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K-band observations of boxy bulges - I. Morphology and surface brightness profiles
In this first paper of a series on the structure of boxy andpeanut-shaped (B/PS) bulges, Kn-band observations of a sample of 30edge-on spiral galaxies are described and discussed. Kn-bandobservations best trace the dominant luminous galactic mass and areminimally affected by dust. Images, unsharp-masked images, as well asmajor-axis and vertically summed surface brightness profiles arepresented and discussed. Galaxies with a B/PS bulge tend to have a morecomplex morphology than galaxies with other bulge types, more oftenshowing centred or off-centred X structures, secondary maxima along themajor-axis and spiral-like structures. While probably not uniquelyrelated to bars, those features are observed in three-dimensional N-bodysimulations of barred discs and may trace the main bar orbit families.The surface brightness profiles of galaxies with a B/PS bulge are alsomore complex, typically containing three or more clearly separatedregions, including a shallow or flat intermediate region (Freeman TypeII profiles). The breaks in the profiles offer evidence for bar-driventransfer of angular momentum and radial redistribution of material. Theprofiles further suggest a rapid variation of the scaleheight of thedisc material, contrary to conventional wisdom but again as expectedfrom the vertical resonances and instabilities present in barred discs.Interestingly, the steep inner region of the surface brightness profilesis often shorter than the isophotally thick part of the galaxies, itselfalways shorter than the flat intermediate region of the profiles. Thesteep inner region is also much more prominent along the major-axis thanin the vertically summed profiles. Similarly to other recent work butcontrary to the standard `bulge + disc' model (where the bulge is boththick and steep), we thus propose that galaxies with a B/PS bulge arecomposed of a thin concentrated disc (a disc-like bulge) containedwithin a partially thick bar (the B/PS bulge), itself contained within athin outer disc. The inner disc likely formed secularly throughbar-driven processes and is responsible for the steep inner region ofthe surface brightness profiles, traditionally associated with a classicbulge, while the bar is responsible for the flat intermediate region ofthe surface brightness profiles and the thick complex morphologicalstructures observed. Those components are strongly coupled dynamicallyand are formed mostly of the same (disc) material, shaped by the weakbut relentless action of the bar resonances. Any competing formationscenario for galaxies with a B/PS bulge, which represent at least 45 percent of the local disc galaxy population, must explain equally well andself-consistently the above morphological and photometric properties,the complex gas and stellar kinematics observed, and the correlationsbetween them.
| On the nature of bulges in general and of box/peanut bulges in particular: input from N-body simulations
Objects designated as bulges in disc galaxies do not form a homogeneousclass. I distinguish three types: the classical bulges, the propertiesof which are similar to those of ellipticals and which form by collapseor merging; boxy and peanut bulges, which are seen in near-edge-ongalaxies and which are in fact just a part of the bar seen edge-on; and,finally, disc-like bulges, which result from the inflow of (mainly) gasto the centre-most parts, and subsequent star formation. I make adetailed comparison of the properties of boxy and peanut bulges withthose of N-body bars seen edge-on, and answer previously voicedobjections about the links between the two. I also present and analysesimulations where a boxy/peanut feature is present at the same time as aclassical spheroidal bulge, and compare them with observations. Finally,I propose a nomenclature that can help to distinguish between the threetypes of bulges and avoid considerable confusion.
| Bar Diagnostics in Edge-On Spiral Galaxies. III. N-Body Simulations of Disks
Present in over 45% of local spirals, boxy and peanut-shaped bulges aregenerally interpreted as edge-on bars and may represent a key phase inbar evolution. Aiming to test such claims, the kinematic properties ofself-consistent three-dimensional N-body simulations of bar-unstabledisks are studied. Using Gauss-Hermite polynomials to describe themajor-axis stellar kinematics, a number of characteristic bar signaturesare identified in edge-on disks: (1) a major-axis light profile with aquasi-exponential central peak and a plateau at moderate radii (Freemantype II profile); (2) a ``double-hump'' rotation curve; (3) a sometimesflat central velocity dispersion peak with a plateau at moderate radiiand occasional local central minimum and secondary peak; and (4) anh3-V correlation over the projected bar length. All of thesekinematic features are spatially correlated and can easily be understoodfrom the orbital structure of barred disks. They thus provide a reliableand easy-to-use tool to identify edge-on bars. Interestingly, they areall produced without dissipation and are increasingly realized to becommon in spirals, lending support to bar-driven evolution scenarios forbulge formation. So called ``figure-of-eight'' position-velocitydiagrams are never observed, as expected for realistic orbitalconfigurations. Although not uniquely related to triaxiality,line-of-sight velocity distributions with a high-velocity tail (i.e., anh3-V correlation) appear as particularly promising tracers ofbars. The stellar kinematic features identified grow in strength as thebar evolves and vary only slightly for small inclination variations.Many can be used to trace the bar length. Comparisons with observationsare encouraging and support the view that boxy and peanut-shaped bulgesare simply thick bars viewed edge-on.
| Stellar Kinematics of Boxy Bulges: Large-Scale Bars and Inner Disks
Long-slit stellar kinematic observations were obtained along the majoraxis of 30 edge-on spiral galaxies, 24 with a boxy or peanut-shaped(B/PS) bulge and six with other bulge types for comparison. Such B/PSbulges are identified in at least 45% of highly inclined systems, and agrowing body of theoretical and observational work suggests that theyare the edge-on projection of thickened bars. Profiles of the meanstellar velocity V, the velocity dispersion σ, as well as theasymmetric (h3) and symmetric (h4) deviations froma pure Gaussian are presented for all objects. Comparing these profileswith stellar kinematic bar diagnostics developed from N-bodysimulations, we find bar signatures in 24 of our sample galaxies (80%).Galaxies with a B/PS bulge typically show a double-humped rotation curvewith an intermediate dip or plateau. They also frequently show a ratherflat central velocity dispersion profile accompanied by a secondary peakor plateau, and numerous galaxies have a local central σ minimum(>~40%). The h3 profiles display up to three slopereversals. Most importantly, h3 is normally correlated with Vover the presumed bar length, contrary to expectations from axisymmetricdisks. These characteristic bar signatures strengthen the case for aclose relationship between B/PS bulges and bars and leave little roomfor other explanations of the bulges' shape. We also find thath3 is anticorrelated with V in the very center of mostgalaxies (>~60%), indicating that these objects additionally harborcold and dense decoupled (quasi-) axisymmetric central stellar disks,which may be related to the central light peaks. These central diskscoincide with previously identified star-forming ionized-gas disks(nuclear spirals) in gas-rich systems, and we argue that they formed outof gas accumulated by the bar at its center through inflow. As suggestedby N-body models, the asymmetry of the velocity profile (h3)appears to be a reliable tracer of asymmetries in disks, allowing us todiscriminate between axisymmetric and barred disks seen in projection.B/PS bulges (and thus a large fraction of all bulges) appear to be madeup mostly of disk material, which has acquired a large vertical extentthrough bar-driven vertical instabilities. Their formation is thusprobably dominated by secular evolution processes rather than merging.
| Evidence for a large stellar bar in the Low Surface Brightness galaxy UGC 7321
Late-type spiral galaxies are thought to be the dynamically simplesttype of disk galaxy and our understanding of their properties plays akey role in galaxy formation and evolution scenarios. The low surfacebrightness (LSB) galaxy UGC 7321, a nearby, isolated, ``superthin''edge-on galaxy, is an ideal object to study these purely disk-dominatedbulge-less galaxies. Although late type spirals are believed to exhibitthe simplest possible structure, even prior observations showeddeviations from a pure single component exponential disk in the case ofUGC 7321. We present for the first time photometric evidence forpeanut-shaped outer isophotes from a deep optical (R-band) image of UGC7321. Observations and dynamical modeling suggest thatboxy/peanut-shaped (b/p) bulges in general form through the bucklinginstability in bars of the parent galaxy disks. Together with recent HIobservations supporting the presence of a stellar bar in UGC 7321, thiscould be the earliest known case of the buckling process during theevolutionary life of a LSB galaxy, whereby material in the disk-bar hasstarted to be pumped up above the disk, but a genuine bulge has not yetformed.Based on observations obtained at the German-Spanish Astronomical Center(DSAZ), Calar Alto, jointly operated by the Max-Planck-Institut fürAstronomie Heidelberg and the Spanish National Commission for Astronomy.
| Orbital dynamics of three-dimensional bars - III. Boxy/peanut edge-on profiles
We present families, and sets of families, of periodic orbits thatprovide building blocks for boxy and peanut (hereafter b/p) edge-onprofiles. We find cases where the b/p profile is confined to the centralparts of the model and cases where a major fraction of the barparticipates in this morphology. A b/p feature can be built either by 3Dfamilies associated with 3D bifurcations of the x1 family, or, in somemodels, even by families related with the z-axis orbits and existingover large energy intervals. The `X'feature observed inside the boxy bulges of several edge-on galaxies canbe attributed to the peaks of successive x1v1 orbits, provided theirstability allows it. However in general, the x1v1 family has to overcomethe obstacle of a S ->Δ-> S transition in order to supportthe structure of a b/p feature. Other families that can be the backbonesof b/p features are x1v4 and z3.1s. The morphology and the size of theboxy or peanut-shaped structures we find in our models are determined bythe presence and stability of the families that support b/p features.The present study favours the idea that the observed edge-on profilesare the imprints of families of periodic orbits that can be found inappropriately chosen Hamiltonian systems, describing the potential ofthe bar.
| Edge-on boxy profiles in non-barred disc galaxies
Boxy edge-on profiles can be accounted for not only in models of barredgalaxies, but also in models of normal (non-barred) galaxies. Thus thepresence of a bar is not a sine qua non condition for the appearance ofthis feature, as often assumed. We show that a `boxy' or a `peanut'structure in the central parts of a model is due to the presence ofvertical resonances at which stable families of periodic orbitsbifurcate from the planar x1 family. The orbits of these families reachin their projections on the equatorial plane a maximum distance from thecentre, beyond which they increase their mean radii by increasing onlytheir deviations from the equatorial plane. The resulting orbitalprofiles are `stair-type' and constitute the backbone for the observedboxy structures in edge-on views of N-body models and, we believe, inedge-on views of disc galaxies. Since the existence of verticalresonances is independent of barred or spiral perturbations in the disc,`boxy' profiles may appear also in almost axisymmetric cases.
| 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.
| 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.
| 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
| Box- and peanut-shaped bulges. II. NIR observations
We have observed 60 edge-on galaxies in the NIR in order to study thestellar distribution in galaxies with box/peanut-shaped bulges. The muchsmaller amount of dust extinction at these wavelengths allows us toidentify in almost all target galaxies with box/peanut-shaped bulges anadditional thin, central component in cuts parallel to the major axis.This structure can be identified with a bar. The length of thisstructure scaled by the length of the bulge correlates with themorphologically classified shape of the bulge. This newly establishedcorrelation is therefore mainly interpreted as the projection of the barat different aspect angles. Galaxies with peanut bulges have a bar seennearly edge-on and the ratio of bar length to thickness, 14 +/- 4, canbe directly measured for the first time. In addition, the correlation ofthe boxiness of bulges with the bar strength indicates that the barcharacteristic could partly explain differences in the bulge shape.Furthermore, a new size relation between the box/peanut structure andthe central bulge is found. Our observations are discussed in comparisonto a N-body simulation for barred galaxies (Pfenniger & Friedli\cite{pfe}). We conclude that the inner region of barred disk galaxiesare build up by three distinct components: the spheroidal bulge, a thinbar, and a b/p structure most likely representing the thick part of thebar. Based on observations collected at ESO/La Silla (61.A-0143),DSAZ/Calar Alto, and TIRGO/Gornergrat.}
| At the Heart of Barred Galaxies
Not Available
| The Nature of Boxy/Peanut-Shaped Bulges in Spiral Galaxies
We present a systematic observational study of the relationship betweenbars and boxy/peanut-shaped (B/PS) bulges. We first review and discussproposed mechanisms for their formation, focusing on accretion andbar-buckling scenarios. Using new methods relying on the kinematics ofedge-on disks, we then look for bars in a large sample of edge-on spiralgalaxies with a B/PS bulge and in a smaller control sample of edge-onspirals with more spheroidal bulges. We present position-velocitydiagrams of the ionized gas obtained from optical long-slitspectroscopy. We show that almost all B/PS bulges are due to a thick barviewed edge-on, while only a few extreme cases may be due to theaccretion of external material. This strongly supports the bar-bucklingmechanism for the formation of B/PS bulges. None of the galaxies in thecontrol sample show evidence for a bar, which suggests conversely thatbars are generally B/PS.We consider the effects of dust in the disk ofthe galaxies but conclude that it does not significantly affect ourresults. Unusual emission-line ratios correlating with kinematicalstructures are observed in many objects, and we argue that this isconsistent with the presence of strong bars in the disk of the galaxies.As expected from N-body simulations, the boxy-peanut transition appearsto be related to the viewing angle, but more work is required to derivethe precise orientation of the bars in the bulges. The reliableidentification of bars in edge-on spiral galaxies opens up for the firsttime the possibility of studying observationally the vertical structureof bars.
| 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
| The nature of boxy/peanut spiral galaxies: Overview and new results
The formation mechanism of boxy/peanut-shaped bulges in spiral galaxieshas been a problem for many years. We briefly review here the possibleformation scenarios of boxy/peanut bulges, concentrating on both thebar-buckling and accretion hypotheses, and then describe anobservational program aimed at testing those various theories andstudying the vertical structure of edge-on bars. Our program includesoptical long-slit spectroscopy, HI line-imaging, near-infrared imaging,and multi-band optical imaging. New spectroscopic results (both opticaland HI) are presented on seven galaxies including five boxy/peanut-bulgespirals. Based on Kuijken & Merrifield's (1995) idea for detectingedge-on bars, we argue that these observations constitute a strong casein favour of the bar-buckling mechanism to form boxy/peanut-shapedbulges, but they also raise many questions and prompt for more detailedmodelling to be made. The implications of the observations concerningthe determination of rotation curves and of the physical conditions inbulges are also discussed.
| The circumnuclear region in the Seyfert 1 galaxy NGC 3227
This article presents Hα and [O iii] narrow-band images andlong-slit optical and near-infrared spectroscopy at position angles 65.5deg and 25 deg through the circumnuclear region in the Seyfert 1 galaxyNGC 3227. After subtraction of a bulge+disc model, the continuum imageat lambda5900A shows an excess of emission aligned with the companiongalaxy NGC 3226. We attribute this emission to a stellar bar induced bythe interaction. Along the leading parts of the bar, we find dust lanesand 70 per cent of the H ii regions detected in the disc. The Hαand [O iii] images show extended emission in the circumnuclear regionwith very different morphologies. [O iii] is elongated to the north andnearly aligned with the bar. This emission is formed by two kinematicalcomponents, a broad component blueshifted with respect to a narrowercomponent. The blue component could be photoionized by radiation fromthe active nucleus, but the red component might be associated with thestarburst detected to the west. The Hα image is aligned alongPA=65 deg, and shows a bright knot at 4arcsec south-west of the nucleusand a shell-like structure; there the line ratios can be fitted byphotoionization by a stellar source. To the north-east, the spectrumshows characteristics of a high-excitation low-ionization nuclearemission region (LINER), and the line ratios can be explained asphotoionization by a blackbody with a temperature of 140 000K,ionization parameter 0.001, and solar chemical composition with anoverabundance of N and S. Even though Hα and [O iii] presentdifferent morphologies, both are extended 500pc from the nucleus, insidethe inner Lindblad resonance; this suggests that gravitational torques,associated with the non-axisymmetric potential produced by the bar andby interaction with the companion galaxy, transport the gas to the innerLindblad resonance (ILR), from where it fuels the circumnuclear regionin NGC 3227.
| 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.
| A Catalog of Stellar Velocity Dispersions. II. 1994 Update
A catalog of central velocity dispersion measurements is presented,current through 1993 September. The catalog includes 2474 measurementsof 1563 galaxies. A standard set of 86 galaxies is defined, consistingof galaxies with at least three reliable, concordant measurements. It issuggested that future studies observe some of these standard galaxies sothat different studies can be normalized to a consistent system. Allmeasurements are reduced to a normalized system using these standards.
| A Merger Origin for X Structures in S0 Galaxies
Using numerical simulation, we study the response of a disk galaxy to amerger involving a low-mass satellite companion. During a progradesatellite accretion, the disk galaxy forms a strong bar in response tothe perturbation of the companion. After the accretion event is over,the bar buckles vertically due to a bending instability, sending diskmaterial well out of the disk plane. The material forms into an X-shapedfeature when seen edge-on, morphologically similar to X structuresobserved in several S0/Sa galaxies. The mechanism described here unitespreviously suggested accretion and bar instability hypotheses forforming X structures into a self-consistent scenario for merger-inducedformation and evolution of S0 galaxies. To complement these models, wealso present observations of the peculiar S0 galaxy Hickson 87a. Thethick disk, isophotal warping, and strong X structure described in themerger model are all evident in Hickson 87a, suggesting this galaxy maybe an excellent example of such merger-induced galaxy evolution.
| Integrated photoelectric magnitudes and color indices of bright galaxies in the Johnson UBV system
The photoelectric total magnitudes and color indices published in theThird Reference Catalogue of Bright Galaxies (RC3) are based on ananalysis of approximately equals 26,000 B, 25,000 B-V, and 17,000 U-Bmultiaperture measurements available up to mid 1987 from nearly 350sources. This paper provides the full details of the analysis andestimates of internal and external errors in the parameters. Thederivation of the parameters is based on techniques described by theVaucouleurs & Corwin (1977) whereby photoelectric multiaperture dataare fitted by mean Hubble-type-dependent curves which describe theintegral of the B-band flux and the typical B-V and U-B integrated colorgradients. A sophisticated analysis of the residuals of thesemeasurements from the curves was made to allow for the random andsystematic errors that effect such data. The result is a homogeneous setof total magnitudes BTA total colors(B-V)T and (U-B)T, and effective colors(B-V)e and (U-B)e for more than 3000 brightgalaxies in RC3.
| Hα velocity fields and rotation curves of galaxies in clusters. III. Nine galaxies in DC 1842-63.
Hα maps (continuum and line), velocity contour maps and rotationcurves are presented for 9 galaxies in the Southern cluster DC 1842-63.These data have been obtained from two-dimensional Hα observationsat the 3.60-m ESO Telescope equipped with CIGALE, a scanning Fabry-Perotinterferometer. They complete the set of 36 galaxies already observedwith the same kind of instrumentation at CFHT (Amram et al. 1992, 1994).
| Forming X-shapes in Disk Galaxies Through Minor Mergers
We have run fully self-consistent stellar dynamical simulations of theaccretion of a small galaxy by a large disk galaxy and found that anX-shaped structure forms in the disk after the merger is complete. Wewish to emphasize that this structure consists mostly of disk materialrather than accreted material. The result is morphologically similar tosuch peculiar S0 galaxies as NGC 128, NGC 7332, Hickson 87A, and IC4767, an assertion quantitatively supported by the ``a_4'' (cos 4 theta) coefficient. A possible evolutionary link between spiral and S0galaxies is suggested.
| The dynamics and structure of the S0 galaxy NGC 7332
Spectroscopic and photometric observations of the edge-on S0 galaxy NGC7332 are presented. The spectra show the galaxy to possess a rapidlycounter-rotating extended gas disk as detected from both (O III) 5007 Aand H alpha emission. Multiple slit orientations at a variety ofposition angles clearly show the decoupling of the angular momentabetween the stellar and gaseous components. The gas is distributedasymmetrically and displays noncircular motions indicating that it hasnot reached equilibrium. These observations are strong evidence insupport of an accretion process having occurred in NGC 7332. Broad R andB band CCD images show the boxy isophotes that NGC 7332 has long beenknown to possess while offset spectra taken parallel to the major andminor axes display the cylindrical rotation common to galaxies withbox-shaped bulges. The bulge of NGC 7332 is well described by anr1/4-law on both the major and minor axes while the outerdisk is exponential. The B-R color of the disk is uniform; the onlyindication of a trend to blue colors is a Delta(B-Rc)/Deltalog r= -0.04 +/- 0.01 gradient seen perpendicular to the bulge and disk.There exists a 10 sec long region of nearly constant surface brightnessalong the major axis between the bulge and disk components. Not likelydue to absorbing material, the relation of this feature to the alreadycomplicated structure of the galaxy is considered.
| Kinematics of extragalactic bulges: evidence that some bulges are really disks
Not Available
| General study of group membership. II - Determination of nearby groups
We present a whole sky catalog of nearby groups of galaxies taken fromthe Lyon-Meudon Extragalactic Database. From the 78,000 objects in thedatabase, we extracted a sample of 6392 galaxies, complete up to thelimiting apparent magnitude B0 = 14.0. Moreover, in order to considersolely the galaxies of the local universe, all the selected galaxieshave a known recession velocity smaller than 5500 km/s. Two methods wereused in group construction: a Huchra-Geller (1982) derived percolationmethod and a Tully (1980) derived hierarchical method. Each method gaveus one catalog. These were then compared and synthesized to obtain asingle catalog containing the most reliable groups. There are 485 groupsof a least three members in the final catalog.
| Nuclear molecular gas in the Virgo cluster S0 galaxy NGC 4710
The CO (J=1 yields 0) emission from NGC 4710, a star forming S0 galaxyin the Virgo Cluster, was synthesized with spatial and velocityresolutions of 7 arcsec and 26 km/s 1 respectively. The CO shows acompact morphology and corotates with the galaxy's stars and nuclearoptical emission-line gas. Analysis of the CO distribution andkinematics indicates that the nuclear molecular gas is probablygravitationally unstable, and this may explain why the galaxy ispresently forming stars. Four possible origins for the nuclear moleculargas are considered. An origin via bulge star ejecta being deposited intoa residual interstellar medium is favored.
| Dynamics of clusters of galaxies with central dominant galaxies. I - Galaxy redshifts
Optical redshifts are presented for a sample of 638 galaxies in thefields of the clusters Abell 85, DC 0107-46, Abell 496, Abell 2052, andDC 1842-63. The velocity histograms and wedge diagrams show evidence fora foreground sheet of galaxies in Abell 85 and background sheets ofgalaxies in DC 0107-46 and Abell 2052. The foreground group projectedagainst the center of Abell 85 found by Beers et al. (1991) isconfirmed. No evidence of substructure was found in Abell 496, Abell2052, and DC 1842-63. The clusters have global velocity dispersionsranging from 551 km/s for DC 1842-63 to 714 km/s for A496, and flatdispersion profiles. Mass estimates using the virial theorem and theprojected mass method range from 2.3 x 10 exp 14 solar masses for DC0107-46 to 1.1 x 10 exp 15 solar masses for A85.
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