified galaxies with redshifts up to 3.4 including 3 QSOs. Here we compare the spectroscopic and previously determined photometric redshifts of these objects. Additionally we present first spectra of the high redshifted (> 2.5) young galaxies in our sample.


Like candles on the Moon: optical observations of neutron stars
R. Mignani

Abstract: While neutron stars are conspicuous emitters at other wavelengths, in the optical they are the intrinsically faintest stellar objects. After the discovery of the Baade’s star as the optical counterpart of the Crab pulsar, about ten years were necessary to achieve the identification of the 700 times fainter pulsar PSR B0833-45 in the Vela Supernova Remnant. The chase for neutron stars, boosted in the last decade with the advent of the new generation of telescopes (NTT and HST), has now produced 11 likely identifications. The state of the art of the observations and our knowledge of the optical emission properties of neutron stars is reviewed.


Mining for AGN in the Marano field
M. Mignoli

Abstract: Mining for AGN in the Marano FieldA deep optical multi-colour catalogue of an area of ~0.13 sq.deg. in the "Marano Field" has been obtained in the past years through CCD photometry at the ESO NTT telescope. From this catalog we have selected faint quasar candidates with magnitudes up to B=23.50. A significant fraction of these candidates has been recently observed spectroscopically with FORS1 at the VLT. Here we present some preliminary results on the faint AGN population based on these new spectroscopic data.


High resolution radio imaging of the Hubble Deep Field and flanking fields
T. Muxlow, M. Garrett, A. Richards, E. Richards, S. Garrington

Abstract: 42 hours of A-array VLA data and 18 days MERLIN data at 1.4GHz have been combined to image a 10 arcminute field centred on the Hubble Deep Field. This area encloses both the Hubble Deep and Flanking Fields. A complete sample of 91 sources have been detected with flux densities above 40 uJy. All these have been imaged with the MERLIN+VLA combination to produce images with 0.2, 0.3 and 0.5 arcsecond resolution. These are the most sensitive 1.4GHz images yet made with rms noise levels of 3.3 uJy/beam in the 0.2 arcsecond images. About 70% of the microJy sources are found to be starburst type systems associated with major disk galaxies in the redshift range 0.4 – 1. Some 20% are found to be low–luminosity AGN systems identified with field ellipticals at redshifts close to 1. The remaining 10% are associated with optically faint systems close to or beyond the HDF limit; many of these may be dust-shrouded starbursts at high redshift. Recent wide-field EVN observations of the HDF (Garrett et al, these procs.) confirm that one of these objects (J123642+621331) is probably a dust enshrouded starburst system at z=4.424 with an embedded AGN.


The discovery of a forming cluster around a high redshift radio galaxy
L. Pentericci

Abstract: Deep VLT narrow band and spectroscopic observations haveled to the discovery of 15 galaxies in the field of the powerful radio galaxy 1138-262 at redshift 2.2. All galaxies have Ly alpha emission within a velocity range of 2800 km s-1 from the radio galaxy and are located within a projected physical distance of 1.5 Mpc from it. We argue that this large scale structure is probably the progenitorof a local rich cluster.


GASPHOT: a tool for Galaxy Automated Surface PHOTometry of galaxies
E. Pignatelli, G. Fasano

Abstract: The usual tools for galaxy surface photometry are optimized to be used on single objects and always involve some amount of interactivity. With the new generation of wide instruments, and the very deep high resolution images of field galaxies obtained with HST, we have to deal with a large number of objects in each image, not easily handled interactively.
We present a tool for Galaxy Automated Surface PHOTometry (GASPHOT) in deep and wide fields. By fitting the surface photometry with a Sersic law we automatically obtain the total magnitude mT, the half-luminosity radius Re, the ellipticity and the Sersic index n for each galaxy in the image.
We analize the performances of this tool for simulated, HDF-like images. For galaxies having V magnitudes in the range 24-27, we obtain a D M = 0.02-0.1, D log Re = 0.03, D n = 0.02-0.5.
We also present the comparison of GASPHOT morphological classification against the visual one for a set of clusters of low and intermediate redshift, and the results of the application of the tool to the Hubble Deep Fields.


The HDF as seen by the Advanced Camera for Survey s
N. Pirzkal, A. Pasquali, R.N. Hook, J.R. Walsh, W. Freudling, R. Albrecht

Abstract: The Advanced Camera for Survey (ACS) is to be installed on the Hubble Space Telescope during the SM3-B servicing mission scheduled for late 2001. This instrument features a large format array, the Wide Field Channel (WFC) which covers a full area of 4096 x 4096 pixels2 with a resolution of 0.05" per pixel. The sensitivity of the instrument is expected to be twice that of WFPC2 which, together with a FOV of 3.4' x 3.4', will make ACS a powerful instrument to observe deep fields. In this paper, we present our simulations of the HDF-N Deep Field as seen by ACS in the U,B, and V bands as well as using the ACS grism mode (slistless spectroscopic mode). These simulations have relatively low integration times but illustrate the wealth of data that can be obtained using this instrument. We also present spectra of high redshift galaxies to show what we expect to obtain using the ACS grism mode.


Micro-lensing influence on spectral line shapes from relativistic accretion disc of AGNs
L.C. Popovic, E. Mediavilla and J.A. Munoz Lozano

Abstract: Gravitational microlensing by stars in galaxies or a massive object near the source can affect the continuum as well as the emission lines of deep field objects. This effect can be especially important on emission lines of Active Galactic Nuclei – AGNs (quasars and Seyfert 1 galaxies) where bulk motions of emitting gas give rise to very broad line profiles. We have considered the gravitational microlensing on spectral line profiles originated in a relativistic accretion disc model. We have used the model developed by Chen & Halpern (1989, ApJ 244, 115) and discussed the shape of the emission lines of Arp 102B. According to the present results the changes in the spectral line profile found in Arp 102B and other similar AGNs could be explained by gravitational microlensing.


A method to solve age and dust degeneracy for Extremely Red Galaxies (ERGs)
L. Pozzetti

Abstract: The extremely red galaxies (ERGs) are defined in terms of their very red optical-to-near IR colours (as R-K > 5 or I-K > 4). Originally this selection was aimed at selecting old ( > 1 Gyr) passively evolving elliptical galaxies at intermediate redshift (1 < z < 2), but it was soon discovered that young star-forming dusty galaxies can show similar colours and therefore be selected in the same surveys.
It is crucial to distinguish between these two populations because they have very different consequences on the models of galaxy formation. Here we show that old ellipticals and dusty starburst are expected to show different colours in the (I-K) vs. (J-K) diagram for redshift range 1 < z < 2, providing thus a useful tool to classify ERGs in large samples up to K < 20. This is mainly due to the fact that old galaxies at these redshifts have a strong 4000 Å break at l <1.2 mm (J band), while dusty galaxies show a smoother spectral energy distributions and therefore redder J-K colours.
We discuss this difference in detail both in the framework of the stellar population synthesis models and by using observed spectra. The selection criterion is also compared with the properties of ERGs of known nature. We also show that this colour selection criterion is also useful to separate the ERGs from brown dwarf stars showing similar optical-to-IR colours.


The ATESP Radio Survey: optical identifications and spectroscopy in the EIS-A region
I. Prandoni, L. Gregorini, P. Parma, H.R. de Ruiter, P. Vettolani, M.H. Wieringa, R.D. Ekers

Abstract: The change in the slope of the radio source counts suggests the emergence of a new population of radio galaxies at mJy and sub-mJy levels. Our understanding of such faint radio sources has advanced over the last decade through increasingly sensitive radio surveys and follow-up works at optical wavelength. The sub–mJy population seems to include either star forming galaxies or classical (AGN-powered) radio sources, but the relative importance of the two classes is still debated. We present the first results of the ATESP radio survey and its optical follow-up. The ATESP 1.4 GHz survey covers ~26 sq. degrees near the South Galactic Pole and has produced a catalogue of 2960 radio sources down to a flux limit of ~0.5 mJy. In a sub–region of ~3 sq. degrees deep optical CCD images (I<22) are available from the ESO Imaging Survey (EIS Patch A) and ~57% (218/384) of the ATESP sources present in that region could be identified.The spectroscopical follow--up of such optical counterparts is in progress.Currently all the galaxies brighter than I=19 have measured spectra (74 sources) and spectral classification. Using these data we have compared the ATESP results with the ones coming from previous deep radio surveys. It turns out that the existing discrepancies can be explained, at least in part, as a consequence of incompleteness, selection biases and other effects.


Dynamics of the X-ray clusters Abell 222-223, Abell 520 and Abell 521
D. Proust

Abstract: We present the results of a dynamical analysis as well as the population content of the rich, X-ray luminous galaxy clusters, Abell 222, Abell 223, Abell 520 and Abell 521 that are at intermediate redshifts. There are many indications that these clusters are presently undergoing strong dynamical evolution. Gravitational lensing might be present in Abell 521


Cosmological implications from an X-ray flux-limited sample of galaxy clusters
T.H. Reiprich and H. Böhringer

Abstract: The X-ray brightest galaxy clusters in the sky, excluding the galactic band, have been compiled based on surveys exploiting the ROSAT All-Sky Survey. Physical cluster parameters have been determined in a homogeneous way. It is shown that a good correlation between the gravitational mass and the X-ray luminosity exists with a scatter of about 50% for the mass. The gravitational mass function is determined and compared to previous determinations, where large differences are found depending mainly on the definition of the cluster outer boundary. The observational mass function is further compared to numerical and theoretical mass functions in order to constrain the amplitude of the initial density fluctuations. First results from X-ray observations with XMM-Newton are presented.


Deep VLT imaging of NGC 5128
M. Rejkuba, D. Minniti, D. Silva, T. Bedding

Abstract: We used VLT Antu (UT1) telescope with FORS1 and ISAAC to obtain high resolution optical and near-IR images of two fields in the halo of the nearest (d ~ 3.6 Mpc) giant elliptical galaxy NGC 5128. This galaxy, also known as a bright radio source Centaurus A, displays a rich system of shells, optical filaments, radio lobes, as well as a radio and X-ray jet from an active nucleus. These all make it a classical example of a merger of an elliptical galaxy with a smaller gas-rich galaxy. Our Field 1 is centered on the prominent diffuse north-eastern shell, approximately 14 kpc away from the center of the galaxy and Field 2 is in the halo 9 kpc away from the center. The shell in Field 1 can be naturally explained to be the stellar debris of the smaller galaxy accreted by NGC 5128 approximately 160 to 500 Myr ago (Quinn 1984, Ebneter & Balick 1983). We are investigating the stellar populations in this shell and comparing it to the halo population of Field 2.
Here we present the first results obtained from the analysis of the UV and VK color-magnitude diagrams (CMDs). The star formation history in the two fields is very different. The most striking difference is the presence of the young blue stars present in Field 1. From the comparison with the theoretical isochrones of Padova group (Bertelli et al. 1994, Girardi et al. 2000) we estimate the age of the young blue population to be ~10-15 Myr. These stars are aligned with the prominent radio jet and there is also a vertical structure located at the edge of the large HI cloud found in the vicinity of the shell (Schiminovich 1994). Molecular CO gas is also present in the northern part of the field (Charmandaris et al. 2000). The diffused ionized gas, clearly evident in our U-band images, is excited either by the ionizing emission from the young stars and HII regions (Graham 1998), or by high energy photons coming directly from the active nucleus (Morganti et al. 1991). After subtracting the blue stars projected on the shell, the remaining stars that belong to the "pure" shell population are similar to the halo population observed in our Field 2. In Field 2 a very strong red giant branch is observed in the near-IR. Its mean metallicity derived from the optical-IR color is [Fe/H] = -0.4. The spread in V-K color of the RGB is larger than that of the photometric errors, indicating a significant spread in the metallicity in both fields.


Clustering of X-ray selected AGN
J. Retzlaff

Abstract: We present the analysis of the spatial clustering of the brightest X-ray selected AGN from the ROSAT All Sky Survey. The adopted countrate limit of the sample corresponds to a flux of about 2.5x 10-12 erg s-1 cm-2 in the hard ROSAT band (0.5-2 keV). The sample comprises 227 AGN being predominantly Seyfert galaxies (65%) and QSO. The two-point correlation function shows a weak signal at a low significance level which is compatible with the clustering of optically selected galaxies. Finally we present a predictions for AGN clustering which will be obtained in the course of the upcoming XMM-LSS project.


The Large Area Lyman Alpha Survey
J.E. Rhoads, S. Malhotra, A. Dey, D. Stern, H. Spinrad, B. Jannuzi

Abstract: We report on a new survey for high redshift Lyman-a sources, the Large Area Lyman Alpha (LALA) survey. Our survey achieves an unprecedented combination of volume and sensitivity by using narrow-band filters on the new 81922 pixel CCD Mosaic Camera at the 4 meter Mayall telescope of Kitt Peak National Observatory.
Well-detected sources with flux and equivalent width matching known high redshift Lyman-a galaxies (i.e., observed equivalent width EW > 80 Å, 2.6 < (line + continuum flux)/ (10-17 erg cm-2 s-1) < 5.2, and d(EW) / EW < 0.25) have an observed surface density corresponding to 11000 ± 700 per square degree per unit redshift at z=4.5. Spatial variation in this surface density is apparent on comparison between counts in 6561 ± 40 Å and 6730 ± 40 Å filters.
Early spectroscopic followup results from the Keck telescope has confirmed four z = 4.5 Lyman-a emitters so far. These results lead us to estimate that 30 to 50% of our good candidates are bona fide Lyman-a emitters, implying a net density of ~4000 Lyman-a emitters per square degree per unit redshift at z = 4.5.
Recently obtained data in narrowband filters at 8200 Å will be used to extend the survey to z = 5.7 and to study the evolution of the Lyman-a emission line galaxy population.


Measuring the rest-frame V-band luminosity density to z~2.5 with FIRES at the VLT
G. Rudnick, H.-W. Rix, M. Franx

Abstract: At high redshifts, the rest-frame UV light of galaxies is shifted into optical bandpasses. This light is dominated by the radiation from young stars in galaxies and hence is a measure of their star formation rates. At the rest-frame optical wavelengths however, older stars contribute significantly to the stellar light budget and hence the optical light is a better indicator of the stellar mass of a galaxy than of its star formation rate. At z = 0.5 unfortunately, the rest-frame V-Band moves out of the optical and into the near infrared (NIR). The Faint InfraRed Extra-galactic Survey (FIRES) supplements the WFPC2 imaging of the Hubble Deep Field South with deep, high spatial resolution Js H Ks imaging taken with ISAAC at the VLT. Using the seven band information from the HST + VLT data, we obtain photometric redshifts of all galaxies brighter than Ks=21.5. Our photometric redshift code fits linear combinations of redshifted, empirical spectral templates to the observed fluxes. This routine not only finds the most likely redshift of the galaxy, but also recovers the rest-frame spectral energy distribution (SED). If we limit ourselves to a sample of galaxies which are fit well by the best fit template combination, we can use the derived SED to predict rest-frame properties of these galaxies.


A combined comparison of the HDF-S and AXAF fields through ISAAC deep observations
P. Saracco, E. Giallongo, S. Cristiani, E. Vanzella, S. D'Odorico, A. Fontana

Abstract: Deep near-IR observations (in J, H, and Ks) centered on the Hubble Deep Field-South (HDF-S) and on the AXAF Deep Field (AXAF-DF, in J and Ks) have been carried out with the ISAAC imager/spectrometer at the ESO-VLT telescope at comparable depth. The co-addition of short, dithered, images leads to a total exposure time of ~8 hours in Ks for both fields with a measured FWHM on the co-added images better than 0.6 arcsec and 0.75 arcsec in the HDF-S and in the AXAF-DF, respectively. The limiting magnitudes for a point source with a S/N=5 are J~25 (JAB~25.9) and Ks~23.5 (KAB~25), both comparable with the deepest Keck observations (Bershady et al. 1998; Djorgovski et al. 1995) although on a much larger area (~12 arcmin2).
Preliminary results in our analysis are:
o No significantly different behaviors are present between the Ks-band number counts derived in the two fields;
o Galaxy counts in both fields show a decline at the magnitude limit resulting in a systematic lower surface density of galaxies fainter than Ks=21.5 and J=22.5 with respect to previous surveys with comparable depth;
o About 25% of the Ks-selected galaxies are redder than J-K=1.9. They represent the lower limit to the number of z>1 galaxies according to Eisenhardt et al. (2000).
o About 30% of them are redder than J-K=2.5 which is the expected color of EROs at redshift z>2 (Pozzetti et al. 2000).


Distant galaxy clusters: new detections and follow-up observations in the optical. II. Spectroscopic results
M. Serote Roos

Abstract: We have applied a new cluster detection algorithm to the ESO Imaging Survey, thus producing a new catalogue of cluster candidates up to redshift 1. Such a catalogue enables one to perform statistically significant studies as well as detailed research on some of these systems individually and on their member galaxies. The ongoing follow-up of the candidates, in multi-waveband photometry (see companion poster) and VLT spectroscopy, is now starting to produce its first results and shall be used later to study the role of environment in the evolution of galaxy populations. We present spectroscopic results for three cluster candidates pre-selected via their colors to be observed with FORS1 at the VLT. The spectra taken turned out to confirm the presence of a system in each field. Redshifts were determined to be z=0.64, 0.66 and 0.71, respectively. Along the line of sight of each candidate, other systems, including a group of actively star forming galaxies at z=0.25, also seem to be present and will be the aim of further research.


Search for FIR emission from intracluster dust in Abell Clusters
M. Stickel, U. Klaas, D. Lemke, K. Mattila

Abstract: The presence of dust distributed in the intergalactic medium of galaxy clusters is of considerable interest for studies of the large scale structure and cosmology such as the number counts of galaxies and quasars as well as the study of the evolution of galaxies and clusters of galaxies.
ISOPHOT FIR observations have been used to search for spatially extended intracluster dust in six Abell clusters in the redshift range 0.015 < z < 0.075. Scanning measurements crossing the clusters were used to derive the 120 µm / 180 µm FIR color ratio which is expected to show a systematic change such as a dip or a bump centered on the cluster if intracluster dust with properties different from the foreground galactic cirrus is present.
Since the expected signal from intracluster dust is weak a careful data analysis including the subtraction of the zodiacal light component was carried out. In no case has the characteristic intracluster dust signature of a color ratio changing across the cluster been found. These data do not confirm the evidence for intracluster dust in two promising candidates where hints for extended FIR emission had been found from the shorter wavelength IRAS data.


The SIRTF First Look Survey. Characterizing the Mid-Infrared Sky
L.J. Storrie-Lombardi, and the SSC FLS Team

Abstract: The First-Look Survey (FLS) will be first science program executed by the Space InfraRed Telescope Facility (SIRTF), the last of NASA's Great Observatories. The FLS will characterize the mid-infrared sky to levels up to two orders of magnitude deeper than presently known. The extragalactic component of the FLS comprises imaging of 5 square degrees of sky at high ecliptic latitude at 3, 4.5, 5.6, and 8 microns using the InfraRed Array Camera (IRAC) and 24, 70, and 160 microns using the Multiband Imaging Photometer for SIRTF (MIPS). The 5 s flux limits for the IRAC bands will be = 50 µJ and for the MIPS bands will be ~ 1.5 - 30 mJ. In addition, 'verification' surveys with approximately 10 times the exposure time of the main surveys will be carried out covering 0.1 - 0.25 square degree regions.
Ancillary data is already being obtained for the selected fields. NOAO provided time for deep R-band imaging (5 s ~25.5) with the Mosaic camera and VLA time has been allocated for a radio survey at 1.4 GHz to a 5 s sensitivity of 90µJ. We are exploring options to obtain near-infrared data as well to K ~ 19.0.
The data from the FLS will be made publically available as soon as they are deemed reliable for scientific analysis. All of the FLS data will be publicly available in time to support the second General Observer Call for Proposals.


The influence of the photometric redshift error on the convergence due to gravitational lensing
M. Suginohara

Abstract: The gravitational convergence is an indicator which shows the extent of the gravitational lensing effects. We consider the gravitational convergence constructed using data of the coming wide-field-surveys of galaxies.
First, we calculate the mass density fields from the data supposing the appropriate biasing. Secondly, we calculate the gravitational convergence originated from such density fields. That is to say, we make a two-dimensional map of the gravitational convergence fields on celestial sphere. Finally, in principal, we can estimate how features of any given source vary in the case taking account of the gravitational lensing effects, compared to the case without lensing.
The Sloan Digital Sky Survey will directly determine redshifts of galaxies up to z = 0.2 with spectroscopic method. Furthermore, we expect to obtain photometric redshifts of galaxies up to z = 1. We investigate how the error originated from the inference of the photometric redshifts affects the uncertainties of the gravitational convergence.


First results from the Chandra Deep Field South: groups and clusters of galaxies
P. Tozzi

Abstract: No abstract submitted.


Widefield imaging with OmegaCAM
E.A. Valentijn

Abstract: No abstract submitted.


Radiative transfer models for young galaxies with Lyman-alpha halos
R. Wehrse

Abstract: For the interpretation of spatially resolved line profiles from young galaxies and their Lya halos we have performed 3D radiative transfer calculations for various density and velocity distributions as well as excitation geometries. It is demonstrated that for the Lya line the apparent brightness distributions as could be seen on the sky are determined by an intricate interplay of the densities and velocities, the angle dependence of the exciting radiation being usually of minor importance. In non-spherical cases self-absorptions are weaker than in 1D geometries and the role of dust is reduced. The visibility of objects in the Lya cloud and possibilities for parameter determinations by combining information from optically thick and thin (e.g. forbidden) lines are discussed.


An NRAO VLBA survey of first sources in the NOAO Deep Wide Field J1432-3416
J.M. Wrobel, G.B. Taylor, S.T. Myers and C.D. Fassnacht

Abstract: The astrophysical impact of traditional VLBI surveys is limited by (a) the paucity of optical redshifts and (b) biases introduced by targeting bright and, often, flat-spectrum radio sources. We have begun an NRAO VLBA survey of FIRST sources in the NOAO Deep Wide Field J1432+3416 that overcomes both limitations. One hundred FIRST sources in that field are less than 5 arcseconds in size and stronger than 10 mJy at 1.4 GHz. We are using the VLBA to image each FIRST source at 8.4~GHz with an angular resolution of 1 milliarcsecond and a root-mean-square sensitivity of 0.3 mJy. We expect to detect 30 sources, with implications ranging from the discovery of 1-3 compact symmetric objects to detecting, or constraining the number of, graviationally lensed sources on milliarcsecond scales. All detections will be astrometrically anchored to the International Celestial Reference Frame. The 70 or so nondetections will still have astrophysical value, because of their visibility-function constraints on milliarcsecond scales and their ancillary identification and distance information from the field's optical database. The data acquisition and analysis techniques developed for our VLBA survey will be applicable to any deep wide field with delta(J2000) >= -30 degrees. NRAO is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc.


Galaxy morphology in a cluster at z~1.26 versus the field
K. Wu

Abstract: The observed morphology of galaxies may change quite dramatically as one approaches ultraviolet wavelengths. As we study galaxies at higher and higher redshifts, we observe them at increasingly blue (and, eventually, ultraviolet) rest wavelengths. It is desirable, therefore, to study the morphology of higher redshift galaxies at infrared wavelengths, which correspond roughly to optical rest wavelengths at z ~ 1-2.
We have obtained images of a cluster of galaxies in Lynx at a redshift of z ~ 1.26 using NICMOS on the HST. Preliminary studies indicate that almost all of the galaxies in this cluster display an exponential profile characteristic of disks. These galaxies have spectral energy distributions similar to those expected for the passively evolving elliptical galaxies found in clusters. If such disky galaxies are indeed the progenitors to today's cluster elliptical and S0 galaxies, they must undergo substantial morphological evolution. The same analysis will be applied to a sample of K<20 field galaxies in four fields (Lynx, Cetus, Pisces, SA57) to determine whether similar objects appear in the field. The potential impact on current theories of galaxy evolution will be discussed.


A quantitative study of the evolution of peculiarities in galaxy morphology
K. Wu

Abstract: Peculiarities in galaxy morphology are generally accepted to be indications of galaxy interactions and mergers. A study of such peculiarities, therefore, will provide valuable clues to the formation and evolution of galaxies. I have developed a pair of indices (rotational asymmetry and concentration), based on the work of R. Abraham and collaborators, to identify galaxies with peculiar morphology. These indices are applied to a large sample of galaxies in the Hubble Deep Field for which photometric redshifts have been determined by A. Connolly. This powerful combination of deep, high resolution HST data and photometric redshifts allows investigation of trends at redshifts which have been largely inaccessible until now. I will present the evolution of the distribution of galaxies in the asymmetry-concentration parameter space and discuss implications on the current views of galaxy evolution.


Source size measurement from observed quasar microlensing
A. Yonehara

Abstract: Owing to the large distance, it is hard to directly measure the source size of the central engine (accretion disk) of AGN and quasar. However, there exists a strong tool to perform such measurement. That is quasar microlensing. Spatial resolution of quasar microlensing is estimated as less than expected angular size of quasar accretion disk (~ 1 µ as). Therefore, in principle, we are able to obtain the structure of the central region of quasar via quasar microlensing events.
Recently, a quasar microlensing event is detected in Q2237+0305 ("Einstein Cross" or "Huchra's lens") by OGLE team. In this study, we have performed light curve fittings for the light curve and present the results. Compared with simple microlensing like galactic microlensing event, e.g., MACHO microlensing, magnification pattern is complicated in quasar microlensing event. Thus, we have used approximated magnification formulae near caustics (i.e., critical region of magnification pattern) for light curve fitting. Unfortunately, even if we used the approximation formulae, there remains some ambiguities and varieties, it is possible to reproduce the observed light curve in many cases (e.g., "fold caustic" crossing and "cusp caustic" gazing, scaling of caustics). Nevertheless, in the range of "Chang and Refsdal"-lens approximation, we successively limit the size of the source. From the results of light curve fitting, the size is, at least, less than ~ 10^17 cm (more than 90% confidence level). The result strongly supports the existence of an accretion disk in quasar.


AGNs in deep X-ray surveys and the X-ray background
R. Gilli

Abstract: The hard X-ray background (XRB) is commonly believed to be produced by the integrated emission of AGNs. ROSAT and Chandra deep surveys have already resolved most of the 0.5-2 keV and 2-10 keV background, respectively. ROSAT sources were found to be mainly AGNs. Also, AGNs seem to constitute the major population for Chandra sources, although the optical identifications are not complete. We worked out AGN synthesis models for the XRB in agreement with all the available X-ray constraints, making predictions on the sources which should be observed in deep XÐray surveys. In this context some debated issues, e.g. the AGN space density at high redshift and the existence of a population of luminous obscured AGNs, the QSO2s, can be addressed and settled.