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Globular Cluster Systems in Brightest Cluster Galaxies: Bimodal Metallicity Distributions and the Nature of the High-Luminosity Clusters
We present new (B, I) photometry for the globular cluster systems ineight brightest cluster galaxies (BCGs), obtained with the ACS/WFCcamera on the Hubble Space Telescope. In the very rich cluster systemsthat reside within these giant galaxies, we find that all have stronglybimodal color distributions that are clearly resolved by themetallicity-sensitive (B-I) index. Furthermore, the mean colors andinternal color range of the blue subpopulation are remarkably similarfrom one galaxy to the next, to well within the +/-0.02-0.03 maguncertainties in the foreground reddenings and photometric zero points.By contrast, the mean color and internal color range for the redsubpopulation differ from one galaxy to the next by twice as much as theblue population. All the BCGs show population gradients, with muchhigher relative numbers of red clusters within 5 kpc of their centers,consistent with their having formed at later times than the blue,metal-poor population. A striking new feature of the color distributionsemerging from our data is that for the brightest clusters(MI<-10.5) the color distribution becomes broad and lessobviously bimodal. This effect was first noticed by Ostrov et al. andDirsch et al. for the Fornax giant NGC 1399; our data suggest that itmay be a characteristic of many BCGs and perhaps other large galaxies.Our data indicate that the blue (metal-poor) clusters brighter thanMI~=-10 become progressively redder with increasingluminosity, following a mass/metallicity scaling relationZ~M0.55. A basically similar relation has been found for M87by Strader et al. (2005). We argue that these GCS characteristics areconsistent with a hierarchical-merging galaxy formation picture in whichthe metal-poor clusters formed in protogalactic clouds or densestarburst complexes with gas masses in the range107-1010 Msolar, but where the moremassive clusters on average formed in bigger clouds with deeperpotential wells where more preenrichment could occur.
| Density-potential pairs for spherical stellar systems with Sérsic light profiles and (optional) power-law cores
Popular models for describing the luminosity-density profiles ofdynamically hot stellar systems (e.g. Jaffe, Hernquist, Dehnen) wereconstructed with the desire to match the deprojected form of anR1/4 light profile. Real galaxies, however, are now known tohave a range of different light-profile shapes that scale with mass.Consequently, although highly useful, the above models have implicitlimitations, and this is illustrated here through their application to anumber of real galaxy density profiles. On the other hand, theanalytical density profile given by Prugniel & Simien closelymatches the deprojected form of Sérsic R1/n lightprofiles - including deprojected exponential light profiles. It is thusapplicable for describing bulges in spiral galaxies, dwarf ellipticalgalaxies, and both ordinary and giant elliptical galaxies. Moreover, theobserved Sérsic quantities define the parameters of the densitymodel. Here we provide simple equations, in terms of elementary andspecial functions, for the gravitational potential and force associatedwith this density profile. Furthermore, to match galaxies with partiallydepleted cores, and better explore the supermassive black hole/galaxyconnection, we have added a power-law core to this density profile andderived similar expressions for the potential and force of this hybridprofile. Expressions for the mass and velocity dispersion, assumingisotropy, are also given. These spherical models may also proveappropriate for describing the dark matter distribution in haloes formedfrom ΛCDM cosmological simulations.
| A dichotomy in the orientation of dust and radio jets in nearby low-power radio galaxies
We examine the properties of central dust in nearby quiescent and activeearly-type galaxies. The active galaxies are low-power radio galaxieswith Fanaroff & Riley type I or I/II radio jets. We focus on (a) thecomparison of the dust distributions in the active and quiescent galaxysamples; and (b) the relation between the radio jet and dustorientations. Our main observational conclusions are: (i) in line withprevious studies, the dust detection rate is higher in radio-jetgalaxies than in non radio-jet galaxies; (ii) radio galaxies contain ahigher fraction of regular dust “ellipses” compared toquiescent galaxies which contain more often irregular dustdistributions; (iii) the morphology, size and orientation of dustellipses and lanes in quiescent early-types and active early-types withkpc-scale radio jets is very similar; (iv) dust ellipses are alignedwith the major axis of the galaxy, dust lanes do not show a preferredalignment except for large (>kpc) dust lanes which are aligned withthe minor axis of the galaxy; and (v) as projected on the sky, jets donot show a preferred orientation relative to the galaxy major axis (andhence dust ellipses), but jets are preferentially perpendicular to dustlanes. We show that the dust ellipses are consistent with being nearlycircular thin disks viewed at random viewing angles. The lanes arelikely warped dust structures, which may be in the process of settlingdown to become regular disks or are being perturbed by anon-gravitational force. We use the observed dust-jet orientations toconstrain the three-dimensional angle θDJ between jetand dust. For dust-lane galaxies, the jet is approximately perpendicularto the dust structure, while for dust-ellipse galaxies there is a muchwider distribution of θDJ. We discuss two scenariosthat could explain the dust/jet/galaxy orientation dichotomy. If lanesare indeed settling, then the jet orientation apparently is roughlyaligned with the angular momentum of the dust before it settles. Iflanes are perturbed by a jet-related force, it appears that it causesthe dust to move out of its equilibrium plane in the galaxy into a planewhich is perpendicular to the jet.
| Core Depletion from Coalescing Supermassive Black Holes
New measurements of the stellar-mass deficits at the centers of luminouselliptical galaxies are presented. These were derived considering thefollowing observational facts. First, ``core'' galaxies, which arethought to have had their inner region depleted from the coalescence ofsupermassive black holes, show an abrupt downward deviation of theirinner light profile relative to their outer Sérsic profile.Second, ``power-law'' galaxies, having undisturbed profiles and nopartially depleted core, have inner light profiles that display nodeparture from the inward extrapolation of their outer Sérsicprofile. The central stellar deficits have therefore been derived fromthe difference in flux between the Hubble Space Telescope observedgalaxy light profiles and the inward extrapolation of each galaxy'souter Sérsic profile. This approach gives flux deficits ~0.1% ofthe total galaxy light and mass deficits that are ~2 times each galaxy'scentral supermassive black hole mass. These results are in agreementwith the theoretical expectations of mass ejection from binary blackhole mergers and also with popular ΛCDM models of hierarchicalgalaxy formation. It is also explained why this result is some 10 timessmaller than current observational estimates of the central mass deficitand therefore implies a merger history for giant elliptical galaxiesthat is 1 order of magnitude less violent than previously suggested.
| 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.
| Evidence for a New Elliptical-Galaxy Paradigm: Sérsic and Core Galaxies
We fitted the surface-brightness profiles of 21 elliptical galaxiesusing both the Sérsic function and a new empirical model thatcombines an inner power law with an outer Sérsic function. Theprofiles are combinations of deconvolved Hubble Space Telescope (HST)profiles from the literature and ellipse fits to the full WFPC2 mosaicimages and thus span a radial range from ~0.02" to about twice thehalf-light radius. We are able to accurately fit the entire profilesusing either the Sérsic function or our new model. In doing so,we demonstrate that most, if not all, so-called ``power-law'' galaxiesare better described as ``Sérsic galaxies''-they are well modeledby the three-parameter Sérsic profile into the limits of HSTresolution-and that ``core'' galaxies are best understood as consistingof an outer Sérsic profile with an inner power-law cusp, which isa downward deviation from the inward extrapolation of the Sérsicprofile. This definition of cores resolves ambiguities that result whenthe popular ``Nuker law'' is fitted to the profiles of ellipticals andbulges, particularly at lower luminosities. We also find that using theNuker law to model core-galaxy nuclear profiles systematicallyoverestimates the core radii by factors of 1.5-4.5 and underestimatesthe inner power-law slope by ~20%-40% or more.
| A New Empirical Model for the Structural Analysis of Early-Type Galaxies, and A Critical Review of the Nuker Model
The Nuker law was designed to match the inner few (~3-10) arcseconds ofpredominantly nearby (<~30 Mpc) early-type galaxy light profiles; itwas never intended to describe an entire profile. The Sérsicmodel, on the other hand, was developed to fit the entire profile;however, because of the presence of partially depleted galaxy cores, theSérsic model cannot always describe the very inner region. Wehave therefore developed a new empirical model consisting of an innerpower law, a transition region, and an outer Sérsic model toconnect the inner and outer structure of elliptical galaxies. We haveadditionally explored the stability of the Nuker model parameters.Surprisingly, none are found to be stable quantities; all are shown tovary systematically with a profile's fitted radial extent, and often bymore than 100%. Considering elliptical galaxies spanning a range of 7.5mag, we reveal that the central stellar densities of the underlying hostgalaxies increase with galaxy luminosity until the onset of coreformation, detected only in the brightest elliptical galaxies. Wesuggest that the so-called power-law galaxies may actually be describedby the Sérsic model over their entire radial range.Based on observations made with the NASA/ESA Hubble Space Telescope,obtained at the Space Telescope Science Institute, which is operated bythe Association of Universities for Research in Astronomy, Inc., underNASA contract NAS 5-26555.
| 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
| Galaxy cores as relics of black hole mergers
We investigate the hypothesis that the cores of elliptical galaxies andbulges are created from the binding energy liberated by the coalescenceof supermassive binary black holes during galaxy mergers. Assuming thatthe central density profiles of galaxies were initially steep powerlaws, ρ ~r -2 , we define the `mass deficit' as the massin stars that had to be removed from the nucleus in order to produce theobserved core. We use non-parametric deprojection to compute the massdeficit in a sample of 35 early-type galaxies with high-resolutionimaging data. We find that the mass deficit correlates well with themass of the nuclear black hole, consistent with the predictions ofmerger models. We argue that cores in haloes of non-interacting darkmatter particles should be comparable in size to those observed in thestars.
| Nuclear Cusps and Cores in Early-Type Galaxies as Relics of Binary Black Hole Mergers
We present an analysis of the central cusp slopes and core parameters ofearly-type galaxies using a large database of surface brightnessprofiles obtained from Hubble Space Telescope observations. We examinethe relation between the central cusp slopes, core parameters, and blackhole masses in early-type galaxies, in light of two models that attemptto explain the formation of cores and density cusps via the dynamicalinfluence of black holes. Contrary to the expectations fromadiabatic-growth models, we find that the cusp slopes do not steepenwith increasing black hole mass fraction. Moreover, a comparison ofkinematic black hole mass measurements with the masses predicted by theadiabatic models shows that they overpredict the masses by a factor of~3. Simulations involving binary black hole mergers predict that boththe size of the core and the central mass deficit correlate with thefinal black hole mass. These relations are qualitatively supported bythe present data.
| Bar Galaxies and Their Environments
The prints of the Palomar Sky Survey, luminosity classifications, andradial velocities were used to assign all northern Shapley-Ames galaxiesto either (1) field, (2) group, or (3) cluster environments. Thisinformation for 930 galaxies shows no evidence for a dependence of barfrequency on galaxy environment. This suggests that the formation of abar in a disk galaxy is mainly determined by the properties of theparent galaxy, rather than by the characteristics of its environment.
| Relation between dust and radio luminosity in optically selected early type galaxies
We have surveyed an optical/IR selected sample of nearby E/S0 galaxieswith and without nuclear dust structures with the VLA at 3.6 cm to asensitivity of 100 mu Jy. We can construct a Radio Luminosity Function(RLF) of these galaxies to ~ 1019 W Hz-1 and findthat ~ 50% of these galaxies have AGNs at this level. The space densityof these AGNs equals that of starburst galaxies at this luminosity.Several dust-free galaxies have low luminosity radio cores, and theirRLF is not significantly less than that of the dusty galaxies.
| Dusty Nuclear Disks and Filaments in Early-Type Galaxies
We examine the dust properties of a nearby distance-limited sample ofearly-type galaxies using WFPC2 of the Hubble Space Telescope. Dust isdetected in 29 out of 67 galaxies (43%), including 12 with small nucleardusty disks. In a separate sample of 40 galaxies biased for thedetection of dust by virtue of their detection in IRAS 100 μm band,dust is found in ~78% of the galaxies, 15 of which contain dusty disks.In those galaxies with detectable dust, the apparent mass of the dustcorrelates with radio and far-infrared luminosity, becoming moresignificant for systems with filamentary dust. A majority of IRAS andradio detections are also associated with dusty galaxies rather thandustless galaxies. This indicates that thermal emission from clumpy,filamentary dust is the main source of the far-IR radiation inearly-type galaxies. Dust in small disklike morphology tends to be wellaligned with the major axis of the host galaxies, while filamentary dustappears to be more randomly distributed with no preference for alignmentwith any major galactic structure. This suggests that, if the dustydisks and filaments have a common origin, the dust originates externallyand requires time to dynamically relax and settle in the galaxypotential in the form of compact disks. More galaxies with visible dustthan without dust display emission lines, indicative of ionized gas,although such nuclear activity does not show a preference for dusty diskover filamentary dust. There appears to be a weak relationship betweenthe mass of the dusty disks and central velocity dispersion of thegalaxy, suggesting a connection with a similar recently recognizedrelationship between the latter and the black hole mass. Based onobservations with the NASA/ESA Hubble Space Telescope, obtained at theSpace Telescope Science Institute, which is operated by the Associationof Universities for Research in Astronomy, Inc., under NASA contractNAS5-26555.
| WFPC2 Images of the Central Regions of Early-Type Galaxies. I. The Data
We present high-resolution R-band images of the central regions of 67early-type galaxies obtained with the Wide Field and Planetary Camera 2(WFPC2) aboard the Hubble Space Telescope (HST). This homogeneouslyselected sample roughly doubles the number of early-type galaxies thathave now been imaged at HST resolution and complements similar data onthe central regions of radio galaxies and the bulges of spiral galaxies.Our sample strikingly confirms the complex morphologies of the centralregions of early-type galaxies which have become apparent from previousstudies with HST. In particular, we detect dust, either in the form ofnuclear disks or with a filamentary distribution, in 43% of allgalaxies, in good agreement with previous estimates. In addition, wefind evidence for embedded stellar disks in a remarkably large fractionof 51%. In 14 of those galaxies the disklike structures are misalignedwith the main galaxy, suggesting that they correspond to stellar bars inS0 galaxies. We analyze the luminosity profiles of the galaxies in oursample and classify galaxies according to their central cusp slope. To alarge extent we confirm the results from previous HST surveys in thatearly-type galaxies reveal a clear dichotomy: the bright ellipticals(MB<~-20.5) are generally boxy and have luminosityprofiles that break from steep outer power laws to shallow inner cusps(referred to as ``core'' galaxies). The fainter ellipticals, on theother hand, typically have disky isophotes and luminosity profiles thatlack a clear break and have a steep central cusp (referred to as``power-law'' galaxies). The advantages and shortcomings ofclassification schemes utilizing the extrapolated central cusp slopeγ are discussed, and it is shown that γ might be aninadequate representation for galaxies whose luminosity profile slopechanges smoothly with radius rather than resembling a broken power law.Thus, we introduce a new, alternative parameter and show how thisaffects the classification. In fact, we find evidence for an``intermediate'' class of galaxies that cannot unambiguously beclassified as either core or power-law galaxies and that have centralcusp slopes and absolute magnitudes intermediate between those of coreand power-law galaxies. It is unclear at present, however, whether thesegalaxies make up a physically distinct class or whether distance and/orresolution effects cause them to lose their distinct core or power-lawcharacteristics.
| 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.
| Accurate Positions for MCG Galaxies
We have measured accurate celestial coordinates for 4741 extragalacticobjects, primarily drawn from a list of MCG galaxies with no recentlypublished accurate positions. The standard deviations in the newpositions depend slightly on the measurement method but are on the orderof 1.0" to 1.2". Standard deviations in the original MCG positions areconfirmed to be at the 1.5′-2.0′ level. These new positionswere integrated into NED in 1997 December.
| 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 Search for ``Dwarf'' Seyfert Nuclei. III. Spectroscopic Parameters and Properties of the Host Galaxies
We have completed an optical spectroscopic survey of the nuclear regions(r <~ 200 pc) of a large sample of nearby galaxies. Although the mainobjectives of the survey are to search for low-luminosity activegalactic nuclei and to quantify their luminosity function, the databasecan be used for a variety of other purposes. This paper presentsmeasurements of the spectroscopic parameters for the 418 emission-linenuclei, along with a compilation of the global properties of all 486galaxies in the survey. Stellar absorption generally poses a seriousobstacle to obtaining accurate measurement of emission lines in nearbygalactic nuclei. We describe a procedure for removing the starlight fromthe observed spectra in an efficient and objective manner. The mainparameters of the emission lines (intensity ratios, fluxes, profilewidths, and equivalent widths) are measured and tabulated, as areseveral stellar absorption-line and continuum indices useful forstudying the stellar population. Using standard nebular diagnostics, wedetermine the probable ionization mechanisms of the emission-lineobjects. The resulting spectral classifications provide extensiveinformation on the demographics of emission-line nuclei in the nearbyregions of the universe. This new catalog contains over 200 objectsshowing spectroscopic evidence for recent star formation and an equallylarge number of active galactic nuclei, including 46 that show broad Halpha emission. These samples will serve as the basis of future studiesof nuclear activity in nearby galaxies.
| 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.
| A search for 'dwarf' Seyfert nuclei. 2: an optical spectral atlas of the nuclei of nearby galaxies
We present an optical spectral atlas of the nuclear region (generally 2sec x 4 sec, or r approximately less than 200 pc) of a magnitude-limitedsurvey of 486 nearby galaxies having BT less than or = 12.5mag and delta greater than 0 deg. The double spectrograph on the Hale 5m telescope yielded simultaneous spectral coverage of approximately4230-5110 A and approximately 6210-6860 A, with a spectral resolution ofapproximately 4 A in the blue half and approximately 2.5 A in the redhalf. This large, statistically significant survey contains uniformlyobserved and calibrated moderate-dispersion spectra of exceptionallyhigh quality. The data presented in this paper will be used for varioussystematic studies of the physical properties of the nuclei of nearbygalaxies, with special emphasis on searching for low-luminosity activegalactic nuclei, or 'dwarf' Seyferts. Our survey led to the discovery offour relatively obvious but previously uncataloged Seyfert galaxies (NGC3735, 492, 4639, and 6951), and many more galactic nuclei showingevidence for Seyfert activity. We have also identified numerouslow-ionization nuclear emission-line regions (LINERs), some of which maybe powered by nonstellar processes. Of the many 'starburst' nuclei inour sample, several exhibit the spectral features of Wolf-Rayet stars.
| Stellar population gradients in bright cluster galaxies at Z = 0.2
Slit spectra, covering the rest frame near-ultraviolet and bluewavelength regions, are combined with moderately deep g and R images toinvestigate radial population gradients in the brightest components ofsize z = 0.2 galaxy clusters selected according to x-ray brightness. Weconclude that the brightest members of the EMSS 0440+02, and EMSS0906+11, and EMSS 1231+15 clusters have global stellar contents similarto nearby elliptical galaxies, although all three galaxies studied inEMSS 0440 contain a central blue component, suggesting that a young orintermediate-age population is also present. Our ability to investigatethe stellar content of the brightest cluster galaxies (BGCs) in theclusters EMSS 0839+29, EMSS 1455+22, and Abell 2390 is complicated byionized gas, which is detected over large portions of all the systems.The presence of significant stellar population gradients in the BCGssuggests that the material from which they formed experienceddissipation during the collapse phases, and it seems likely that thesegalaxies could not have been formed solely from the merging of gas-poorgalaxies.
| 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.
| Line-strength gradients in the bulge components of NGC 3190 and 1023.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1994MNRAS.271...39S&db_key=AST
| The metallicity of elliptical galaxies.
Not Available
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