Hernan Quintana

The XMM-LSS survey. Survey design and first results

We have designed a medium deep large area X-ray survey with XMM - the XMM Large Scale Structure survey, XMM-LSS - with the scope of extending the cosmological tests attempted using ROSAT cluster samples to two redshift bins between 0

X-Ray Overluminous Elliptical Galaxies: A New Class of Mass Concentrations in the Universe?

We detect four isolated, X-ray overluminous [Lx > 2 × 1043 -2 ergs s-1] elliptical galaxies (OLEGs) in our 160 deg2 ROSAT PSPC survey. The extent of their X-ray emission, total X-ray luminosity, total mass, and mass of the hot gas in these systems corresponds to poor clusters, and the optical luminosity of the central galaxies (MR 7 keV clusters.

The 160 Square Degree ROSAT Survey: The revised catalog of 201 clusters with spectroscopic redshifts

We present the revised catalog of galaxy clusters detected as extended X-ray sources in the 160 Square Degree ROSAT Survey, including spectroscopic redshifts and X-ray luminosities for 200 of the 201 members. The median redshift is zmedian = 0.25, and the median X-ray luminosity is LX,median = 4.2 × 1043 h ergs s-1 (0.5-2.0 keV). This is the largest high-redshift sample of X-ray-selected clusters published to date. There are 73 objects at z > 0.3 and 22 objects at z > 0.5 drawn from a statistically complete flux-limited survey with a median object flux of 1.4 × 10-13 ergs cm-2 s-1. We describe the optical follow-up of these clusters with an emphasis on our spectroscopy, which has yielded 155 cluster redshifts, 110 of which are presented here for the first time. These measurements, combined with 45 from the literature and other sources, provide near-complete spectroscopic coverage for our survey. We discuss the final optical identifications for the extended X-ray sources in the survey region and compare our results to similar X-ray cluster searches.

The Atacama Cosmology Telescope: Extragalactic Sources at 148 GHz in the 2008 Survey

We report on extragalactic sources detected in a 455 deg2 map of the southern sky made with data at a frequency of 148 GHz from the Atacama Cosmology Telescope (ACT) 2008 observing season. We provide a catalog of 157 sources with flux densities spanning two orders of magnitude: from 15 mJy to 1500 mJy. Comparison to other catalogs shows that 98% of the ACT detections correspond to sources detected at lower radio frequencies. Three of the sources appear to be associated with the brightest cluster galaxies of low-redshift X-ray-selected galaxy clusters. Estimates of the radio to millimeter-wave spectral indices and differential counts of the sources further bolster the hypothesis that they are nearly all radio sources, and that their emission is not dominated by re-emission from warm dust. In a bright (>50 mJy) 148 GHz selected sample with complete cross-identifications from the Australia Telescope 20 GHz survey, we observe an average steepening of the spectra between 5, 20, and 148 GHz with median spectral indices of α5-20 = –0.07 ± 0.06, α20-148 = –0.39 ± 0.04, and α5-148 = –0.20 ± 0.03. When the measured spectral indices are taken into account, the 148 GHz differential source counts are consistent with previous measurements at 30 GHz in the context of a source count model dominated by radio sources. Extrapolating with an appropriately rescaled model for the radio source counts, the Poisson contribution to the spatial power spectrum from synchrotron-dominated sources with flux density less than 20 mJy is C Sync = (2.8 ± 0.3) × 10–6μK2.

Structure and dynamics of the Shapley Supercluster - Velocity catalogue, general morphology and mass

We present results of our wide-field redshift survey of galaxies in a 285 square degree region of the Shapley Supercluster (SSC), based on a set of 10 529 velocity measurements (including 1201 new ones) on 8632 galaxies obtained from various telescopes and from the literature. Our data reveal that the main plane of the SSC (v ≈ 14 500 km s −1 ) extends further than previous estimates, filling the whole extent of our survey region of 12 degrees by 30 degrees on the sky (30 × 75 h −1 Mpc). There is also a connecting structure associated with the slightly nearer Abell 3571 cluster complex (v ≈ 12 000 km s −1 ). These galaxies seem to link two previously identified sheets of galaxies and establish a connection with a third one at v = 15 000 km s −1 near RA = 13 h . They also tend to fill the gap of galaxies between the foreground Hydra-Centaurus region and the more distant SSC. In the velocity range of the Shapley Supercluster (9000 km s −1 < cz < 18 000 km s −1 ), we found redshift-space overdensities with bj < 17. 5o f� 5.4 over the 225 square degree central region and � 3.8 in a 192 square degree region excluding rich clusters. Over the large region of our survey, we find that the intercluster galaxies make up 48 per cent of the observed galaxies in the SSC region and, accounting for the different completeness, may contribute nearly twice as much mass as the cluster galaxies. In this paper, we discuss the completeness of the velocity catalogue, the morphology of the supercluster, the global overdensity, and some properties of the individual galaxy clusters in the Supercluster.

Future evolution of bound superclusters in an accelerating Universe

The evolution of marginally bound supercluster-like objects in an acceleratingcold dark matter (� CDM) Universe is followed, by means of cosmological simulations, from the present time to an expansion factor a = 100. The objects are identified on the basis of the binding density criterion introduced by D¨ unner et al. Superclusters are identified with the ones whose mass M> 10 15 h −1 M� , the most massive one with M ∼ 8 × 10 15 h −1 M� , comparable to the Shapley supercluster. The spatial distribution of the superclusters remains essentially the same after the present epoch, reflecting the halting growth of the cosmic web asgets to dominate the expansion of the Universe. The same trend can be seen in the stagnation of the development of the mass function of virialized haloes and bound objects. The situation is considerably different when looking at the internal evolution, quantified in terms of their shape, compactness and density profile, and substructure in terms of their multiplicity function. We find a continuing evolution from a wide range of triaxial shapes at a = 1 to almost perfect spherical shapes at a = 100. We also find a systematic trend towards a higher concentration. Meanwhile, we see their substructure gradually disappearing, as the surrounding subclumps fall in and merge to form one coherent, virialized system.

The XMM-Large scale structure catalogue: X-ray sources and associated optical data. Version I

Following the presentation of the XMM-Large Scale Structure (XMM-LSS) survey X-ray source detection package by Pacaud et al., we provide the source lists for the first surveyed 5.5 deg 2 . The catalogues pertain to the [0.5-2] and [2-10] keV bands and contain in total 3385 point-like or extended sources above a detection likelihood of 15 in either band. The agreement with deep log N- log S is excellent. The main parameters considered are position, count rate, source extent with associated likelihood values. A set of additional quantities such as astrometric corrections and fluxes are further calculated while errors on the position and count rate are deduced from simulations. We describe the construction of the band-merged catalogue allowing rapid subsample selection and easy cross-correlation with external multiwavelength catalogues. A small optical Canada-France-Hawaii Telescope Legacy Survey multiband subset of objects are associated with each source along with an X-ray/optical overlay. We make the full X-ray images available in FITS format. The data are available at the Centre de Donnees de Strasbourg and, in a more extended form, at the Milan XMM-LSS survey data base.

EVOLUTION OF THE CLUSTER X-RAY LUMINOSITY FUNCTION

The evolution of the X-ray luminosity function of clusters of galaxies has been measured to z=0.85 using over 150 X-ray selected clusters found in the WARPS survey. We find no evidence for evolution of the luminosity function at any luminosity or redshift. The observations constrain the evolution of the space density of moderate luminosity clusters to be very small, and much less than predicted by most models of the growth of structure with Omega=1.

Deconstructing Abell 3266: A Major Merger in a Quiet Cluster

We present results of simple N-body simulations that strengthen the suggestion that Abell 3266 is composed of two subunits of comparable mass that have merged recently. Both the real cluster and the N-body dark-matter cluster show mixed signals of substructure under statistical tests. However, in a decidedly nonstatistical approach allowed by the wide-area coverage and the large number of redshifts Quintana, Ramirez, & Way measured in A3266, they sliced the real cluster in redshift space to uncover a peculiar spatial distribution of galaxies that they suggested was the result of a recent merger. In our simulations, a similar distribution is the result of an ongoing merger between two comparable-mass units that started about 2 × 109 yr ago in the N-body simulations. We also find that the distribution of emission-line galaxies in A3266 traces the same structure. We discuss further tests of our merger hypothesis and speculate on the possibility that a similar process might be occurring in other, apparently relaxed clusters at the present epoch.

New optical polarization measurements of quasi-stellar objects. The data

New linear polarization measurements (mainly in the V band) are presented for 203 quasi-stellar objects (QSOs). The sample is made up of 94 QSOs located in the North Galactic Pole (NGP) region and of 109 QSOs in the South Galactic Pole (SGP) region. First time measurements have been obtained for 184 QSOs. Among them, 109 known radio-emitters, 42 known Broad Absorption Line (BAL) QSOs, and 1 gravitationally lensed quasi-stellar object. We found high polarization levels (p > 3%) for 12 QSOs, including the BAL QSO SDSS J1409+0048. For 10 objects, measurements obtained at different epochs do exist. Two of them show evidence for variability: the highly polarized BL Lac candidate PKS 1216-010 and the radio source PKS 1222+037.