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X-ray scaling properties of early-type galaxies
We present an analysis of 39 X-ray luminous early-type galaxies observedwith the ROSAT PSPC. Using multicomponent spectral and spatial fits tothese data, we have measured halo abundance, temperature, luminosity andsurface brightness profile. We compare these measurements to similarresults from galaxy groups and clusters, fitting a number of relationscommonly used in the study of these larger objects. In particular, wefind that the σ-TX relation for our sample is similarto that reported for clusters, consistent with βspec= 1,and that the LX-TX relation has a steep slope(gradient 4.8 +/- 0.7) comparable with that found for galaxy groups.Assuming isothermality, we construct three-dimensional models of ourgalaxies, allowing us to measure gas entropy. We find no correlationbetween gas entropy and system mass, but do find a trend forlow-temperature systems to have reduced gas fractions. We conclude thatthe galaxies in our sample are likely to have developed their haloesthrough galaxy winds, influenced by their surrounding environment.
| An X-Ray Atlas of Groups of Galaxies
A search was conducted for a hot intragroup medium in 109 low-redshiftgalaxy groups observed with the ROSAT PSPC. Evidence for diffuse,extended X-ray emission is found in at least 61 groups. Approximatelyone-third of these detections have not been previously reported in theliterature. Most of the groups are detected out to less than half of thevirial radius with ROSAT. Although some spiral-rich groups do contain anintragroup medium, diffuse emission is restricted to groups that containat least one early-type galaxy.
| Redshift-Distance Survey of Early-Type Galaxies: Spectroscopic Data
We present central velocity dispersions and Mg2 line indicesfor an all-sky sample of ~1178 elliptical and S0 galaxies, of which 984had no previous measures. This sample contains the largest set ofhomogeneous spectroscopic data for a uniform sample of ellipticalgalaxies in the nearby universe. These galaxies were observed as part ofthe ENEAR project, designed to study the peculiar motions and internalproperties of the local early-type galaxies. Using 523 repeatedobservations of 317 galaxies obtained during different runs, the dataare brought to a common zero point. These multiple observations, takenduring the many runs and different instrumental setups employed for thisproject, are used to derive statistical corrections to the data and arefound to be relatively small, typically <~5% of the velocitydispersion and 0.01 mag in the Mg2 line strength. Typicalerrors are about 8% in velocity dispersion and 0.01 mag inMg2, in good agreement with values published elsewhere.
| 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.
| A new catalogue of ISM content of normal galaxies
We have compiled a catalogue of the gas content for a sample of 1916galaxies, considered to be a fair representation of ``normality''. Thedefinition of a ``normal'' galaxy adopted in this work implies that wehave purposely excluded from the catalogue galaxies having distortedmorphology (such as interaction bridges, tails or lopsidedness) and/orany signature of peculiar kinematics (such as polar rings,counterrotating disks or other decoupled components). In contrast, wehave included systems hosting active galactic nuclei (AGN) in thecatalogue. This catalogue revises previous compendia on the ISM contentof galaxies published by \citet{bregman} and \citet{casoli}, andcompiles data available in the literature from several small samples ofgalaxies. Masses for warm dust, atomic and molecular gas, as well asX-ray luminosities have been converted to a uniform distance scale takenfrom the Catalogue of Principal Galaxies (PGC). We have used twodifferent normalization factors to explore the variation of the gascontent along the Hubble sequence: the blue luminosity (LB)and the square of linear diameter (D225). Ourcatalogue significantly improves the statistics of previous referencecatalogues and can be used in future studies to define a template ISMcontent for ``normal'' galaxies along the Hubble sequence. The cataloguecan be accessed on-line and is also available at the Centre desDonnées Stellaires (CDS).The catalogue is available in electronic form athttp://dipastro.pd.astro.it/galletta/ismcat and at the CDS via anonymousftp to\ cdsarc.u-strasbg.fr (130.79.128.5) or via\http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/405/5
| 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 AWM and MKW Poor Clusters
We have measured 1365 redshifts to a limiting magnitude of R~15.5 in 15AWM/MKW clusters and have collected another 203 from the literature inMKW 4s, MKW 2, and MKW 2s. In AWM 7 we have extended the redshift sampleto R~18 in the cluster center. We have identified 704 cluster members in17 clusters; 201 are newly identified. We summarize the kinematics anddistributions of the cluster galaxies and provide an initial discussionof substructure, mass and luminosity segregation, spectral segregation,velocity-dispersion profiles, and the relation of the central galaxy toglobal cluster properties. We compute optical mass estimates, which wecompare with X-ray mass determinations from the literature. The clustersare in a variety of dynamical states, reflected in the three classes ofbehavior of the velocity-dispersion profile in the core: rising,falling, or flat/ambiguous. The velocity dispersion of the emission-linegalaxy population significantly exceeds that of the absorption-linegalaxies in almost all of the clusters, and the presence ofemission-line galaxies at small projected radii suggests continuinginfall of galaxies onto the clusters. The presence of a cD galaxy doesnot constrain the global cluster properties; these clusters are similarto other poor clusters that contain no cD. We use the similarity of thevelocity-dispersion profiles at small radii and the cD-like galaxies'internal velocity dispersions to argue that cD formation is a localphenomenon. Our sample establishes an empirical observational baselineof poor clusters for comparison with simulations of similar systems.Observations reported in this paper were obtained at the Multiple MirrorTelescope Observatory, a facility operated jointly by the University ofArizona and the Smithsonian Institution; at the Whipple Observatory, afacility operated jointly by the Smithsonian Astrophysical Observatoryand Harvard University; and at the WIYN Observatory, a joint facility ofthe University of Wisconsin-Madison, Indiana University, YaleUniversity, and the National Optical Astronomy Observatories.
| A catalogue and analysis of X-ray luminosities of early-type galaxies
We present a catalogue of X-ray luminosities for 401 early-typegalaxies, of which 136 are based on newly analysed ROSAT PSPC pointedobservations. The remaining luminosities are taken from the literatureand converted to a common energy band, spectral model and distancescale. Using this sample we fit the LX:LB relationfor early-type galaxies and find a best-fit slope for the catalogue of~2.2. We demonstrate the influence of group-dominant galaxies on the fitand present evidence that the relation is not well modelled by a singlepower-law fit. We also derive estimates of the contribution to galaxyX-ray luminosities from discrete-sources and conclude that they provideLdscr/LB~=29.5ergs-1LBsolar-1. Wecompare this result with luminosities from our catalogue. Lastly, weexamine the influence of environment on galaxy X-ray luminosity and onthe form of the LX:LB relation. We conclude thatalthough environment undoubtedly affects the X-ray properties ofindividual galaxies, particularly those in the centres of groups andclusters, it does not change the nature of whole populations.
| Diffuse X-Ray Emission in Three Poor Clusters of Galaxies
We report on ROSAT PSPC soft X-ray observations of three poor clustersof galaxies at distances above 100 Mpc (cz>8000 km s-1). Inall three cases the emission is centered on the dominant member of thecluster, i.e., NGC 4104, NGC 6269, and NGC 6329, respectively. X-rayemission was detected out to radii of 400-600 kpc. The bolometric X-rayluminosities range from 2.6 to 8.6x1042 ergs s-1.The soft X-ray emission characteristics and the physical propertiesdeduced from our observations of all three poor clusters resemble thoseof downscaled rich clusters. In each case, the soft X-ray spectrum iswell represented by a thermal model with kT~=1.1-1.3 keV and near-solarmetallicity in the center, increasing to kT~=1.4-1.6 keV toward theouter boundaries while the metallicity, Z, decreases to about 0.1 solar.Equally good fits can be achieved if the metallicity is left at thesolar value and an additional gas component with kT~=0.5 keV isintroduced. The central electron densities in all three poor clustersstudied here are enhanced with respect to a King profile by factors of2-6. This, together with the results of the spectral fits, can beinterpreted as either indicating the presence of cooling flows or of atwo-phase medium in the central areas. The spatial electron densitydistribution in the outer regions of each cluster can be fitted by Kingprofiles with core radii of 17-60 kpc and exponents of β=0.38-0.44.Using the derived radial temperature and density distributions, thetotal gravitating mass is obtained. We deriveMtot=3.7+/-0.7x1013 Msolar within aradius of 300 kpc for each of the three systems, as opposed to1014-1015 Msolar for rich clusters. Wefind that the LX versus kT relation found by A. C. Edge andG. C. Stewart (1991) for rich clusters of galaxies scales into thedomain of poor clusters and groups of galaxies. The spectral fits of thecentral regions show that none of the first-ranking galaxies of thethree poor clusters hosts a Seyfert 1 active galactic nucleus thatcontributes significantly to the emission in the ROSAT band (0.1-2.4keV).
| The peculiar motions of early-type galaxies in two distant regions - II. The spectroscopic data
We present the spectroscopic data for the galaxies studied in the EFARproject, which is designed to measure the properties and peculiarmotions of early-type galaxies in two distant regions. We have obtained1319 spectra of 714 early-type galaxies over 33 observing runs on 10different telescopes. We describe the observations and data reductionsused to measure redshifts, velocity dispersions and the Mgb and Mg_2Lick linestrength indices. Detailed simulations and intercomparison ofthe large number of repeat observations lead to reliable error estimatesfor all quantities. The measurements from different observing runs arecalibrated to a common zero-point or scale before being combined,yielding a total of 706 redshifts, 676 velocity dispersions, 676 Mgblinestrengths and 582 Mg_2 linestrengths. The median estimated errors inthe combined measurements are Delta cz=20 km s^-1, Delta sigma sigma=9.1 per cent, Delta Mgb Mgb=7.2 per cent and Delta Mg_2=0.015 mag.Comparison of our measurements with published data sets shows nosystematic errors in the redshifts or velocity dispersions, and onlysmall zero-point corrections to bring our linestrengths on to thestandard Lick system. We have assigned galaxies to physical clusters byexamining the line-of-sight velocity distributions based on EFAR andZCAT redshifts, together with the projected distributions on the sky. Wederive mean redshifts and velocity dispersions for these clusters, whichwill be used in estimating distances and peculiar velocities and to testfor trends in the galaxy population with cluster mass. The spectroscopicparameters presented here for 706 galaxies combine high-quality data,uniform reduction and measurement procedures, and detailed erroranalysis. They form the largest single set of velocity dispersions andlinestrengths for early-type galaxies published to date.
| X-ray luminosities for a magnitude-limited sample of early-type galaxies from the ROSAT All-Sky Survey
For a magnitude-limited optical sample (B_T <= 13.5 mag) ofearly-type galaxies, we have derived X-ray luminosities from the ROSATAll-Sky Survey. The results are 101 detections and 192 useful upperlimits in the range from 10^36 to 10^44 erg s^-1. For most of thegalaxies no X-ray data have been available until now. On the basis ofthis sample with its full sky coverage, we find no galaxy with anunusually low flux from discrete emitters. Below log (L_B) ~ 9.2L_⊗ the X-ray emission is compatible with being entirely due todiscrete sources. Above log (L_B) ~ 11.2 L_osolar no galaxy with onlydiscrete emission is found. We further confirm earlier findings that L_xis strongly correlated with L_B. Over the entire data range the slope isfound to be 2.23 (+/- 0.12). We also find a luminosity dependence ofthis correlation. Below log L_x = 40.5 erg s^-1 it is consistent with aslope of 1, as expected from discrete emission. Above this value theslope is close to 2, as expected from gaseous emission. Comparing thedistribution of X-ray luminosities with the models of Ciotti et al.leads to the conclusion that the vast majority of early-type galaxiesare in the wind or outflow phase. Some of the galaxies may have alreadyexperienced the transition to the inflow phase. They show X-rayluminosities in excess of the value predicted by cooling flow modelswith the largest plausible standard supernova rates. A possibleexplanation for these super X-ray-luminous galaxies is suggested by thesmooth transition in the L_x--L_B plane from galaxies to clusters ofgalaxies. Gas connected to the group environment might cause the X-rayoverluminosity.
| 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.
| Detailed Surface Photometry of Dwarf Elliptical and Dwarf S0 Galaxies in the Virgo Cluster
We analyze new V-band images of 14 dwarf S0 galaxies and 10 dwarfelliptical galaxies in the Virgo Cluster, in combination with R-bandimages of 70 dwarf elliptical galaxies from an earlier paper. We computethe intensity-weighted mean ellipticity, the mean deviations fromelliptical isophotes, and a newly defined parameter to measure isophotaltwists. We also fit each major-axis profile to a power lawSigma(a)~exp[-(a/a_s)^n], where n is allowed to vary. Consistent withother studies of the Virgo dwarf ellipticals, we find that the profileshapes for the entire sample is strongly peaked near n=1 (exponentialprofiles) and that no galaxies have n=1/4 (de Vaucouleurs profile). Thefaintest galaxies all have nearly exponential profiles, while thebrighter ones on average have n<1. The correlation betweenellipticity and the boxy/disky parameter is similar to that of largeelliptical galaxies, suggesting that dwarfs may also be divided into twogroups with differing internal dynamics. The Virgo dEs also show agreater degree of isophotal twisting than more luminous ellipticalgalaxies. There does not seem to be any combination of parameters fromthe surface photometry that statistically correlates with the dE/dS0designation: in particular, the dS0 galaxies do not, on average, havemore pointed (disky) isophotes than the dEs.
| Tides, Interactions, and Fine-Scale Substructures in Galaxy Clusters
We present the results of a study on galaxy interactions, tides, andother processes that produce luminous fine-scale substructures in thegalaxy clusters: Coma, Perseus, Abell 2199, AWM 3, and AWM 5. Allunusual structures in these clusters can be categorized into sevenmorphologies: interacting galaxies, multiple galaxies (noninteracting),distorted galaxies, tailed galaxies, line galaxies, dwarf galaxy groups,and galaxy aggregates. The various morphologies are described, and acatalog is presented, of 248 objects in these five clusters along withcolor, and positional information obtained from CCD images taken withthe WIYN 3.5 m telescope in broadband B and R filters. Distorted,interacting, and fine-scale substructures have a range of colorsextending from blue objects with B-R~0 to redder colors at B-R~2.5. Wealso find that the structures with the most disturbed morphology havethe bluest colors. In addition, the relative number distributions ofthese structures suggest that two separate classes of galaxy clustersexist: one dominated by distorted structures and the other dominated bygalaxy associations. The Coma and Perseus clusters, respectively, areproposed as models for these types of clusters. These structures avoidthe deep potentials of the dominant D or cD galaxies in the Coma andPerseus clusters, and tend to clump together. Possible mechanisms forthe production of fine-scale substructure are reviewed and compared withobservations of z~0.4 Butcher-Oemler clusters. We conclude, based oncolor, positional, and statistical data, that the most likely mechanismfor the creation of these structures is through an interaction with thegravitational potential of the cluster, possibly coupled with effects ofweak interactions with cluster ellipticals.
| An Arecibo Search for Broad 21 Centimeter Lines of Atomic Hydrogen in Clusters of Galaxies
We present the results of sensitive observations of the inner3.3′ (~100 kpc) of 21 clusters of galaxies with the Arecibotelescope utilizing the autocorrelation spectrometer in complex-samplingmode to obtain a total bandwidth of 40 MHz, which corresponds to avelocity coverage of ~7000-8000 km s^-1. These are the most sensitiveobservations capable of detecting H i with line widths expected for gasin the intracluster medium (ICM). We did not detect any significantemission features with 500 km s^-1 <= FWHM <= 4000 km s^-1 throughthe centers of these clusters. Limits on optically thin H i from``narrow'' galaxy-type features are typically ~5 x 10^8 M_ȯ, whilefrom broad cluster-type features they are about an order of magnitudehigher. We derive constraints on the covering factor of any opticallythick H i within the Arecibo beam. We obtain upper limits c_f ~ 3 x10^-3 assuming that the temperature of the H i is 10 K. This correspondsto a limited range of parameter space for the clouds in which the cloudtemperature is typically less than a few tens of kelvins and the numberof clouds along the line of sight is less than a few tens of clouds.Cloud temperatures this low are probably inconsistent with cloud heatingdue to X-rays from the ICM; however, this is uncertain. The very smallrange of parameter space that is allowed by the observations makes itunlikely that there is very much atomic hydrogen in the ICM of theseclusters. The Arecibo Observatory is part of the National Astronomy andIonosphere Center, which is operated by Cornell University undercooperative agreement with the National Science Foundation.
| 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.
| ROSAT HRI observations of six early-type galaxies
High-resolution ROSAT HRI soft X-ray observations of four E/S0 galaxieswere conducted by us. The data show no signs of Seyfert activity in theX-ray regime. The central emission peaks of the four galaxies, NGC533,NGC2832, NGC4104 and NGC6329, are associated with their cooling flows.The half intensity radii of the cooling flows range from 0.8 to 3.5 kpc.We find a trend (based up to now on only five objects) of the radiopower of the cores in E/S0 galaxies to increase with the size and theaccretion rates of their cooling flows. In one galaxy, NGC4921, nocentrally peaked extended gaseous envelope was found, which is mostlikely due to the fact that it is not an E/S0 galaxy, but an early-typespiral. NGC2885, the sixth galaxy in our initial sample, shows signs ofX-ray emission from an AGN. It has also been classified as a Sy-1 AGN byBade et al. (1995). However, optical imaging suggests that this galaxyis probably not an E or S0 type system either, but rather an early-typespiral galaxy. Thus, in the context of accretion rate vs. galaxy typemodels of low-luminosity AGNs, the presence of an X-ray luminous Sy-1nucleus in NGC2885 is no surprise.
| The peculiar motions of early-type galaxies in two distant regions. III - The photometric data
We present R-band CCD photometry for 776 galaxies observed in the EFARproject. The photometry is compared with photoelectric data, showingthat a common zero-point good to better than 1 per cent and a precisionof 0.03 mag per zero-point have been achieved. We give the circularlyaveraged surface brightness profiles and the photometric parameters ofthe 762 program galaxies, D(n) diameters, half-luminosity radii, totalmagnitudes, and average effective surface brightnesses. More than 80percent of the profiles have a global S/N ratio larger than 300. Theextrapolation needed to derive total magnitudes is less than 10 percentfor 80 percent of the fits. More than 80 percent of the galaxies havemean effective surface brightness larger than the observed skybrightness. In 90 percent of the profiles the estimate of thecontamination of the sky by the galaxy light is less than 1 percent. Wederive total magnitudes and half-luminosity radii to better than 0.15mag and 25 percent, respectively, for 90 percent of our sample. Incontrast, external comparisons show that data in the literature can bestrongly affected by systematic errors due to large extrapolations,small radial range, sky subtraction errors, seeing effects, and the useof a simple R exp 1/4 fit. The resulting errors can easily amount tomore than 0.5 mag in the total magnitudes and 50 percent in thehalf-luminosity radii.
| The Peculiar Motions of Early-Type Galaxies in Two Distant Regions. I. Cluster and Galaxy Selection
The EFAR project is a study of 736 candidate elliptical galaxies in 84clusters lying in two regions, toward Hercules-Corona Borealis andPerseus-Pisces-Cetus, at distances cz ~ 6000-15,000 km s^-1^. In thispaper (the first of a series), we present an introduction to the EFARproject and describe in detail the selection of the clusters andgalaxies in our sample. Fundamental data for the galaxies and clustersare given, including accurate new positions for each galaxy andredshifts for each cluster. The galaxy selection functions aredetermined by using diameters measured from Schmidt sky survey imagesfor 2185 galaxies in the cluster fields. Future papers in this serieswill present the spectroscopic and photometric observations of thissample, investigate the properties of the fundamental plane forelliptical galaxies, and determine the large- scale peculiar velocityfields in these two regions of the universe.
| The Effects of Dust on Broadband Color Gradients in Elliptical Galaxies
In order to examine the possibility that dust effects cause colorgradients in elliptical galaxies, we have constructed a set ofelliptical galaxy models spanning a wide range of dust properties,including mass, spatial distribution, and spectral properties. Thesemodels are spherically symmetric and include the effects of scattering.We have calculated the emergent broadband colors from the far-UV bandsthrough K. These results were then compared with the color propertiesfor a sample of 52 galaxies taken from the literature. In the optical,we can reproduce the magnitude, morphology, and color gradient ratios[i.e., {DELTA}U - R)/{DELTA}(B - R)] observed in many of the galaxies.The best fits are found for distributions with ρ_d_ ~ r^-1^ andτT ~ 1, which corresponds to dust masses on the order of 10^6^M_sun_ within the central 10-30 kpc. More condensed dust profiles alsoproduce strong color gradients, but only in the central regions (r <0.5 kpc). For many of the objects in this sample, the implied dustmasses are in reasonable agreement with the dust masses inferred fromIRAS observations, although a number of objects require significantlyhigher dust masses than their IRAS observations imply if their colorproperties are to be attributed solely to reddening by dust. Our modelssuggest that a simple dusty elliptical galaxy scenario can reproduce themagnitude, morphology, and ratios of observed broadband color gradientsin many ellipticals. We find that currently available color gradientmeasurements are consistent with our model results but that thesemeasurements are not precise enough in many objects to provide tightconstraints on the models. Extended dust distributions will greatlycomplicate the interpretation of all broadband data. Any broadbandanalysis hindered by age-metallicity degeneracy will also be hindered bydust effects. In effect, all broadband observations of ellipticalgalaxies may be age-metallicity-dust degenerate. We also consider theeffects of dust on several global relationships in ellipticals, such asthe color-magnitude relation and various distance indicators.
| The Intragroup Medium in Poor Groups of Galaxies
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1996ApJ...456...80M&db_key=AST
| 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.
| 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.
| Kinematics and dynamics of the MKW/AWM poor clusters
We report 472 new redshifts for 416 galaxies in the regions of the 23poor clusters of galaxies originally identified by Morgan, Kayser, andWhite (MKW), and Albert, White, and Morgan (AWM). Eighteen of the poorclusters now have 10 or more available redshifts within 1.5/h Mpc of thecentral galaxy; 11 clusters have at least 20 available redshifts. Basedon the 21 clusters for which we have sufficient velocity information,the median velocity scale is 336 km/s, a factor of 2 smaller than foundfor rich clusters. Several of the poor clusters exhibit complex velocitydistributions due to the presence of nearby clumps of galaxies. We checkon the velocity of the dominant galaxy in each poor cluster relative tothe remaining cluster members. Significantly high relative velocities ofthe dominant galaxy are found in only 4 of 21 poor clusters, 3 of whichwe suspect are due to contamination of the parent velocity distribution.Several statistical tests indicate that the D/cD galaxies are at thekinematic centers of the parent poor cluster velocity distributions.Mass-to-light ratios for 13 of the 15 poor clusters for which we havethe required data are in the range 50 less than or = M/LB(0)less than or = 200 solar mass/solar luminosity. The complex nature ofthe regions surrounding many of the poor clusters suggests that thesegroupings may represent an early epoch of cluster formation. Forexample, the poor clusters MKW7 and MKWS are shown to be gravitationallybound and likely to merge to form a richer cluster within the nextseveral Gyrs. Eight of the nine other poor clusters for which simpletwo-body dynamical models can be carried out are consistent with beingbound to other clumps in their vicinity. Additional complex systems withmore than two gravitationally bound clumps are observed among the poorclusters.
| 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.
| Photoelectric and CCD photometry of E and S0 galaxies
We present BR photoelectric photometry for 352 E and S0 galaxies thatare part of a large survey of the properties and peculiar motions ofgalaxies in distant clusters. Repeat measurements show our internalerrors to be 2-3 percent in B and R and 1-2 percent in B-R. Comparisonsof BR and BVR reductions for 10 galaxies also observed in V show smallsystematic errors due to differences between the spectral energydistributions of stars and galaxies. External comparisons with B-Vcolors in the literature confirm that these colors are good to 1percent. We also describe R-band CCD observations for 95 of the galaxiesand place these on a BR photometric system for photoelectric and CCDphotomerry, with a common zero-point good to better than 1 percent. Wefind the rms precision of both our photoelectric and CCD R magnitudes tobe 2-3 percent for galaxies as faint as R = 15.
| Do elliptical galaxies have r1/4 brightness profiles?
The intermediate axis surface brightness distribution of a large sampleof elliptical galaxies is studied in detail. It is shown that the deVaucouleurs law provides an excellent fit to the observed brightnessdistribution for all galaxies within the radius range 0.1 Reless than or equal to R less than or equal to 1.5 Re, withmean deviations smaller than 0.1 mag arcsec-2 and maximumdeviations smaller than 0.2 mag arcsec-2. In addition, asmall but well defined change in the slope of the best fittingr1/4-law is observed at a radius R approximately equals 0.4Re. The fact that ellipticals fit the de Vaucouleurs lawwithin the same effective radius range indicates that they not only havea remarkably similar surface density distribution but also an underlyinguniversal volume density profile which can be well represented by aJaffe or Hernquist Law. These results will provide strong constraintsfor theoretical models of E-galaxy formation.
| On the external origin for dust in elliptical galaxies
Large samples of elliptical galaxies, observed at high signal-to-noiseratio with CCDs, are used with ADDSCAN 100 micron fluxes from IRAS toexamine evidence for the external origin of dust in these galaxies. Foursmall sets of galaxies are picked which show features stronglyindicative of a merger, that is, infalling H I gas, extensive dustlanes, and kinematically peculiar cores and shells. Though somecounterexamples exist, it is shown that the dust and isophotalproperties are consistent with the current merger model for thesegalaxies.
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