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Companions to Isolated Elliptical Galaxies: Revisiting the Bothun-Sullivan Sample
We investigate the number of physical companion galaxies for a sample ofrelatively isolated elliptical galaxies. The NASA/IPAC ExtragalacticDatabase (NED) has been used to reinvestigate the incidence of satellitegalaxies for a sample of 34 elliptical galaxies, first investigated byBothun & Sullivan using a visual inspection of Palomar Sky Surveyprints out to a projected search radius of 75 kpc. We have repeatedtheir original investigation using data cataloged in NED. Nine of theseelliptical galaxies appear to be members of galaxy clusters; theremaining sample of 25 galaxies reveals an average of +1.0+/-0.5apparent companions per galaxy within a projected search radius of 75kpc, in excess of two equal-area comparison regions displaced by 150-300kpc. This is significantly larger than the +0.12+/-0.42companions/galaxy found by Bothun & Sullivan for the identicalsample. Making use of published radial velocities, mostly availablesince the completion of the Bothun-Sullivan study, identifies thephysical companions and gives a somewhat lower estimate of +0.4companions per elliptical galaxy. This is still 3 times larger than theoriginal statistical study, but given the incomplete and heterogeneousnature of the survey redshifts in NED, it still yields a firm lowerlimit on the number (and identity) of physical companions. An expansionof the search radius out to 300 kpc, again restricted to sampling onlythose objects with known redshifts in NED, gives another lower limit of4.5 physical companions per galaxy. (Excluding five elliptical galaxiesin the Fornax Cluster, this average drops to 3.5 companions perelliptical.) These physical companions are individually identified andlisted, and the ensemble-averaged radial density distribution of theseassociated galaxies is presented. For the ensemble, the radial densitydistribution is found to have a falloff consistent withρ~R-0.5 out to approximately 150 kpc. For non-FornaxCluster companions the falloff continues out to the 300 kpc limit of thesurvey. The velocity dispersion of these companions is found to reach amaximum of 350 km s-1 at around 120 kpc, after which theyfall at a rate consistent with Keplerian falloff. This falloff may thenindicate the detection of a cut-off in the mass-density distribution inthe elliptical galaxies' dark matter halo at ~100 kpc.
| 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
| Early-type galaxy distances from the Fundamental Plane and surface brightness fluctuations
We compare two of the most popular methods for deriving distances toearly-type galaxies: the Fundamental Plane (FP) and surface brightnessfluctuations (SBF). Distances for 170 galaxies are compared. A third setof distances is provided by predictions derived from the density fieldof the IRAS redshift survey. Overall there is good agreement between thedifferent distance indicators. We investigate systematic trends in theresiduals of the three sets of distance comparisons. First, we find thatseveral nearby, low-luminosity, mainly S0 galaxies have systematicallylow FP distances. Because these galaxies also have Mg2indices among the lowest in the sample, we conclude that they deviatefrom the FP partly because of recent star formation and consequently lowmass-to-light ratios; differences in their internal velocity structuresmay also play a role. Secondly, we find some evidence that theground-based I -band SBF survey distances (Tonry et al. 2001) begin toshow a bias near the survey limit at , which is expected for this sortof distance-limited survey, but had not previously been demonstrated.Although SBF and FP distances are affected in opposite senses by errorsin the Galactic extinction estimates, we find no evidence for biases inthe distances due to Galactic extinction. The tie between theCepheid-calibrated SBF distances (Mpc) and the far-field calibrated FPdistances (kms-1 ) yields a Hubble constant , while thecomparison between SBF and the IRAS -reconstructed distances yields(independent errors only). Thus there is a marginal inconsistency in thedirect and IRAS -reconstructed ties to the Hubble flow (this can be seenindependently of the SBF distances). Possible explanations includesystematic errors in the redshift survey completeness estimates or inthe FP aperture corrections, but at this point the best estimate of H0 may come from a simple average of the above two estimates.After revising the SBF distances downward by 2.8 per cent to be inagreement with the final set of Key Project Cepheid distances (Freedmanet al.), we conclude that from early-type galaxies, where the seconderror bar represents the total systematic uncertainty in the distancezero-point. We also discuss the `fluctuation star count', recentlyintroduced by Tonry et al. (2001) as a less demanding alternative to forcalibrating SBF distances. The N -calibrated SBF method is akin to ahybrid SBF-FP distance indicator, and we find that the use of N actuallyimproves the SBF distances. Further study of the behaviour of thisquantity may provide an important new test for models of ellipticalgalaxy formation.
| 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.
| A synthesis of data from fundamental plane and surface brightness fluctuation surveys
We perform a series of comparisons between distance-independentphotometric and spectroscopic properties used in the surface brightnessfluctuation (SBF) and fundamental plane (FP) methods of early-typegalaxy distance estimation. The data are taken from two recent surveys:the SBF Survey of Galaxy Distances and the Streaming Motions of AbellClusters (SMAC) FP survey. We derive a relation between(V-I)0 colour and Mg2 index using nearly 200galaxies and discuss implications for Galactic extinction estimates andearly-type galaxy stellar populations. We find that the reddenings fromSchlegel et al. for galaxies with E(B-V)>~0.2mag appear to beoverestimated by 5-10 per cent, but we do not find significant evidencefor large-scale dipole errors in the extinction map. In comparison withstellar population models having solar elemental abundance ratios, thegalaxies in our sample are generally too blue at a given Mg2;we ascribe this to the well-known enhancement of the α-elements inluminous early-type galaxies. We confirm a tight relation betweenstellar velocity dispersion σ and the SBF `fluctuation count'parameter N, which is a luminosity-weighted measure of the total numberof stars in a galaxy. The correlation between N and σ is eventighter than that between Mg2 and σ. Finally, we deriveFP photometric parameters for 280 galaxies from the SBF survey data set.Comparisons with external sources allow us to estimate the errors onthese parameters and derive the correction necessary to bring them on tothe SMAC system. The data are used in a forthcoming paper, whichcompares the distances derived from the FP and SBF methods.
| The SBF Survey of Galaxy Distances. IV. SBF Magnitudes, Colors, and Distances
We report data for I-band surface brightness fluctuation (SBF)magnitudes, (V-I) colors, and distance moduli for 300 galaxies. Thesurvey contains E, S0, and early-type spiral galaxies in the proportionsof 49:42:9 and is essentially complete for E galaxies to Hubblevelocities of 2000 km s-1, with a substantial sampling of Egalaxies out to 4000 km s-1. The median error in distancemodulus is 0.22 mag. We also present two new results from the survey.(1) We compare the mean peculiar flow velocity (bulk flow) implied byour distances with predictions of typical cold dark matter transferfunctions as a function of scale, and we find very good agreement withcold, dark matter cosmologies if the transfer function scale parameterΓ and the power spectrum normalization σ8 arerelated by σ8Γ-0.5~2+/-0.5. Deriveddirectly from velocities, this result is independent of the distributionof galaxies or models for biasing. This modest bulk flow contradictsreports of large-scale, large-amplitude flows in the ~200 Mpc diametervolume surrounding our survey volume. (2) We present adistance-independent measure of absolute galaxy luminosity, N and showhow it correlates with galaxy properties such as color and velocitydispersion, demonstrating its utility for measuring galaxy distancesthrough large and unknown extinction. Observations in part from theMichigan-Dartmouth-MIT (MDM) Observatory.
| The Frequency of Active and Quiescent Galaxies with Companions: Implications for the Feeding of the Nucleus
We analyze the idea that nuclear activity, either active galactic nuclei(AGNs) or star formation, can be triggered by interactions by studyingthe percentage of active, H II, and quiescent galaxies with companions.Our sample was selected from the Palomar survey and avoids selectionbiases faced by previous studies. This sample was split into fivedifferent groups, Seyfert galaxies, LINERs, transition galaxies, H IIgalaxies, and absorption-line galaxies. The comparison between the localgalaxy density distributions of the different groups showed that in mostcases there is no statistically significant difference among galaxies ofdifferent activity types, with the exception that absorption-linegalaxies are seen in higher density environments, since most of them arein the Virgo Cluster. The comparison of the percentage of galaxies withnearby companions showed that there is a higher percentage of LINERs,transition galaxies, and absorption-line galaxies with companions thanSeyfert and H II galaxies. However, we find that when we consider onlygalaxies of similar morphological types (elliptical or spiral), there isno difference in the percentage of galaxies with companions amongdifferent activity types, indicating that the former result was due tothe morphology-density effect. In addition, only small differences arefound when we consider galaxies with similar Hα luminosities. Thecomparison between H II galaxies of different Hα luminositiesshows that there is a significantly higher percentage of galaxies withcompanions among H II galaxies with L(Hα)>1039 ergss-1 than among those with L(Hα)<=1039ergs s-1, indicating that interactions increase the amount ofcircumnuclear star formation, in agreement with previous results. Thefact that we find that galaxies of different activity types have thesame percentage of companions suggests that interactions betweengalaxies is not a necessary condition to trigger the nuclear activity inAGNs. We compare our results with previous ones and discuss theirimplications.
| 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.
| A Test for Large-Scale Systematic Errors in Maps of Galactic Reddening
Accurate maps of Galactic reddening are important for a number ofapplications, such as mapping the peculiar velocity field in the nearbyuniverse. Of particular concern are systematic errors which vary slowlyas a function of position on the sky, as these would induce spuriousbulk flow. We have compared the reddenings of Burstein & Heiles (BH)and those of Schlegel, Finkbeiner, & Davis (SFD) to independentestimates of the reddening, for Galactic latitudes |b|>10^deg. Ourprimary source of Galactic reddening estimates comes from comparing thedifference between the observed B-V colors of early-type galaxies, andthe predicted B-V color determined from the B-V-Mg_2 relation. We havefitted a dipole to the residuals in order to look for large-scalesystematic deviations. There is marginal evidence for a dipolar residualin the comparison between the SFD maps and the observed early-typegalaxy reddenings. If this is due to an error in the SFD maps, then itcan be corrected with a small (13%) multiplicative dipole term. Weargue, however, that this difference is more likely to be due to a small(0.01 mag) systematic error in the measured B-V colors of the early-typegalaxies. This interpretation is supported by a smaller, independentdata set (globular cluster and RR Lyrae stars), which yields a resultinconsistent with the early-type galaxy residual dipole. BH reddeningsare found to have no significant systematic residuals, apart from theknown problem in the region 230^deg
| 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.
| Stellar populations in dwarf elliptical galaxies.
Not Available
| Groups of galaxies. III. Some empirical characteristics.
Not Available
| A catalogue of Mg_2 indices of galaxies and globular clusters
We present a catalogue of published absorption-line Mg_2 indices ofgalaxies and globular clusters. The catalogue is maintained up-to-datein the HYPERCAT database. The measurements are listed together with thereferences to the articles where the data were published. A codeddescription of the observations is provided. The catalogue gathers 3541measurements for 1491 objects (galaxies or globular clusters) from 55datasets. Compiled raw data for 1060 galaxies are zero-point correctedand transformed to a homogeneous system. Tables 1, 3, and 4 areavailable in electronic form only at the CDS, Strasbourg, via anonymousftp 130.79.128.5. Table 2 is available both in text and electronic form.
| 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.
| A catalogue of spatially resolved kinematics of galaxies: Bibliography
We present a catalogue of galaxies for which spatially resolved data ontheir internal kinematics have been published; there is no a priorirestriction regarding their morphological type. The catalogue lists thereferences to the articles where the data are published, as well as acoded description of these data: observed emission or absorption lines,velocity or velocity dispersion, radial profile or 2D field, positionangle. Tables 1, 2, and 3 are proposed in electronic form only, and areavailable from the CDS, via anonymous ftp to cdsarc.u-strasbg.fr (to130.79.128.5) or via http://cdsweb.u-strasbg.fr/Abstract.html
| 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.
| Line-of-Sight Velocity Distributions of Elliptical Galaxies
The line-of-sight velocity distributions (LOSVDs) have been measured to> R_e_/2 along the major axes of 44 elliptical galaxies (more than 80per cent of all ellipticals north of δ = -10^deg^ and brighterthan B_T_ = 12.0), together with stellar rotational velocity andvelocity dispersion profiles. For 19 of these 44 objects, minor axisprofiles are also given. Monte Carlo simulations have been used toestimate errors. LOSVDs are found to deviate from Gaussians by no morethan ~10 per cent. If rotation is present, LOSVDs are asymmetric withthe prograde wings being always steeper than the retrograde wings. Thedegree of asymmetry (measured by the H_3_ Gauss-Hermite coefficient)correlates with ν/σ. Round and boxy ellipticals have lowerasymmetries than flat and discy ones. On the whole, both types must haveintrinsically asymmetric velocity distributions. Symmetric deviations(measured by the H_4_ Gauss-Hermite coefficient) are generally smallerthan asymmetric ones. On the basis of the observed LOSVD shapes, thevalidity of two- integral models can be ruled out for most of thenon-discy objects observed here (discy ellipticals require detailedmodelling before similar conclusions can be drawn). Discy ellipticalshave H_3_ and H_4_ major and minor axis profiles which appear consistentwith a bulge+disc superposition. The observed H_4_ profile in M87 arguesfor radially anisotropic spherical or oblate models. Velocity dispersionprofiles show significant individuality, but typically become flatoutside R_e_/4. Major and minor axis slopes are mostly correlated one toone. We confirm that, with increasing luminosity, ellipticals becomemore anisotropic and that discy ellipticals have more rotationalsupport. The Fundamental Plane of elliptical galaxies is tighter iftotal kinetic energy is used instead of central velocity dispersion.Both the small scatter about the Fundamental Plane and the homogenousand systematic properties of the LOSVDs imply that only a small range ofdynamical models is realized in elliptical galaxies.
| The RSA survey of dwarf galaxies, 1: Optical photometry
We present detailed surface photometry, based on broad B-band chargecoupled device (CCD) images, of about 80 dwarf galaxies. Our samplerepresents approximately 10% of all dwarf galaxies identified in thevicinity of Revised Shapley-Ames (RSA) galaxies on high resolution bluephotographic plates, referred to as the RSA survey of dwarf galaxies. Wederive global properties and radial surface brightness profiles, andexamine the morphologies. The radial surface brightness profiles ofdwarf galaxies, whether early or late type, display the same varietiesin shape and complexity as those of classical giant galaxies. Only a feware well described by a pure r1/4 law. Exponential profilesprevail. Features typical of giant disk galaxies, such as exponentialprofiles with a central depression, lenses, and even, in one case (IC2041), a relatively prominent bulge are also found in dwarf galaxies.Our data suggest that the central region evolves from being bulge-like,with an r1/4 law profile, in bright galaxies to a lens-likestructure in dwarf galaxies. We prove detailed surface photometry to bea helpful if not always sufficient tool in investigating the structureof dwarf galaxies. In many cases kinematic information is needed tocomplete the picture. We find the shapes of the surface brightnessprofiles to be loosely associated with morphological type. Our samplecontains several new galaxies with properties intermediate between thoseof giant and dwarf ellipticals (but no M32-like objects). This showsthat such intermediate galaxies exist so that at least a fraction ofearly-type dwarf ellipticals is structurally related to early-typegiants instead of belonging to a totally unrelated, disjunct family.This supports an origin of early-type dwarf galaxies as originally moremassive systems that acquired their current morphology as a result ofsubstantial, presumable supernova-driven, mass loss. On the other hand,several early-type dwarfs in our sample are merger candidates. Mergerevents may lead to anisotropic velocity distributions in systems of anyluminosity, including dwarfs. The RSA sample of dwarf galaxies is morelikely to contain mergers because, in contrast to earlier dwarf galaxysurveys that have focused on clusters and rich groups of galaxies, theRSA dwarfs are typically located in low density environments. Theoccurrence of mergers among dwarf galaxies is of interest in connectionwith the rapid evolution of faint blue galaxy counts at redshift z lessthan 1 which suggests that dwarf galaxies were about five times morenumerous in the recent past.
| Dynamically hot galaxies. II - Global stellar populations
The global relationship between the stellar populations and thestructural properties of dynamically hot galaxies (DHGs) is investigatedusing the same sample as was analyzed by Bender et al. (1992), whichincludes giant ellipticals, low-luminosity ellipticals, compactellipticals, diffuse dwarf ellipticals, dwarf spheroidals, and bulges.It was found that all DHGs follow a single relationship between globalstellar population (represented by Mg2 index or B-V color) and centralvelocity dispersion sigma(0), and that the Mg2-sigma(0) relation issignificantly tighter than the relation between the Mg2 index andabsolute luminosity. The relation between central Mg2 index and bulk B-Vcolor was also found to be tight.
| 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.
| Dynamically hot galaxies. I - Structural properties
Results are reported from an analysis of the structural properties ofdynamically hot galaxies which combines central velocity dispersion,effective surface brightness, and effective radius into a new 3-space(k), in which the axes are parameters that are physically meaningful.Hot galaxies are found to divide into groups in k-space that closelyparallel conventional morphological classifications, namely, luminousellipticals, compacts, bulges, bright dwarfs, and dwarf spheroidals. Amajor sequence is defined by luminous ellipticals, bulges, and mostcompacts, which together constitute a smooth continuum in k-space.Several properties vary smoothly with mass along this continuum,including bulge-to-disk ratio, radio properties, rotation, degree ofvelocity anisotropy, and 'unrelaxed'. A second major sequence iscomprised of dwarf ellipticals and dwarf spheroidals. It is suggestedthat mass loss is a major factor in hot dwarf galaxies, but the dwarfsequence cannot be simply a mass-loss sequence, as it has the wrongdirection in k-space.
| Radio-continuum sources in nearby and bright E/S0 galaxies - Active nuclei versus star formation
Results of a sensitive VLA survey of nearby E/S0 galaxies are presented.The 204 galaxies surveyed, plus 12 additional galaxies with existing VLAimages, comprise a volume- and optical magnitude-limited sample. Thediscussion focuses on the relation between radio powers and opticalluminosities, whether the radio emission is driven by an active nucleusor by recent star formation, and what galaxian properties might enhancenuclear activity in an elliptical galaxy. It is suggested that the 67ellipticals in the sample should be targets of sensitive searches forHI, optical emission-line gas, and X-ray emitting gas.
| Radio-continuum sources in nearby and bright E/S0 galaxies - Sample selection and well-studied cases
A volume-limited sample of 216 nearby and optically bright E/S0 galaxieshas been compiled. Twelve of the galaxies are confirmed radio sourcesfor which VLA images are available. Most of the remaining galaxies havepowers less than or of the order of 10 to the 21st-22nd W/Hz, and thisinformation is used to establish the parameters of a new VLA survey ofthese galaxies. The basic optical properties of the galaxies in thesample are tabulated.
| Counts of serendipitous 6 centimeter sources in E/S0 galaxy fields
One hundred and sixty-eight VLA images from a 6 cm survey of E/S0galaxies were searched for serendipitous sources at millijansky (mJy)levels. Fifty-eight sources with integrated flux densities between 1.5and 15 mJy were found within a total solid angle of 2.27 sq deg. Thesources show no radial clustering relative to the galaxy centers and soare not, statistically, associated with the galaxies. The 58 sources areassumed to be background sources suitable for cosmological studies todetermine new differential source counts. These new counts areconsistent with previous, but much less accurate, counts at mJy levels,meaning that the background source population is not measurably alteredby the presence of the foreground E/S0 galaxies.
| Internal kinematics of low-luminosity ellipsoidal galaxies
Spectroscopic observations are presented of ten low-mass ellipsoidalgalaxies having luminosities in the range where the luminosity functionsof luminous ellipticals and low surface-brightness dwarf ellipticalsoverlap. The sample covers a large range in effective surfacebrightness, from values typical of genuine dwarfs to those of compact, M32-like, ellipticals. In contrast to what may be expected from theextrapolation of the result of Davies et al. (1983), about half of theobjects are not rotationally flattened. However, only objects fainterthan M(T) = -18.0 mag and having low surface brightness are considerablyanisotropic, indicating that: (1) the result of Davies et al. (1983)still describes the overall trend between kinematics and luminosity forelliptical galaxies brighter than M(T) = -18 mag in the correct way, and(2) low surface brightness dwarf ellipsoidals may be in general notrotationally flattened.
| The low-mass extension of the fundamental plane of elliptical galaxies
A sample of 17 low-mass elliptical and elliptical-like galaxies wasbuilt with accurate photometric and spectroscopic data. This sample,covering a wide range in surface brightness, is in or near the low-massextension of the 'fundamental plane' defined by bright ellipticals, butshows a scatter which cannot be accounted for by measurement errors andwhich is thus probably due to a large variety of internal structures.Extending the analysis to globular clusters and dwarf spheroidals, it isfound that they are also near or within the fundamental plane, exceptfor two dwarfs suspected of having a high M/L. The range thus covered is20 in absolute magnitude. These results suggest that the fundamentalplane is a robust representation of the virial theorem, valid forellipticals and for other types of pressure-supported stellar systems aswell. It also indicates that the standard parameter relations are littlesensitive to specific formation processes, local environment, andstructural details, that may have an effect at a subtler level.
| 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.
| Hierarchical pairs and the evolution of elliptical galaxies
Consideration is given to the photometric and kinematic characteristicsof galaxies in eight close pairs of ellipticals consisting of a brightgalaxy and a compact faint companion. Redshifts and central velocitydispersions are determined from high-dispersion spectra. Evidence ispresented for interaction in the pairs. The mean surface brightness andcentral velocity dispersions of the galaxies are tightly correlated withluminosity. Two sequences of ellipticals are defined, based on the workof Michard (1979). The galaxies in this study are sequence I galaxies.It is suggested that sequence II galaxies evolve toward sequence Igalaxies through dissipation of internal energy and loss of angularmomentum.
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