A 20cm VLA Survey of Abell Clusters of Galaxies VI. Radio/Optical Luminosity Functions

From a statistically complete sample of 188 radio galaxies in Abell clusters, we examine the radio/optical correlations, the FR I/II division, and the univariate and bivariate luminosity functions. As suggested by Owen (1993), the FR I/II division is shown to be a strong function of the optical luminosity of the host galaxy (proportional to L_opt^2). This dependence is also seen in the bivariate luminosity function, which suggests that the evolutionary tracks of radio sources and/or the initial conditions in the source are governed by the host galaxy properties. The probability for detecting radio emission increases with optical luminosity. The optical dependence is clearly separated in the integral luminosity functions which can be used as a constraint to models of FR I radio power evolution. Additionally, the source counts from the integrated univariate radio luminosity function (RLF) are consistent with our suggestion in paper V that radio sources may be a transient phenomenon which occurs in all elliptical galaxies at some time (or several times) over their lifetime. We find no statistically significant differences in the luminosity functions between rich cluster samples and radio sources not selected to reside in clusters. These results suggest that all radio galaxies live in similar environments in that the optical luminosity and the properties of the host galaxy are the most important parameters which affect radio source formation and evolution.Comment: 21 pages LaTeX, 3 tables, 12 figures. To appear in July 1996 A

New Velocity Distribution in the Context of the Eddington Theory

Exotic dark matter together with the vacuum energy (associated with the cosmological constant) seem to dominate the Universe. Thus its direct detection is central to particle physics and cosmology. Supersymmetry provides a natural dark matter candidate, the lightest supersymmetric particle (LSP). One essential ingredient in obtaining the direct detection rates is the density and velocity distribution of the LSP. The detection rate is proportional to this density in our vicinity. Furthermore, since this rate is expected to be very low, one should explore the two characteristic signatures of the process, namely the modulation effect, i.e. the dependence of the event rate on the Earth's motion and the correlation of the directional rate with the motion of the sun. Both of these crucially depend on the LSP velocity distribution. In the present paper we study simultaneously density profiles and velocity distributions based on the Eddington theory.Comment: 40 LaTex pages, 19 figures and one table. The previous version was expanded to include new numerical solutions to Poisson's equation. Sheduled to appear in vol. 588, ApJ, May 1, 300

Identifying space use at foraging arena scale within the home ranges of large herbivores.

An intermediate spatiotemporal scale of food procurement by large herbivores is evident within annual or seasonal home ranges. It takes the form of settlement periods spanning several days or weeks during which foraging activity is confined to spatially discrete foraging arenas, separated by roaming interludes. Extended by areas occupied for other activities, these foraging arenas contribute towards generating the home range structure. We delineated and compared the foraging arenas exploited by two African large herbivores, sable antelope (a ruminant) and plains zebra (a non-ruminant), using GPS-derived movement data. We developed a novel approach to specifically delineate foraging arenas based on local change points in distance relative to adjoining clusters of locations, and compared its output with modifications of two published methods developed for home range estimation and residence time estimation respectively. We compared how these herbivore species responded to seasonal variation in food resources and how they differed in their spatial patterns of resource utilization. Sable antelope herds tended to concentrate their space use locally, while zebra herds moved more opportunistically over a wider set of foraging arenas. The amalgamated extent of the foraging arenas exploited by sable herds amounted to 12-30 km2, compared with 22-100 km2 for the zebra herds. Half-day displacement distances differed between settlement periods and roaming interludes, and zebra herds generally shifted further over 12h than sable herds. Foraging arenas of sable herds tended to be smaller than those of zebra, and were occupied for period twice as long, and hence exploited more intensively in days spent per unit area than the foraging arenas of zebra. For sable both the intensity of utilization of foraging arenas and proportion of days spent in foraging arenas relative to roaming interludes declined as food resources diminished seasonally, while zebra showed no seasonal variation in these metrics. Identifying patterns of space use at foraging arena scale helps reveal mechanisms generating the home range extent, and in turn the local population density. Thereby it helps forge links between behavioural ecology, movement ecology and population ecology

VLA 1.4GHz observations of the GOODS-North Field: Data Reduction and Analysis

We describe deep, new, wide-field radio continuum observations of the Great Observatories Origins Deep Survey -- North (GOODS-N) field. The resulting map has a synthesized beamsize of ~1.7" and an r.m.s. noise level of ~3.9uJy/bm near its center and ~8uJy/bm at 15', from phase center. We have cataloged 1,230 discrete radio emitters, within a 40' x 40' region, above a 5-sigma detection threshold of ~20uJy at the field center. New techniques, pioneered by Owen & Morrison (2008), have enabled us to achieve a dynamic range of 6800:1 in a field that has significantly strong confusing sources. We compare the 1.4-GHz (20-cm) source counts with those from other published radio surveys. Our differential counts are nearly Euclidean below 100uJy with a median source diameter of ~1.2". This adds to the evidence presented by Owen & Morrison (2008) that the natural confusion limit may lie near ~1uJy. If the Euclidean slope of the counts continues down to the natural confusion limit as an extrapolation of our log N - log S, this indicates that the cutoff must be fairly sharp below 1uJy else the cosmic microwave background temperature would increase above 2.7K at 1.4 GHz.Comment: Accepted for publication in ApJS. 16 pages, 19 figures. Radio data and source list can be found at http://www.ifa.hawaii.edu/~morrison/GOODSN

An X-ray and Optical Investigation of the Environments Around Nearby Radio Galaxies

Investigations of the cluster environment of radio sources have not shown a correlation between radio power and degree of clustering. However, it has been demonstrated that extended X-ray luminosity and galaxy clustering do exhibit a positive correlation. This study investigates a complete sample of 25 nearby (z less than 0.06) radio galaxies which are not cataloged members of Abell clusters. The environment of these radio galaxies is studied in both the X-ray and the optical by means of the ROSAT All-Sky Survey (RASS), ROSAT pointed observations, and the Palomar optical Digitized Sky Survey (DSS). X-ray luminosities and extents are determined from the RASS, and the DSS is used to quantify the degree of clustering via the spatial two-point correlation coefficient, Bgg. Of the 25 sources, 20 are greater than sigma detections in the X-ray and 11 possessed Bgg's significantly in excess of that expected for an isolated galaxy. Adding the criterion that the X-ray emission be resolved, 10 of the radio galaxies do appear to reside in poor clusters with extended X-ray emission suggestive of the presence of an intracluster medium. Eight of these galaxies also possess high spatial correlation coefficients. Taken together, these data suggest that the radio galaxies reside in a low richness extension of the Abell clusters. The unresolved X-ray emission from the other galaxies is most likely associated with AGN phenomena. Furthermore, although the sample size is small, it appears that the environments of FR I and FR II sources differ. FR I's tend to be more frequently associated with extended X-ray emission (10 of 18), whereas FR II's are typically point sources or non-detections in the X-ray (none of the 7 sources exhibit extended X-ray emission).Comment: 28 page postscript file including figures and tables, plus one landscape table and 5 GIF figure