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|Radio continuum spectra of galaxies in the Virgo cluster region|
New radio continuum observations of galaxies in the Virgo cluster regionat 4.85, 8.6, and 10.55 GHz are presented. These observations arecombined with existing measurements at 1.4 and 0.325 GHz. The sampleincludes 81 galaxies where spectra with more than two frequencies couldbe derived. Galaxies that show a radio-FIR excess exhibit centralactivity (HII, LINER, AGN). The four Virgo galaxies with the highestabsolute radio excess are found within 2° of the centerof the cluster. Galaxies showing flat radio spectra also host activecenters. There is no clear trend between the spectral index and thegalaxy's distance to the cluster center.Figure 3 is only available in electronic form athttp://www.edpsciences.orgTable 3 is only available in electronic form at the CDS via anonymousftp to cdsarc.u-strasbg.fr (22.214.171.124) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/418/1
|The QDOT all-sky IRAS galaxy redshift survey|
We describe the construction of the QDOT survey, which is publiclyavailable from an anonymous FTP account. The catalogue consists ofinfrared properties and redshifts of an all-sky sample of 2387 IRASgalaxies brighter than the IRAS PSC 60-μm completeness limit(S_60>0.6Jy), sparsely sampled at a rate of one-in-six. At |b|>10deg, after removing a small number of Galactic sources, the redshiftcompleteness is better than 98per cent (2086/2127). New redshifts for1401 IRAS sources were obtained to complete the catalogue; themeasurement and reduction of these are described, and the new redshiftstabulated here. We also tabulate all sources at |b|>10 deg with noredshift so far, and sources with conflicting alternative redshiftseither from our own work, or from published velocities. A list of 95ultraluminous galaxies (i.e. with L_60μm>10^12 L_solar) is alsoprovided. Of these, ~20per cent are AGN of some kind; the broad-lineobjects typically show strong Feii emission. Since the publication ofthe first QDOT papers, there have been several hundred velocity changes:some velocities are new, some QDOT velocities have been replaced by moreaccurate values, and some errors have been corrected. We also present anew analysis of the accuracy and linearity of IRAS 60-μm fluxes. Wefind that the flux uncertainties are well described by a combination of0.05-Jy fixed size uncertainty and 8per cent fractional uncertainty.This is not enough to cause the large Malmquist-type errors in the rateof evolution postulated by Fisher et al. We do, however, find marginalevidence for non-linearity in the PSC 60-μm flux scale, in the sensethat faint sources may have fluxes overestimated by about 5per centcompared with bright sources. We update some of the previous scientificanalyses to assess the changes. The main new results are as follows. (1)The luminosity function is very well determined overall but is uncertainby a factor of several at the very highest luminosities(L_60μm>5x10^12L_solar), as this is where the remainingunidentified objects are almost certainly concentrated. (2) Thebest-fitting rate of evolution is somewhat lower than our previousestimate; expressed as pure density evolution with density varying as(1+z)^p, we find p=5.6+/-2.3. Making a rough correction for the possible(but very uncertain) non-linearity of fluxes, we find p=4.5+/-2.3. (3)The dipole amplitude decreases a little, and the implied value of thedensity parameter, assuming that IRAS galaxies trace the mass, isΩ=0.9(+0.45, -0.25). (4) Finally, the estimate of density varianceon large scales changes negligibly, still indicating a significantdiscrepancy from the predictions of simple cold dark matter cosmogonies.
|On the local radio luminosity function of galaxies. I. The Virgo cluster|
We cross-correlate the galaxies brighter than m_B=18 in the Virgocluster with the radio sources in the NVSS survey (1.4 GHz), resultingin 180 radio-optical identifications. We determine the radio luminosityfunction of the Virgo galaxies, separately for the early- andlate-types. Late-type galaxies develop radio sources with a probabilityproportional to their optical luminosity. In fact their radio/optical(R_B) distribution is gaussian, centered at log R_B ~ -0.5, i.e. theradio luminosity is ~ 0.3 of the optical one. The probability oflate-type galaxies to develop radio sources is almost independent oftheir detailed Hubble type, except for Sa (and S0+S0a) which are afactor of ~ 5 less frequent than later types at any R_B. Giantelliptical galaxies feed ``monster" radio sources with a probabilitystrongly increasing with mass. However the frequency of fainter radiosources is progressively less sensitive on the system mass. The faintestgiant E galaxies (M_B=-17) have a probability of feeding low power radiosources similar to that of dwarf E galaxies as faint as M_B=-13. Table~1is only available in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (126.96.36.199) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
|21 CM H1 Line Spectra of Galaxies in Nearby Clusters|
A compilation of HI line fluxes, systemic velocities and line widths ispresented for \Ndet detected galaxies, mostly in the vicinities of 30nearby rich clusters out to a redshift of z ~ .04, specifically for usein applications of the Tully-Fisher distance method. New 21 cm HI lineprofiles have been obtained for ~ 500 galaxies in 27 Abell clustersvisible from Arecibo. Upper limits are also presented for \Nnod galaxiesfor which HI emission was not detected. In order to provide ahomogeneous line width determination optimized for Tully-Fisher studies,these new data are supplemented by the reanalysis of previouslypublished spectra obtained both at Arecibo and Green Bank that areavailable in a digital archive. Corrections for instrumental broadening,smoothing, signal-to-noise and profile shape are applied, and anestimate of the error on the width is given. When corrected forturbulent broadening and viewing angle, the corrected velocity widthspresented here will provide the appropriate line width parameter neededto derive distances via the Tully-Fisher relation.
|A Minnesota Automated Plate Scanner Catalog of Galaxies behind the Virgo Cluster and toward Its Antipode|
We present a catalog of 1268 galaxies, essentially complete to B <=17.0, found by scanning glass copies of several fields of the originalPalomar Sky Survey using the Minnesota Automated Plate Scanner in itsisodensitometric mode (as opposed to the threshold densitometric modeused in the APS Catalog of the POSS I). In addition to the differentscanning mode, we have employed a different star-galaxy separationmethod and have visually inspected POSS prints to verify that each imageremaining in the catalog is nonstellar. The scanned fields aredistributed generally in two areas, one around the outskirts of theVirgo Cluster, the other toward the antipode of the cluster (but stillin the northern celestial hemisphere). The catalog gives the position ofthe center of each galaxy; estimates of the blue and red magnitudeswithin the outermost threshold crossing and of the blue magnitudeextrapolated to zero surface brightness; and the blue and red diametersof four ellipses fitted to the four threshold crossings (approximately23.8,23.6,23.2, and 22.7 mag arcsec 2 in blue, and 22.5,22.4,21.5, and21.2 mag arcsec^-2^ in red), and the ellipticities of those fourellipses. The catalog has served as a base from which to draw targetsfor a Tully-Fisher study of the Virgocentric infall velocity of theLocal Group.
|The large-scale distribution of late-type galaxies between Virgo and the Great Wall|
Neutral hydrogen data are presented for 88 of the Virgo Cluster Cataloggalaxies thought on morphological grounds to lie in the background ofthe cluster. We confirm that the morphological assignment of clustermembership works quite well; very few of the 'background' galaxies arein fact at cluster redshifts. The resulting sample of redshifts, alongwith optical redshifts from the literature, allow us to explore thelarge-scale distribution of galaxies in the space between the LocalSupercluster and the Great Wall. Galaxies in a larger window around theVirgo Cluster, but at redshifts between Virgo and the Great Wall, have afairly low average number density, but the distribution is far fromuniform: Some portions resemble voids, but in other portions galaxiescan be assigned to clouds or filaments of appreciable size (sometimescontaining bound groups). We investigate the luminosity function inhigh- and low-density regions of our galaxy sample, which excludes theVirgo Cluster proper. We find no significant difference. However, ourselection procedures are insensitive to galaxies of very low surfacebrightness, which have been reported to be more abundant in low-densityregions. The average probability of a line of sight intersecting theoptical disk of our sample galaxies is derived separately for the VirgoSupercluster region (redshifts below 3500 km/s) and for the regionbehind (out to 10,000 km/s). The number density ratio of Ly-alpha forestlines to galaxies is larger by a factor of order 10 in the far(low-density) region than in the near. A survey of recent literature ongalaxy redshifts uncovers a new candidate, MCG 0-32-16, for the lowestredshift absorption line.
|An infrared-optical study of IRAS point sources in the Virgo region|
Optical identifications for 199 of the 206 IRAS point sources in a 113sq deg area centered on the Virgo cluster are made using four deepIIIa-J plates obtained with the 1.2-m UK Schmidt Telescope. Only 4percent of the E and S0 galaxies brigher than B = 16 are detected, ascompared with 44 percent of the Sc galaxies. Infrared properties of theVirgo cluster are found to be similar to those of field galaxies atsimilar redshifts. Such IRAS galaxies are typical spirals with B of lessthan about 14, infrared to optical luminosity ratios of about 1, andinfrared luminosities of about 10 to the 9th solar luminosities,properties which are independent of neutral hydrogen content for theVirgo cluster galaxies. Data suggest that the optically faint galaxieshave L(IR) of greater than 10 to the 12th solar luminosities.
|HI-observations of galaxies in the Virgo cluster of galaxies. I - The data|
New H I-data for a large number of bright galaxies inside the 10 degradius area of the Virgo cluster of galaxies have been obtained with the100 m radiotelescope at Effelsberg. A total of 234 galaxies was observedfor the first time. Among them, 53 have been detected providing newaccurate radial velocities. Data from the literature have been compiled.Together with the new data, they form a (nearly homogeneous) set of H Iobservations for more than 450 galaxies.
|Studies of the Virgo Cluster. II - A catalog of 2096 galaxies in the Virgo Cluster area.|
The present catalog of 2096 galaxies within an area of about 140 sq degapproximately centered on the Virgo cluster should be an essentiallycomplete listing of all certain and possible cluster members,independent of morphological type. Cluster membership is essentiallydecided by galaxy morphology; for giants and the rare class of highsurface brightness dwarfs, membership rests on velocity data. While 1277of the catalog entries are considered members of the Virgo cluster, 574are possible members and 245 appear to be background Zwicky galaxies.Major-to-minor axis ratios are given for all galaxies brighter than B(T)= 18, as well as for many fainter ones.
|On the Largescale Distribution of Faint Blue Galaxies|
|Faint blue galaxies in the Virgo cluster region|
Finding charts, coordinates, B magnitudes, U-B color estimates, andsurface brightnesses are given for 110 faint blue galaxies located nearthe center of the Virgo cluster of galaxies. The galaxies were found byblinking on plates taken with the Tautenburg 52-in. Schmidt telescope.
|Radial Velocities of Galaxies in the Virgo Cluster|
|New redshifts in the Virgo cluster|
Spectra have been obtained for 23 galaxies near the center of the Virgocluster. A master list of redshifts and morphology was assembled for allgalaxies within 6 deg of the cluster center. Reanalysis of the meanredshift of the total spiral (S) and elliptical-lenticular (E/S0)samples indicates no difference. However, the late-type (Sbc-Scd)spirals are found to have a significantly higher mean radial velocitythan early types. This shows up as an increase in redshift with radius,since the late-type spirals are found at an average distance of 3.8 degfrom the central regions of the cluster. It is shown that the mostsignificant difference in line-of-sight velocity dispersion occursbetween lenticulars (S0) and spirals (S).
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