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The SAURON project - VII. Integral-field absorption and emission-line kinematics of 24 spiral galaxy bulges
We present observations of the stellar and gas kinematics for arepresentative sample of 24 Sa galaxies obtained with our custom-builtintegral-field spectrograph SAURON operating on the William HerschelTelescope. The data have been homogeneously reduced and analysed bymeans of a dedicated pipeline. All resulting data cubes were spatiallybinned to a minimum mean signal-to-noise ratio of 60 per spatial andspectral resolution element. Our maps typically cover thebulge-dominated region. We find a significant fraction of kinematicallydecoupled components (12/24), many of them displaying central velocitydispersion minima. They are mostly aligned and co-rotating with the mainbody of the galaxies, and are usually associated with dust discs andrings detected in unsharp-masked images. Almost all the galaxies in thesample (22/24) contain significant amounts of ionized gas which, ingeneral, is accompanied by the presence of dust. The kinematics of theionized gas are consistent with circular rotation in a disc co-rotatingwith respect to the stars. The distribution of mean misalignmentsbetween the stellar and gaseous angular momenta in the sample suggeststhat the gas has an internal origin. The [OIII]/Hβ ratio is usuallyvery low, indicative of current star formation, and shows variousmorphologies (ring-like structures, alignments with dust lanes oramorphous shapes). The star formation rates (SFRs) in the sample arecomparable with that of normal disc galaxies. Low gas velocitydispersion values appear to be linked to regions of intense starformation activity. We interpret this result as stars being formed fromdynamically cold gas in those regions. In the case of NGC5953, the datasuggest that we are witnessing the formation of a kinematicallydecoupled component from cold gas being acquired during the ongoinginteraction with NGC5954.
| Low-Luminosity Active Galaxies and Their Central Black Holes
Central black hole masses for 117 spiral galaxies representingmorphological stages S0/a through Sc and taken from the largespectroscopic survey of Ho et al. are derived using Ks-banddata from the Two Micron All Sky Survey. Black hole masses are foundusing a calibrated black hole-Ks bulge luminosity relation,while bulge luminosities are measured by means of a two-dimensionalbulge-disk decomposition routine. The black hole masses are correlatedagainst a variety of parameters representing properties of the nucleusand host galaxy. Nuclear properties such as line width (FWHM [N II]), aswell as emission-line ratios (e.g., [O III]/Hβ, [O I]/Hα, [NII]/Hα, and [S II]/Hα), show a very high degree ofcorrelation with black hole mass. The excellent correlation with linewidth supports the view that the emission-line gas is in virialequilibrium with either the black hole or bulge potential. The very goodemission-line ratio correlations may indicate a change in ionizingcontinuum shape with black hole mass in the sense that more massiveblack holes generate harder spectra. Apart from theinclination-corrected rotational velocity, no excellent correlations arefound between black hole mass and host galaxy properties. Significantdifferences are found between the distributions of black hole masses inearly-, mid-, and late-type spiral galaxies (subsamples A, B, and C) inthe sense that early-type galaxies have preferentially larger centralblack holes, consistent with observations that Seyfert galaxies arefound preferentially in early-type systems. The line width distributionsshow a marked difference among subsamples A, B, and C in the sense thatearlier type galaxies have larger line widths. There are also cleardifferences in line ratios between subsamples A+B and C that likely arerelated to the level of ionization in the gas. Finally, aKs-band Simien & de Vaucouleurs diagram shows excellentagreement with the original B-band relation, although there is a largedispersion at a given morphological stage.
| A Comparison of Hα and Stellar Scale Lengths in Virgo and Field Spirals
The scale lengths of the old stars and ionized gas distributions arecompared for similar samples of Virgo Cluster members and field spiralgalaxies via Hα and broad R-band surface photometry. While theR-band and Hα scale lengths are, on average, comparable for thecombined sample, we find significant differences between the field andcluster samples. While the Hα scale lengths of the field galaxiesare a factor of 1.14+/-0.07 longer, on average, than their R-band scalelengths, the Hα scale lengths of Virgo Cluster members are, onaverage, 20% smaller than their R-band scale lengths. Furthermore, inVirgo, the scale length ratios are correlated with the size of thestar-forming disk: galaxies with smaller overall Hα extents alsoshow steeper radial falloff of star formation activity. At the sametime, we find no strong trends in scale length ratio as a function ofother galaxy properties, including galaxy luminosity, inclination,morphological type, central R-band light concentration, or bar type. Ourresults for Hα emission are similar to other results for dustemission, suggesting that Hα and dust have similar distributions.The environmental dependence of the Hα scale length placesadditional constraints on the evolutionary process(es) that cause gasdepletion and a suppression of the star formation rate in clusters ofgalaxies.
| A radio census of nuclear activity in nearby galaxies
In order to determine the incidence of black hole accretion-drivennuclear activity in nearby galaxies, as manifested by their radioemission, we have carried out a high-resolution Multi-ElementRadio-Linked Interferometer Network (MERLIN) survey of LINERs andcomposite LINER/Hii galaxies from a complete magnitude-limited sample ofbright nearby galaxies (Palomar sample) with unknown arcsecond-scaleradio properties. There are fifteen radio detections, of which three arenew subarcsecond-scale radio core detections, all being candidate AGN.The detected galaxies supplement the already known low-luminosity AGN -low-luminosity Seyferts, LINERs and composite LINER/Hii galaxies - inthe Palomar sample. Combining all radio-detected Seyferts, LINERs andcomposite LINER/Hii galaxies (LTS sources), we obtain an overall radiodetection rate of 54% (22% of all bright nearby galaxies) and weestimate that at least ~50% (~20% of all bright nearby galaxies) aretrue AGN. The radio powers of the LTS galaxies allow the construction ofa local radio luminosity function. By comparing the luminosity functionwith those of selected moderate-redshift AGN, selected from the 2dF/NVSSsurvey, we find that LTS sources naturally extend the RLF of powerfulAGN down to powers of about 10 times that of Sgr A*.
| A bar signature and central disc in the gaseous and stellar velocity fields of NGC 5448
We analyse Spectrographic Areal Unit for Research on Optical Nebulae(SAURON) kinematic maps of the inner kiloparsec of the early-type (Sa)barred spiral galaxy NGC 5448. The observed morphology and kinematics ofthe emission-line gas is patchy and perturbed, indicating cleardepartures from circular motion. The kinematics of the stars is moreregular, and display a small inner disc-like system embedded in alarge-scale rotating structure. We focus on the [OIII] gas, and use aharmonic decomposition formalism to analyse the gas velocity field. Thehigher order harmonic terms and the main kinematic features of theobserved data are consistent with an analytically constructed simple barmodel. The bar model is derived using linear theory, considering an m= 2perturbation mode, and with bar parameters that are consistent with thelarge-scale bar detected via imaging. We also study optical and nearinfrared images to reveal the asymmetric extinction in NGC 5448, and werecognize that some of the deviations between the data and theanalytical bar model may be due to these complex dust features. Ourstudy illustrates how the harmonic decomposition formalism can be usedas a powerful tool to quantify non-circular motions in observed gasvelocity fields.
| 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.
| The ISOPHOT 170 μm Serendipity Survey II. The catalog of optically identified galaxies%
The ISOPHOT Serendipity Sky Survey strip-scanning measurements covering≈15% of the far-infrared (FIR) sky at 170 μm were searched forcompact sources associated with optically identified galaxies. CompactSerendipity Survey sources with a high signal-to-noise ratio in at leasttwo ISOPHOT C200 detector pixels were selected that have a positionalassociation with a galaxy identification in the NED and/or Simbaddatabases and a galaxy counterpart visible on the Digitized Sky Surveyplates. A catalog with 170 μm fluxes for more than 1900 galaxies hasbeen established, 200 of which were measured several times. The faintest170 μm fluxes reach values just below 0.5 Jy, while the brightest,already somewhat extended galaxies have fluxes up to ≈600 Jy. For thevast majority of listed galaxies, the 170 μm fluxes were measured forthe first time. While most of the galaxies are spirals, about 70 of thesources are classified as ellipticals or lenticulars. This is the onlycurrently available large-scale galaxy catalog containing a sufficientnumber of sources with 170 μm fluxes to allow further statisticalstudies of various FIR properties.Based on observations with ISO, an ESA project with instruments fundedby ESA Member States (especially the PI countries: France, Germany, TheNetherlands and the UK) and with the participation of ISAS and NASA.Members of the Consortium on the ISOPHOT Serendipity Survey (CISS) areMPIA Heidelberg, ESA ISO SOC Villafranca, AIP Potsdam, IPAC Pasadena,Imperial College London.Full Table 4 and Table 6 are only available in electronic form at theCDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/422/39
| Deprojecting spiral galaxies using Fourier analysis. Application to the Ohio sample
We use two new methods developed recently (Barberàet al.\cite{bar03}, A&A, 415, 849), as well as information obtained fromthe literature, to calculate the orientation parameters of the spiralgalaxies in the Ohio State University Bright Galaxy Survey. We comparethe results of these methods with data from the literature, and find ingeneral good agreement. We provide a homogeneous set of mean orientationparameters which can be used to approximately deproject the disks of thegalaxies and facilitate a number of statistical studies of galaxyproperties.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/421/595
| Do bulges of early- and late-type spirals have different morphology?
We study HST/NICMOS H-band images of bulges of two equal-sized samplesof early- (TRC3 <= 3) and late-type spiral (mainly Sbc-Sc)galaxies matched in outer disk axis ratio. We find that bulges oflate-type spirals are more elongated than their counterparts inearly-type spirals. Using a KS-test we find that the two distributionsare different at the 98.4% confidence level. We conclude that the twodata sets are different, i.e. late-type galaxies have a broaderellipticity distribution and contain more elongated features in theinner regions. We discuss the possibility that these would correspond tobars at a later evolutionary stage, i.e. secularly evolved bars.Consequent implications are raised, and we discuss relevant questionsregarding the formation and structure of bulges. Are bulges ofearly-type and late-type spirals different? Are their formationscenarios different? Can we talk about bulges in the same way fordifferent types of galaxies?
| 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
| The SAURON project - II. Sample and early results
Early results are reported from the SAURON survey of the kinematics andstellar populations of a representative sample of nearby E, S0 and Sagalaxies. The survey is aimed at determining the intrinsic shape of thegalaxies, their orbital structure, the mass-to-light ratio as a functionof radius, the age and metallicity of the stellar populations, and thefrequency of kinematically decoupled cores and nuclear black holes. Theconstruction of the representative sample is described, and itsproperties are illustrated. A comparison with long-slit spectroscopicdata establishes that the SAURON measurements are comparable to, orbetter than, the highest-quality determinations. Comparisons arepresented for NGC 3384 and 4365, where stellar velocities and velocitydispersions are determined to a precision of 6kms-1, and theh3 and h4 parameters of the line-of-sight velocitydistribution to a precision of better than 0.02. Extraction of accurategas emission-line intensities, velocities and linewidths from the datacubes is illustrated for NGC 5813. Comparisons with published linestrengths for NGC 3384 and 5813 reveal uncertainties of <~0.1Åon the measurements of the Hβ, Mg b and Fe5270 indices.Integral-field mapping uniquely connects measurements of the kinematicsand stellar populations to the galaxy morphology. The maps presentedhere illustrate the rich stellar kinematics, gaseous kinematics, andline-strength distributions of early-type galaxies. The results includethe discovery of a thin, edge-on, disc in NGC 3623, confirm theaxisymmetric shape of the central region of M32, illustrate the LINERnucleus and surrounding counter-rotating star-forming ring in NGC 7742,and suggest a uniform stellar population in the decoupled core galaxyNGC 5813.
| Nested and Single Bars in Seyfert and Non-Seyfert Galaxies
We analyze the observed properties of nested and single stellar barsystems in disk galaxies. The 112 galaxies in our sample comprise thelargest matched Seyfert versus non-Seyfert galaxy sample of nearbygalaxies with complete near-infrared or optical imaging sensitive tolength scales ranging from tens of parsecs to tens of kiloparsecs. Thepresence of bars is deduced by fitting ellipses to isophotes in HubbleSpace Telescope (HST) H-band images up to 10" radius and in ground-basednear-infrared and optical images outside the H-band images. This is aconservative approach that is likely to result in an underestimate ofthe true bar fraction. We find that a significant fraction of the samplegalaxies, 17%+/-4%, have more than one bar, and that 28%+/-5% of barredgalaxies have nested bars. The bar fractions appear to be stableaccording to reasonable changes in our adopted bar criteria. For thenested bars, we detect a clear division in length between thelarge-scale (primary) bars and small-scale (secondary) bars, in bothabsolute and normalized (to the size of the galaxy) length. We arguethat this bimodal distribution can be understood within the framework ofdisk resonances, specifically the inner Lindblad resonances (ILRs),which are located where the gravitational potential of the innermostgalaxy switches effectively from three-dimensional to two-dimensional.This conclusion is further strengthened by the observed distribution ofthe sizes of nuclear rings which are dynamically associated with theILRs. While primary bar sizes are found to correlate with the hostgalaxy sizes, no such correlation is observed for the secondary bars.Moreover, we find that secondary bars differ morphologically from singlebars. Our matched Seyfert and non-Seyfert samples show a statisticallysignificant excess of bars among the Seyfert galaxies at practically alllength scales. We confirm our previous results that bars are moreabundant in Seyfert hosts than in non-Seyfert galaxies and that Seyfertgalaxies always show a preponderance of ``thick'' bars compared to thebars in non-Seyfert galaxies. Finally, no correlation is observedbetween the presence of a bar and that of companion galaxies, evenrelatively bright ones. Overall, since star formation and dustextinction can be significant even in the H band, the stellar dynamicsof the central kiloparsec cannot always be revealed reliably by the useof near-infrared surface photometry alone.
| 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.
| The Visibility of Galactic Bars and Spiral Structure at High Redshifts
We investigate the visibility of galactic bars and spiral structure inthe distant universe by artificially redshifting 101 B-band CCD imagesof local spiral galaxies from the Ohio State University Bright SpiralGalaxy Survey. These local galaxy images represent a much fairerstatistical baseline than the galaxy atlas images presented by Frei etal. in 1995, the most commonly used calibration sample for morphologicalwork at high redshifts. Our artificially redshifted images correspond toHubble Space Telescope I814-band observations of the localgalaxy sample seen at z=0.7, with integration times matching those ofboth the very deep northern Hubble Deep Field (HDF) data and the muchshallower HDF flanking field observations. The expected visibility ofgalactic bars is probed in two ways: (1) using traditional visualclassification and (2) by charting the changing shape of the galaxydistribution in ``Hubble space,'' a quantitative two-parameterdescription of galactic structure that maps closely onto Hubble'soriginal tuning fork. Both analyses suggest that over two-thirds ofstrongly barred luminous local spirals (i.e., objects classified as SBin the Third Reference Catalogue) would still be classified as stronglybarred at z=0.7 in the HDF data. Under the same conditions, most weaklybarred spirals (classified SAB in the Third Reference Catalogue) wouldbe classified as regular spirals. The corresponding visibility of spiralstructure is assessed visually, by comparing luminosity classificationsfor the artificially redshifted sample with the corresponding luminosityclassifications from the Revised Shapley-Ames Catalog. We find that forexposure times similar to that of the HDF, spiral structure should bedetectable in most luminous (MB~M*) low-inclination spiralgalaxies at z=0.7 in which it is present. However, obvious spiralstructure is only detectable in ~30% of comparable galaxies in the HDFflanking field data using the Wide Field Planetary Camera 2. Our studyof artificially redshifted local galaxy images suggests that, whenviewed at similar resolution, noise level, and redshift-correctedwavelength, barred spirals are less common at z~0.7 than they are atz=0.0, although more data are needed to definitively rule out thepossibility that cosmic variance is responsible for much of this effect.
| Spiral Galaxies with HST/NICMOS. I. Nuclear Morphologies, Color Maps, and Distinct Nuclei
This is the first of two papers where we present the analysis of anHST/NICMOS2 near-infrared (NIR) snapshot survey in the F160W (H) filterfor a sample of 78 spiral galaxies selected from the UGC and ESOLVcatalogs. For 69 of these objects we provide nuclear color informationderived by combining the H data either with additional NICMOS F110W (J)images or with V WFPC2/HST data. Here we present the NIR images and theoptical-NIR color maps. We focus our attention on the properties of thephotometrically distinct ``nuclei'' which are found embedded in most ofthe galaxies and provide measurements of their half-light radii andmagnitudes in the H (and when available in the J) band. We find that (1)in the NIR the nuclei embedded in the bright early- to intermediate-typegalaxies span a much larger range in brightness than the nuclei whichare typically found embedded in bulgeless late-type disks: the nucleiembedded in the early- to intermediate-type galaxies reach, on thebright end, values up to HAB~-17.7 mag; (2) nuclei are foundin both nonbarred and barred hosts, in large-scale (>~1 kpc) as wellas in nuclear (up to a few 100 pc) bars; (3) there is a significantincrease in half-light radius with increasing luminosity of the nucleusin the early/intermediate types (a decade in radius for ~8 magbrightening), a correlation which was found in the V band and which isalso seen in the NIR data; (4) the nuclei of early/intermediate-typespirals cover a large range of optical-NIR colors, from V-H~-0.5 to 3.Some nuclei are bluer and others redder than the surroundinggalaxy,indicating the presence of activity or reddening by dust in many ofthese systems; (5) someearly/intermediate nuclei are elongated and/orslightly offset from the isophotal center of the host galaxy. Onaverage, however, these nuclei appear as centered, star-cluster-likestructures similar to those whichare found in the late-type disks. Basedon observations with the NASA/ESA Hubble Space Telescope, obtained atthe Space Telescope Science Institute, which is operated by Associationof Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555.
| Local velocity field from sosie galaxies. I. The Peebles' model
Pratton et al. (1997) showed that the velocity field around clusterscould generate an apparent distortion that appears as tangentialstructures or radial filaments. In the present paper we determine theparameters of the Peebles' model (1976) describing infall of galaxiesonto clusters with the aim of testing quantitatively the amplitude ofthis distortion. The distances are determined from the concept of sosiegalaxies (Paturel 1984) using 21 calibrators for which the distanceswere recently calculated from two independent Cepheid calibrations. Weuse both B and I-band magnitudes. The Spaenhauer diagram method is usedto correct for the Malmquist bias. We give the equations for theconstruction of this diagram. We analyze the apparent Hubble constant indifferent regions around Virgo and obtain simultaneously the Local Groupinfall and the unperturbed Hubble constant. We found:[VLG-infall = 208 ± 9 km s-1] [\log H =1.82 ± 0.04 (H ≈ 66 ± 6 km s-1Mpc-1).] The front side and backside infalls can be seenaround Virgo and Fornax. In the direction of Virgo the comparison ismade with the Peebles' model. We obtain: [vinfall} =CVirgo/r0.9 ± 0.2] withCVirgo=2800 for Virgo and CFornax=1350 for Fornax,with the adopted units (km s-1 and Mpc). We obtain thefollowing mean distance moduli: [μVirgo=31.3 ± 0.2(r=18 Mpc )] [μFornax=31.7 ± 0.3 (r=22 Mpc). ] Allthese quantities form an accurate and coherent system. Full Table 2 isonly available in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/393/57
| Asymmetry in Isolated, Morphologically Normal SA Galaxies
We have examined the morphological and dynamical H I symmetry propertiesof a sample of moderately inclined Sa galaxies classified asmorphologically normal. The sample galaxies were known a priori toexhibit kinematic peculiarities ranging from warps to independent,wholly decoupled disks and are possibly the remnants of minor mergers.We compare the asymmetry of the rotation curves to global kinematicasymmetry and find a relationship between rotation curve asymmetry andthe kinematic n=2 mode. We have also examined the kinematics of thesegalaxies following the discussion of Briggs and find that the warpsobserved in the H I disks of these galaxies deviate significantly fromthe simple rules for warps that commonly apply.
| 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.
| Kinematic Evidence of Minor Mergers in Normal SA Galaxies: NGC 3626, NGC 3900, NGC 4772, and NGC 5854
BVRI and Hα imaging and long-slit optical spectroscopic data arepresented for four morphologically normal and relatively isolated Sagalaxies, NGC 3626, NGC 3900, NGC 4772, and NGC 5854. VLA H I synthesisimaging is presented for the first three objects. In all four galaxies,evidence of kinematic decoupling of ionized gas components is found inthe long-slit spectroscopic data; the degree and circumstances of thedistinct kinematics vary from complete counterrotation of all of the gasfrom all of the stars (NGC 3626) to nuclear gas disks decoupled from thestars (NGC 5854) to anomalous velocity central gas components (NGC 3900and NGC 4772). In the three objects mapped in H I, the neutral gasextends far beyond the optical radius, RHI/R25>=2. In general, the H I surface density isvery low, and the outer H I is patchy and asymmetric (NGC 3900) or foundin a distinct ring, exterior to the optical edge (NGC 3626 and NGC4772). While the overall H I velocity fields are dominated by circularmotions, strong warps are suggested in the outer regions by bending ofthe minor axis isovelocity contours (NGC 3900) and/or systematic shiftsin position angle between inner and outer rings (NGC 3626 and NGC 4772).In the interior, coincidence is found between the Hα and H I inrings, sometimes partial and crisscrossed by dust lanes. Optical imagingis also presented for NGC 4138 previously reported by Jore et al. toshow counterrotating stellar components. The multiwavelength evidence isinterpreted in terms of the kinematic ``memory'' of past minor mergersin objects that otherwise exhibit no morphological signs of interaction.
| Box- and peanut-shaped bulges. I. Statistics
We present a classification for bulges of a complete sample of ~ 1350edge-on disk galaxies derived from the RC3 (Third Reference Catalogue ofBright Galaxies, de Vaucouleurs et al. \cite{rc3}). A visualclassification of the bulges using the Digitized Sky Survey (DSS) inthree types of b/p bulges or as an elliptical type is presented andsupported by CCD images. NIR observations reveal that dust extinctiondoes almost not influence the shape of bulges. There is no substantialdifference between the shape of bulges in the optical and in the NIR.Our analysis reveals that 45% of all bulges are box- and peanut-shaped(b/p). The frequency of b/p bulges for all morphological types from S0to Sd is > 40%. In particular, this is for the first time that such alarge frequency of b/p bulges is reported for galaxies as late as Sd.The fraction of the observed b/p bulges is large enough to explain theb/p bulges by bars. Partly based on observations collected at ESO/LaSilla (Chile), DSAZ/Calar Alto (Spain), and Lowell Observatory/Flagstaff(AZ/U.S.A.). Tables 6 and 7 are only available in electronic form at CDSvia anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| Arcsecond Positions of UGC Galaxies
We present accurate B1950 and J2000 positions for all confirmed galaxiesin the Uppsala General Catalog (UGC). The positions were measuredvisually from Digitized Sky Survey images with rms uncertaintiesσ<=[(1.2")2+(θ/100)2]1/2,where θ is the major-axis diameter. We compared each galaxymeasured with the original UGC description to ensure high reliability.The full position list is available in the electronic version only.
| The Centers of Early- to Intermediate-Type Spiral Galaxies: A Structural Analysis
A recent Hubble Space Telescope (HST)/WFPC2 visual survey of early- andintermediate-type spiral galaxies has unveiled a great complexity in theinner regions of these systems, which include a high fraction ofphotometrically distinct compact sources sitting at the galactic centers(``nuclei''). The faint nuclei (M_V>~-12) are typically hosted byrather amorphous, quiescent, bulgelike structures with an exponential(rather than the classical R^1/4) light profile. These ``exponentialbulges'' are commonly found inside the intermediate-type disks,consistent with previous studies. Brighter nuclei (M_V<~-12) aretypically found instead in the centers of galaxies with circumnuclearrings/arms of star formation or dust and an active, i.e., H II- orAGN-type, central spectrum at ground-based resolution. On the structuralplane of half-light radius (R_e) versus mean surface brightness withinthe half-light radius (mu_e), faint and bright nuclei overlap with, andfill the region of parameter space between, the old Milky Way globularclusters and the young star clusters, respectively, with typical R_e ofabout a few up to ~20 pc. On the same plane, the exponential bulges havesignificantly fainter mu_e than R^1/4 bulges for any given radius andfollow a mu_e-R_e relation typical of disks, which strengthens thesuggestion that the exponential bulges grow inside the disks as a resultof the secular evolution of the latter. Under the likely assumption thatthe visual light from the faint nuclei embedded in the quiescentexponential bulges is of stellar origin and of a similar (>~1 Gyr)age for the central star clusters and their host bulges, the massesinferred for the former agree with those required to disrupt barscomparable in size to the latter. This offers support to scenarios inwhich the exponential bulges grow inside the disks owing to the orbitaldisruption of progenitor bars caused by the growth of a centralconcentration of mass and suggests that this specific mode of bulgeformation is (still) active in the present-day universe. On the otherhand, the presence of the massive clusters at the very center of thelow-density exponential bulges should prevent any other ``nuclear'' barfrom forming, thereby preventing further infall of dissipative fuel tothe nuclear regions. This may argue against the possibility of evolvingthe exponential bulges into denser, R^1/4 bulges by a simple looping forseveral cycles of the bar formation/disruption mechanism.
| Groups of galaxies. III. Some empirical characteristics.
Not Available
| Bulge-Disk Decomposition of 659 Spiral and Lenticular Galaxy Brightness Profiles
We present one of the largest homogeneous sets of spiral and lenticulargalaxy brightness profile decompositions completed to date. The 659galaxies in our sample have been fitted with a de Vaucouleurs law forthe bulge component and an inner-truncated exponential for the diskcomponent. Of the 659 galaxies in the sample, 620 were successfullyfitted with the chosen fitting functions. The fits are generally welldefined, with more than 90% having rms deviations from the observedprofile of less than 0.35 mag. We find no correlations of fittingquality, as measured by these rms residuals, with either morphologicaltype or inclination. Similarly, the estimated errors of the fittedcoefficients show no significant trends with type or inclination. Thesedecompositions form a useful basis for the study of the lightdistributions of spiral and lenticular galaxies. The object base issufficiently large that well-defined samples of galaxies can be selectedfrom it.
| Spiral Galaxies with WFPC2. II. The Nuclear Properties of 40 Objects
We report the analysis of Hubble Space Telescope Wide Field PlanetaryCamera 2 F606W images of 40 spiral galaxies belonging to the sampleintroduced in Paper I, where 35 other targets were discussed. Wedescribe the optical morphological properties of the new 40 galaxies,derive the surface brightness profiles for 25 of them, and present theresults of photometric decompositions of these profiles into a ``bulge''(R^1/4 or exponential) and a disk component. The analysis of theenlarged sample of 75 galaxies puts on a statistically more solid groundthe main results presented in Paper I: (1) In ~30% of the galaxies, theinner, morphologically distinct structures have an irregular appearance.Some of these ``irregular bulges'' are likely to be currently formingstars. (2) Resolved, central compact sources are detected in about 50%of the galaxies. (3) The central compact sources in galaxies withnuclear star formation are brighter, for similar sizes, than those innon-star-forming galaxies. (4) The luminosity of the compact sourcescorrelates with the total galactic luminosity. Furthermore, the analysisof the enlarged sample of 75 objects shows the following: (a) Several ofthe nonclassical inner structures are well fitted by an exponentialprofile. These ``exponential bulges'' are typically fainter than R^1/4bulges, for a given total galaxy luminosity and (catalog) Hubble typelater than Sab. (b) Irregular/exponential bulges typically host centralcompact sources. (c) The central sources are present in all types ofdisk galaxies, starting with systems as early as S0a. About 60% of Sb toSc galaxies host a central compact source. Many of the galaxies thathost compact sources contain a barred structure. (d) Galaxies withapparent nuclear star formation, which also host the brightest compactsources, are preferentially the early- and intermediate-type (S0a-Sb)systems. (e) None of the features depend on environment: isolated andnonisolated galaxies show indistinguishable properties. Independent ofthe physical nature of the nonclassical inner structures, our mainconclusion is that a significant fraction of galaxies classified fromthe ground as relatively early-type spirals show a rich variety ofcentral properties and little or no morphological/photometric evidencefor a smooth, R^1/4 law bulge. Based on observations with the NASA/ESAHubble Space Telescope, obtained at the Space Telescope ScienceInstitute, which is operated by the Association of Universities forResearch in Astronomy, Inc., under NASA contract NAS 5-26555.
| Catalogue of HI maps of galaxies. I.
A catalogue is presented of galaxies having large-scale observations inthe HI line. This catalogue collects from the literature the informationthat characterizes the observations in the 21-cm line and the way thatthese data were presented by means of maps, graphics and tables, forshowing the distribution and kinematics of the gas. It containsfurthermore a measure of the HI extension that is detected at the levelof the maximum sensitivity reached in the observations. This catalogueis intended as a guide for references on the HI maps published in theliterature from 1953 to 1995 and is the basis for the analysis of thedata presented in Paper II. The catalogue is only available inelectronic form at the CDS via anonymous ftp 130.79.128.5 orhttp://cdsweb.u-strasbg.fr/Abstract.html
| 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.
| Hubble constant from sosie galaxies and HIPPARCOS geometrical calibration
New distances, larger than previous ones, have been obtained for M 31and M 81 based on the geometrical zero-point of the CepheidPeriod-luminosity relation provided by the HIPPARCOS satellite. Bycombining them with independent determinations we define reasonableranges for the distances of these important calibrating galaxies. Onthis basis, we determine the Hubble constant from the method of sosies(look-alike) galaxies, galaxies having the same characteristics than thecalibrators. The method is quite secure because it is purelydifferential and it does not depend on any assumption (apart from thenatural one that two sosies galaxies have similar absoluteluminosities). Nevertheless, the Malmquist bias has to be taken intoaccount. The observations behave exactly as predicted from theanalytical formulation of the bias. Thus, rejecting galaxies which areaffected by the Malmquist bias we derive the Hubble constant: H_o = 60+/- 10 (external) km.s^{-1}.Mpc^{-1} If we strictly use the calibrationobtained with HIPPARCOS and if the bias found in the Period-LuminosityRelation is considered, the Hubble constant is smaller than this (~ 55km.s(-1}.Mpc({-1)) ). This gives arguments in favour of thelong-distance scale. We briefly discuss possible improvements aiming atstill reducing the uncertainty.
| A Search for ``Dwarf'' Seyfert Nuclei. III. Spectroscopic Parameters and Properties of the Host Galaxies
We have completed an optical spectroscopic survey of the nuclear regions(r <~ 200 pc) of a large sample of nearby galaxies. Although the mainobjectives of the survey are to search for low-luminosity activegalactic nuclei and to quantify their luminosity function, the databasecan be used for a variety of other purposes. This paper presentsmeasurements of the spectroscopic parameters for the 418 emission-linenuclei, along with a compilation of the global properties of all 486galaxies in the survey. Stellar absorption generally poses a seriousobstacle to obtaining accurate measurement of emission lines in nearbygalactic nuclei. We describe a procedure for removing the starlight fromthe observed spectra in an efficient and objective manner. The mainparameters of the emission lines (intensity ratios, fluxes, profilewidths, and equivalent widths) are measured and tabulated, as areseveral stellar absorption-line and continuum indices useful forstudying the stellar population. Using standard nebular diagnostics, wedetermine the probable ionization mechanisms of the emission-lineobjects. The resulting spectral classifications provide extensiveinformation on the demographics of emission-line nuclei in the nearbyregions of the universe. This new catalog contains over 200 objectsshowing spectroscopic evidence for recent star formation and an equallylarge number of active galactic nuclei, including 46 that show broad Halpha emission. These samples will serve as the basis of future studiesof nuclear activity in nearby galaxies.
| Optical and I-band surface photometry of spiral galaxies. I. The data.
We present V- and I-band CCD surface photometry on 234 inclined Sa-Sdgalaxies, completed by similar data in B and R for a reduced subsample.In this first paper of a series, the reduction of the data is discussed,and several comparisons are made with other recent works. Radialprofiles are presented for the surface brightness and thecharacteristics of ellipses fitted to isophotes; global, effective, andisophotal parameters are listed. All the results are available inelectronic form.
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