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Eridanus - a supergroup in the local Universe?
We examine a possible supergroup in the direction of the Eridanusconstellation using 6dF Galaxy Survey second data release (6dFGS DR2)positions and velocities together with Two-Micron All-Sky Survey andHyper-Lyon-Meudon Extragalactic DAtabase photometry. We perform afriends-of-friends analysis to determine which galaxies are associatedwith each substructure before examining the properties of theconstituent galaxies. The overall structure is made up of threeindividual groups that are likely to merge to form a cluster of mass ~7× 1013Msolar. We conclude that thisstructure is a supergroup. We also examine the colours, morphologies andluminosities of the galaxies in the region with respect to their localprojected surface density. We find that the colours of the galaxiesredden with increasing density, the median luminosities are brighterwith increasing environmental density and the morphologies of thegalaxies show a strong morphology-density relation. The colours andluminosities of the galaxies in the supergroup are already similar tothose of galaxies in clusters; however, the supergroup contains morelate-type galaxies, consistent with its lower projected surface density.Due to the velocity dispersion of the groups in the supergroup, whichare lower than those of clusters, we conclude that the properties of theconstituent galaxies are likely to be a result of merging orstrangulation processes in groups outlying this structure.
| Nearby early-type galaxies with ionized gas. II. Line-strength indices for 18 additional galaxies
We previously presented a data-set of line-strength indices for 50early-type galaxies in the nearby Universe. The galaxy sample is biasedtoward galaxies showing emission lines, located in environmentscorresponding to a broad range of local galaxy densities, althoughpredominantly in low density environments. The present addendum enlargesthe above data-set of line-strength indices by analyzing 18 additionalearly-type galaxies (three galaxies, NGC 3607, NGC 5077 and NGC 5898were presented in the previous set). We measured 25 line-strengthindices, defined by the Lick IDS "standard" system (Trager et al. 1998,ApJS, 116, 1; Worthey & Ottaviani 1997, ApJS, 111, 377), for 7luminosity weighted apertures and 4 gradients of each galaxy. Thisaddendum presents the line-strength data-set and compares it with theavailable data in the literature.
| Star Formation Histories of Nearby Elliptical Galaxies. I. Volume-Limited Sample
This work presents high signal-to-noise ratio spectroscopic observationsof a representative sample of nearby elliptical galaxies. Theseobservations provide a strong test of models for the formation ofelliptical galaxies and their star formation histories. Combining thesedata with the González data set, a volume-limited sample of 45galaxies has been defined. Results are in agreement with previousstudies: the existence of the metallicity hyperplane and the Z-plane ofTrager and coworkers is confirmed, and the distribution is clearly dueto physical variations in stellar population parameters and notmeasurement uncertainty. Trends between stellar population parametersand galaxy structural parameters suggest that angular momentum maydetermine the chemical abundance of a galaxy at a given mass.
| Nearby early-type galaxies with ionized gas. I. Line-strength indices of the underlying stellar population
With the aim of building a data-set of spectral properties of wellstudied early-type galaxies showing emission lines, we presentintermediate resolution spectra of 50 galaxies in the nearby Universe.The sample, which covers several of the E and S0 morphologicalsub-classes, is biased toward objects that might be expected to haveongoing and recent star formation, at least in small amounts, because ofthe presence of the emission lines. The emission is expected to comefrom the combination of active galactic nuclei and star formationregions within the galaxies. Sample galaxies are located in environmentscorresponding to a broad range of local galaxy densities, althoughpredominantly in low density environments. Our long-slit spectra coverthe 3700-7250 Å wavelength range with a spectral resolution of≈7.6 Å at 5550 Å. The specific aim of this paper, and ourfirst step in the investigation, is to map the underlying galaxy stellarpopulation by measuring, along the slit positioned along the galaxymajor axis, line-strength indices at several, homogeneousgalacto-centric distances. For each object we extracted 7luminosity-weighted apertures (with radii 1.5´´,2.5´´, 10´´, r_e/10, r_e/8, r_e/4 and r_e/2)corrected for the galaxy ellipticity and 4 gradients (0 ≤ r ≤r_e/16, r_e/16 ≤ r ≤ r_e/8, r_e/8 ≤ r ≤ r_e/4 and r_e/4≤ r ≤ r_e/2). For each aperture and gradient we measured 25line-strength indices: 21 of the set defined by the Lick-IDS“standard” system (Trager et al. [CITE], ApJS, 116, 1) and 4introduced by Worthey & Ottaviani ([CITE], ApJS, 111, 377).Line-strength indices have been transformed to the Lick-IDS system.Indices derived then include Hβ, Mg1, Mg2, Mgb, MgFe, Fe5270,Fe5335 commonly used in classic index-index diagrams. The paperintroduces the sample, presents the observations, describes the datareduction procedures, the extraction of apertures and gradients, thedetermination and correction of the line-strength indices, the procedureadopted to transform them into the Lick-IDS System and the proceduresadopted for the emission correction. We finally discuss the comparisonsbetween our dataset and line-strength indices available in theliterature. A significant fraction, about 60%, of galaxies in thepresent sample has one previous measurement in the Lick-IDS system butbasically restricted within the r_e/8 region. Line-strength measuresobtained both from apertures and gradients outside this area and withinthe r_e/8 region, with the present radial mapping, are completely new.Full appendix and Figs. 8 to 13 are only available in electronic form athttp://www.edpsciences.org Full Tables 6, 7, 9 and 10 are only availableat the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) orvia http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/433/497 Based onobservations obtained at the European Southern Observatory, La Silla,Chile (Programs Nr. 60.A-0647 and 61.A-0406).
| BUDDA: A New Two-dimensional Bulge/Disk Decomposition Code for Detailed Structural Analysis of Galaxies
We present BUDDA (Bulge/Disk Decomposition Analysis), a new code devotedto perform a two-dimensional bulge/disk decomposition directly from theimages of galaxies. The bulge component is fitted with a generalizedSérsic profile, whereas disks have an exponential profile. Noother components are included. Bars and other substructures, likelenses, rings, inner bars, and inner disks, are studied with theresidual images obtained through the subtraction of bulges and disksfrom the original images. This means that a detailed structural analysisof galaxies may be performed with a small number of parameters, andsubstructures may be directly studied with no a priori assumptions. Ashas been already shown by several studies, two-dimensional fitting ismuch more reliable than one-dimensional profile fitting. Moreover, ourcode has been thoroughly tested with artificial data, and we demonstrateit to be an accurate tool for determining structural parameters ofgalaxies. We also show that our code is useful in various kinds ofstudies, including galaxies of, e.g., different morphological types, andinclinations, which also may be observed at different spatialresolutions. Thus, the code has a broader range of potentialapplications than most of the previous codes, which are developed totackle specific problems. To illustrate its usefulness, we present theresults obtained with a sample of 51 mostly early-type galaxies (butcovering the whole Hubble sequence). These results show some of theapplications in which the code may be used: the determination ofparameters for fundamental plane and structural studies, quantitativemorphological classification of galaxies, and the identification andstudy of hidden substructures. We have determined the structuralparameters of the galaxies in our sample and found many examples ofhidden inner disks in ellipticals, secondary bars, nuclear rings anddust lanes in lenticulars and spirals, and also wrong morphologicalclassification cases. We now make BUDDA generally available to theastronomical community.Based on observations made at the Pico dos Dias Observatory(PDO/LNA-CNPq), Brazil.
| Peculiarities and populations in elliptical galaxies. I. An old question revisited
Morphological peculiarities, as defined from isophote asymmetries andnumber of detected shells, jets or similar features, have been estimatedin a sample of 117 E classified galaxies, and qualified by an ad hocΣ2 index. The overall frequency of ``peculiar'' objects(Pec subsample) is 32.5%. It decreases with the cosmic density of theenvironment, being minimal for the Virgo cluster, the densestenvironment in the sampled volume. This environmental effect is strongerfor galaxies with relatively large Σ2.The Pec subsample objects are compared with ``normal'' objects (Nopsubsample) as regards their basic properties. Firstly, theysystematically deviate from the Fundamental Plane and the Faber-Jacksonrelation derived for the Nop subsample, being too bright for their mass.Secondly, the dust content of galaxies, as estimated from IRAS fluxes,are similar in both subsamples. Third, the same is true of the frequencyof Kinematically Distinct cores (KDC), suggesting that KDC andmorphological peculiarities do not result from the same events in thehistory of E-galaxies.Using the Nop sample alone, we obtain very tight reference relationsbetween stellar population indicators (U-B, B-V, B-R, V-I,Mg2, Hβ, , Mgb) and the central velocitydispersion σ0. The discussion of the residuals of theserelations allows us to classify the Pec galaxies in two families i.e.the YP or NGC 2865 family, and the NP or NGC 3923 one. Galaxies in thefirst group show consistent evidence for a younger stellar populationmixed with the old one, in agreement with classical results (Schweizeret al. \cite{Schweizer1990}; Schweizer & Seitzer\cite{Schweizer1992}). The second group, however, has ``normal``, orreddish, populations. It is remarkable that a fraction (circa 40%) ofmorphologically perturbed objects do not display any signature of ayoung population, either because the event responsible for thepecularity is too ancient, or because it did not produce significantstar formation (or eventually that the young sub-population has highmetallicity).A preliminary attempt is made to interpret the populations of Pecobjects by combining a young Single Stellar Population with a Nopgalaxy, with only limited success, perhaps largely due to uncertaintiesin the SSP indices used.Based in part on observations collected at the Observatoire deHaute-Provence.Figures \ref{fig1}-\ref{fig3} are only available in electronic form athttp://www.edpsciences.orgTable 10 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/423/833
| Redshift-Distance Survey of Early-Type Galaxies: Spectroscopic Data
We present central velocity dispersions and Mg2 line indicesfor an all-sky sample of ~1178 elliptical and S0 galaxies, of which 984had no previous measures. This sample contains the largest set ofhomogeneous spectroscopic data for a uniform sample of ellipticalgalaxies in the nearby universe. These galaxies were observed as part ofthe ENEAR project, designed to study the peculiar motions and internalproperties of the local early-type galaxies. Using 523 repeatedobservations of 317 galaxies obtained during different runs, the dataare brought to a common zero point. These multiple observations, takenduring the many runs and different instrumental setups employed for thisproject, are used to derive statistical corrections to the data and arefound to be relatively small, typically <~5% of the velocitydispersion and 0.01 mag in the Mg2 line strength. Typicalerrors are about 8% in velocity dispersion and 0.01 mag inMg2, in good agreement with values published elsewhere.
| Redshift-Distance Survey of Early-Type Galaxies: Circular-Aperture Photometry
We present R-band CCD photometry for 1332 early-type galaxies, observedas part of the ENEAR survey of peculiar motions using early-typegalaxies in the nearby universe. Circular apertures are used to tracethe surface brightness profiles, which are then fitted by atwo-component bulge-disk model. From the fits, we obtain the structuralparameters required to estimate galaxy distances using theDn-σ and fundamental plane relations. We find thatabout 12% of the galaxies are well represented by a pure r1/4law, while 87% are best fitted by a two-component model. There are 356repeated observations of 257 galaxies obtained during different runsthat are used to derive statistical corrections and bring the data to acommon system. We also use these repeated observations to estimate ourinternal errors. The accuracy of our measurements are tested by thecomparison of 354 galaxies in common with other authors. Typical errorsin our measurements are 0.011 dex for logDn, 0.064 dex forlogre, 0.086 mag arcsec-2 for<μe>, and 0.09 for mRC,comparable to those estimated by other authors. The photometric datareported here represent one of the largest high-quality and uniformall-sky samples currently available for early-type galaxies in thenearby universe, especially suitable for peculiar motion studies.Based on observations at Cerro Tololo Inter-American Observatory (CTIO),National Optical Astronomy Observatory, which is operated by theAssociation of Universities for Research in Astronomy, Inc., undercooperative agreement with the National Science Foundation (NSF);European Southern Observatory (ESO); Fred Lawrence Whipple Observatory(FLWO); and the MDM Observatory on Kitt Peak.
| A new catalogue of ISM content of normal galaxies
We have compiled a catalogue of the gas content for a sample of 1916galaxies, considered to be a fair representation of ``normality''. Thedefinition of a ``normal'' galaxy adopted in this work implies that wehave purposely excluded from the catalogue galaxies having distortedmorphology (such as interaction bridges, tails or lopsidedness) and/orany signature of peculiar kinematics (such as polar rings,counterrotating disks or other decoupled components). In contrast, wehave included systems hosting active galactic nuclei (AGN) in thecatalogue. This catalogue revises previous compendia on the ISM contentof galaxies published by \citet{bregman} and \citet{casoli}, andcompiles data available in the literature from several small samples ofgalaxies. Masses for warm dust, atomic and molecular gas, as well asX-ray luminosities have been converted to a uniform distance scale takenfrom the Catalogue of Principal Galaxies (PGC). We have used twodifferent normalization factors to explore the variation of the gascontent along the Hubble sequence: the blue luminosity (LB)and the square of linear diameter (D225). Ourcatalogue significantly improves the statistics of previous referencecatalogues and can be used in future studies to define a template ISMcontent for ``normal'' galaxies along the Hubble sequence. The cataloguecan be accessed on-line and is also available at the Centre desDonnées Stellaires (CDS).The catalogue is available in electronic form athttp://dipastro.pd.astro.it/galletta/ismcat and at the CDS via anonymousftp to\ cdsarc.u-strasbg.fr (130.79.128.5) or via\http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/405/5
| A catalogue and analysis of local galaxy ages and metallicities
We have assembled a catalogue of relative ages, metallicities andabundance ratios for about 150 local galaxies in field, group andcluster environments. The galaxies span morphological types from cD andellipticals, to late-type spirals. Ages and metallicities were estimatedfrom high-quality published spectral line indices using Worthey &Ottaviani (1997) single stellar population evolutionary models. Theidentification of galaxy age as a fourth parameter in the fundamentalplane (Forbes, Ponman & Brown 1998) is confirmed by our largersample of ages. We investigate trends between age and metallicity, andwith other physical parameters of the galaxies, such as ellipticity,luminosity and kinematic anisotropy. We demonstrate the existence of agalaxy age-metallicity relation similar to that seen for local galacticdisc stars, whereby young galaxies have high metallicity, while oldgalaxies span a large range in metallicities. We also investigate theinfluence of environment and morphology on the galaxy age andmetallicity, especially the predictions made by semi-analytichierarchical clustering models (HCM). We confirm that non-clusterellipticals are indeed younger on average than cluster ellipticals aspredicted by the HCM models. However we also find a trend for the moreluminous galaxies to have a higher [Mg/Fe] ratio than the lowerluminosity galaxies, which is opposite to the expectation from HCMmodels.
| A Search for H2O Maser Emission in Southern Active Galactic Nuclei and Star-forming Galaxies: Discovery of a Maser in the Edge-on Galaxy IRAS F01063-8034
We report the cumulative results of five surveys for H2Omaser emission at 1.35 cm wavelength in 131 active galactic nuclei(AGNs) and star-forming galaxies, conducted at the Parkes Observatorybetween 1993 and 1998. We detected one new maser, in the edge-on galaxyIRAS F01063-8034, which exhibits a single ~0.1 Jy spectral feature at4282+/-6 km s-1 (heliocentric) with an unusually large54+/-16 km s-1 half-power full width. The centroid velocityof the emission increased to 4319.6+/-0.6 km s-1 (38+/-2 kms-1 width) over the 13 days between discovery andconfirmation of the detection. A similarly broad-line width and largechange in velocity has been noted for the maser in NGC 1052, wherein jetactivity excites the emission. Neither optical spectroscopy,radio-infrared correlations, nor infrared colors provide compellingevidence of unusual activity in the nucleus of IRAS F01063-8034. Sincethe galaxy appears to be outwardly normal at optical and infraredwavelengths, detection of an H2O maser therein is unique. Themaser emission is evidence that the galaxy harbors an AGN that isprobably obscured by the edge-on galactic disk. The detection highlightsthe possibility that undetected AGNs could be hidden in other relativelynearby galaxies. No other maser emission features have been identifiedat velocities between 3084 and 6181 km s-1.
| Bar Galaxies and Their Environments
The prints of the Palomar Sky Survey, luminosity classifications, andradial velocities were used to assign all northern Shapley-Ames galaxiesto either (1) field, (2) group, or (3) cluster environments. Thisinformation for 930 galaxies shows no evidence for a dependence of barfrequency on galaxy environment. This suggests that the formation of abar in a disk galaxy is mainly determined by the properties of theparent galaxy, rather than by the characteristics of its environment.
| Line-strength indices and velocity dispersions for 148 early-type galaxies in different environments
We have derived high quality line-strength indices and velocitydispersions for a sample of 148 early-type galaxies in differentenvironments. The wavelength region covered by the observations (lambda=~ 4600 to 6600 Å) includes the Lick/IDS indices Hβ,Mg1, Mg2, Mgb, Fe5015, Fe5270, Fe5335, Fe5406,Fe5709, Fe5782, NaD, TiO1 and TiO2. The data areintended to address possible differences of the stellar populations ofearly-type galaxies in low- and high-density environments. This paperdescribes the sample properties, explains the data reduction andpresents the complete list of all the measurements. Most galaxies of thesample (85%) had no previous measurements of any Lick/IDS indices andfor 30% of the galaxies we present first-time determinations of theirvelocity dispersions. Special care is taken to identify galaxies withemission lines. We found that 62 per cent of the galaxies in the samplehave emission lines, as measured by the equivalent width of the [OIII]5007Å line, EW[OIII] > 0.3 Å. Tables 5 and 6 are onlyavailable in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/ A+A/395/431. They are also available via ftp atftp.mpe.mpg.de in the directory people/dthomas/Beuing02 or via WWW atftp://ftp.mpe.mpg.de/people/dthomas/Beuing02.
| A catalogue and analysis of X-ray luminosities of early-type galaxies
We present a catalogue of X-ray luminosities for 401 early-typegalaxies, of which 136 are based on newly analysed ROSAT PSPC pointedobservations. The remaining luminosities are taken from the literatureand converted to a common energy band, spectral model and distancescale. Using this sample we fit the LX:LB relationfor early-type galaxies and find a best-fit slope for the catalogue of~2.2. We demonstrate the influence of group-dominant galaxies on the fitand present evidence that the relation is not well modelled by a singlepower-law fit. We also derive estimates of the contribution to galaxyX-ray luminosities from discrete-sources and conclude that they provideLdscr/LB~=29.5ergs-1LBsolar-1. Wecompare this result with luminosities from our catalogue. Lastly, weexamine the influence of environment on galaxy X-ray luminosity and onthe form of the LX:LB relation. We conclude thatalthough environment undoubtedly affects the X-ray properties ofindividual galaxies, particularly those in the centres of groups andclusters, it does not change the nature of whole populations.
| 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.
| Cold gas in elliptical galaxies
We explore the evolution of the cold gas (molecular and neutralhydrogen) of elliptical galaxies and merger remnants ordered into a timesequence on the basis of spectroscopic age estimates. We find that thefraction of cold gas in early merger remnants decreases significantlyfor ~1-2Gyr, but subsequent evolution toward evolved elliptical systemssees very little change. This trend can be attributed to an initial gasdepletion by strong star formation, which subsequently declines toquiescent rates. This explanation is consistent with the merger picturefor the formation of elliptical galaxies. We also explore the relationbetween the HI-to-H2 mass ratio and spectroscopic galaxy age,but find no evidence for a statistically significant trend. Thissuggests little net HI-to-H2 conversion for the systems inthe present sample.
| Structural evolution in elliptical galaxies: the age-shape relation
We test the hypothesis that the apparent axial ratio of an ellipticalgalaxy is correlated with the age of its stellar population. We findthat old ellipticals (with estimated ages t>7.5Gyr) are rounder onaverage than younger ellipticals. The statistical significance of thisshape difference is greatest at small radii; a Kolmogorov-Smirnov testcomparing the axial ratios of the two populations at R=Re/16yields a statistical significance greater than 99.96 per cent. Therelation between age and apparent shape is linked to the core/power-lawsurface brightness profile dichotomy. Core ellipticals have olderstellar populations, on average, than power-law ellipticals and arerounder in their inner regions. Our findings are consistent with ascenario in which power-law ellipticals are formed in gas-rich mergers,while core ellipticals form in dissipationless mergers, with coresformed and maintained by the influence of a binary black hole.
| The SBF Survey of Galaxy Distances. IV. SBF Magnitudes, Colors, and Distances
We report data for I-band surface brightness fluctuation (SBF)magnitudes, (V-I) colors, and distance moduli for 300 galaxies. Thesurvey contains E, S0, and early-type spiral galaxies in the proportionsof 49:42:9 and is essentially complete for E galaxies to Hubblevelocities of 2000 km s-1, with a substantial sampling of Egalaxies out to 4000 km s-1. The median error in distancemodulus is 0.22 mag. We also present two new results from the survey.(1) We compare the mean peculiar flow velocity (bulk flow) implied byour distances with predictions of typical cold dark matter transferfunctions as a function of scale, and we find very good agreement withcold, dark matter cosmologies if the transfer function scale parameterΓ and the power spectrum normalization σ8 arerelated by σ8Γ-0.5~2+/-0.5. Deriveddirectly from velocities, this result is independent of the distributionof galaxies or models for biasing. This modest bulk flow contradictsreports of large-scale, large-amplitude flows in the ~200 Mpc diametervolume surrounding our survey volume. (2) We present adistance-independent measure of absolute galaxy luminosity, N and showhow it correlates with galaxy properties such as color and velocitydispersion, demonstrating its utility for measuring galaxy distancesthrough large and unknown extinction. Observations in part from theMichigan-Dartmouth-MIT (MDM) Observatory.
| The formation of galaxy bulges: Spectrophotometric constraints
We have measured Mg2, Fe 5270 and Fe 5335 spectrophotometricindices (LICK system) in the bulge of 89 galaxies, mostly spirals fromthe Héraudeau (\cite{her96}) sample. The indices are reduced to anull velocity dispersion and normalized to an aperture of 0.2h-1 kpc. The mean errors are 0.009 mag on Mg2, and0.3 Å on the iron indices. These measurements almost double theamount of similar data already available on spiral galaxies. Our dataconfirm the existence of the relation between Mg2, andsigma0, the central stellar velocity dispersion; we find aneven tighter relation between Mg2, andVmrot, the maximum rotational velocity of thegalaxy, deduced from HI observations. For the most massive bulges, thesecorrelations may be interpreted as a mass-metallicity relation. However,the presence of young stellar populations, traced by the detection of[OIII] lambda 5007 Å, emission, provides clear evidence that ageeffects do play a role. Since the contribution of the young populationis anti-correlated to the mass of the galaxy, it continues theMg2, vs. sigma0 , relation toward thelow-sigma0, region and globally increases its slope. We alsopresent evidence for a new positive correlation between Fe indices andsigma0, and for a significant correlation between theline-strength indices and the total or disk luminosity. We propose tomodel the whole sequence of bulges within the folowing framework: bulgesare composed of a primary population formed prior to the disk, duringthe initial collapse, and of a secondary population formed during itsevolution. The whole family of bulges can be classified into threeclasses: (A) the bulges dominated by young populations are generallysmall, have ionized gas, low velocity dispersion and low line strengths;(B) the bulges dominated by the primary population lie along themass-metallicity sequence defined for elliptical galaxies; and (C) thebulges where the secondary population is significant are lessMg-over-abundant than (B)-type bulges and deviate from theMg2, vs. sigma0, relation of elliptical galaxies.Based on observations collected at the Observatoire de Haute-Provence.Table 3 is presented in electronic form only at the CDS. Tables 1 and 2are also available form at the CDS, Strasbourg, via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/366/68
| Nearby Optical Galaxies: Selection of the Sample and Identification of Groups
In this paper we describe the Nearby Optical Galaxy (NOG) sample, whichis a complete, distance-limited (cz<=6000 km s-1) andmagnitude-limited (B<=14) sample of ~7000 optical galaxies. Thesample covers 2/3 (8.27 sr) of the sky (|b|>20deg) andappears to have a good completeness in redshift (97%). We select thesample on the basis of homogenized corrected total blue magnitudes inorder to minimize systematic effects in galaxy sampling. We identify thegroups in this sample by means of both the hierarchical and thepercolation ``friends-of-friends'' methods. The resulting catalogs ofloose groups appear to be similar and are among the largest catalogs ofgroups currently available. Most of the NOG galaxies (~60%) are found tobe members of galaxy pairs (~580 pairs for a total of ~15% of objects)or groups with at least three members (~500 groups for a total of ~45%of objects). About 40% of galaxies are left ungrouped (field galaxies).We illustrate the main features of the NOG galaxy distribution. Comparedto previous optical and IRAS galaxy samples, the NOG provides a densersampling of the galaxy distribution in the nearby universe. Given itslarge sky coverage, the identification of groups, and its high-densitysampling, the NOG is suited to the analysis of the galaxy density fieldof the nearby universe, especially on small scales.
| A Test for Large-Scale Systematic Errors in Maps of Galactic Reddening
Accurate maps of Galactic reddening are important for a number ofapplications, such as mapping the peculiar velocity field in the nearbyuniverse. Of particular concern are systematic errors which vary slowlyas a function of position on the sky, as these would induce spuriousbulk flow. We have compared the reddenings of Burstein & Heiles (BH)and those of Schlegel, Finkbeiner, & Davis (SFD) to independentestimates of the reddening, for Galactic latitudes |b|>10^deg. Ourprimary source of Galactic reddening estimates comes from comparing thedifference between the observed B-V colors of early-type galaxies, andthe predicted B-V color determined from the B-V-Mg_2 relation. We havefitted a dipole to the residuals in order to look for large-scalesystematic deviations. There is marginal evidence for a dipolar residualin the comparison between the SFD maps and the observed early-typegalaxy reddenings. If this is due to an error in the SFD maps, then itcan be corrected with a small (13%) multiplicative dipole term. Weargue, however, that this difference is more likely to be due to a small(0.01 mag) systematic error in the measured B-V colors of the early-typegalaxies. This interpretation is supported by a smaller, independentdata set (globular cluster and RR Lyrae stars), which yields a resultinconsistent with the early-type galaxy residual dipole. BH reddeningsare found to have no significant systematic residuals, apart from theknown problem in the region 230^deg
| X-ray luminosities for a magnitude-limited sample of early-type galaxies from the ROSAT All-Sky Survey
For a magnitude-limited optical sample (B_T <= 13.5 mag) ofearly-type galaxies, we have derived X-ray luminosities from the ROSATAll-Sky Survey. The results are 101 detections and 192 useful upperlimits in the range from 10^36 to 10^44 erg s^-1. For most of thegalaxies no X-ray data have been available until now. On the basis ofthis sample with its full sky coverage, we find no galaxy with anunusually low flux from discrete emitters. Below log (L_B) ~ 9.2L_⊗ the X-ray emission is compatible with being entirely due todiscrete sources. Above log (L_B) ~ 11.2 L_osolar no galaxy with onlydiscrete emission is found. We further confirm earlier findings that L_xis strongly correlated with L_B. Over the entire data range the slope isfound to be 2.23 (+/- 0.12). We also find a luminosity dependence ofthis correlation. Below log L_x = 40.5 erg s^-1 it is consistent with aslope of 1, as expected from discrete emission. Above this value theslope is close to 2, as expected from gaseous emission. Comparing thedistribution of X-ray luminosities with the models of Ciotti et al.leads to the conclusion that the vast majority of early-type galaxiesare in the wind or outflow phase. Some of the galaxies may have alreadyexperienced the transition to the inflow phase. They show X-rayluminosities in excess of the value predicted by cooling flow modelswith the largest plausible standard supernova rates. A possibleexplanation for these super X-ray-luminous galaxies is suggested by thesmooth transition in the L_x--L_B plane from galaxies to clusters ofgalaxies. Gas connected to the group environment might cause the X-rayoverluminosity.
| Gradients of Absorption-Line Strengths in Elliptical Galaxies
We have restudied line-strength gradients of 80 elliptical galaxies.Typical metallicity gradients of elliptical galaxies areΔ[Fe/H]/Δlogr~=-0.3, which is flatter than the gradientspredicted by monolithic collapse simulations. The metallicity gradientsdo not correlate with any physical properties of galaxies, includingcentral and mean metallicities, central velocity dispersionsσ0, absolute B magnitudes MB, absoluteeffective radii Re, and dynamical masses of galaxies. Byusing the metallicity gradients, we have calculated mean stellarmetallicities for individual ellipticals. Typical mean stellarmetallicities are <[Fe/H]>~=-0.3 and range from<[Fe/H]>~=-0.8 to +0.3, which is contrary to what Gonzalez &Gorgas claimed; the mean metallicities of ellipticals are not universal.The mean metallicities correlate well with σ0 anddynamical masses, though relations for MB and Reinclude significant scatters. We find fundamental planes defined bysurface brightnesses SBe, <[Fe/H]>, and Re(or MB), the scatters of which are much smaller than those ofthe <[Fe/H]>-Re (or <[Fe/H]>-MB)relations. The <[Fe/H]>-logσ0 relation is nearlyparallel to the [Fe/H]0-logσ0 relation butsystematically lower by 0.3 dex; thus the mean metallicities are aboutone-half of the central values. The metallicity-mass relation or,equivalently, the color-magnitude relation of ellipticals holds not onlyfor the central parts of galaxies but also for entire galaxies. Assumingthat Mg2 and Fe1 give [Mg/H] and [Fe/H],respectively, we find <[Mg/Fe]>~=+0.2 in most of ellipticalgalaxies. <[Mg/Fe]> shows no correlation with galaxy mass tracerssuch as σ0, in contrast to what was claimed for thecentral [Mg/Fe]. This can be most naturally explained if the starformation had stopped in elliptical galaxies before the bulk of Type Iasupernovae began to occur. Elliptical galaxies can have significantlydifferent metallicity gradients and <[Fe/H]>, even if they havethe same galaxy mass. This may result from galaxy mergers, but noevidence is found from presently available data to support the sameorigin for metallicity gradients, the scatters around themetallicity-mass relation, and dynamical disturbances. This may suggestthat the scatters have their origin at the formation epoch of galaxies.
| The Mass-to-Light Ratio of Binary Galaxies
We report on the mass-to-light ratio determination based on a newlyselected binary galaxy sample, which includes a large number of pairswhose separations exceed a few hundred kpc. The probabilitydistributions of the projected separation and the velocity differencehave been calculated considering the contamination of optical pairs, andthe mass-to-light (M/L) ratio has been determined based on the maximumlikelihood method. The best estimate of the M/L in the B band for 57pairs is found to be 28-36 depending on the orbital parameters and thedistribution of optical pairs (solar unit: H_0=50 km s^-1 Mpc^-1). Thebest estimate of the M/L for 30 pure spiral pairs is found to be 12-16.These results are relatively smaller than those obtained in previousstudies but are consistent with each other within the errors. Althoughthe number of pairs with large separation is significantly increasedcompared with previous samples, the M/L does not show any tendency ofincrease but is found to be almost independent of the separation ofpairs beyond 100 kpc. The constancy of the M/L beyond 100 kpc mayindicate that the typical halo size of spiral galaxies is less than ~100kpc.
| Central Mg_2 indices for early-type galaxies
We present 210 new measurements of the central absorption line-strength{Mg_2} index for 87 early-type galaxies drawn from the \cite[Prugniel& Simien (1996)]{PS96} sample. 28 galaxies were not observed before.The results are compared to measurements published previously asavailable in HYPERCAT, and rescaled to the Lick system. The meanindividual internal error on these measurements is 0.009m+/-0.003m andthe mean external error is 0.012m+/-0.002m for this series ofmeasurements. Based on observations collected at the Observatoire deHaute-Provence. Tables 1, 3 and 4 are available in electronic form fromthe CDS, Strasbourg (via anonymous ftp to 130.79.128.5). Tables 1 and 3are available from CDS only.
| Structural and Dynamical Analysis of the Hickson Compact Groups
Based on the spectroscopic survey of de Carvalho et al., we analyze thestructural and dynamical properties of 17 Hickson compact groups. Thisanalysis probes a region of 0.dg5 x 0.dg5 around each group and showsthat most of them are part of larger structures. Our results alsosuggest that the Hickson sample is composed of different dynamicalstages of the groups" evolution. Specifically, we identify threepossible evolutionary phases among groups in the sample: loose groups,core + halo systems, and compact groups, each one presenting a distinctsurface density profile. This sequence is consistent with thereplenishment scenario for the formation and evolution of compact groupswithin larger and less dense systems.
| The Southern Sky Redshift Survey
We report redshifts, magnitudes, and morphological classifications for5369 galaxies with m_B <= 15.5 and for 57 galaxies fainter than thislimit, in two regions covering a total of 1.70 sr in the southerncelestial hemisphere. The galaxy catalog is drawn primarily from thelist of nonstellar objects identified in the Hubble Space TelescopeGuide Star Catalog (GSC). The galaxies have positions accurate to ~1"and magnitudes with an rms scatter of ~0.3 mag. We compute magnitudes(m_SSRS2) from the relation between instrumental GSC magnitudes and thephotometry by Lauberts & Valentijn. From a comparison with CCDphotometry, we find that our system is homogeneous across the sky andcorresponds to magnitudes measured at the isophotal level ~26 magarcsec^-2. The precision of the radial velocities is ~40 km s^-1, andthe redshift survey is more than 99% complete to the m_SSRS2 = 15.5 maglimit. This sample is in the direction opposite that of the CfA2; incombination the two surveys provide an important database for studies ofthe properties of galaxies and their large-scale distribution in thenearby universe. Based on observations obtained at Cerro TololoInter-American Observatory, National Optical Astronomy Observatories,operated by the Association of Universities for Research in Astronomy,Inc., under cooperative agreement with the National Science Foundation;Complejo Astronomico El Leoncito, operated under agreement between theConsejo Nacional de Investigaciones Científicas de laRepública Argentina and the National Universities of La Plata,Córdoba, and San Juan; the European Southern Observatory, LaSilla, Chile, partially under the bilateral ESO-ObservatórioNacional agreement; Fred Lawrence Whipple Observatory;Laboratório Nacional de Astrofísica, Brazil; and the SouthAfrican Astronomical Observatory.
| A catalogue of Mg_2 indices of galaxies and globular clusters
We present a catalogue of published absorption-line Mg_2 indices ofgalaxies and globular clusters. The catalogue is maintained up-to-datein the HYPERCAT database. The measurements are listed together with thereferences to the articles where the data were published. A codeddescription of the observations is provided. The catalogue gathers 3541measurements for 1491 objects (galaxies or globular clusters) from 55datasets. Compiled raw data for 1060 galaxies are zero-point correctedand transformed to a homogeneous system. Tables 1, 3, and 4 areavailable in electronic form only at the CDS, Strasbourg, via anonymousftp 130.79.128.5. Table 2 is available both in text and electronic form.
| Total magnitude, radius, colour indices, colour gradients and photometric type of galaxies
We present a catalogue of aperture photometry of galaxies, in UBVRI,assembled from three different origins: (i) an update of the catalogueof Buta et al. (1995) (ii) published photometric profiles and (iii)aperture photometry performed on CCD images. We explored different setsof growth curves to fit these data: (i) The Sersic law, (ii) The net ofgrowth curves used for the preparation of the RC3 and (iii) A linearinterpolation between the de Vaucouleurs (r(1/4) ) and exponential laws.Finally we adopted the latter solution. Fitting these growth curves, wederive (1) the total magnitude, (2) the effective radius, (3) the colourindices and (4) gradients and (5) the photometric type of 5169 galaxies.The photometric type is defined to statistically match the revisedmorphologic type and parametrizes the shape of the growth curve. It iscoded from -9, for very concentrated galaxies, to +10, for diffusegalaxies. Based in part on observations collected at the Haute-ProvenceObservatory.
| A catalogue of spatially resolved kinematics of galaxies: Bibliography
We present a catalogue of galaxies for which spatially resolved data ontheir internal kinematics have been published; there is no a priorirestriction regarding their morphological type. The catalogue lists thereferences to the articles where the data are published, as well as acoded description of these data: observed emission or absorption lines,velocity or velocity dispersion, radial profile or 2D field, positionangle. Tables 1, 2, and 3 are proposed in electronic form only, and areavailable from the CDS, via anonymous ftp to cdsarc.u-strasbg.fr (to130.79.128.5) or via http://cdsweb.u-strasbg.fr/Abstract.html
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