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Toward a clean sample of ultra-luminous X-ray sources
Context: .Observational follow-up programmes for the characterization ofultra-luminous X-ray sources (ULXs) require the construction of cleansamples of such sources in which the contamination byforeground/background sources is minimum. Aims: .We calculate thedegree of foreground/background contaminants among the ULX samplecandidates in a published catalogue and compare these computations withavailable spectroscopic identifications. Methods: .We usestatistics based on known densities of X-ray sources and AGN/QSOsselected in the optical. The analysis is done individually for eachparent galaxy. The existing identifications of the optical counterpartsare compiled from the literature. Results: .More than a half ofthe ULXs, within twice the distance of the major axis of the 25mag/arcsec2 isophote from RC3 nearby galaxies and with X-rayluminosities L_X[ 2-10 keV] ≥ 1039 erg/s, are expected tobe high redshift background QSOs. A list of 25 objects (clean sample)confirmed to be real ULXs or to have a low probability of beingcontaminant foreground/background objects is provided.
| The host galaxy/AGN connection in nearby early-type galaxies. Is there a miniature radio-galaxy in every "core" galaxy?
This is the second of a series of three papers exploring the connectionbetween the multiwavelength properties of AGN in nearby early-typegalaxies and the characteristics of their hosts. We selected two sampleswith 5 GHz VLA radio flux measurements down to 1 mJy, reaching levels ofradio luminosity as low as 1036 erg s-1. In PaperI we presented a study of the surface brightness profiles for the 65objects with available archival HST images out of the 116 radio-detectedgalaxies. We classified early-type galaxies into "core" and "power-law"galaxies, discriminating on the basis of the slope of their nuclearbrightness profiles, following the Nukers scheme. Here we focus on the29 core galaxies (hereafter CoreG). We used HST and Chandra data toisolate their optical and X-ray nuclear emission. The CoreG invariablyhost radio-loud nuclei, with an average radio-loudness parameter of LogR = L5 {GHz} / LB 3.6. The optical and X-raynuclear luminosities correlate with the radio-core power, smoothlyextending the analogous correlations already found for low luminosityradio-galaxies (LLRG) toward even lower power, by a factor of 1000, covering a combined range of 6 orders of magnitude. This supportsthe interpretation of a common non-thermal origin of the nuclearemission also for CoreG. The luminosities of the nuclear sources, mostlikely dominated by jet emission, set firm upper limits, as low asL/L_Edd 10-9 in both the optical and X-ray band, on anyemission from the accretion process. The similarity of CoreG and LLRGwhen considering the distributions host galaxies luminosities and blackhole masses, as well as of the surface brightness profiles, indicatesthat they are drawn from the same population of early-type galaxies.LLRG represent only the tip of the iceberg associated with (relatively)high activity levels, with CoreG forming the bulk of the population. Wedo not find any relationship between radio-power and black hole mass. Aminimum black hole mass of M_BH = 108 Mȯ isapparently associated with the radio-loud nuclei in both CoreG and LLRG,but this effect must be tested on a sample of less luminous galaxies,likely to host smaller black holes. In the unifying model for BL Lacsand radio-galaxies, CoreG likely represent the counterparts of the largepopulation of low luminosity BL Lac now emerging from the surveys at lowradio flux limits. This suggests the presence of relativistic jets alsoin these quasi-quiescent early-type "core" galaxies.
| Stellar populations in a complete sample of local radio galaxies
We investigate the nature of the continuum emission and stellarpopulations in the inner 1-3 kpc of a complete sample of 24 southernradio galaxies, and we compare the results with a control sample of 18non-active early-type galaxies. 12 of the radio galaxies are classifiedas Fanaroff-Riley type I (FR I), eight as FR II and four as intermediateor undefined type (FR x). Optical long-slit spectra are used to performspectral synthesis as a function of distance from the nucleus at anaverage sampling of 0.5-1.0 kpc and to quantify the relativecontributions of a blue featureless continuum and stellar populationcomponents of different ages. Our main finding is a systematicdifference between the stellar populations of the radio and controlsample galaxies: the former have a larger contribution from anintermediate-age (1 Gyr) component, suggesting a connection between thepresent radio activity and a starburst which occurred ~1 Gyr ago. Inaddition, we find a correlation between the contribution of the 1-Gyrcomponent and the radio power, suggesting that more massive starburstshave led to more powerful radio emission. A similar relation is foundbetween the radio power and the mean age of the stellar population, inthe sense that stronger nuclear activity is found in younger galaxies.We also find that the stellar populations of FR I galaxies are, onaverage, older and more homogeneous than those of FR IIs. Significantpopulation gradients were found in only four radio galaxies, which arealso those with more than 10 per cent of their total flux at 4020Åcontributed by age components younger than 100 Myr and/or afeatureless continuum (indistinguishable from a 3-Myr-old stellarpopulation).
| The host galaxy/AGN connection in nearby early-type galaxies. Sample selection and hosts brightness profiles
This is the first of a series of three papers exploring the connectionbetween the multiwavelength properties of AGNs in nearby early-typegalaxies and the characteristics of their hosts. We selected twosamples, both with high resolution 5 GHz VLA observations available andproviding measurements down to 1 mJy level, reaching radio-luminositiesas low as 1019 W Hz-1. We focus on the 116radio-detected galaxies as to boost the fraction of AGN with respect toa purely optically selected sample. Here we present the analysis of theoptical brightness profiles based on archival HST images, available for65 objects. We separate early-type galaxies on the basis of the slope oftheir nuclear brightness profiles, into core and power-law galaxiesfollowing the Nuker's scheme, rather than on the traditionalmorphological classification (i.e. into E and S0 galaxies). Our sampleof AGN candidates is indistinguishable, when their brightness profilesare concerned, from galaxies of similar optical luminosity but hostingweaker (or no) radio-sources. We confirm previous findings thatrelatively bright radio-sources (Lr > 1021.5 WHz-1) are uniquely associated to core galaxies. However,below this threshold in radio-luminosity core and power-law galaxiescoexist and they do not show any apparent difference in theirradio-properties. Not surprisingly, since our sample is deliberatelybiased to favour the inclusion of active galaxies, we found a higherfraction of optically nucleated galaxies. Addressing the multiwavelengthproperties of these nuclei will be the aim of the two forthcomingpapers.
| The distance to Hydra and Centaurus from surface brightness fluctuations: Consequences for the Great Attractor model
We present I-band Surface Brightness Fluctuation (SBF) measurements for16 early-type galaxies (3 giants, 13 dwarfs) in the central region ofthe Hydra cluster, based on deep photometric data in 7 fields obtainedwith VLT FORS1. From the SBF-distances to the galaxies in our sample weestimate the distance of the Hydra cluster to be 41.2 ± 1.4 Mpc((m-M)=33.07 ± 0.07 mag). Based on an improved correction forfluctuations from undetected point sources, we revise the SBF-distanceto the Centaurus cluster from Mieske & Hilker (2003, A&A, 410,455) upwards by 10% to 45.3 ± 2.0 Mpc ((m-M)=33.28 ± 0.09mag). The relative distance modulus of the two clusters then is(m-M)_Cen-(m-M)_Hyd=0.21 ± 0.11 mag. With H_0= 72 ± 4 kms-1 Mpc-1, we estimate a positive peculiarvelocity of 1225 ± 235 km s-1 for Hydra and 210± 295 km s-1 for the Cen30 component of Centaurus.Allowing for a thermal velocity dispersion of 200 km s-1,this rules out a common peculiar flow velocity for both clusters at 98%confidence. We find that the 9× 1015 Mȯ“Great Attractor” at a distance of ≃45 Mpc can explainthe observed peculiar velocities if shifted about 15° towards theHydra cluster position. Our results are inconsistent at 94% confidencewith a scenario where the Centaurus cluster is identical to the GA. Inorder to better restrict partially degenerate Great Attractor parameterslike its mass and distance, a recalculation of the local flow model withupdated distance information over a larger area than covered by us wouldbe needed.
| A catalogue of ultraluminous X-ray sources in external galaxies
We present a catalogue of ultraluminous X-ray sources (ULXs) in externalgalaxies. The aim of this catalogue is to provide easy access to theproperties of ULXs, their possible counterparts at other wavelengths(optical, IR, and radio), and their host galaxies. The cataloguecontains 229 ULXs reported in the literature until April 2004. Most ULXsare stellar-mass-black hole X-ray binaries, but it is not excluded thatsome ULXs could be intermediate-mass black holes. A small fraction ofthe candidate ULXs may be background Active Galactic Nuclei (AGN) andSupernova Remnants (SNRs). ULXs with luminosity above 1040ergs s-1 are found in both starburst galaxies and in thehalos of early-type galaxies.Table 1 is only available in electronic form at the CDS via anonymousftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/429/1125
| Circumnuclear Structure and Black Hole Fueling: Hubble Space Telescope NICMOS Imaging of 250 Active and Normal Galaxies
Why are the nuclei of some galaxies more active than others? If mostgalaxies harbor a central massive black hole, the main difference isprobably in how well it is fueled by its surroundings. We investigatethe hypothesis that such a difference can be seen in the detailedcircumnuclear morphologies of galaxies using several quantitativelydefined features, including bars, isophotal twists, boxy and diskyisophotes, and strong nonaxisymmetric features in unsharp-masked images.These diagnostics are applied to 250 high-resolution images of galaxycenters obtained in the near-infrared with NICMOS on the Hubble SpaceTelescope. To guard against the influence of possible biases andselection effects, we have carefully matched samples of Seyfert 1,Seyfert 2, LINER, starburst, and normal galaxies in their basicproperties, taking particular care to ensure that each was observed witha similar average scale (10-15 pc pixel-1). Severalmorphological differences among our five different spectroscopicclassifications emerge from the analysis. The H II/starburst galaxiesshow the strongest deviations from smooth elliptical isophotes, whilethe normal galaxies and LINERs have the least disturbed morphology. TheSeyfert 2s have significantly more twisted isophotes than any othercategory, and the early-type Seyfert 2s are significantly more disturbedthan the early-type Seyfert 1s. The morphological differences betweenSeyfert 1s and Seyfert 2s suggest that more is at work than simply theviewing angle of the central engine. They may correspond to differentevolutionary stages.
| 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.
| 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.
| A synthesis of data from fundamental plane and surface brightness fluctuation surveys
We perform a series of comparisons between distance-independentphotometric and spectroscopic properties used in the surface brightnessfluctuation (SBF) and fundamental plane (FP) methods of early-typegalaxy distance estimation. The data are taken from two recent surveys:the SBF Survey of Galaxy Distances and the Streaming Motions of AbellClusters (SMAC) FP survey. We derive a relation between(V-I)0 colour and Mg2 index using nearly 200galaxies and discuss implications for Galactic extinction estimates andearly-type galaxy stellar populations. We find that the reddenings fromSchlegel et al. for galaxies with E(B-V)>~0.2mag appear to beoverestimated by 5-10 per cent, but we do not find significant evidencefor large-scale dipole errors in the extinction map. In comparison withstellar population models having solar elemental abundance ratios, thegalaxies in our sample are generally too blue at a given Mg2;we ascribe this to the well-known enhancement of the α-elements inluminous early-type galaxies. We confirm a tight relation betweenstellar velocity dispersion σ and the SBF `fluctuation count'parameter N, which is a luminosity-weighted measure of the total numberof stars in a galaxy. The correlation between N and σ is eventighter than that between Mg2 and σ. Finally, we deriveFP photometric parameters for 280 galaxies from the SBF survey data set.Comparisons with external sources allow us to estimate the errors onthese parameters and derive the correction necessary to bring them on tothe SMAC system. The data are used in a forthcoming paper, whichcompares the distances derived from the FP and SBF methods.
| 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.
| The SBF Survey of Galaxy Distances. IV. SBF Magnitudes, Colors, and Distances
We report data for I-band surface brightness fluctuation (SBF)magnitudes, (V-I) colors, and distance moduli for 300 galaxies. Thesurvey contains E, S0, and early-type spiral galaxies in the proportionsof 49:42:9 and is essentially complete for E galaxies to Hubblevelocities of 2000 km s-1, with a substantial sampling of Egalaxies out to 4000 km s-1. The median error in distancemodulus is 0.22 mag. We also present two new results from the survey.(1) We compare the mean peculiar flow velocity (bulk flow) implied byour distances with predictions of typical cold dark matter transferfunctions as a function of scale, and we find very good agreement withcold, dark matter cosmologies if the transfer function scale parameterΓ and the power spectrum normalization σ8 arerelated by σ8Γ-0.5~2+/-0.5. Deriveddirectly from velocities, this result is independent of the distributionof galaxies or models for biasing. This modest bulk flow contradictsreports of large-scale, large-amplitude flows in the ~200 Mpc diametervolume surrounding our survey volume. (2) We present adistance-independent measure of absolute galaxy luminosity, N and showhow it correlates with galaxy properties such as color and velocitydispersion, demonstrating its utility for measuring galaxy distancesthrough large and unknown extinction. Observations in part from theMichigan-Dartmouth-MIT (MDM) Observatory.
| ROSAT-HRI observations of six southern galaxy pairs
We present the detailed analysis of the X-ray data for 6 pairs, isolatedor in poor groups, observed at high resolution with the ROSAT HRI . Inall cases, the stronger X-ray source is associated with the brighterearly-type member and is extended. The extent varies from galactic togroup scale, from 3 (RR 210b) to 182 kpc( RR 22a). The fainter membersare detected only in two pairs, RR 210 and RR 259. Except for one case,no significant substructures have been detected in the X-ray maps,possibly also as a consequence of the poor statistics. The core radii ofthe X-ray surface brightness profiles are in the range 1-3 kpc. Thedistribution of the luminosities of galaxies in pairs encompasses a verywide range of both luminosities and LX / LBratios, in spite of the very small number of objects studied so far. Ourdata provide no evidence that pair membership affects the X-rayproperties of galaxies. Observation are discussed in the context of thepair/group evolution.
| The calibration of the extragalactic distance scale: methods and problems.
Not Available
| The IRAS PSCz dipole
We use the PSCz IRAS galaxy redshift survey to analyse the cosmologicalgalaxy dipole out to a distance of 300h-1Mpc. The masked areais filled in three different ways, first by sampling the whole sky atrandom, secondly by using neighbouring areas to fill a masked region,and thirdly using a spherical harmonic analysis. The method of treatmentof the mask is found to have a significant effect on the finalcalculated dipole. The conversion from redshift space to real space isaccomplished by using an analytical model of the cluster and voiddistribution, based on 88 nearby groups, 854 clusters and 163 voids,with some of the clusters and all of the voids found from the PSCz database. The dipole for the whole PSCz sample appears to have convergedwithin a distance of 200h-1Mpc and yields a value forβΩ0.6b0.750.11-0.08, consistent with earlier determinations from IRAS samples bya variety of methods. For b=1, the 2σ range forΩ0 is 0.43-1.02. The direction of the dipole is within13° of the cosmic microwave background (CMB) dipole, the mainuncertainty in direction being associated with the masked area behindthe Galactic plane. The improbability of further major contributions tothe dipole amplitude coming from volumes larger than those surveyed heremeans that the question of the origin of the CMB dipole is essentiallyresolved.
| 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.
| 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.
| The Hubble Space Telescope Key Project on the Extragalactic Distance Scale. XXVIII. Combining the Constraints on the Hubble Constant
Since the launch of Hubble Space Telescope (HST) 9 yr ago, Cepheiddistances to 25 galaxies have been determined for the purpose ofcalibrating secondary distance indicators. Eighteen of these have beenmeasured by the HST Key Project team, six by the Supernova CalibrationProject, and one independently by Tanvir. Collectively, this work setsout an array of survey markers over the region within 25 Mpc of theMilky Way. A variety of secondary distance indicators can now becalibrated, and the accompanying four papers employ the full set of 25galaxies to consider the Tully-Fisher relation, the fundamental plane ofelliptical galaxies, Type Ia supernovae, and surface brightnessfluctuations. When calibrated with Cepheid distances, each of thesemethods yields a measurement of the Hubble constant and a correspondingmeasurement uncertainty. We combine these measurements in this paper,together with a model of the velocity field, to yield the best availableestimate of the value of H0 within the range of thesesecondary distance indicators and its uncertainty. The uncertainty inthe result is modeled in an extensive simulation we call the ``virtualKey Project.'' The velocity-field model includes the influence of theVirgo cluster, the Great Attractor, and the Shapley supercluster, butdoes not play a significant part in determining the result. The resultis H0=71+/-6 km s-1 Mpc-1. The largestcontributor to the uncertainty of this 67% confidence level result isthe distance of the Large Magellanic Cloud, which has been assumed to be50+/-3 kpc. This takes up the first 6.5% of our 9% error budget. Othercontributors are the photometric calibration of the WFPC2 instrument,which takes up 4.5%, deviations from uniform Hubble flow in the volumesampled (<~2%), the composition sensitivity of the Cepheidperiod-luminosity relation (4%), and departures from a universalreddening law (~1%). These are the major components that , when combinedin quadrature, make up the 9% total uncertainty. If the LMC distancemodulus were systematically smaller by 1 σ than that adopted here,the derived value of the Hubble constant would increase by 4 kms-1 Mpc-1. Most of the significant systematicerrors are capable of amelioration in future work. These include theuncertainty in the photometric calibration of WFPC2, the LMC distance,and the reddening correction. A NICMOS study is in its preliminaryreduction phase, addressing the last of these concerns. Variousempirical analyses have suggested that Cepheid distance moduli areaffected by metallicity differences. If we adopted the compositionsensitivity obtained in the Key Project's study of M101, and employedthe oxygen abundances measured spectroscopically in each of the Cepheidfields we have studied, the value of the Hubble constant would bereduced by 4%+/-2% to 68+/-6 km s-1 Mpc-1. Basedon observations with the NASA/ESA Hubble Space Telescope, obtained atthe Space Telescope Science Institute, which is operated by AURA, Inc.,under NASA contract NAS 5-26555.
| 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.
| 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
| The NICMOS Snapshot Survey of Nearby Galaxies
We present ``snapshot'' observations with the Near-Infrared Camera andMulti-Object Spectrometer (NICMOS) on board the Hubble Space Telescope(HST) of 94 nearby galaxies from the Revised Shapley Ames Catalog.Images with 0.2" resolution were obtained in two filters, a broadbandcontinuum filter (F160W, roughly equivalent to the H band) and anarrowband filter centered on the Paα line (F187N or F190N,depending on the galaxy redshift) with the 51^''x51^'' field of view ofthe NICMOS camera 3. A first-order continuum subtraction is performed,and the resulting line maps and integrated Paα line fluxes arepresented. A statistical analysis indicates that the average Paαsurface brightness in the central regions is highest in early-type(Sa-Sb) spirals.
| Detection of Surface Brightness Fluctuations in NGC 4373 Using the Hubble Space Telescope
Surface brightness fluctuations (SBF) have been detected for threeelliptical galaxies-NGC 3379 in the Leo group, NGC 4406 in the Virgocluster, and NGC 4373 in the Hydra-Centaurus supercluster-usingmarginally sampled, deep images taken with the Planetary Camera of theWFPC2 instrument on the Hubble Space Telescope (HST). The power spectrumof the fluctuations image is well fitted by an empirical model of thepoint-spread function constructed using point sources identified in thefield. Comparison with high-quality ground-based observations of allthree galaxies show excellent agreement in the measurement of thedistance modulus over a substantial range in distance. This demonstratesthe capability of the Planetary Camera of WFPC2 to measure distancesusing the SBF technique despite the marginal sampling and small spatialcoverage of the images. The residual variance due to unresolved sourcesin all three galaxies is only 2%-5% of the detected fluctuations signal,which confirms the advantage of HST imaging in minimizing theuncertainty of this SBF correction. Extensive consistency checks,including an independent SBF analysis using an alternate softwarepackage, suggest that our internal uncertainties are <0.02 mag. Thefluctuations magnitude for NGC 4373 is I_F814W=31.31+/-0.05 mag,corresponding to a distance modulus of (m-M)_0=32.99+/-0.11. Thisimplies a peculiar velocity for this galaxy of 415+/-330 km s^-1, whichis smaller than derived from the D_n-sigma relation.
| 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.
| The SBF Survey of Galaxy Distances. I. Sample Selection, Photometric Calibration, and the Hubble Constant
We describe a program of surface brightness fluctuation (SBF)measurements for determining galaxy distances. This paper presents thephotometric calibration of our sample and of SBF in general. Basing ourzero point on observations of Cepheid variable stars, we find that theabsolute SBF magnitude in the Kron-Cousins I band correlates well withthe mean (V - I)0 color of a galaxy according to M barI=(-1.74+/-0.07)+(4.5+/-0.25)[(V-I)0-1.15] for 1.0< (V - I) < 1.3. This agrees well with theoretical estimates fromstellar population models. Comparisons between SBF distances and avariety of other estimators, including Cepheid variable stars, theplanetary nebula luminosity function (PNLF), Tully-Fisher (TF), Dn-sigma , SN II, and SN Ia, demonstrate that the calibration of SBF isuniversally valid and that SBF error estimates are accurate. The zeropoint given by Cepheids, PNLF, TF (both calibrated using Cepheids), andSN II is in units of megaparsecs; the zero point given by TF (referencedto a distant frame), Dn- sigma , and SN Ia is in terms of a Hubbleexpansion velocity expressed in km s-1. Tying together these two zeropoints yields a Hubble constant of H0=81+/-6 {km} {s}^{-1}{Mpc}^{-1} . As part of this analysis, we present SBF distances to 12nearby groups of galaxies where Cepheids, SN II, and SN Ia have beenobserved.
| The visible environment of polar ring galaxies.
A statistical study of the environment around Polar Ring Galaxies ispresented. Two kinds of search are performed: 1) a study of theconcentration and diameters of all the objects surrounding the PolarRings, within a search field 5 times the ring diameter. New magnitudesfor polar ring galaxies are presented. 2) a search, in a wider field,for galaxies of similar size that may have encountered the polar ringhost galaxy in a time of the order of 1Gyr. Differently from the resultsof similar searches in the fields of active galaxies, the environment ofthe Polar Ring Galaxies seems to be similar to that of normal galaxies.This result may give support to the models suggesting long times forformation and evolution of the rings. If the rings are old (and stableor in equilibrium), no traces of the past interaction are expected intheir surroundings. In addition, the formation of massive polar rings,too big to derive from the ingestion of a present-day dwarf galaxy, maybe easily placed in epochs with a higher number of gas-rich galaxies.
| Surface photometry of binary galaxies. I. A multicolour study of morphologies due to the interaction.
We present the multicolour (B, V, R) surface photometry of 53 doublegalaxies. All the pairs belong to the catalogue of Reduzzi &Rampazzo (1995) containing objects selected according to theKarachentsev (1972) criteria. We comment on the morphological,structural and photometric characteristics of pairs and their members.Different classes of interaction induced phenomena, both among early andlate-type galaxies, are considered. We found that few early-typegalaxies show fine structures. Grand design structure is more frequentlydetected in binary than in field spirals both for barred and non barred,confirming Elmegreen & Elmegreen's (1982) study. The colour of thetails is consistent with the stripping hypothesis since it is similar tothe progenitor galaxy outskirts. Among our objects we have no evidentsign of induced star formation in tails. Rings appear on average bluerthan the disc as a whole.
| 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.
| Candidates for a southern extension of the Karachentsev catalogue of isolated pairs of galaxies.
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