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The X-ray emission properties and the dichotomy in the central stellar cusp shapes of early-type galaxies
The Hubble Space Telescope has revealed a dichotomy in the centralsurface brightness profiles of early-type galaxies, which havesubsequently been grouped into two families: core, boxy, anisotropicsystems; and cuspy (`power-law'), discy, rotating ones. Here weinvestigate whether a dichotomy is also present in the X-ray propertiesof the two families. We consider both their total soft emission(LSX,tot), which is a measure of the galactic hot gascontent, and their nuclear hard emission (LHX,nuc), mostlycoming from Chandra observations, which is a measure of the nuclearactivity. At any optical luminosity, the highest LSX,totvalues are reached by core galaxies; this is explained by their beingthe central dominant galaxies of groups, subclusters or clusters, inmany of the logLSX,tot (ergs-1) >~ 41.5 cases.The highest LHX,nuc values, similar to those of classicalactive galactic nuclei (AGNs), in this sample are hosted only by core orintermediate galaxies; at low luminosity AGN levels, LHX,nucis independent of the central stellar profile shape. The presence ofoptical nuclei (also found by HST) is unrelated to the level ofLHX,nuc, even though the highest LHX,nuc are allassociated with optical nuclei. The implications of these findings forgalaxy evolution and accretion modalities at the present epoch arediscussed.
| Study of the Structure of the Coma Cluster Based on a Hierarchical Force Clustering Method
Six subclusters in the Coma cluster have been selected on the basis of ahierarchical clustering method that takes the gravitational interactionamong galaxies into account. Of these, 3 central subclusters around thegalaxies NGC 4889, NGC 4874, and NGC 4839 have been singled out. We haveused the objective statistical criterion applied by Vennik and Anosovain studies of close groups of galaxies to evaluate each member includedin a subcluster with a high probability. Galaxies with a significantdeficit of hydrogen HI, including objects from the Bravo-Alfaro list,have been identified with members of the subclusters, with the greatestnumber of them in the subclusters around NGC 4874 and NGC 4839. Aquantitative estimate of the hydrogen deficit using the HI index in theRCG3 catalog reveals a statistically significant excess value for thosegalaxies that are members of the subclusters compared to galaxies with ahydrogen deficit in the overall Coma cluster field. A substantial numberof the spiral galaxies with a hydrogen deficit in the subclusters turnedout to be radio galaxies as well.
| 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.
| 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.
| The impact of high pressure cluster environment on the X-ray luminosity of Coma early-type galaxies
We present an observational study of the LX vs. LBσ2 relation for early-type galaxies in the Coma clusterbased on the XMM-Newton survey data. Compared to a similar relation fora sample dominated by field early-type galaxies, the Coma clustergalaxies show a flatter slope. Our calculations show that adiabaticcompression produces a flattening in the LX vs.LBσ2 relation that is in remarkableagreement with the observed effect. Our scenario is further supported bythe observed compactness of the X-ray emission of Coma galaxies.
| Metallicity distributions of globular cluster systems in galaxies
We collected a sample of 100 galaxies for which different observers havedetermined colour indices of globular cluster candidates. The sampleincludes representatives of galaxies of various morphological types anddifferent luminosities. Colour indices (in most cases (V-I), but also(B-I) and (C-T_1)) were transformed into metallicities [Fe/H] accordingto a relation by Kissler-Patig (1998). These data were analysed with theKMM software in order to estimate similarity of the distribution withuni- or bimodal Gaussian distribution. We found that 45 of 100 systemshave bimodal metallicity distributions. Mean metallicity of themetal-poor component for these galaxies is < [Fe/H]> = -1.40 +/-0.02, of the metal-rich component < [Fe/H]> = -0.69 +/- 0.03.Dispersions of the distributions are 0.15 and 0.18, respectively.Distribution of unimodal metallicities is rather wide. These data willbe analysed in a subsequent paper in order to find correlations withparameters of galaxies and galactic environment.
| 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
| H0 measurement from VLT deep I-band surface brightness fluctuations in NGC 564 and NGC 7619
We have measured the Hubble constant H0 in NGC 564 at cz ~5800 km s-1 and in NGC 7619 at cz ~ 3700 km s-1with deep I-band Surface Brightness Fluctuation distance measurements atthe ESO Very Large Telescope (VLT). We obtain H0 = 70 +/- 7+/- 6 km s-1/Mpc for NGC 564 and H0 = 68 +/- 6 +/-6 for NGC 7619. The actual SBF sample used for the measurement ofH0 in the Hubble Space Telescope Key Project on theExtragalactic Distance Scale (Freedman et al. 2001) amounts to sixgalaxies. When we combine the measurements from this work with ourprevious VLT I-band SBF distance measurement in IC 4296 (Mei et al.2000), we obtain: H0 = 68 +/- 5 +/- 6 km s-1/Mpc.When we add the Freedman et al. (2001) SBF sample, we obtainH0 = 71 +/- 4 +/- 6 km s-1/Mpc.Based on observations performed at the European Southern Observatory,Paranal, Chile ESO program No 66.A-0361.
| 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.
| 1.65-μm (H -band) surface photometry of galaxies - VIII. The near-IR κ space at z =0
We present the distribution of a statistical sample of nearby galaxiesin the κ -space (κ 1 ~logM , κ 2~logI e 3 M /L , κ 3 ~logM /L ).Our study is based on near-IR (H -band: λ =1.65μm)observations, for the first time comprising early- and late-typesystems. Our data confirm that the mean effective dynamicalmass-to-light ratio M /L of the E+S0+S0a galaxies increases withincreasing effective dynamical mass M , as expected from the existenceof the Fundamental Plane relation. Conversely, spiral and Im/BCDgalaxies show a broad distribution in M /L with no detected trend of M/L with M , the former galaxies having M /L values about twice largerthan the latter, on average. For all the late-type galaxies, the M /Lincreases with decreasing effective surface intensity I e ,consistent with the existence of the Tully-Fisher relation. Theseresults are discussed on the basis of the assumptions behind theconstruction of the κ -space and their limitations. Our study iscomplementary to a previous investigation in the optical (B -band:λ =0.44μm) and allows us to study wavelength dependences ofthe galaxy distribution in the κ -space. As a first result, wefind that the galaxy distribution in the κ 1 -κ2 plane reproduces the transition from bulgeless tobulge-dominated systems in galaxies of increasing dynamical mass.Conversely, it appears that the M /L of late-types is higher (lower)than that of early-types with the same M in the near-IR (optical). Theorigins of this behaviour are discussed in terms of dust attenuation andstar formation history.
| New clues to the evolution of dwarf early-type galaxies
Surface photometry of 18 Virgo cluster dwarf elliptical (dE) and dwarflenticular (dS0) galaxies, made by Gavazzi et al. in the H band(1.65μm) and in the B band (0.44μm), shows that the ratio of theeffective radii of these stellar systems in the B and H bands, r eB /r eH , ranges between 0.7 and 2.2. In particular,dwarf ellipticals and lenticulars with a red total colour index B -H(i.e. with 3.2
| Globular Cluster Systems in Four Brightest Cluster Galaxies: A262, A3560, A3565, and A3742
We have used deep I-band (F814W) images from the Hubble Space Telescopearchive to study the globular cluster systems around the brightestcluster galaxies (BCGs) in A262, A3560, A3565, and A3742. Three of theseBCGs have inner dust lanes and peculiar structural features thatindicate past histories of low-level interaction and accretion. The deepI-band WFPC2 images have photometric limits that, for all four galaxies,reach near or just beyond the globular cluster luminosity function(GCLF) turnover point. Their specific frequencies are 8.24+/-1.65,4.66+/-0.93, 2.58+/-0.52, and 2.62+/-0.52, respectively, all within afactor of 2 of the normal range for giant elliptical galaxies. We obtainnew estimates of the GCLF turnover magnitudes, which are shown to beconsistent with an adopted Hubble constant of H0~=70 kms-1 Mpc-1 on the ``Hubble diagram'' of GCLFturnover apparent magnitude versus redshift, on a distance scale wherethe fundamental GCLF calibrator E galaxies (M87 and others) in Virgo areat d=16 Mpc. Based on observations with the NASA/ESA Hubble SpaceTelescope, obtained at the Space Telescope Science Institute, which isoperated by the Association of Universities for Research in Astronomy,Inc., under NASA contract NAS 5-26555. These observations are associatedwith proposal ID 5910.
| Redshift-Distance Survey of Early-Type Galaxies. I. The ENEARc Cluster Sample
This paper presents data on the ENEARc subsample of the larger ENEARsurvey of nearby early-type galaxies. The ENEARc galaxies belong toclusters and were specifically chosen to be used for the construction ofa Dn-σ template. The ENEARc sample includes newmeasurements of spectroscopic and photometric parameters (redshift,velocity dispersion, line index Mg2, and the angular diameterdn), as well as data from the literature. New spectroscopicdata are given for 229 cluster early-type galaxies, and new photometryis presented for 348 objects. Repeat and overlap observations withexternal data sets are used to construct a final merged catalogconsisting of 640 early-type galaxies in 28 clusters. Objectivecriteria, based on catalogs of groups of galaxies derived from completeredshift surveys of the nearby universe, are used to assign galaxies toclusters. In a companion paper, these data are used to construct thetemplate Dn-σ distance relation for early-typegalaxies, which has been used to estimate galaxy distances and derivepeculiar velocities for the ENEAR all-sky sample. Based on observationsat Complejo Astronomico El Leoncito, operated under agreement betweenthe Consejo Nacional de Investigaciones Científicas de laRepública Argentina and the National Universities of La Plata,Córdoba, and San Juan; Cerro Tololo Inter-American Observatory,National Optical Astronomical Observatory, which is operated by theAssociation of Universities for Research in Astronomy, Inc., undercooperative agreement with the National Science Foundation; the EuropeanSouthern Observatory (ESO), partially under the ESO-ON agreement; theFred Lawrence Whipple Observatory; the Observatório do Pico dosDias, operated by the Laboratório Nacional de Astrofísicaand the MDM Observatory at Kitt Peak.
| The UZC-SSRS2 Group Catalog
We apply a friends-of-friends algorithm to the combined Updated ZwickyCatalog and Southern Sky Redshift Survey to construct a catalog of 1168groups of galaxies; 411 of these groups have five or more members withinthe redshift survey. The group catalog covers 4.69 sr, and all groupsexceed the number density contrast threshold, δρ/ρ=80. Wedemonstrate that the groups catalog is homogeneous across the twounderlying redshift surveys; the catalog of groups and their membersthus provides a basis for other statistical studies of the large-scaledistribution of groups and their physical properties. The medianphysical properties of the groups are similar to those for groupsderived from independent surveys, including the ESO Key Programme andthe Las Campanas Redshift Survey. We include tables of groups and theirmembers.
| The Colors of Globular Clusters
A compilation has been made of available data on the ratio of the numberof metal-rich ([Fe/H]>-1.0) to metal-poor ([Fe/H]<-1.0) clustersin various globular cluster systems. Among early-type galaxies of typesE, E/S0, and S0, the ratio of blue to red globular clusters is found tovary by almost 2 orders of magnitude. The data suggest that cD galaxieshave the widest range of evolutionary histories. The fraction ofmetal-rich red clusters is largest among early-type galaxies and appearsto decrease toward later Hubble types.
| Galaxy associations within the Coma cluster.
The mean redshift of the core of the Coma cluster -- cz=6953 kms-1 and its dispersion σ=949 km s-1 areobtained by means of the analysis of the substructures of this clusterby using the S-tree method. The existence of three subgroups of galaxiesis revealed, one of them is associated with the cD galaxy NGC 4874, theother -- with NGC 4889. It is argued that these subgroups are galaxyassociations, i.e. galactic dynamical entities moving within the maincluster. Thus, we conclude that the non-stationarity of the dynamicalprocesses ongoing in the Coma core is due to the merging of small-scalegalaxy associations, rather than of two equal sized clusters. We providethe lists of the galaxies of the associations, the observational studyof which can be of particular interest.
| On the dependence of spectroscopic indices of early-type galaxies on age, metallicity and velocity dispersion
We investigate the Mg-σ and -σ relations in asample of 72 early-type galaxies drawn mostly from cluster and groupenvironments using a homogeneous data set which is well calibrated on tothe Lick/IDS system. The small intrinsic scatter in Mg at a givenσ gives upper limits on the spread in age and metallicity of 49and 32 per cent respectively, if the spread is attributed to onequantity only, and if the variations in age and metallicity areuncorrelated. The age/metallicity distribution as inferred from theHβ versus diagnostic diagram reinforces this conclusion,as we find mostly galaxies with large luminosity-weighted ages spanninga range in metallicity. Using Monte Carlo simulations, we show that thegalaxy distribution in the Hβ versus plane cannot bereproduced by a model in which galaxy age is the only parameter drivingthe index-σ relation. In our sample we do not find significantevidence for an anticorrelation of ages and metallicities which wouldkeep the index-σ relations tight while hiding a large spread inage and metallicity. As a result of correlated errors in theage-metallicity plane, a mild age-metallicity anticorrelation cannot becompletely ruled out by the current data. Correcting the line-strengthindices for non-solar abundance ratios, following the recent paper byTrager et al., leads to higher mean metallicity and slightly younger ageestimates while preserving the metallicity sequence. The [Mg/Fe] ratiois mildly correlated with the central velocity dispersion, and rangesfrom [Mg/Fe]=0.05 to 0.3 for galaxies withσ>100kms-1. Under the assumption that there is noage gradient along the index-σ relations, theabundance-ratio-corrected Mg-σ, Fe-σ and Hβ-σrelations give consistent estimates ofΔ[M/H]/Δlogσ~=0.9+/-0.1. The slope of theHβ-σ relation limits a potential age trend as a function ofσ to 2-3Gyr along the sequence.
| A Photometric and Spectroscopic Study of Dwarf and Giant Galaxies in the Coma Cluster. II. Spectroscopic Observations
This is the second paper in a series studying the photometric andspectroscopic properties of galaxies of different luminosities in theComa Cluster. We present the sample selection, spectroscopicobservations, and completeness functions. To study the spectralproperties of galaxies as a function of their local environment, twofields were selected for spectroscopic observations to cover both thecore (Coma 1) and outskirts (i.e., southwest of the core and centered onNGC 4839; Coma 3) of the cluster. To maximize the efficiency ofspectroscopic observations, two subsamples were defined, consisting of``bright'' and ``faint'' galaxies, both drawn from magnitude-limitedparent samples. Medium-resolution spectroscopy (6-9 Å) was thencarried out for a total of 490 galaxies in both fields (302 in Coma 1and 188 in Coma 3), using the WYFFOS multifiber spectrograph on theWilliam Herschel Telescope. The galaxies cover a range of 122. The completeness functions for our sampleare calculated. These show that the bright sample is 65% complete atR<17 mag, becoming increasingly incomplete toward fainter magnitudes,while the faint sample follows a monotonically decreasing completenessfunction at R>19 mag. Based on observations made with the WilliamHerschel Telescope, operated on the island of La Palma by the IsaacNewton Group in the Spanish Observatorio del Roque de los Muchachos ofthe Instituto de Astrofisica de Canarias.
| Infrared Surface Brightness Fluctuations of the Coma Elliptical Galaxy NGC 4874 and the Value of the Hubble Constant
We have used the Keck I telescope to measure K-band surface brightnessfluctuations (SBFs) of NGC 4874, the dominant elliptical galaxy in theComa Cluster. We use deep Hubble Space Telescope (HST) WFPC2 opticalimaging to account for the contamination due to faint globular clustersand improved analysis techniques to derive measurements of the SBFapparent magnitude. Using a new SBF calibration that accounts for thedependence of K-band SBFs on the integrated color of the stellarpopulation, we measure a distance modulus of 34.99+/-0.21 mag (100+/-10Mpc) for the Coma Cluster. The resulting value of the Hubble constant is71+/-8 km s-1 Mpc-1, not including any systematicerror in the HST Cepheid distance scale. Based in part on observationsobtained at the W. M. Keck Observatory, which is operated as ascientific partnership among the California Institute of Technology, theUniversity of California, and the National Aeronautics and SpaceAdministration.
| Final Results from the Hubble Space Telescope Key Project to Measure the Hubble Constant
We present here the final results of the Hubble Space Telescope (HST)Key Project to measure the Hubble constant. We summarize our method, theresults, and the uncertainties, tabulate our revised distances, and givethe implications of these results for cosmology. Our results are basedon a Cepheid calibration of several secondary distance methods appliedover the range of about 60-400 Mpc. The analysis presented here benefitsfrom a number of recent improvements and refinements, including (1) alarger LMC Cepheid sample to define the fiducial period-luminosity (PL)relations, (2) a more recent HST Wide Field and Planetary Camera 2(WFPC2) photometric calibration, (3) a correction for Cepheidmetallicity, and (4) a correction for incompleteness bias in theobserved Cepheid PL samples. We adopt a distance modulus to the LMC(relative to which the more distant galaxies are measured) ofμ0(LMC)=18.50+/-0.10 mag, or 50 kpc. New, reviseddistances are given for the 18 spiral galaxies for which Cepheids havebeen discovered as part of the Key Project, as well as for 13 additionalgalaxies with published Cepheid data. The new calibration results in aCepheid distance to NGC 4258 in better agreement with the maser distanceto this galaxy. Based on these revised Cepheid distances, we find values(in km s-1 Mpc-1) of H0=71+/-2(random)+/-6 (systematic) (Type Ia supernovae), H0=71+/-3+/-7(Tully-Fisher relation), H0=70+/-5+/-6 (surface brightnessfluctuations), H0=72+/-9+/-7 (Type II supernovae), andH0=82+/-6+/-9 (fundamental plane). We combine these resultsfor the different methods with three different weighting schemes, andfind good agreement and consistency with H0=72+/-8 kms-1 Mpc-1. Finally, we compare these results withother, global methods for measuring H0. Based on observationswith the NASA/ESA Hubble Space Telescope, obtained at the SpaceTelescope Science Institute, which is operated by AURA, Inc., under NASAcontract NAS5-26555.
| Gravitational Lensing by Nearby Clusters of Galaxies
We present an estimation of the expected number of arcs and arclets in asurvey of nearby (z<0.1) clusters of galaxies, which takes intoaccount the observational constraints. We show that strong lensingeffects are not common, but also that they are not as rare as usuallystated. Indeed, for a given cluster, the predicted number of arcsstrongly depends on the magnitude limit of the survey and the actualvalue of the seeing. We also describe the procedures and results of asearch for gravitational arcs and arclets in a sample of 33 galaxyclusters, representative of the local cluster distribution and spanningthe redshift range of 0.014
| A Database of Cepheid Distance Moduli and Tip of the Red Giant Branch, Globular Cluster Luminosity Function, Planetary Nebula Luminosity Function, and Surface Brightness Fluctuation Data Useful for Distance Determinations
We present a compilation of Cepheid distance moduli and data for foursecondary distance indicators that employ stars in the old stellarpopulations: the planetary nebula luminosity function (PNLF), theglobular cluster luminosity function (GCLF), the tip of the red giantbranch (TRGB), and the surface brightness fluctuation (SBF) method. Thedatabase includes all data published as of 1999 July 15. The mainstrength of this compilation resides in the fact that all data are on aconsistent and homogeneous system: all Cepheid distances are derivedusing the same calibration of the period-luminosity relation, thetreatment of errors is consistent for all indicators, and measurementsthat are not considered reliable are excluded. As such, the database isideal for comparing any of the distance indicators considered, or forderiving a Cepheid calibration to any secondary distance indicator, suchas the Tully-Fisher relation, the Type Ia supernovae, or the fundamentalplane for elliptical galaxies. This task has already been undertaken byFerrarese et al., Sakai et al., Kelson et al., and Gibson et al.Specifically, the database includes (1) Cepheid distances, extinctions,and metallicities; (2) reddened apparent λ5007 Å magnitudesof the PNLF cutoff; (3) reddened apparent magnitudes and colors of theturnover of the GCLF (in both the V and B bands); (4) reddened apparentmagnitudes of the TRGB (in the I band) and V-I colors at 0.5 mag fainterthan the TRGB; and (5) reddened apparent surface brightness fluctuationmagnitudes measured in Kron-Cousin I, K', andKshort, and using the F814W filter with the Hubble SpaceTelescope (HST) WFPC2. In addition, for every galaxy in the database wegive reddening estimates from IRAS/DIRBE as well as H I maps, J2000coordinates, Hubble and T-type morphological classification, apparenttotal magnitude in B, and systemic velocity.
| The Globular Cluster Systems in the Coma Ellipticals. I. The Luminosity Function in NGC 4874 and Implications for Hubble's Constant
We have used deep Hubble Space Telescope WFPC2 images in V (F606W) and I(F814W) to measure the luminosity distribution of the globular clustersin NGC 4874, the central cD galaxy of the Coma cluster. We find the``turnover'' point of the globular cluster luminosity function (GCLF) tolie at V=27.88+/-0.12, while the overall GCLF shape matches the standardGaussian-like form with dispersion σV=1.49+/-0.12. Weuse the GCLF as a standard candle by matching the turnover points in NGC4874 and another Coma elliptical, IC 4051, with those of the giantellipticals in the Virgo cluster (M87 and five others). The result isΔ(m-M) (Coma-Virgo)=4.06+/-0.11 mag, which converts to a Comadistance d=102 Mpc if the Virgo distance modulus is(m-M)0=30.99+/-0.04. The Hubble constant which emerges fromour GCLF measurement is then H0=(69+/-9) km s-1Mpc-1. We confirm this H0 value with a novelpresentation of the ``Hubble diagram'' for GCLFs in giant E galaxies.Measurements of additional GCLFs in the Coma ellipticals, as well ascalibrating galaxies in Virgo and Fornax, have excellent potential torefine this result in the near future. Based on observations obtainedwith the NASA/ESA Hubble Space Telescope, obtained at the SpaceTelescope Science Institute, which is operated by the Association ofUniversities for Research in Astronomy, Inc., under NASA contract NAS5-26555.
| Luminosity versus Phase-Space-Density Relation of Galaxies Revisited
We reexamined the correlation between the BTmagnitude and the phase-space-density parameterw=(D225vc)-1 of galaxies forthe Virgo, the Coma, the Fornax, and the Perseus clusters in an effortto better understand the physical underpinning of the fundamental plane.A tight correlation (BT=alog w+b) common to differentmorphological types of galaxies (E, S0, S) was found for the Virgo andthe Coma clusters, with a=1.87+/-0.10 and 1.33+/-0.11, respectively. Aninvestigation using only E galaxies was made for the four clusters. Theresults indicated that the empirical linear relation might be commonamong the Coma, the Fornax, and the Perseus clusters, with the VirgoCluster showing deviation. This relation, which is another way toproject the fundamental plane, has an expression insensitive to themorphology and may be suitable for treating galaxies of differentmorphological types collectively.
| The Hubble Space Telescope Key Project on the Extragalactic Distance Scale. XXVI. The Calibration of Population II Secondary Distance Indicators and the Value of the Hubble Constant
A Cepheid-based calibration is derived for four distance indicators thatutilize stars in old stellar populations: the tip of the red giantbranch (TRGB), the planetary nebula luminosity function (PNLF), theglobular cluster luminosity function (GCLF), and the surface brightnessfluctuation method (SBF). The calibration is largely based on theCepheid distances to 18 spiral galaxies within cz=1500 km s-1obtained as part of the Hubble Space Telescope (HST) Key Project on theExtragalactic Distance Scale, but relies also on Cepheid distances fromseparate HST and ground-based efforts. The newly derived calibration ofthe SBF method is applied to obtain distances to four Abell clusters inthe velocity range 3800-5000 km s-1. Combined with clustervelocities corrected for a cosmological flow model, these distancesimply a value of the Hubble constant of H0=69+/-4(random)+/-6 (systematic) km s-1 Mpc-1. Thisresult assumes that the Cepheid PL relation is independent of themetallicity of the variable stars; adopting a metallicity correction asin Kennicutt et al. would produce a 5%+/-3% decrease in H0.Finally, the newly derived calibration allows us to investigatesystematics in the Cepheid, PNLF, SBF, GCLF, and TRGB distance scales.
| The Globular Cluster Systems in the Coma Ellipticals. III. The Unique Case of IC 4051
IC 4051 is a giant E galaxy on the outskirts of the Coma Cluster core.Using archival HST WFPC2 data, we derive the metallicity distribution,luminosity function, and spatial structure of its globular clustersystem (GCS). The metallicity distribution derived from the V-I colorshas a mean ~=-0.3, a near-complete lack of metal-poorclusters, and only a small metallicity gradient with radius. Wetentatively suggest that the GCS has two roughly equal metallicitysubcomponents, one centered at [Fe/H]~0.0 and the second at [Fe/H]~-1.0,although their identification is blurred by the photometricuncertainties. The luminosity distribution (globular cluster luminosityfunction) has the standard Gaussian-like form observed in all othergiant E galaxies, with a peak (turnover) at V0=27.8,consistent with a Coma distance of 100 Mpc. The radial profiles of boththe GCS and the halo light show an unusually steep falloff, which mayindicate that the halo of this galaxy has been tidally truncated.Lastly, the specific frequency of the GCS is remarkably large: we findSN=11+/-2, at a level that rivals M87 and most others in thecentral cD-type category, even though IC 4051 is not a cD or brightestcluster elliptical. This galaxy exhibits a combination of GCScharacteristics found nowhere else. A formation model consistent withmost of the observations would be that this galaxy was subjected toremoval of a large fraction of its protogalactic gas shortly after itsmain phase of globular cluster formation, probably by its first passagethrough the Coma core. Since then, no significant additions due toaccretions or mergers have taken place, in strong contrast to thecentral Coma galaxy NGC 4874.
| 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
| Extensive near-infrared (H-band) photometry in Coma
We present extensive and accurate photometry in the near-infrared H bandof a complete sample of objects in an area of about 400arcmin2 toward the Coma cluster of galaxies. The sample,including about 300 objects, is complete down to H ~ 17 mag, the exactvalue depending on the type of magnitude (isophotal, aperture, Kron) andthe particular region studied. This is six magnitudes below thecharacteristic magnitude of galaxies, well into the dwarfs' regime atthe distance of the Coma cluster. For each object (star or galaxy) weprovide aperture magnitudes computed within five different apertures,the magnitude within the 22 mag arcsec-2 isophote, the Kronmagnitude and radius, magnitude errors, as well as the coordinates, theisophotal area, and a stellarity index. Photometric errors are 0.2 magat the completness limit. This sample is meant to be the zero-redshiftreference for evolutionary studies of galaxies. Based on observationscollected with the Telescope Bernard Lyot, at the Pic du MidiObservatory, operated by INSU (CNRS).
| 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
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