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|HI content in galaxies in loose groups|
Gas deficiency in cluster spirals is well known and ram-pressurestripping is considered the main gas removal mechanism. In some compactgroups too gas deficiency is reported. However, gas deficiency in loosegroups is not yet well established. Lower dispersion of the membervelocities and the lower density of the intragroup medium in small loosegroups favour tidal stripping as the main gas removal process in them.Recent releases of data from the HI Parkes All-Sky Survey (HIPASS) andcatalogues of nearby loose groups with associated diffuse X-ray emissionhave allowed us to test this notion. In this paper, we address thefollowing questions: (i) do galaxies in groups with diffuse X-rayemission statistically have lower gas content compared to the ones ingroups without diffuse X-ray emission? (ii) does HI deficiency vary withthe X-ray luminosity, LX, of the loose group in a systematicway? We find that (i) galaxies in groups with diffuse X-ray emission, onaverage, are HI deficient, and have lost more gas compared to those ingroups without X-ray emission; the latter are found not to havesignificant HI deficiency; (ii) no systematic dependence of the HIdeficiency with LX is found. Ram-pressure-assisted tidalstripping and evaporation by thermal conduction are the two possiblemechanisms to account for this excess gas loss.
|Star Formation Histories of Early-Type Galaxies. I. Higher Order Balmer Lines as Age Indicators|
We have obtained blue integrated spectra of 175 nearby early-typegalaxies, covering a wide range in galaxy velocity dispersion andemphasizing those with σ<100 km s-1. Galaxies havebeen observed both in the Virgo Cluster and in lower densityenvironments. The main goals are the evaluation of higher order Balmerlines as age indicators and differences in stellar populations as afunction of mass, environment, and morphology. In this first paper, ouremphasis is on presenting the methods used to characterize the behaviorof the Balmer lines through evolutionary population synthesis models.Lower σ galaxies exhibit a substantially greater intrinsicscatter, in a variety of line-strength indicators, than do higherσ galaxies, with the large intrinsic scatter setting in below aσ of 100 km s-1. Moreover, a greater contrast inscatter is present in the Balmer lines than in the lines of metalfeatures. Evolutionary synthesis modeling of the observed spectralindexes indicates that the strong Balmer lines found primarily among thelow-σ galaxies are caused by young age, rather than by lowmetallicity. Thus we find a trend between the population age and thecentral velocity dispersion, such that low-σ galaxies have youngerluminosity-weighted mean ages. We have repeated this analysis usingseveral different Balmer lines and find consistent results from onespectral indicator to another.
|Redshift-Distance Survey of Early-Type Galaxies: Circular-Aperture Photometry|
We present R-band CCD photometry for 1332 early-type galaxies, observedas part of the ENEAR survey of peculiar motions using early-typegalaxies in the nearby universe. Circular apertures are used to tracethe surface brightness profiles, which are then fitted by atwo-component bulge-disk model. From the fits, we obtain the structuralparameters required to estimate galaxy distances using theDn-σ and fundamental plane relations. We find thatabout 12% of the galaxies are well represented by a pure r1/4law, while 87% are best fitted by a two-component model. There are 356repeated observations of 257 galaxies obtained during different runsthat are used to derive statistical corrections and bring the data to acommon system. We also use these repeated observations to estimate ourinternal errors. The accuracy of our measurements are tested by thecomparison of 354 galaxies in common with other authors. Typical errorsin our measurements are 0.011 dex for logDn, 0.064 dex forlogre, 0.086 mag arcsec-2 for<μe>, and 0.09 for mRC,comparable to those estimated by other authors. The photometric datareported here represent one of the largest high-quality and uniformall-sky samples currently available for early-type galaxies in thenearby universe, especially suitable for peculiar motion studies.Based on observations at Cerro Tololo Inter-American Observatory (CTIO),National Optical Astronomy Observatory, which is operated by theAssociation of Universities for Research in Astronomy, Inc., undercooperative agreement with the National Science Foundation (NSF);European Southern Observatory (ESO); Fred Lawrence Whipple Observatory(FLWO); and the MDM Observatory on Kitt Peak.
|Redshift-Distance Survey of Early-Type Galaxies. I. The ENEARc Cluster Sample|
This paper presents data on the ENEARc subsample of the larger ENEARsurvey of nearby early-type galaxies. The ENEARc galaxies belong toclusters and were specifically chosen to be used for the construction ofa Dn-σ template. The ENEARc sample includes newmeasurements of spectroscopic and photometric parameters (redshift,velocity dispersion, line index Mg2, and the angular diameterdn), as well as data from the literature. New spectroscopicdata are given for 229 cluster early-type galaxies, and new photometryis presented for 348 objects. Repeat and overlap observations withexternal data sets are used to construct a final merged catalogconsisting of 640 early-type galaxies in 28 clusters. Objectivecriteria, based on catalogs of groups of galaxies derived from completeredshift surveys of the nearby universe, are used to assign galaxies toclusters. In a companion paper, these data are used to construct thetemplate Dn-σ distance relation for early-typegalaxies, which has been used to estimate galaxy distances and derivepeculiar velocities for the ENEAR all-sky sample. Based on observationsat Complejo Astronomico El Leoncito, operated under agreement betweenthe Consejo Nacional de Investigaciones Científicas de laRepública Argentina and the National Universities of La Plata,Córdoba, and San Juan; Cerro Tololo Inter-American Observatory,National Optical Astronomical Observatory, which is operated by theAssociation of Universities for Research in Astronomy, Inc., undercooperative agreement with the National Science Foundation; the EuropeanSouthern Observatory (ESO), partially under the ESO-ON agreement; theFred Lawrence Whipple Observatory; the Observatório do Pico dosDias, operated by the Laboratório Nacional de Astrofísicaand the MDM Observatory at Kitt Peak.
|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.
|Nearby Optical Galaxies: Selection of the Sample and Identification of Groups|
In this paper we describe the Nearby Optical Galaxy (NOG) sample, whichis a complete, distance-limited (cz<=6000 km s-1) andmagnitude-limited (B<=14) sample of ~7000 optical galaxies. Thesample covers 2/3 (8.27 sr) of the sky (|b|>20deg) andappears to have a good completeness in redshift (97%). We select thesample on the basis of homogenized corrected total blue magnitudes inorder to minimize systematic effects in galaxy sampling. We identify thegroups in this sample by means of both the hierarchical and thepercolation ``friends-of-friends'' methods. The resulting catalogs ofloose groups appear to be similar and are among the largest catalogs ofgroups currently available. Most of the NOG galaxies (~60%) are found tobe members of galaxy pairs (~580 pairs for a total of ~15% of objects)or groups with at least three members (~500 groups for a total of ~45%of objects). About 40% of galaxies are left ungrouped (field galaxies).We illustrate the main features of the NOG galaxy distribution. Comparedto previous optical and IRAS galaxy samples, the NOG provides a densersampling of the galaxy distribution in the nearby universe. Given itslarge sky coverage, the identification of groups, and its high-densitysampling, the NOG is suited to the analysis of the galaxy density fieldof the nearby universe, especially on small scales.
|Kinematical data on early-type galaxies. V.|
We present kinematical data for a sample of 26 galaxies. Rotation curvesand velocity-dispersion profiles are determined for all objects. This isour fifth paper in a series devoted to the presentation of data onelliptical and S0 galaxies, derived from long-slit absorptionspectroscopy; the series now gathers 119 galaxies with homogeneous data.Based on observations collected at the Observatoire de Haute-Provence.Tables 2 and 3 are presented in electronic form only; Tables 1 through 3are available from the CDS, Strasbourg, via anonymous ftp tocdsarc.u-strasbg.fr (18.104.22.168) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
|Arcsecond Positions of UGC Galaxies|
We present accurate B1950 and J2000 positions for all confirmed galaxiesin the Uppsala General Catalog (UGC). The positions were measuredvisually from Digitized Sky Survey images with rms uncertaintiesσ<=[(1.2")2+(θ/100)2]1/2,where θ is the major-axis diameter. We compared each galaxymeasured with the original UGC description to ensure high reliability.The full position list is available in the electronic version only.
|Groups of galaxies. III. Some empirical characteristics.|
|The Universality of the Fundamental Plane of E and S0 Galaxies: Spectroscopic Data|
We present central velocity dispersion measurements for 325 early-typegalaxies in eight clusters and groups of galaxies, including newobservations for 212 galaxies. The clusters and groups are the A262,A1367, Coma (A1656), A2634, Cancer, and Pegasus Clusters and the NGC 383and NGC 507 Groups. The new measurements were derived frommedium-dispersion spectra that cover 600 Å centered on the Mg I btriplet at lambda ~ 5175 Å. Velocity dispersions were measuredusing the Tonry & Davis cross-correlation method, with a typicalaccuracy of 6%. A detailed comparison with other data sources is made.
|The Universality of the Fundamental Plane of E and S0 Galaxies: Sample Definition and I-Band Photometric Data|
As part of a project to compare the fundamental plane and Tully-Fisherdistance scales, we present here I-band CCD photometry for 636early-type galaxies in eight clusters and groups of galaxies. These arethe A262, A1367, Coma (A1656), A2634, Cancer and Pegasus Clusters, andthe NGC 383 and NGC 507 Groups. Sample selection, cluster properties,and cluster membership assignment criteria are discussed. We presentphotometric parameters that are used in the fundamental plane relation,the effective radius r_e, and the effective surface brightness mu_e, asderived from a r^1/4 fit to the observed radial photometric profile ofeach galaxy. A comparison with similar data found in the literature forthe Coma Cluster shows that large systematic uncertainties can beintroduced in the measurement of r_e and mu_e by the particular methodused to derive those parameters. However, the particular combination ofthese two parameters that enters in the fundamental plane relation is aquantity that can be measured with high accuracy.
|Total magnitude, radius, colour indices, colour gradients and photometric type of galaxies|
We present a catalogue of aperture photometry of galaxies, in UBVRI,assembled from three different origins: (i) an update of the catalogueof Buta et al. (1995) (ii) published photometric profiles and (iii)aperture photometry performed on CCD images. We explored different setsof growth curves to fit these data: (i) The Sersic law, (ii) The net ofgrowth curves used for the preparation of the RC3 and (iii) A linearinterpolation between the de Vaucouleurs (r(1/4) ) and exponential laws.Finally we adopted the latter solution. Fitting these growth curves, wederive (1) the total magnitude, (2) the effective radius, (3) the colourindices and (4) gradients and (5) the photometric type of 5169 galaxies.The photometric type is defined to statistically match the revisedmorphologic type and parametrizes the shape of the growth curve. It iscoded from -9, for very concentrated galaxies, to +10, for diffusegalaxies. Based in part on observations collected at the Haute-ProvenceObservatory.
|Photoelectric UBV Photometry of 179 Bright Galaxies|
This paper presents photoelectric UBV multiaperture photometry of 179bright galaxies that was used to compute total magnitudes and colorindices published in the Third Reference Catalog of Bright Galaxies(RC3). The observations were made at the McDonald Observatory from 1983December to 1986 September with an Amperex 56-DVP photometer attached tothe 0.76 and 0.91 m telescopes. The observations can also be used tocalibrate CCD images.
|Photoelectric UBV Photometry of Galaxies in the Clusters Pegasus I, Pegasus II, Abell 262, Abell 1367, and Abell 2197-9|
This paper presents photoelectric UBV multiaperture photometry of 144galaxies, 139 of which are associated with six nearby bright clusters.The observations were made at the McDonald Observatory from 1986September to 1987 November and were part of the production of the ThirdReference Catalogue of Bright Galaxies (RC3). The observations were usedto compute total magnitudes and color indices published in RC3. Theobservations can also be used to calibrate CCD images.
|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.
|The fundamental plane of early-type galaxies: stellar populations and mass-to-light ratio.|
We analyse the residuals to the fundamental plane (FP) of ellipticalgalaxies as a function of stellar-population indicators; these are basedon the line-strength parameter Mg_2_ and on UBVRI broad-band colors, andare partly derived from new observations. The effect of the stellarpopulations accounts for approximately half the observed variation ofthe mass-to-light ratio responsible for the FP tilt. The residual tiltcan be explained by the contribution of two additional effects: thedependence of the rotational support, and possibly that of the spatialstructure, on the luminosity. We conclude to a constancy of thedynamical-to-stellar mass ratio. This probably extends to globularclusters as well, but the dominant factor would be here the luminositydependence of the structure rather than that of the stellar population.This result also implies a constancy of the fraction of dark matter overall the scalelength covered by stellar systems. Our compilation ofinternal stellar kinematics of galaxies is appended.
|A Catalog of Stellar Velocity Dispersions. II. 1994 Update|
A catalog of central velocity dispersion measurements is presented,current through 1993 September. The catalog includes 2474 measurementsof 1563 galaxies. A standard set of 86 galaxies is defined, consistingof galaxies with at least three reliable, concordant measurements. It issuggested that future studies observe some of these standard galaxies sothat different studies can be normalized to a consistent system. Allmeasurements are reduced to a normalized system using these standards.
|Integrated photoelectric magnitudes and color indices of bright galaxies in the Johnson UBV system|
The photoelectric total magnitudes and color indices published in theThird Reference Catalogue of Bright Galaxies (RC3) are based on ananalysis of approximately equals 26,000 B, 25,000 B-V, and 17,000 U-Bmultiaperture measurements available up to mid 1987 from nearly 350sources. This paper provides the full details of the analysis andestimates of internal and external errors in the parameters. Thederivation of the parameters is based on techniques described by theVaucouleurs & Corwin (1977) whereby photoelectric multiaperture dataare fitted by mean Hubble-type-dependent curves which describe theintegral of the B-band flux and the typical B-V and U-B integrated colorgradients. A sophisticated analysis of the residuals of thesemeasurements from the curves was made to allow for the random andsystematic errors that effect such data. The result is a homogeneous setof total magnitudes BTA total colors(B-V)T and (U-B)T, and effective colors(B-V)e and (U-B)e for more than 3000 brightgalaxies in RC3.
|A revised catalog of CfA1 galaxy groups in the Virgo/Great Attractor flow field|
A new identification of groups and clusters in the CfA1 Catalog ofHuchra et al. is presented, using a percolation algorithm to identifydensity enhancements. It is shown that in the resulting catalog,contamination by interlopers is significantly reduced. The Schechterluminosity function is redetermined, including the Malmquist bias.
|General study of group membership. II - Determination of nearby groups|
We present a whole sky catalog of nearby groups of galaxies taken fromthe Lyon-Meudon Extragalactic Database. From the 78,000 objects in thedatabase, we extracted a sample of 6392 galaxies, complete up to thelimiting apparent magnitude B0 = 14.0. Moreover, in order to considersolely the galaxies of the local universe, all the selected galaxieshave a known recession velocity smaller than 5500 km/s. Two methods wereused in group construction: a Huchra-Geller (1982) derived percolationmethod and a Tully (1980) derived hierarchical method. Each method gaveus one catalog. These were then compared and synthesized to obtain asingle catalog containing the most reliable groups. There are 485 groupsof a least three members in the final catalog.
|The product of the globular cluster collapse|
In this paper we calculate the number of close binaries formed duringthe evolution process of a globular cluster core. The globular clustercore is assumed to contain a massive black hole at its center. We showthat the central black hole can drive binary formation in the core andthe rate of binary formation depends on the mass of the black hole atits center. Whether cluster X-ray is produced mainly by the centralblack hole or by binaries in the core depends on the mass of the centralblack hole. Therefore, two cases arise: black hole accretion domination,and binary radiation domination. The possibility of the existence of acentral black hole exists even when binary radiation characteristicshave been observed in globular cluster X-ray sources.
|The Butcher-Oemler effect in a nearby cluster of galaxies?|
The integrated spectra of early-type galaxies in the nearby Abell 262,Pegasus I, and Virgo clusters are compared with those of several 'field'galaxies. The spectra of five galaxies in Pegasus I and one galaxy inthe Virgo Cluster show evidence of recent star formation. The averageblue magnitude for the star-forming galaxies is M(B) = -20. Thestar-formation activity in Pegasus I is found to be similar to that ofstarburst and poststarburst galaxies in Butcher-Oemler clusters atredshifts greater than 2.
|On the relationship between radio emission and optical properties in early-type galaxies|
To study the origin of radio activity in early-type galaxies, thepossible dependence of their radio emission on basic optical parameters,such as the absolute magnitude, the central velocity dispersion sigma,and the mean surface brightness mu is explored. A sample of 743 E and SOgalaxies is used which is based on three independent radio surveys ofoptically selected galaxies with virtually complete information onmagnitudes, morphological types, redshift distances, diameters, andradio fluxes. For both E and SO galaxies, only the absolute magnitudeappears to be directly related to the radio activity, while sigma and mudo not. Also, a significant dependence of the apparent flattening onradio power is confirmed for E galaxies. Some relevant implications ofthese results are discussed.
|Determination of the relative spectrophotometric gradients of galaxies. IV|
Relative spectrophotometric gradients of continua are determined for 195galaxies. The spectra have been obtained with the 70-cm meniscustelescope of the Abastumani Astrophysical Observatory using a 2-degpreobjective prism (the reverse linear dispersion was 1200 A/mm inH-gamma). The gradient values were reduced to the AO spectral class andcorrected for light absorption in the Galaxy.
|The statistical distribution of the neutral-hydrogen content of S0 galaxies|
The distribution of relative global H I content M(H I)/L(B) has beenderived for galaxies of types S0 and S0/a using a data set derived fromrecent H I observations in the literature. The relative H I content ofthese galaxies is found to show transitional properties betweenelliptical and spiral galaxies. The distribution of M(H I)/L(B) forS0/a's resembles that for spirals, and these galaxies may represent'fossil' spirals, i.e., galaxies whose gas has been severely depleted bystar formation. The distribution for S0's, however, resembles that forellipticals. The form of this distribution strongly suggests an externalorigin for most of the H I in S0 galaxies.
|A catalog of stellar velocity dispersions. I - Compilation and standard galaxies|
A catalog of central stellar velocity dispersion measurements ispresented, current through June 1984. The catalog includes 1096measurements of 725 galaxies. A set of 51 standard galaxies is definedwhich consists of galaxies with at least three reliable, concordantmeasurements. It is suggested that future studies observed some of thesestandard galaxies in the course of their observations so that differentstudies can be normalized to the same system. Previous studies arecompared with the derived standards to determine relative accuracies andto compute scale factors where necessary.
|A catalog of radio, optical, and infrared observations of spiral galaxies in clusters|
The results of a major observational program on the luminosities,colors, and gas contents of spiral galaxies in clusters of galaxies arepresented. The data have been used as part of a detailed investigationinto the nature of cluster spirals and for revisions of the distancescale using the infrared Tully-Fisher relation. The observationalstrategies, reduction procedures, and sources or error are brieflydiscussed. The data include 21-cm H I observations, UBVR multiaperturephotometry, and H-band photometry of several hunderd spiral galaxies in10 clusters.
|Catalogue of central velocity dispersions of galaxies|
A total of 880 measurements of velocity dispersions for 546 galaxieshave been compiled. These data have been used to look for biasesintroduced by the observational techniques and reduction procedures. Twomain effects have been corrected for, due to the reference and the slitwidth. A catalog of homogeneous data has been compiled, where the rawdata are corrected for these effects.
|A survey of galaxy redshifts. IV - The data|
The complete list of the best available radial velocities for the 2401galaxies in the merged Zwicky-Nilson catalog brighter than 14.5mz and with b (II) above +40 deg or below -30 deg ispresented. Almost 60 percent of the redshifts are from the CfA surveyand are accurate to typically 35 km/s.
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