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|Radio emission from AGN detected by the VLA FIRST survey|
Using the most recent (April 2003) version of the VLA FIRST survey radiocatalog, we have searched for radio emission from >2800 AGN takenfrom the most recent (2001) version of the Veron-Cetty and Veron AGNcatalog. These AGN lie in the 9033 square degrees of sky alreadycovered by the VLA FIRST survey. Our work has resulted in positivedetection of radio emission from 775 AGN of which 214 are new detectionsat radio wavelengths.Tables 3 and 4 are only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (18.104.22.168) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/416/35
|The ROSAT/IRAS Galaxy Sample Revisited|
Galaxies in the ROSAT/IRAS sample were selected by their soft X-ray(0.1-2.4 keV) and far-infrared (lambda = 60 μm) emission. Therelatively large uncertainties in the original ROSAT and IRAS positionscaused some contamination by close pairs and forced the exclusion ofmost ``high-flux'' (S > 10 Jy at lambda = 100 μm) IRAS sourcesfrom the original sample. We used new 1.4 GHz VLA images of all objectsnorth of delta = -45 deg along with improved X-ray and far-infraredpositions to eliminate incorrect identifications, many of which appearedto be starburst galaxies with high X-ray luminosities, log [X(ergs^-1)]> 43. We also used VLA images to search for new X-ray identificationsamong the ``high-flux'' sources with delta > -45 deg. Only two werefound, indicating that luminous starburst galaxies have relatively lowsoft X-ray luminosities, in part due to absorption by a denseinterstellar medium. No starburst galaxies in our revised sample haveX-ray luminosities approaching log [X(ergs^-1)] = 43. We conclude thatmost galaxies in the revised ROSAT/IRAS sample contain X-ray-emittingactive galactic nuclei (AGNs) residing in star-forming disks that emitmost of the lambda = 60 μm radiation. Normal and starburst galaxiesprobably do not account for a significant fraction of the soft X-raybackground.
|ROSAT All-Sky Survey observations of IRAS galaxies. I. Soft X-ray and far-infrared properties|
The 120 000 X-ray sources detected in the RASS II processing of theROSAT All-Sky Survey are correlated with the 14 315 IRAS galaxiesselected from the IRAS Point Source Catalogue: 372 IRAS galaxies showX-ray emission within a distance of 100 arcsec from the infraredposition. By inspecting the structure of the X-ray emission in overlayson optical images we quantify the likelihood that the X-rays originatefrom the IRAS galaxy. For 197 objects the soft X-ray emission is verylikely associated with the IRAS galaxy. Their soft X-ray properties aredetermined and compared with their far-infrared emission. X-ray contourplots overlaid on Palomar Digitized Sky Survey images are given for eachof the 372 potential identifications. All images and tables displayedhere are also available in electronic form.
|Classification of IRAS-selected X-Ray Galaxies in the ROSAT All-Sky Survey|
To explore the possibility that star-forming galaxies or obscuredSeyfert galaxies, both of which are known to be luminous infraredsources, contribute significantly to the cosmic X-ray background, wehave carried out an extensive program to obtain accurate spectroscopicclassifications of the BoIler et al. (1992) catalog of IRAS sourcesdetected in the ROSAT All-Sky Survey. This has involved careful opticalspectroscopy, a review of the literature, and efforts to reveal thecontaminants in the sample. Classifications have been determined for 210of the 241 X-ray sources in the catalog; 105 are presented here for thefirst time. A large number of IR/X-ray source chance coincidences arefound in this sample; of the 40-50 expected, we have identified 18firmly and have established strong cases for 29 others. Most chancecoincidences involve bright stars or Seyfert galaxies close (inprojection) to IR- bright H II galaxies. Although this work wasmotivated initially by the report that a new class of X-ray-luminous,normal spiral galaxies was to be found in this sample, we find noevidence for such a class. Most of the extragalactic X-ray sources areactive galactic nuclei (AGNs), consistent with the results of previousstudies of X-ray-selected objects. However, many of these AGNs exhibitweak or heavily reddened Seyfert features in their optical spectra. Inaddition, two rare types of AGNs are found in this sample withsurprising frequency: I Zw 1 objects (also called narrow-line Seyfert 1galaxies) and starburst/Seyfert composite galaxies, a new class ofluminous X-ray sources. We have shown that the Boller et al. object202103 - 223434 (= IRAS 20181-2244), reported to be the best example ofa narrow-line quasar, is actually a member of the I Zw 1 class. Theenigmatic starburst/Seyfert composite galaxies have optical spectradominated by the features of H II galaxies but X-ray luminositiestypical for Seyfert galaxies. Close examination of their optical spectrareveals subtle Seyfert signatures: [O III] lines broader than all otherlines in the spectrum and, in some cases, a weak, broad Hαcomponent. Obscuration of the active nucleus is likely to explain theX-ray and optical properties of these objects. We describe a scenario inwhich such optically innocuous, obscured AGNs could comprise animportant new component of the X-ray background.
|The complex structure of Abell 2151 (Hercules)|
We analyzed the space distribution of 117 galaxies in an area of 0.9 degradius centered on NGC 6045 in the Hercules cluster in the velocityrange 9000 to 14,000 km/s. By taking advantage of 74 morphologies basedon CCD images, we succeed in isolating a cluster of galaxies with anaverage velocity of 11,467 km/s located to the NE of the assumedcentroid of A2151, where early and late type galaxies share the samedynamical properties. The implications of this result for the nature andidentification of the x-ray source is briefly discussed.
|Dark matter and dynamics in the Hercules Cluster (A2151)|
New 21-cm observations of faint spiral galaxies in the Hercules cluster(A2151) are presented in order to investigate the dynamics throughoutthe cluster core, out to a projected radius of 1.8/h Mpc. The globaldynamical mass of Hercules is calculated using the virial theorem andthe projected mass estimator. These masses lie in the range 3-9 x 10 exp14 solar masses. The importance of subclustering in A2151 by eye isexamined via the statistical test of Dressler & Shectman (1988), andby considering the effects of the detected substructure on the dynamicalmass determination. The clumpy distribution is interpreted as a signthat the galaxies in the cluster have not reached dynamical equilibriumin the gravitational potential.
|ROSAT All Sky Survey observations of IRAS galaxies|
Cross-correlations are established between 14,708 selected IRAS sourcesand the ROSAT All Sky Survey X-ray sources. The resulting catalog of 244IRAS galaxies positionally coincident with ROSAT X-ray sources ispresented. For 222 of them, optical counterparts could be identified bya comparison with the NASA/IPAC Extragalactic Database. An unexpectedresult was the discovery of several spiral galaxies with luminosities upto 10 exp 43 erg/s, well above those found with the Einstein satellite.
|The evolution of galaxies in clusters. IV - Photometry of 10 low-redshift clusters|
Colors and magnitudes, obtained from Palomar 48 inch (1.2 m) Schmidtplates in the J and F bands, and morphological types are presented forgalaxies in the cores of 10 nearby clusters of galaxies. In the typicalcluster, the sample includes all galaxies within a radius of 1.5 Mpc(assuming H(0) = 50 km/s/Mpc) of the cluster center and brighter than J= 17.5.The accuracy of the photometry varies with cluster, but mostmagnitudes are accurate to 0.10 mag, and typical errors in the colorsare of the same order. As expected, the colors of the elliptical and S0galaxies show a narrow dispersion about a mean color which decreaseswith magnitude. However, the colors of the spiral galaxies are notentirely as expected, having a smaller dispersion than would have beenpredicted from their morphological types.
|A catalog of morphological types in 55 rich clusters of galaxies|
Data are presented from a study of 55 rich clusters of galaxies. Thedata include positions, morphological types, estimated total magnitudes,bulge sizes, and ellipticities for about 6000 galaxies, as determinedfrom high scale photographic plates. Data reduction procedures aredescribed, and a brief analysis of cluster richness, which indicatesthat Abell richness classes are only rough indicators of total clustermembership, is included.
|Notes on the Hercules Galaxy Cluster|
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1971PASP...83..320C&db_key=AST
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