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M/L, Hα Rotation Curves, and H I Gas Measurements for 329 Nearby Cluster and Field Spirals. II. Evidence for Galaxy Infall
We have conducted a study of optical and H I properties of spiralgalaxies (size, luminosity, Hα flux distribution, circularvelocity, and H I gas mass) to explore the role of gas stripping as adriver of morphological evolution in clusters. We find a strongcorrelation between the spiral and S0 fractions within clusters, and thespiral fraction scales tightly with cluster X-ray gas luminosity. Weexplore young star formation and identify spirals that are (1)asymmetric, with truncated Hα emission and H I gas reservoirs onthe leading edge of the disk, on a first pass through the denseintracluster medium in the cores of rich clusters; (2) strongly H Ideficient and stripped, with star formation confined to the inner 5h-1 kpc and 3 disk scale lengths; or (3) reddened, extremelyH I deficient, and quenched, where star formation has been halted acrossthe entire disk. We propose that these spirals are in successive stagesof morphological transformation, between infalling field spirals andcluster S0's, and that the process that acts to remove the H I gasreservoir suppresses new star formation on a similarly fast timescale.These data suggest that gas stripping plays a significant role inmorphological transformation and rapid truncation of star formationacross the disk.
| M/L, Hα Rotation Curves, and H I Measurements for 329 Nearby Cluster and Field Spirals. I. Data
A survey of 329 nearby galaxies (redshift z<0.045) has been conductedto study the distribution of mass and light within spiral galaxies overa range of environments. The 18 observed clusters and groups span arange of richness, density, and X-ray temperature and are supplementedby a set of 30 isolated field galaxies. Optical spectroscopy taken withthe 200 inch (5 m) Hale Telescope provides separately resolved Hαand [N II] major-axis rotation curves for the complete set of galaxies,which are analyzed to yield velocity widths and profile shapes, extents,and gradients. H I line profiles provide an independent velocity widthmeasurement and a measure of H I gas mass and distribution. I-bandimages are used to deconvolve profiles into disk and bulge components,to determine global luminosities and ellipticities, and to checkmorphological classification. These data are combined to form a unifieddata set ideal for the study of the effects of environment upon galaxyevolution.
| The UZC-SSRS2 Group Catalog
We apply a friends-of-friends algorithm to the combined Updated ZwickyCatalog and Southern Sky Redshift Survey to construct a catalog of 1168groups of galaxies; 411 of these groups have five or more members withinthe redshift survey. The group catalog covers 4.69 sr, and all groupsexceed the number density contrast threshold, δρ/ρ=80. Wedemonstrate that the groups catalog is homogeneous across the twounderlying redshift surveys; the catalog of groups and their membersthus provides a basis for other statistical studies of the large-scaledistribution of groups and their physical properties. The medianphysical properties of the groups are similar to those for groupsderived from independent surveys, including the ESO Key Programme andthe Las Campanas Redshift Survey. We include tables of groups and theirmembers.
| Kinematics of the Hercules supercluster
The Hercules supercluster consists of the Abell clusters A2147, A2151,and A2152. Previous studies of the kinematics have been confounded bythe difficulty of correctly assigning galaxies to the individualclusters, which are not well separated. Our study has a total of 468available velocities for galaxies in the region, 175 of them new. Thereare 414 galaxies in the supercluster, about three times the number usedin the previous supercluster study. We verify the existence of the threeindividual clusters and compute their individual dynamical parameters.We investigate several techniques for assigning galaxy membership toclusters in this crowded field. We use the KMM mixture-modelingalgorithm to separate the galaxies into clusters; we find that A2152 hasa higher mean velocity than previous studies have reported. A2147 andA2152 also have lower velocity dispersions: 821 and 715 km/s,respectively. The assignment of galaxies to either A2152 or A2147requires velocity and position information. We study the kinematics ofthe supercluster using the two-body formalism of Beers et al. (1982) andconclude that A2147 and A2151 are probably bound to each other and thatthe supercluster as a whole may also be bound. The mass of thesupercluster, if bound, is (7.6 +/- 2.0) 10 exp 15/h M(solar); with thesupercluster luminosity, (1.4 +/- 0.2) 10 exp 13/sq h L(solar), thisyields 0.34 +/- 0.1.
| 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.
| The Einstein Two-Sigma Catalog: Silver Needles in the X-Ray Haystack
To facilitate the study of X-ray sources fainter than those contained inthe Einstein Medium-Sensitivity Survey (EMSS), we have constructed a newcatalog of sources and fluctuations exceeding 2 σ significance in2520 high-latitude Einstein IPCC images. We have employed various teststo validate our source-search algorithm for both high- and low-significance sources, and to identify and remove the small number ofspurious sources induced by our detection procedure. Based on the knownvignetting and background characteristics of the IPC and the measured X-ray log N-log S relation, we have modeled the number of real sourcesexpected in the catalog in order to evaluate its statistical propertiesbelow 4 σ significance. Our modeling suggests that ~13,000 sourcesin the catalog are real celestial X-ray sources, an increase of ~9100over the number found in previous analyses of the same IPC images. Wefind that not only is the reliability of the Two-Sigma Catalog afunction of source significance σ, it is a function of off-axisangle on the detector as well. The application of differentsignal-to-noise thresholds at different off-axis angles thus enables oneto tune the reliability of the catalog. The chief motivation forstudying large numbers of faint X-ray sources is to search for possiblenew components of the cosmic X-ray background. To select out realcelestial X-ray sources in the Two-Sigma Catalog, we apply astronomicalcatalogs at other wavelengths as filters. For example, thecross-correlation of the Two-Sigma Catalog with catalogs from surveys ofthe radio and infrared sky has yielded large samples of faint X-raysources that are ~90% reliable. Optical spectroscopy of 77 unidentifiedfaint X-ray sources has turned up several surprises, illustrating themerits of selecting X-ray sources using a variety of methods: high-redshift quasars (one at z = 4.30), which are absent in the EMSS, X-ray-luminous (L_x_ ~ 10^43^ ergs s^-1^) radio-loud elliptical galaxies withoptical spectra devoid of emission lines, and infrared-bright activegalactic nuclei whose optical spectra are dominated by starburst galaxyfeatures. Follow-up observations are scheduled to determine whether anyof these types of objects represent a previously unrecognized componentof the X-ray background.
| An image database. II. Catalogue between δ=-30deg and δ=70deg.
A preliminary list of 68.040 galaxies was built from extraction of35.841 digitized images of the Palomar Sky Survey (Paper I). For eachgalaxy, the basic parameters are obtained: coordinates, diameter, axisratio, total magnitude, position angle. On this preliminary list, weapply severe selection rules to get a catalog of 28.000 galaxies, wellidentified and well documented. For each parameter, a comparison is madewith standard measurements. The accuracy of the raw photometricparameters is quite good despite of the simplicity of the method.Without any local correction, the standard error on the total magnitudeis about 0.5 magnitude up to a total magnitude of B_T_=17. Significantsecondary effects are detected concerning the magnitudes: distance toplate center effect and air-mass effect.
| Radio Identifications of Extragalactic IRAS Sources
Extragalactic sources detected at λ= 60 microns were selectedfrom the IRAS Faint Source Catalog, Version 2 by the criterion S_60microns_ >= S_12_ microns. They were identified by positioncoincidence with radio sources stronger than 25 mJy at 4.85 GHz in the6.0 sr declination band 0^deg^ < δ < +75^deg^ (excluding the0.05 sr region 12^h^40^m^< α < 14^h^40^m^, 0^deg^<+5^deg^) and with radio sources stronger than 80 mJy in the 3.4 sr areao^h^ <α < 2o^h^, -40^deg^ < δ < 0^deg^ (plus theregion 12^h^40^m^ < α < 14^h^40^m^, 0^deg^<δ<+5^deg^). Fields containing new candidate identifications weremapped by the VLA at 4.86 GHz with about 15" FWHM resolution. Difficultcases were confirmed or rejected with the aid of accurate (σ ~ 1")radio and optical positions. The final sample of 354 identifications in{OMEGA} = 9.4 sr is reliable and large enough to contain statisticallyuseful numbers of radio-loud FIR galaxies and quasars. The logarithmicFIR radio flux ratio parameter q can be used to distinguish radiosources powered by "starbursts" from those powered by "monsters."Starbursts and normal spiral galaxies in a λ = 60 micronflux-limited sample have a narrow (σ_q_ = 0.14 +/- 0.01) qdistribution with mean = 2.74 +/- 0.01, and none have "warm"FIR spectra [α(25 microns, 60 microns) < 1.5]. The absence ofradio- quiet (but not completely silent) blazars indicates that nearlyall blazars become optically thin at frequencies v<~100 GHz.Nonthermal sources with steep FIR/optical spectra and dusty-embeddedsources visible only at FIR and radio wavelengths must be very rare.
| Subcluster mergers and galaxy infall in A2151
We have obtained a 12.5 ks image of the Hercules Cluster, A2151, withthe ROSAT PSPC. Comparison of the optical and X-ray emission coincideswith the highest-density peak in the distribution, and is bimodal. Thenorthern subclummp, distinct in position and velocity, has no detectableX-ray gas. The eastern subclump, apparent in the optical contour map, isindistinguishable from the clump in velocity space, but is clearlyvisible in the X-ray image. X-ray spectra derived from the central peakof emission yield a best-fit temperature of 1.6 keV. The emissioncoincident with the eastern clump of galaxies is cooler, 0.8 keV, and isoutside the 90% confidence intervals of the central peak temperature. Wesuggest that the eastern and central subclusters have recently undergonea merger event. The lack of X-ray emission to the north suggests thatthose galaxies do not form a physically distinct structure (i.e., theyare not located within a distinct gravitational potential), but ratherthat they are falling into the cluster core along the filament definedby the Hercules Supercluster.
| A CCD survey of galaxies. III. Observations with the Loiano 1.5m telescope.
Continuing a CCD survey of galaxies belonging or projected onto the Comaand Hercules Superclusters and to the A262, Virgo and Cancer clusters,we present isophote maps and photometric profiles in the Johnson systemof 127 galaxies (126 taken in the V, 28 of which also in the B band, oneonly in B). For the objects in common we compare our results with thosein the RC3.
| 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.
| UGC galaxies stronger than 25 mJy at 4.85 GHz
UGC galaxies in the declination band +5 to +75 deg were identified byposition coincidence with radio sources stronger than 25 mJy on theGreen Bank 4.85 GHz sky maps. Candidate identifications were confirmedor rejected with the aid of published aperture-synthesis maps and new4.86 GHz VLA maps having 15 or 18 arcsec resolution, resulting in asample of 347 nearby radio galaxies plus five new quasar-galaxy pairs.The radio energy sources in UGC galaxies were classified as 'starbursts'or 'monsters' on the basis of their infrared-radio flux ratios, infraredspectral indices, and radio morphologies. The rms scatter in thelogarithmic infrared-radio ratio q is not more than 0.16 for starburstgalaxies selected at 4.85 GHz. Radio spectral indices were obtained fornearly all of the UGC galaxies, and S0 galaxies account for adisproportionate share of the compact flat-spectrum (alpha less than0.5) radio sources. The extended radio jets and lobes produced bymonsters are preferentially, but not exclusively, aligned within about30 deg of the optical minor axes of their host galaxies. The tendencytoward minor-axis ejection appears to be independent of radio-sourcesize and is strongest for elliptical galaxies.
| Associations between quasi-stellar objects and galaxies
A table is presented here listing all close pairs of QSOs and galaxiesthat were found in a computer-aided search of catalogs of QSOs andbright galaxies and an extensive search of the literature. There is alarge excess of pairs with separations of 2 arcmin lor less, or about 60kpc, over the numbers expected if the configurations were accidental.The angular separation for 392 pairs adds to the evidence for physicalassociation, and it is shown that selection effects are not important. Ageneral rule is stated that QSOs tend to lie in the vicinity of normalgalaxies much more often than is expected by chance whether or not thegalaxies and the QSOs have the same redshifts. It is emphasized thatthis rule cannot be explained in terms of gravitational microlensing,and it is concluded that some part of the redshift of all classes ofactive nuclei is not associated with the expansion of the universe.
| Far-infrared properties of cluster galaxies
Far-infrared properties are derived for a sample of over 200 galaxies inseven clusters: A262, Cancer, A1367, A1656 (Coma), A2147, A2151(Hercules), and Pegasus. The IR-selected sample consists almost entirelyof IR normal galaxies, with Log of L(FIR) = 9.79 solar luminosities, Logof L(FIR)/L(B) = 0.79, and Log of S(100 microns)/S(60 microns) = 0.42.None of the sample galaxies has Log of L(FIR) greater than 11.0 solarluminosities, and only one has a FIR-to-blue luminosity ratio greaterthan 10. No significant differences are found in the FIR properties ofHI-deficient and HI-normal cluster galaxies.
| A catalog of galaxies in Hercules from the Palomar Sky Survey and the Minnesota Automated Plate Scanner
The development of galaxies catalogs from the Palomar Sky Survey usingthe Minnesota Automated Plate Scanner (APS) is examined. The design andoperation of APS are described. The algorithm used to distinguish starsfrom galaxies is discussed, and the completeness and confusion of thealgorithm as a function of magnitude are estimated. The quality of thephotometric calibration for galaxy magnitudes and surface-brightnessthresholds is evaluated. The relation between the distribution of colorsand morphological types is studied. The luminosity functions forHercules galaxies are calculated and presented. The catalog generatedusing the APS is 80 percent complete; photometry good to 0.23 mag rms ispossible; and J-F colors are good to 0.17 mag rms.
| 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.
| Gas deficiency in cluster galaxies - A comparison of nine clusters
The available 21 cm line data in the literature for galaxies in nineclusters is combined with new high-sensitivity observations of 51galaxies in five of the nine clusters in order to test fordiscriminating circumstances between those clusters which show H Ideficiency among their spiral population and those which do not. An H Ideficiency for the complete cluster sample is derived employing acomparison sample of galaxies chosen from the Catalog of IsolatedGalaxies. The deficiency and its radial dependence is summarized foreach cluster and a composite. A comparison of the environments indifferent clusters leads to the conclusion that the occurrence of H Ideficiency is correlated with the presence of a hot X-ray intraclustermedium, and that an ongoing interaction process is active through thecores of X-ray clusters.
| Photoelectric Observations of Interacting and Compact Galaxies
Not Available
| 1.4 GHz continuum sources in the Hercules cluster
Observational results are presented of a continuum survey of theHercules Cluster (A2151) near 1.4 GHz. The observations were carried outusing the VLA in the D configuration with a total bandwidth of 25 MHz.Positions and fluxes are given for 65 sources, 21-25 of which areassociated with galaxies. Separation between the radio and opticalpositions of the galaxies was five arcsec for most cases. A group ofthree small rectangles near the classical center of the Hercules Clusteris examined, and it is found that each rectangle contains one opticallybright galaxy and one strongly emitting radio galaxy. It is suggestedthat these regions are physical subcores of A2151 and that they containintergalactic gas. Five sources were found with 1.4 GHz fluxes greaterthan 10 mJy which are not associated with any galaxy. It is conjecturedthat the galaxyless objects are not background objects, but are insteadthe result of a plasma effect in the subcore medium. The radio flux ofthe galaxyless sources correlates well with the 60-micron flux obtainedby IRAS for spiral galaxies. A table is presented which lists thesources associated with galaxies.
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