arXiv subjects

H. Quintana

Publications and source records attributed to H. Quintana.

61 records · Page 4Linked to original sources

arXiv1998

A Catalog of 200 Galaxy Clusters Serendipitously Detected in the ROSAT PSPC Pointed Observations

We present a catalog of 200 clusters of galaxies serendipitously detected in 647 ROSAT PSPC pointings covering 158 square degrees. This is one of the largest X-ray selected cluster samples, comparable in size only to the ROSAT All-Sky Survey sample of nearby clusters (Ebeling et al. 1997). We detect clusters in the inner 17.5 arcmin of the ROSAT PSPC field of view using the spatial extent of their X-ray emission. Cluster X-ray luminosities range from 10^42 erg/s to ~5x10^44 erg/s, i.e. from poor groups to rich clusters. The cluster redshifts range from z=0.015 to z>0.5. The catalog lists X-ray fluxes, core-radii, spectroscopic redshifts for 73 clusters and photometric redshifts for the remainder. We have optically confirmed 200 of 223 X-ray sources as clusters of galaxies. Of the remaining 23 sources, 18 are likely false detections arising from blends of unresolved point X-ray sources, and for 5 we have not obtained deep CCD images. Above a flux of 2e-13 erg/s/cm**2, 98\% of extended X-ray sources are optically confirmed clusters. The log N-log S relation derived from our catalog shows excellent agreement with previous results: EMSS and ROSAT All-Sky survey BCS in teh bright end and WARPS at intermediate fluxes. Our cluster counts appear to be systematically higher than those from a 50 deg^2 survey of Rosati et al. (1998). In particular, at a flux of 2e-13 erg/s/cm**2, we find a surface density of clusters of 0.57+/-0.07 per square degree, which is a factor of 1.3 more than found by Rosati et al. This difference is marginally significant at the ~2 sigma level. The large area of our survey makes it possible to study the evolution of the X-ray luminosity function in the high luminosity range inaccessible with other, smaller area ROSAT surveys.

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arXiv1998

Evolution of Cluster X-Ray Luminosities and Radii: Results from the 160 Square Degree ROSAT Survey

We searched for cluster X-ray luminosity and radius evolution using our sample of 200 galaxy clusters detected in the 160 deg^2 survey with the ROSAT PSPC (Vikhlinin et al. 1998, astro-ph/9803099). With such a large area survey, it is possible, for the first time with ROSAT, to test the evolution of luminous clusters, Lx > 3x10^44 erg/s, in the 0.5-2 keV band. We detect a factor of 3-4 deficit of such luminous clusters at z>0.3 compared to the present. The evolution is much weaker or absent at modestly lower luminosities, 1-3x10^44 erg/s. At still lower luminosities, we find no evolution from the analysis of the log N - log S relation. The results in the two upper Lx bins are in agreement with the Einstein EMSS evolution result (Gioia et al. 1990a, Henry et al. 1992) while being obtained using a completely independent cluster sample. The low-Lx results are in agreement with other ROSAT surveys (e.g. Rosati et al. 1998, Jones et al. 1998). We also compare the distribution of core radii of nearby and distant (z>0.4) luminous (with equivalent temperatures 4-7 keV) clusters, and detect no evolution. The ratio of average core radius for z~0.5 and z<0.1 clusters is 0.9+/-0.1, and the core radius distributions are remarkably similar. A decrease of cluster sizes incompatible with our data is predicted by self-similar evolution models for high-Omega universe.

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arXiv1997

The Dynamics of the cD Clusters Abell 119 and Abell 133

A dynamical analysis of the structure of the clusters of galaxies Abell 119 and Abell 133 is presented, using new redshift data combined with existing data from the literature. We compare our results with those from the X-ray data for these clusters, and with those from radio data for the central cD galaxy in each cluster. A comparison of the mass estimate based on X-ray data and that obtained here after subgroups are eliminated shows them to be comparable. After the elimination of subgroups, 125 galaxy members in Abell 119 and 120 in Abell 133 give dispersions of 472 km/s and 735 km/s respectively. However, our dynamical analysis of the optical data shows little substructure in the velocity field of Abell 133, conflicting with what is seen in the Rosat X-ray map. Abell 119 seems to have multiple structures along the line of sight. We derive virial mass estimates of 3.05 X 10E14 Solar Masses for Abell 119 and 7.79 X 10E14 Solar Masses for Abell 133 within 1.5 Mpc, which agree well with the X-ray-derived masses within errors.

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arXiv1997

Statistics of AGN in Rich Clusters Revisited

Using spectrophotometry of a large sample of galaxies in 19 Abell Clusters, we have selected 42 candidate AGN by the criteria used by Dressler et.al. 1985 (DTS) in their analysis of the statistics of 22 AGN in 14 rich cluster fields, which are based on the equivalent width of [OII]3727, Hbeta, and [OIII]5007 emission. We have then discriminated AGN from HII region-like galaxies (hereafter HII galaxies) in the manner developed by Veilleux & Osterbrok 1987 using the additional information provided by Halpha and [NII]6583 or Halpha and [SII]6716+6731 emission, in order to test the reliability of the selection criteria used by DTS. We find that our sample is very similar to that of DTS before we discriminate AGN from HII galaxies, and would lead to similar conclusions. However, we find that their method inevitably mixes HII galaxies with AGN, even for the most luminous objects in our sample. Other authors have attempted to quantify the relative fraction of cluster to field AGN since the study of DTS (Hill & Oegerle 1993, Biviano et al. 1997) reaching similar conclusions, but using similar criteria to theirs to select AGN (or using the [OIII]5007/Hbeta flux ratio test that also mixes HII galaxies with AGN). Our sample of true AGN is left too small to reach statistically meaningful conclusions, therefore a new study with the more time-consuming method that includes the other lines will be required to quantify the true relative fraction of cluster to field AGN.

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arXiv1996

Globular cluster systems of early--type galaxies in Fornax

We studied the properties of the globular cluster systems of five early--type galaxies in the Fornax galaxy cluster: NGC 1374, NGC 1379, NGC 1387, NGC 1427, and the central giant elliptical NGC 1399. From the investigation of their number of globular clusters, specific frequency, color distribution, surface density profile, and spatial distribution, we conclude that our faint ellipticals have no more globular clusters than spirals of the same mass, and neither differ in their other properties. For these galaxies there is no need to imply a different formation scenario of the globular cluster system. The central giant elliptical has far more globular clusters and show signatures of a different history in the building up of its globular cluster system.

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arXiv1996

The distance of the Fornax Cluster based on Globular Cluster Luminosity Functions

We present Globular Cluster Luminosity Functions for four ellipticals and one S0-Galaxy in the Fornax cluster of galaxies, derived from CCD photometry in V and I. The averaged turnover magnitudes are $V_{TO} = 23.80 \pm 0.06$ and $I_{TO} =22.39 \pm 0.05$, respectively. We derive a relative distance modulus $(m-M)_{Fornax} - (m-M)_{M87} = 0.08 \pm 0.09$ mag using the turnover of M87 based on HST data.

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arXiv1994

The Medium Redshift Clusters CL0017-20 and CL0500-24

We present magnitudes and redshifts of galaxies in the cluster of galaxies CL0017-20 and in the double cluster CL0500-24. Luminosity functions and velocity distributions have been derived. CL0017-20 possesses a virial mass of $2.9 \times 10^{14}$ M$_\odot$ and a \vmag band luminosity of $2.3 \pm 0.5 \times 10^{12}$ L$_\odot$ ($M/L_{\rm V} = 127$), much of it in a very compact core of size 113 kpc. Our new velocities and photometry of CL0500-24 confirm its double nature. Our group algorithm clearly detects two subconcentrations with masses 1.9 and $2.2 \times 10^{14}$ M$_{\odot}$. Its total \vmag band luminosity amounts to $2.7 \pm 0.8 \times 10^{12}$ L$_{\odot}$ ($M/L_{\rm V}$ of 157). Since the crossing and collapse times in both clusters are smaller than the age of the Universe, they appear bound and virialized. It is surprising that although $M/L$ is small in these clusters, giant arcs have been detected in both.

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