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Kinematic properties and stellar populations of faint early-type galaxies - I. Velocity dispersion measurements of central Coma galaxies
We present velocity dispersion measurements for 69 faint early-typegalaxies in the core of the Coma cluster, spanning -22.0<~MR<~-17.5 mag. We examine the L-σ relation forour sample and compare it to that of bright elliptical galaxies (Es)from the literature. The distribution of the the faint early-typegalaxies in the L-σ plane follows the relationL~σ2.01+/-0.36, which is significantly shallower fromL~σ4 as defined for the bright Es. While increasedrotational support for fainter early-type galaxies could account forsome of the difference in slope, we show that it cannot explain it. Wealso investigate the colour-σ relation for our Coma galaxies.Using the scatter in this relation, we constrain the range of galaxyages as a function of their formation epoch for different formationscenarios. Assuming a strong coordination in the formation epoch offaint early-type systems in Coma, we find that most had to be formed atleast 6 Gyr ago and over a short 1-Gyr period.
| Quantitative Morphology of Galaxies in the Core of the Coma Cluster
We present a quantitative morphological analysis of 187 galaxies in aregion covering the central 0.28 deg2 of the Coma Cluster.Structural parameters from the best-fitting Sérsicr1/n bulge plus, where appropriate, exponential disk model,are tabulated here. This sample is complete down to a magnitude of R=17mag. By examining the recent compilation by Edwards et al. of galaxyredshifts in the direction of Coma, we find that 163 of the 187 galaxiesare Coma Cluster members and that the rest are foreground and backgroundobjects. For the Coma Cluster members, we have studied differences inthe structural and kinematic properties between early- and late-typegalaxies and between the dwarf and giant galaxies. Analysis of theelliptical galaxies reveals correlations among the structural parameterssimilar to those previously found in the Virgo and Fornax Clusters.Comparing the structural properties of the Coma Cluster disk galaxieswith disk galaxies in the field, we find evidence for an environmentaldependence: the scale lengths of the disk galaxies in Coma are 30%smaller. An analysis of the kinematics shows marginal differencesbetween the velocity distributions of elliptical galaxies withSérsic index n<2 (dwarfs) and those with n>2 (giants), thedwarf galaxies having a greater (cluster) velocity dispersion. Finally,our analysis of all 421 background galaxies in the catalog of Edwards etal. reveals a nonuniform distribution in redshift with contrasts indensity of ~3, characterized by a void extending from ~10,000 to ~20,000km s-1, and two dense and extended structures centered at~20,000 and ~47,000 km s-1.
| The X-ray luminosity function of galaxies in the Coma cluster
The XMM-Newton survey of the Coma cluster of galaxies covers an area of1.86 square degrees with a mosaic of 16 pointings and has a total usefulintegration time of 400 ks. Detected X-ray sources with extent less than10'' were correlated with cataloged galaxies in the Comacluster region. The redshift information, which is abundant in thisregion of the sky, allowed us to separate cluster members frombackground and foreground galaxies. For the background sources, werecover a typical Log N-Log S in the flux range10-15-10-13 ergs s-1 cm-2 inthe 0.5-2.0 keV band. The X-ray emission from the cluster galaxiesexhibits X-ray colors typical of thermal emission. The luminosities ofComa galaxies lie in the 1039-1041 ergss-1 interval in the 0.5-2.0 keV band. The luminosity functionof Coma galaxies reveals that their X-ray activity is suppressed withrespect to the field by a factor of 5.6, indicating a lower level ofX-ray emission for a given stellar mass.
| 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.
| Stellar populations in early-type Coma cluster galaxies - I. The data
We present a homogeneous and high signal-to-noise ratio data set (meanS/N ratio of ~60 Å-1) of Lick/IDS stellar populationline indices and central velocity dispersions for a sample of 132 bright(bj<= 18.0) galaxies within the central 1°(≡1.26h-1 Mpc) of the nearby rich Coma cluster (A1656). Ourobservations include 73 per cent (100 out of 137) of the totalearly-type galaxy population (bj<= 18.0). Observationswere made with the William Herschel 4.2-m telescope and theAUTOFIB2/WYFFOS multi-object spectroscopy instrument (resolution of~2.2-Å FWHM) using 2.7-arcsec diameter fibres (≡0.94h-1 kpc). The data in this paper have well-characterizederrors, calculated in a rigorous and statistical way. Data are comparedwith previous studies and are demonstrated to be of high quality andwell calibrated on to the Lick/IDS system. Our data have median errorsof ~0.1 Å for atomic line indices, ~0.008 mag for molecular lineindices and 0.015 dex for velocity dispersions. This work provides awell-defined, high-quality baseline at z~ 0 for studies of medium- tohigh-redshift clusters. Subsequent papers will use this data set toprobe the stellar populations (which act as fossil records of galaxyformation and evolution) and the spectrophotometric relations of thebright early-type galaxies within the core of the Coma cluster.
| The Color-Magnitude Relation in Coma: Clues to the Age and Metallicity of Cluster Populations
We have observed three fields of the Coma Cluster of galaxies with anarrowband (modified Strömgren) filter system. Observed galaxiesinclude 31 in the vicinity of NGC 4889, 48 near NGC 4874, and 60 nearNGC 4839, complete to M5500=-18 in all three subclusters.Spectrophotometric classification finds all three subclusters of Coma tobe dominated by red, E-type (elliptical/S0) galaxies with a mean bluefraction, fB, of 0.10. The blue fraction increases to fainterluminosities, possible remnants of dwarf starburst population or theeffects of dynamical friction removing bright, blue galaxies from thecluster population by mergers. We find the color-magnitude (CM) relationto be well defined and linear over the range of M5500=-13 to-22. The observational error is lower than the true scatter around theCM relation, indicating that galaxies achieve their final positions inthe mass-metallicity plane by stochastic processes. After calibration tomultimetallicity models, bright elliptical galaxies are found to haveluminosity-weighted mean [Fe/H] values between -0.5 and +0.5, whereaslow-luminosity elliptical galaxies have [Fe/H] values ranging from -2 tosolar. The lack of CM relation in our continuum color suggests that asystematic age effect cancels the metallicity effects in this bandpass.This is confirmed with our age index Δ(bz-yz), which finds a weakcorrelation between luminosity and mean stellar age in ellipticalgalaxies such that the stellar populations of bright elliptical galaxiesare 2-3 Gyrs younger than low-luminosity elliptical galaxies. Withrespect to environmental effects, there is a slight decreasingmetallicity gradient with respect to distance to each subcluster center,strongest around NGC 4874. Since NGC 4874 is the dynamic and X-raycenter of the Coma Cluster, this implies that environmental effects onlow-luminosity elliptical galaxies are strongest at the cluster corecompared with outlying subgroups.
| Redshift-Distance Survey of Early-Type Galaxies. I. The ENEARc Cluster Sample
This paper presents data on the ENEARc subsample of the larger ENEARsurvey of nearby early-type galaxies. The ENEARc galaxies belong toclusters and were specifically chosen to be used for the construction ofa Dn-σ template. The ENEARc sample includes newmeasurements of spectroscopic and photometric parameters (redshift,velocity dispersion, line index Mg2, and the angular diameterdn), as well as data from the literature. New spectroscopicdata are given for 229 cluster early-type galaxies, and new photometryis presented for 348 objects. Repeat and overlap observations withexternal data sets are used to construct a final merged catalogconsisting of 640 early-type galaxies in 28 clusters. Objectivecriteria, based on catalogs of groups of galaxies derived from completeredshift surveys of the nearby universe, are used to assign galaxies toclusters. In a companion paper, these data are used to construct thetemplate Dn-σ distance relation for early-typegalaxies, which has been used to estimate galaxy distances and derivepeculiar velocities for the ENEAR all-sky sample. Based on observationsat Complejo Astronomico El Leoncito, operated under agreement betweenthe Consejo Nacional de Investigaciones Científicas de laRepública Argentina and the National Universities of La Plata,Córdoba, and San Juan; Cerro Tololo Inter-American Observatory,National Optical Astronomical Observatory, which is operated by theAssociation of Universities for Research in Astronomy, Inc., undercooperative agreement with the National Science Foundation; the EuropeanSouthern Observatory (ESO), partially under the ESO-ON agreement; theFred Lawrence Whipple Observatory; the Observatório do Pico dosDias, operated by the Laboratório Nacional de Astrofísicaand the MDM Observatory at Kitt Peak.
| 1.65 μm (H-band) surface photometry of galaxies. III. observations of 558 galaxies with the TIRGO 1.5 m telescope
We present near-infrared H-band (1.65 μm ) surface photometry of 558galaxies in the Coma Supercluster and in the Virgo cluster. This dataset, obtained with the Arcetri NICMOS3 camera ARNICA mounted on theGornergrat Infrared Telescope, is aimed at complementing, withobservations of mostly early-type objects, our NIR survey of spiralgalaxies in these regions, presented in previous papers of this series.Magnitudes at the optical radius, total magnitudes, isophotal radii andlight concentration indices are derived. We confirm the existence of apositive correlation between the near-infrared concentration index andthe galaxy H-band luminosity Based on observations taken at TIRGO(Gornergrat, Switzerland). TIRGO is operated by CAISMI-CNR, Arcetri,Firenze, Italy. Tables 1 and 2 are only available in electronic form atthe CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| 1.65 μm (H-band) surface photometry of galaxies. V. Profile decomposition of 1157 galaxies
We present near-infrared H-band (1.65 μm) surface brightness profiledecomposition for 1157 galaxies in five nearby clusters of galaxies:Coma, A1367, Virgo, A262 and Cancer, and in the bridge between Coma andA1367 in the ``Great Wall". The optically selected (mpg≤16.0) sample is representative of all Hubble types, from E to Irr+BCD,except dE and of significantly different environments, spanning fromisolated regions to rich clusters of galaxies. We model the surfacebrightness profiles with a de Vaucouleurs r1/4 law (dV), withan exponential disk law (E), or with a combination of the two (B+D).From the fitted quantities we derive the H band effective surfacebrightness (μe) and radius (re) of each component, theasymptotic magnitude HT and the light concentration indexC31. We find that: i) Less than 50% of the Ellipticalgalaxies have pure dV profiles. The majority of E to Sb galaxies is bestrepresented by a B+D profile. All Scd to BCD galaxies have pureexponential profiles. ii) The type of decomposition is a strong functionof the total H band luminosity (mass), independent of the Hubbleclassification: the fraction of pure exponential decompositionsdecreases with increasing luminosity, that of B+D increases withluminosity. Pure dV profiles are absent in the low luminosity rangeLH<1010 L\odot and become dominantabove 1011 L\odot . Based on observations taken atTIRGO, Gornergrat, Switzerland (operated by CAISMI-CNR, Arcetri,Firenze, Italy) and at the Calar Alto Observatory (operated by theMax-Planck-Institut für Astronomie (Heidelberg) jointly with theSpanish National Commission for Astronomy). Table 2 and Figs. 2, 3, 4are available in their entirety only in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| Gravo-thermal properties and formation of elliptical galaxies
We have analyzed a sample of galaxies belonging to three clusters: Coma,Abell 85, and Abell 496 (real galaxies) and a sample of simulatedelliptical galaxies formed in a hierarchical merging scheme (virtualgalaxies). We use the Sérsic law to describe their light profile.The specific entropy (Boltzmann-Gibbs definition) is then calculatedsupposing that the galaxies behave as spherical, isotropic,one-component systems. We find that, to a good approximation ( ~ 10%),both real and virtual galaxies have an almost unique specific entropy.Within this approximation the galaxies are distributed in a thin planein the space defined by the three Sérsic law parameters, which wecall the Entropic Plane. A further analysis shows that both real andvirtual galaxies are in fact located on a thin line, thereforeindicating the existence of another - and yet unknown - physicalproperty, besides the uniqueness of the specific entropy. A more carefulexamination of the virtual galaxies sample indicates a very smallincrease of their specific entropy with merging generation. In ahierarchical scenario, this implies a correlation between the specificentropy and the total mass, which is indeed seen in our data. Thescatter and tilt of the Entropic Line, defined by Lima Neto et al.(1999a), are reduced when this correlation is taken into account.Although one cannot distinguish between various generations for realgalaxies, the distribution of their specific entropy is similar to thatin the virtual sample, suggesting that hierarchical merging processescould be an important mechanism in the building of elliptical galaxies.Based on observations collected at the Canada France Hawaii Telescopeand at the European Southern Observatory, La Silla, Chile
| The specific entropy of elliptical galaxies: an explanation for profile-shape distance indicators?
Dynamical systems in equilibrium have a stationary entropy; we suggestthat elliptical galaxies, as stellar systems in a stage ofquasi-equilibrium, may have in principle a unique specific entropy. Thisuniqueness, a priori unknown, should be reflected in correlationsbetween the fundamental parameters describing the mass (light)distribution in galaxies. Following recent photometrical work onelliptical galaxies by Caon et al., Graham & Colless and Prugniel& Simien, we use the Sérsic law to describe the light profileand an analytical approximation to its three-dimensional deprojection.The specific entropy is then calculated, supposing that the galaxybehaves as a spherical, isotropic, one-component system in hydrostaticequilibrium, obeying the ideal-gas equations of state. We predict arelation between the three parameters of the Sérsic law linked tothe specific entropy, defining a surface in the parameter space, an`Entropic Plane', by analogy with the well-known Fundamental Plane. Wehave analysed elliptical galaxies in two rich clusters of galaxies (Comaand ABCG 85) and a group of galaxies (associated with NGC 4839, nearComa). We show that, for a given cluster, the galaxies follow closely arelation predicted by the constant specific entropy hypothesis with atypical dispersion (one standard deviation) of 9.5per cent around themean value of the specific entropy. Moreover, assuming that the specificentropy is also the same for galaxies of different clusters, we are ableto derive relative distances between Coma, ABGC 85, and the group of NGC4839. If the errors are due only to the determination of the specificentropy (about 10per cent), then the error in the relative distancedetermination should be less than 20per cent for rich clusters. Wesuggest that the unique specific entropy may provide a physicalexplanation for the distance indicators based on the Sérsicprofile put forward by Young & Currie and recently discussed byBinggeli & Jerjen.
| E and S0 galaxies in the central part of the Coma cluster: ages, metal abundances and dark matter
Mean ages and metal abundances are estimated for the stellar populationsin a sample of 115 E and S0 galaxies in the central 64 arcmin × 70arcmin of the Coma cluster. The estimates are based on the absorptionline indices Mg2, and HβG, and themass-to-light ratios (M/L). Single stellar population models fromVazdekis et al. were used to transform from the measured line indicesand M/L ratios to mean ages and mean metal abundances ([Mg/H] and[Fe/H]). The non-solar abundance ratios [Mg/Fe] were taken into accountby assuming that for a given age and iron abundance, a [Mg/Fe] differentfrom solar will affect the Mg2 index but not the M/L ratio orthe and HβG indices. The derived ages andabundances are the luminosity-weighted mean values for the stellarpopulations in the galaxies.By comparing the mean ages derived from theMg2-HβG diagram with those derived from theMg2-M/L diagram, we estimate the variations of the fractionof dark matter. Alternatively, the difference between the two estimatesof the mean age may be caused by variations in the initial mass functionor any non-homology of the galaxies.The distributions of the derived mean ages and abundances show thatthere are real variations in both the mean ages and the abundances. Wefind an intrinsic rms scatter of [Mg/H], [Fe/H] and [Mg/Fe] of 0.2 dex,and an intrinsic rms scatter of the derived ages of 0.17 dex. Themagnesium abundances [Mg/H] and the abundance ratios [Mg/Fe] are bothstrongly correlated with the central velocity dispersions of thegalaxies, while the iron abundances [Fe/H] are uncorrelated with thevelocity dispersions. Further, [Mg/H] and [Fe/H] are stronglyanticorrelated with the mean ages of the galaxies. This is not the casefor [Mg/Fe].We have tested whether the slopes of the scaling relations between theglobal parameters for the galaxies (the Mg2-σ relation,the -σ relation, the HβG-σrelation and the Fundamental Plane) are consistent with the relationbetween the ages, the abundances and the velocity dispersions. We findthat all the slopes, except the slope of the Fundamental Plane, can beexplained in a consistent way as resulting from a combination betweenvariations of the mean ages and the mean abundances as functions of thevelocity dispersions. The slope of the Fundamental Plane is `steeper'than predicted from the variations in the ages and abundances.Because of the correlation between the mean ages and the meanabundances, substantial variations in the ages and the abundances arepossible while maintaining a low scatter of all the scaling relations.When this correlation is taken into account, the observed scatter of thescaling relations is consistent with the rms scatter in the derived agesand abundances at a given velocity dispersion.
| The Universality of the Fundamental Plane of E and S0 Galaxies: Spectroscopic Data
We present central velocity dispersion measurements for 325 early-typegalaxies in eight clusters and groups of galaxies, including newobservations for 212 galaxies. The clusters and groups are the A262,A1367, Coma (A1656), A2634, Cancer, and Pegasus Clusters and the NGC 383and NGC 507 Groups. The new measurements were derived frommedium-dispersion spectra that cover 600 Å centered on the Mg I btriplet at lambda ~ 5175 Å. Velocity dispersions were measuredusing the Tonry & Davis cross-correlation method, with a typicalaccuracy of 6%. A detailed comparison with other data sources is made.
| The Universality of the Fundamental Plane of E and S0 Galaxies: Sample Definition and I-Band Photometric Data
As part of a project to compare the fundamental plane and Tully-Fisherdistance scales, we present here I-band CCD photometry for 636early-type galaxies in eight clusters and groups of galaxies. These arethe A262, A1367, Coma (A1656), A2634, Cancer and Pegasus Clusters, andthe NGC 383 and NGC 507 Groups. Sample selection, cluster properties,and cluster membership assignment criteria are discussed. We presentphotometric parameters that are used in the fundamental plane relation,the effective radius r_e, and the effective surface brightness mu_e, asderived from a r^1/4 fit to the observed radial photometric profile ofeach galaxy. A comparison with similar data found in the literature forthe Coma Cluster shows that large systematic uncertainties can beintroduced in the measurement of r_e and mu_e by the particular methodused to derive those parameters. However, the particular combination ofthese two parameters that enters in the fundamental plane relation is aquantity that can be measured with high accuracy.
| Total magnitude, radius, colour indices, colour gradients and photometric type of galaxies
We present a catalogue of aperture photometry of galaxies, in UBVRI,assembled from three different origins: (i) an update of the catalogueof Buta et al. (1995) (ii) published photometric profiles and (iii)aperture photometry performed on CCD images. We explored different setsof growth curves to fit these data: (i) The Sersic law, (ii) The net ofgrowth curves used for the preparation of the RC3 and (iii) A linearinterpolation between the de Vaucouleurs (r(1/4) ) and exponential laws.Finally we adopted the latter solution. Fitting these growth curves, wederive (1) the total magnitude, (2) the effective radius, (3) the colourindices and (4) gradients and (5) the photometric type of 5169 galaxies.The photometric type is defined to statistically match the revisedmorphologic type and parametrizes the shape of the growth curve. It iscoded from -9, for very concentrated galaxies, to +10, for diffusegalaxies. Based in part on observations collected at the Haute-ProvenceObservatory.
| The distribution of the rotation axes of the disk galaxies in the Coma cluster: statistical samples.
Not Available
| Abell 2199 and Abell 2634 revisited
Previous D_n-sigma work found surprisingly large negative peculiarvelocities for Abell 2199 and Abell 2634. In order to assess theseresults independently we have made new spectroscopic and photometricobservations. We report 141 new redshift, velocity dispersion (sigma)and Mg_2 index measurements, and photometry for 79 early-type galaxies.Special attention has been paid to linking the new sigma measurements onto a standard system that minimizes systematic errors. While the Abell2199 sigma measurements are in good agreement with our previouslyreported FLEX values, for Abell 2634 galaxies the new sigmas aresystematically lower. The FLEX measurements for some Abell 2634 galaxiesappear to have been erroneous due to a smearing problem with the CCDdetector. The new photometric data are in excellent agreement withpreviously reported values. We also present a new compilation of datafor 72 early-type Coma cluster galaxies. Assuming that the Coma clusterlies at rest with respect to the cosmic microwave background frame, wederive peculiar velocities of -160+/-380 and -670+/-490 km s^-1 forAbell 2199 and Abell 2634 respectively. We estimate that the likelysystematic errors on these measurements are less than 200kms^-1. Thederived peculiar velocities are considerably less than previousestimates and are not significantly different from zero.
| The Relative Distance Between the Clusters of Galaxies A2634 and Coma
The Tully-Fisher (TF) and Fundamental Plane (FP) relations are used toobtain two independent estimates of the relative distance between theclusters A2634 and Coma. Previously published studies of A2634 showed alarge discrepancy between the distance estimates obtained with the TFand the \dns\ relations, questioning the reliability ofredshift-independent distances obtained using these relations. Becauseof the importance of this issue, we have obtained new distance estimatesfor A2634, based on much larger samples than previously used, andselected according to rigorous membership criteria. New I band CCDphotometry for 175 galaxies, new 21 cm observations of 11 galaxies, andnew velocity dispersion measurements for 62 galaxies are used togetherwith previously published data in building these samples. As part of alarger project to compare the TF and FP distance-scales, we haveobtained a new FP template using for the first time I band photometry.The template is derived using a sample of 109 E and S0 galaxies that aremembers of the Coma cluster. Its parameters are in very good agreementwith recent determinations of the FP obtained at shorter wavelengths.The uncertainty with which the FP can provide peculiar velocityestimates for single galaxies is =~ 0.43 mag in the distance modulus, or20% of the distance. This uncertainty is slightly larger than thetypical uncertainty that characterizes TF estimates. However thisdisadvantage is partly compensated by the fact that the sampleincompleteness bias has a less severe effect on FP cluster distanceestimates than it has on the corresponding TF distance estimates. Also,cluster membership is more readily established for early-type objectsthan for spirals. After the appropriate corrections for sampleincompleteness have been taken into account, we find the TF and FPdistance estimates to be in good agreement, both indicating that A2634has a negligibly small peculiar velocity with respect to the CosmicMicrowave Background reference frame. Because of the high accuracy withwhich the two distance estimates have been obtained, their agreementstrongly supports the universality of the TF and FP relations, andtherefore their reliability for the estimate of redshift-independentdistances.
| Morphological classification and structural parameters for early-type galaxies in the Coma cluster.
We present the results of an isophotal shape analysis of three samplesof galaxies in the Coma cluster. Quantitative morphology, together withstructural and photometric parameters, is given for each galaxy. Specialemphasis has been placed on the detailed classification of early-typegalaxies. The three samples are: i) a sample of 97 early-type galaxiesbrighter than m_B_=17.00 falling within one degree from the center ofthe Coma cluster; these galaxies were observed with CCD cameras, mostlyin good to excellent resolution conditions; ii) a magnitude completesample of 107 galaxies of all morphological types down to m_B_=17.00falling in a circular region of 50arcmin diameter, slightly offcenteredto the North-West of the cluster center; the images for this and thenext sample come from digitized photographic plates; iii) a completecomparison sample of 26 galaxies of all morphological types down tom_R_=16.05 (or m_B_=~17.5), also in a region of 50arcmin diameter, butcentered 2.6degrees West of the cluster center. The reliability of ourmorphological classifications and structural parameters of galaxies,down to the adopted magnitude limits, is assessed by comparing theresults on those galaxies for which we had images taken with differentinstrumentation and/or seeing conditions, and by comparing our resultswith similar data from other observers.
| Spectroscopy for E and S0 galaxies in nine clusters
Central velocity dispersions, Mg_2 line indices and radial velocitiesfor 220 E and S0 galaxies are derived on the basis of intermediateresolution spectroscopy. Galaxies in the following clusters have beenobserved: Abell 194, Abell 539, Abell 3381, Abell 3574, S639, S753,Doradus, HydraI (Abell 1060) and Grm 15. For 151 of the galaxies, thevelocity dispersion has not previously been measured. 134 of the Mg_2determinations are for galaxies with no previous measurement. Thespectra cover either 500 or 1000A, centred on the magnesium triplet at5177A. The observations were obtained with the Boller & Chivensspectrograph at the ESO 1.5-m telescope and with the OPTOPUS, amulti-object fibre-fed B&C spectrograph, at the ESO 3.6-m telescope.The data are part of our ongoing study of the large-scale motions in theUniverse and the physical background for the Fundamental Plane. TheFourier fitting method was used to derive the velocity dispersions andradial velocities. The velocity dispersions have been corrected for theeffect of the size of the aperture. The correction was established onthe basis of velocity dispersion profiles available in the literature. Acomparison with results from Davies et al. shows that the derivedcentral velocity dispersions have an rms error of 0.036 in logsigma.There is no offset relative to the velocity dispersions from Davies etal. The offset relative to data from Lucey & Carter is-0.017+/-0.011 in logsigma, with our velocity dispersions being thesmallest. The velocity dispersions derived from the B&C and theOPTOPUS observations, as well as the velocity dispersions published byDavies et al., Dressler, Lucey & Carter and Lucey et al., can bebrought on a system consistent within 3 per cent. The Mg_2 line indiceshave been corrected for the size of the apertures, transformed to theLick system, and corrected for the effect of the velocity dispersion.From comparison with data from Davies et al. and from Faber, we findthat the rms error of Mg_2 is 0.013. Comparisons of the radialvelocities with data from the literature show that our determinationsare accurate to within ~=35 km s^-1. The accuracies reached for theseobservations are adequate for the study of the large-scale motions inthe Universe and for investigations of the Fundamental Plane.
| Multicolour CCD surface photometry for E and S0 galaxies in 10 clusters
CCD surface photometry for 232 E and S0 galaxies is presented. Thegalaxies are observed in Gunn r and Johnson B, or Gunn r and g. For 48of the galaxies surface photometry in Johnson U is also presented.Aperture magnitudes in Gunn nu are derived for half of the galaxies.Galaxies in the following clusters have been observed: Abell 194, Abell539, Abell 3381, Abell 3574, Abell S639, Abell S753, HydraI (Abell1060), DC2345-28, Doradus and Grm15. The data are part of our ongoingstudy of the large-scale motions in the Universe and the physicalbackground for the fundamental plane. We use a full model fittingtechnique for analysing the CCD images. This gives radial profiles oflocal surface brightness, colour, ellipticity and position angle. Theresiduals relative to the elliptical isophotes are describedquantitatively by Fourier expansions. Effective radius, mean surfacebrightness and total magnitude are derived by fitting a de Vaucouleursr^¼ growth curve. We have derived a characteristic radius r_nsimilar to the diameter D_n introduced by Dressler et al. The derivationof the effective parameters and of r_n takes the seeing into account. Weconfirm the results by Saglia et al. that the effects of the seeing canbe substantial. Seeing-corrected values of the effective parameters andr_n are also presented for 147 E and S0 galaxies in the Coma cluster.Colours, colour gradients and geometrical parameters are derived. Thephotometry is internally consistent within 0.016 mag. Comparison withthe photoelectric aperture photometry from Burstein et al. shows a meanoffset of 0.010 mag with an rms scatter of 0.034 mag. The globalphotometric parameters are compared with data from Faber et al., Luceyet al. and Lucey & Carter. These comparisons imply that the typicalrms errors are as follows - log r_n:+/-0.015 log r_e:+/-0.045m_T:+/-0.09 mag; _e:+/-0.16 mag. The rms error on thecombination log r_e-0.35_e which enters the fundamental planeis +/-0.020. Also, comparisons with data from Saglia et al. arepresented. The accuracy of the absolute photometry, as well as thederived parameters, makes the data suitable for our investigations ofthe fundamental plane and of the large-scale motions in the Universe.
| Automated surface photometry for the Coma Cluster galaxies: The catalog
A homogeneous photometry catalog is presented for 450 galaxies withB25.5 less than or equal to 16 mag located in the 9.8 deg x9.8 deg region centered on the Coma Cluster. The catalog is based onphotographic photometry using an automated surface photometry softwarefor data reduction applied to B-band Schmidt plates. The catalogprovides accurate positions, isophotal and total magnitudes, major andminor axes, and a few other photometric parameters including rudimentarymorphology (early of late type).
| The Infrared Diameter-Velocity Dispersion Relation for Elliptical Galaxies
Using single channel K -band photometric data from the literature, aprovisional infrared diameter-velocity dispersion relation forelliptical galaxies in the Coma and Virgo clusters is derived. The Comacluster relation has ~1.5 times lower scatter at K band than in B or V.Excluding 4 outliers, the rms scatter at K for 24 galaxies in Coma isonly 4.8% in distance, close to the limit implied by the observationalerrors. Distance estimates based on the IR D - σ, relation will bemore accurate than those derived from optical data. The improvement inthe infrared is attributed to a decrease in sensitivity to stellarpopulation parameters (age, metallicity, and slope of the IMF), as wellas lower internal extinction from dust compared to the optical. That theD - σ, relation has a larger scatter in the optical indicates thatthere are detectable, but small, stellar population or dust contentdifferences among the Coma ellipticals. Since the D -σ relationsare based on the fundamental plane, this result promises that thefundamental plane is thinner in the infrared than it is in the optical.Infrared photometric data available for Virgo are limited to just 13objects; the spread in distance due to the depth of the clusterprecludes any significant improvement over B and V. A relativeComa-Virgo distance of 5.56 is derived from the K band data, inagreement with estimates in other colors and using other techniques,indicating that there is no significant age difference between Virgo andComa ellipticals.
| The far-infrared-radio relation in cluster spiral galaxies
We present a study of the far-infrared (FIR) and radio emission in asample of group and cluster spiral galaxies. Galaxies are separated intorich and poor cluster samples based the value of the galaxy-galaxycorrelation coeffiient (Andersen & Owen 1994) of their parentcluster. Galaxies in the rich clusters have lower-FIR-radio ratios thana radio selected sample of field galaxies, while galaxies in poorclusters do not. We find that the degree of radio enhancement withrespect to FIR emission is consistent with a model where the radioemitting interstellar medium (ISM) is compressed by the ram pressure asthe galaxy moves through the intracluster medium. We suggest thatgalaxy-galaxy tidal interactions are important in the poorer clusters,but in general of much less importance in richer clusters.
| Integrated photoelectric magnitudes and color indices of bright galaxies in the Johnson UBV system
The photoelectric total magnitudes and color indices published in theThird Reference Catalogue of Bright Galaxies (RC3) are based on ananalysis of approximately equals 26,000 B, 25,000 B-V, and 17,000 U-Bmultiaperture measurements available up to mid 1987 from nearly 350sources. This paper provides the full details of the analysis andestimates of internal and external errors in the parameters. Thederivation of the parameters is based on techniques described by theVaucouleurs & Corwin (1977) whereby photoelectric multiaperture dataare fitted by mean Hubble-type-dependent curves which describe theintegral of the B-band flux and the typical B-V and U-B integrated colorgradients. A sophisticated analysis of the residuals of thesemeasurements from the curves was made to allow for the random andsystematic errors that effect such data. The result is a homogeneous setof total magnitudes BTA total colors(B-V)T and (U-B)T, and effective colors(B-V)e and (U-B)e for more than 3000 brightgalaxies in RC3.
| A catalogue of velocities in the central regions of the Coma cluster.
We present a catalogue of velocities for 305 objects in a field of48x25arcmin^2^, centered between the galaxies NGC 4889 and NGC 4874, aswell as in a field of 10x10arcmin^2^ centered on NGC 4839, in the Comacluster. Of these velocities, 225 are new measurements, 78 of which forobjects with at least one velocity already available in the literaturebefore our survey. Our sample is 95% complete in redshift up to amagnitude b_26.5_=18.0.
| The nature of E and S0 galaxies: A study of magnitude-limited sample of galaxies in the Coma Cluster
Differences and similarities of E and S0 galaxies have been investigatedon basis of new CCD surface photometry in Gunn r for 171 galaxies withinthe central square degree of the Coma Cluster; 146 of the galaxies areclassified as E or S0. The galaxies form a magnitude-limited sample withGunn r less than or equal to 15.3 mag. Together with the sample of Virgogalaxies compiled by Caon et al. (1993), this sample is one of the firstvolume-limited samples. The isophotal shapes of the galaxies have beenstudied in terms of ellipticity, c4 and c6. Thesample is deficit of apparently round S0 galaxies. The distribution ofthe apparent ellipticities for the S0 galaxies cannot be fittedsatisfactorily with any simple distribution of the intrinsicellipticities. This suggests that face-on S0 galaxies have beenclassified as ellipticals. It is shown that theellipticity-c4 diagram can be used for determination ofrelative disk luminosities, LD/Ltot. Thedistribution of LD/Ltot for galaxies fainter thanMB(sub T) = -22 mag is very broad (H0 = 50 km/(sMpc) is used). The distribution is best fitted by a model where 10% ofthe galaxies are diskless and 90% of the galaxies are drawn from adistribution which is uniform from zero to one. This model also predictsdistributions of apparent ellipticities, c4, and inclinationswhich are in agreement with the data. E galaxies brighter thanMB(sub T) = -22 mag do not show any evidence of disks and mayform another class. The sample contains no S0 galaxies brighter thanMB(sub T) = -22 mag. Our analysis implies that the E and S0galaxies fainter than MB(sub T) = -22 mag form one class ofgalaxies with a continuous change in LD/Ltot.Face-on members of this class are mostly classified as E galaxies whilemore edge-on members are classified as S0 galaxies. Further, it is foundthat only 12% of all the galaxies in the sample are truly disklesssystems. The diskless systems contribute approximately 30% to the totalluminosity of the sample, most of this originates from the six brightestgalaxies.
| The Fundamental Plane and the Surface Brightness Test for the Expansion of the Universe
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1993ApJ...418..617K&db_key=AST
| Star formation in early-type galaxies in the Coma cluster
The Hydra bench spectrograph on the 4 m telescope at Kitt Peak is usedto obtain multifiber spectra of 125 early-type galaxies in the Comacluster of galaxies. About one-third of all galaxies in a field locatedabout 40 arcmin SW of the center of the cluster exhibits enhanced Balmerabsorption lines or emission lines, indicative of recent star formationor nuclear activity. In contrast, very few such galaxies are found inthe central field of the cluster. It is argued that the anomalousspectral features cannot arise from morphological misidentifications. Itis suggested that an environmental process similar to that frequentlyfound in clusters at moderate redshift is occurring at the present epochin the outskirts of the Coma cluster.
| The intrinsic shape of early-type galaxies and the scatter around the fundamental plane
The results of an analysis of the isophotal shapes of 61 galaxies of theComa cluster are presented. A modified classification based on isophotalshape parameters is given and photometric quantities are derived usingdifferent fitting techniques. If elliptical galaxies with values of theisophotal shape parameter a4/a less than or equal to 0 onlyare considered, their scatter around the Fundamental Plane (FP) isreduced to 10% of the distance for the single object. Galaxiespossessing a disk component appear to be shifted from this relation;these deviations are correlated with ellipticity. This suggests thatprojection effects and the (unresolved) rotation of the disk componentsare causing positive shifts from the Fundamental Plane. The effect isalso present when the Dn - sigma relation is considered. Theobserved trend with ellipticity is evidence against a prolate geometryfor elliptical galaxies. Distances of a distant cluster estimated usingthe FP equation can be overestimated by up to 14% if the sample ofgalaxies considered is heavily contaminated by disky galaxies. However,the isophotal shape analysis can be applied to galaxies as distant as15,000 km/s, providing a tool to eliminate this potential problem.
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