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Ionized gas and stellar kinematics of seventeen nearby spiral galaxies
Ionized gas and stellar kinematics have been measured along the majoraxes of seventeen nearby spiral galaxies of intermediate to latemorphological type. We discuss the properties of each sample galaxy,distinguishing between those characterized by regular or peculiarkinematics. In most of the observed galaxies, ionized gas rotates morerapidly than stars and has a lower velocity dispersion, as is to beexpected if the gas is confined in the disc and supported by rotationwhile the stars are mostly supported by dynamical pressure. In a fewobjects, gas and stars show almost the same rotational velocity and lowvelocity dispersion, suggesting that their motion is dominated byrotation. Incorporating the spiral galaxies studied by Bertola et al.(\cite{Bertola1996}), Corsini et al. (\cite{Corsini1999},\cite{Corsini2003}) and Vega Beltrán et al. (\cite{Vega2001}) wehave compiled a sample of 50 S0/a-Scd galaxies, for which the major-axiskinematics of the ionized gas and stars have been obtained with the samespatial (≈1'') and spectral (≈50 km;s-1) resolution,and measured with the same analysis techniques. This allowed us toaddress the frequency of counter-rotation in spiral galaxies. It turnsout that less than 12% and less than 8% (at the 95% confidence level) ofthe sample galaxies host a counter-rotating gaseous and stellar disc,respectively. The comparison with S0 galaxies suggests that theretrograde acquisition of small amounts of external gas gives rise tocounter-rotating gaseous discs only in gas-poor S0s, while in gas-richspirals the newly acquired gas is swept away by the pre-existing gas.Counter-rotating gaseous and stellar discs in spirals are formed onlyfrom the retrograde acquisition of large amounts of gas exceeding thatof pre-existing gas, and subsequent star formation, respectively.Based on observations carried out at the European Southern Observatory,La Silla (Chile) (ESO 56.A-0684 and 57.A-0569).Tables 3 and 4 are only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/424/447Full Fig. \ref{fig:kinematics} and Figs. \ref{fig:gascomparison} and\ref{fig:starcomparison} are only available in electronic form athttp://www.edpsciences.org
| A search for Low Surface Brightness galaxies in the near-infrared. III. Nançay H I line observations
A total of 334 Low Surface Brightness galaxies detected in the 2MASSall-sky near-infrared survey have been observed in the 21 cm H I lineusing the Nançay telescope. All have a Ks-band meancentral surface brightness, measured within a 5'' radius, fainter than18 mag arcsec-2 and a Ks-band isophotal radius atthe 20 mag arcsec-2 level larger than 20''. We present globalH I line parameters for the 171 clearly detected objects and the 23marginal detections, as well as upper limits for the undetected objects.The 171 clear detections comprise 50 previously uncatalogued objects and41 objects with a PGC entry only.Tables 3-5 are only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/408/465Figures 1 and 2 are only available in electronic form athttp://www.edpsciences.org
| A search for Low Surface Brightness galaxies in the near-infrared. I. Selection of the sample
A sample of about 3800 Low Surface Brightness (LSB) galaxies wasselected using the all-sky near-infrared (J, H and Ks-band)2MASS survey. The selected objects have a mean central surfacebrightness within a 5'' radius around their centre fainter than 18 magarcsec-2 in the Ks band, making them the lowestsurface brightness galaxies detected by 2MASS. A description is given ofthe relevant properties of the 2MASS survey and the LSB galaxy selectionprocedure, as well as of basic photometric properties of the selectedobjects. The latter properties are compared to those of other samples ofgalaxies, of both LSBs and ``classical'' high surface brightness (HSB)objects, which were selected in the optical. The 2MASS LSBs have aBT_c-KT colour which is on average 0.9 mag bluerthan that of HSBs from the NGC. The 2MASS sample does not appear tocontain a significant population of red objects.All tables and Figs. 2a-c are only available in electronic form athttp://www.edpsciences.org
| Position-velocity diagrams of ionized gas in the inner regions of disk galaxies
We use long-slit spectroscopy along the major axis of a sample of 23nearby disk galaxies to study the kinematic properties of theionized-gas component in their inner regions. For each galaxy, we derivethe position-velocity diagram of the ionized gas from its emissionlines. We discuss the variety of shapes observed in suchposition-velocity diagrams by comparing the gas velocity gradient,velocity dispersion and integrated flux measured in the inner (r =~+/-1'') and outer regions (r =~ +/-4''). This kind of analysis allowsthe identification of galaxies which are good candidates to host acircumnuclear Keplerian gaseous disk rotating around a central massconcentration, and to follow up with Hubble Space Telescopeobservations. Based on observations carried out at European SouthernObservatory (ESO N.58, A-0564), at the Multiple Mirror Telescope, whichis a joint facility of the Smithsonian Institution and the University ofArizona, and at the Isaac Newton Telescope operated by the Isaac Newtongroup at the La Palma island at the Spanish Observatorio del Roque delos Muchachos of the Instituto de Astrofisica de Canarias.
| Modelling gaseous and stellar kinematics in the disc galaxies NGC 772, 3898 and 7782
We present V-band surface photometry and major-axis kinematics of starsand ionized gas of three early-type spiral galaxies, namely NGC 772,3898 and 7782. For each galaxy we present a self-consistent Jeans modelfor the stellar kinematics, adopting the light distribution of bulge anddisc derived by means of a two-dimensional parametric photometricdecomposition. This allows us to investigate the presence ofnon-circular gas motions, and derive the mass distribution of luminousand dark matter in these objects. NGC 772 and 7782 have apparentlynormal kinematics with the ionized gas tracing the gravitationalequilibrium circular speed. This is not true in the innermost region(|r|<~8arcsec) of NGC 3898, where the ionized gas is rotating moreslowly than the circular velocity predicted by dynamical modelling. Thisphenomenon is common in the bulge-dominated galaxies for which dynamicalmodelling enables us to make the direct comparison between the gasvelocity and the circular speed, and it poses questions about thereliability of galaxy mass distributions derived by the directdecomposition of the observed ionized-gas rotation curve into thecontributions of luminous and dark matter.
| The Radio Galaxy Populations of Nearby Northern Abell Clusters
We report on the use of the NRAO VLA Sky Survey (NVSS) to identify radiogalaxies in 18 nearby Abell clusters. The listings extend from the coresof the clusters out to radii of 3 h-175 Mpc, whichcorresponds to 1.5 Abell radii and approximately 4 orders of magnitudein galaxy density. To create a truly useful catalog, we have collectedoptical spectra for nearly all of the galaxies lacking public velocitymeasurements. Consequently, we are able to discriminate between thoseradio galaxies seen in projection on the cluster and those that are inactuality cluster members. The resulting catalog consists of 329 clusterradio galaxies plus 138 galaxies deemed foreground or backgroundobjects, and new velocity measurements are reported for 273 of theseradio galaxies. The motivation for the catalog is the study of galaxyevolution in the cluster environment. The radio luminosity function is apowerful tool in the identification of active galaxies, as it isdominated by star-forming galaxies at intermediate luminosities andactive galactic nuclei (AGNs) at higher luminosities. The flux limit ofthe NVSS allows us to identify AGNs and star-forming galaxies down tostar formation rates less than 1 Msolar yr-1. Thissensitivity, coupled with the all-sky nature of the NVSS, allows us toproduce a catalog of considerable depth and breadth. In addition tothese data, we report detected infrared fluxes and upper limits obtainedfrom IRAS data. It is hoped that this database will prove useful in anumber of potential studies of the effect of environment on galaxyevolution. Based in part on observations obtained with the Apache PointObservatory 3.5 m telescope, which is owned and operated by theAstrophysical Research Consortium (ARC).
| Kinematics of Gas and Stars in 20 Disc Galaxies
In this paper we present the kinematics of the gas and/or the stars of asample of 20 disc galaxies. We investigate whether there is any relationbetween the kinematics of the gas and stars and the classicalmorphological type of the galaxies in the sample. We deduce that, inmost of the late-type spirals we have studied, the stars and the ionizedgas are moving with virtually circular velocity, except when thespectroscopic slit crosses a bar region. On the other hand, we found inthe central parts of early-type disc galaxies a wider variety ofdifferent behaviour of stars and gas. We find many possible factors thatcomplicate the classification of the kinematical properties of thegalaxies by their morphological type: the presence of counter-rotations(star vs. stars or star vs. gas), misalignment between the differentkinematic components present in the galaxy, the presence of a barstructure and its orientation with respect to the line of nodes of thegalaxy, and interactions and mergers or external accretion processes aresome of the problems we find in the study of the kinematics of a galaxy.
| Kinematics of Gas and Stars Along the Hubble Sequence
We present a comparison between the ionized gas and stellar kinematicsfor a sample of five early-to-intermediate disc galaxies. We measuredthe major axis V and σ radial profiles for both gas and stars, andthe h_3 and h_4 radial profiles of the stars. We also derived from theR-band surface photometry of each galaxy the light contribution of theirbulges and discs. In order to investigate the differences between thevelocity fields of the sample galaxies we adopted the self-consistentdynamical model by Pignatelli and Galletta (1999), which takes intoaccount the asymmetric drift effects, the projection effects along theline of sight and the non-Gaussian shape of the line profiles due to thepresence of different components with distinct dynamical behaviour. Wefind for the stellar component a sizeable asymmetric drift effect in theinner regions of all the sample galaxies, as results from comparingtheir stellar rotation curves with the circular velocity predicted bythe models. The galaxy sample is not wide enough to draw generalconclusions. However, we have found a possible correlation between thepresence of slowly rising gas rotation curves and the ratio of thebulge/disc half-luminosity radii, while there is no obvious correlationwith the key parameter represented by the morphological classification,namely the bulge/disc luminosity ratio. Systems with a diffuse,dynamically hot component (bulge or lens) with a scale length comparableto that of the disc are characterized by slowly rising gas rotationcurves. On the other hand, in systems with a small bulge the gas followsalmost circular motions, regardless of the luminosity of the bulgeitself. We noticed a similar behaviour also in the gas and stellarkinematics of the two early-type spiral galaxies modelled by Corsini etal. (1998).
| Kinematic properties of gas and stars in 20 disc galaxies
Ionized gas and stellar kinematical parameters have been measured alongthe major axis of 20 nearby disc galaxies. We discuss the properties ofeach sample galaxy, distinguishing between those characterized byregular or peculiar kinematics. In early-type disc galaxies, ionized gastends to rotate faster than stars and to have a lower velocitydispersion (Vg > Vstar and sigmag< sigmastar), whereas in late-type spirals, gas andstars show almost the same rotation velocities and velocity dispersions(Vg =~ Vstar and sigmag =~sigmastar ). Incorporating the early-type disc galaxiesstudied by Bertola et al. (1995), Fisher (1997) and Corsini et al.(1999), we have compiled a sample of some 40 galaxies for which themajor-axis radial profiles of both the stellar and gaseous componentshave been measured. The value of sigmastar measured atRe/4 turns out to be strongly correlated with the galaxymorphological type, while sigmag is not and sometimes takesvalues above the range expected from thermal motions or small-scaleturbulence. Based on observations carried out at the European SouthernObservatory, at the Multiple Mirror Telescope Observatory, at theObservatorio del Roque de los Muchachos, at the Observatorio del Teide,and at the Mount Graham International Observatory. Tables 5 and 6 areonly 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/374/394
| An Hα survey of eight Abell clusters: the dependence of tidally induced star formation on cluster density
We have undertaken a survey of Hα emission in a substantiallycomplete sample of CGCG galaxies of types Sa and later within 1.5 Abellradii of the centres of eight low-redshift Abell clusters (Abell 262,347, 400, 426, 569, 779, 1367 and 1656). Some 320 galaxies weresurveyed, of which 116 were detected in emission (39 per cent ofspirals, 75 per cent of peculiars). Here we present previouslyunpublished data for 243 galaxies in seven clusters. Detected emissionis classified as `compact' or `diffuse'. From an analysis of the fullsurvey sample, we confirm our previous identification of compact anddiffuse emission with circumnuclear starburst and disc emissionrespectively. The circumnuclear emission is associated either with thepresence of a bar, or with a disturbed galaxy morphology indicative ofongoing tidal interactions (whether galaxy-galaxy, galaxy-group, orgalaxy-cluster). The frequency of such tidally induced (circumnuclear)starburst emission in spirals increases from regions of lower to higherlocal galaxy surface density, and from clusters with lower to highercentral galaxy space density. The percentages of spirals classed asdisturbed and of galaxies classified as peculiar show a similar trend.These results suggest that tidal interactions for spirals are morefrequent in regions of higher local density and for clusters with highercentral galaxy density. The prevalence of such tidal interactions inclusters is expected from recent theoretical modelling of clusters witha non-static potential undergoing collapse and infall. Furthermore, inaccord with this picture, we suggest that peculiar galaxies arepredominantly ongoing mergers. We conclude that tidal interactions arelikely to be the main mechanism for the transformation of spirals to S0sin clusters. This mechanism operates more efficiently in higher densityenvironments, as is required by the morphological type-local surfacedensity (T-Σ) relation for galaxies in clusters. For regions ofcomparable local density, the frequency of tidally induced starburstemission is greater in clusters with higher central galaxy density. Thisimplies that, for a given local density, morphological transformation ofdisc galaxies proceeds more rapidly in clusters of higher central galaxydensity. This effect is considered to be the result of subclustermerging, and could account for the previously considered anomalousabsence of a significant T-Σ relation for irregular clusters atintermediate redshift.
| 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.
| Kinematics of gas and stars in spiral galaxies.
Not Available
| Arm structure in normal spiral galaxies, 1: Multivariate data for 492 galaxies
Multivariate data have been collected as part of an effort to develop anew classification system for spiral galaxies, one which is notnecessarily based on subjective morphological properties. A sample of492 moderately bright northern Sa and Sc spirals was chosen for futurestatistical analysis. New observations were made at 20 and 21 cm; thelatter data are described in detail here. Infrared Astronomy Satellite(IRAS) fluxes were obtained from archival data. Finally, new estimatesof arm pattern radomness and of local environmental harshness werecompiled for most sample objects.
| A list of some corrections to Zwicky's Catalogue of Galaxies and Clusters of Galaxies
Not Available
| Alignments of galaxies in the Perseus supercluster
The relative orientations of the galaxies belonging to the Perseussupercluster are investigated. The result is a lack of alignment in anypreferred direction of the supercluster galaxies (ellipticals, spiralsand both), except in a selected region of the supercluster, whosesignificance is low. Moreover no evidence of anisotropy in the relativeorientations of neighboring galaxies has been found.
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