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Dust properties of NGC 3801.
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| BIMA Millimeter-Wave Observations of the Core-Jet and Molecular Gas in the FR I Radio Galaxy NGC 3801
We present BIMA 3 mm observations of the radio continuum source and themolecular gas disk in the radio-loud Fanaroff and Riley type I (FR I)galaxy NGC 3801. We have detected a continuum source in the nucleus anddetermined that it has a flat millimeter-wave spectrum, suggesting thatthe emission is nonthermal and due to an AGN; the radio core is notevident in existing VLA observations. We also map the extended 3 mmemission from the previously known radio jets. In addition, we detect CO(1-0) emission associated with the dust disk observed in previous HSTimages. A velocity gradient is observed, indicating a 2 kpc radiusrotating gas ring or disk oriented roughly perpendicular to the radiojets. The inferred molecular gas mass of the disk isM(H2)=3×108 Msolar, about 1% ofthe dynamical mass. We also find a ~108 Msolarmolecular gas clump not associated with the gas disk. There is evidencethat this gas is associated with a merger and is infalling. Thissuggests that FR I activity is related to merger activity, as is thoughtto be the case for FR II radio galaxies. We also find indications thatone of the radio jets is entraining gas from the infalling moleculargas.
| The HST view of the nuclear emission line region in low luminosity radio-galaxies
We study the properties of the emission line regions in two samples oflow luminosity radio-galaxies, while focusing on the Compact EmissionLine Region (CELR) revealed to be a characteristic feature of theseobjects by HST narrow-band imaging. We find a strong correlation betweenline and optical continuum nuclear emission, which suggests that theoptical cores (most likely of non-thermal origin) can be directlyassociated to the source of ionizing photons, i.e. that we are seeing ajet-ionized narrow line region. A photon budget argument indicates thatthe optical nuclear sources produce sufficient photon flux provided thatthe covering factor of the circum-nuclear gas is rather large, onaverage 0.3. Analysis of HST images and spectra suggests that the CELRmay take the form of a pc-scale, high filling factor structure, possiblyan optically thin torus. Estimates of the CELR mass lead to values assmall as 10{-}10^3 Mȯ, and photon counting sets a limitto the Broad Line Region mass of M_BLR < 10-2Mȯ. When considered together with the low accretion rateand the tenuous torus structure, a general paucity of gas in theinnermost regions of low luminosity radio-galaxies emerges as the maincharacterizing difference from more powerful Active Galactic Nuclei.
| A dichotomy in the orientation of dust and radio jets in nearby low-power radio galaxies
We examine the properties of central dust in nearby quiescent and activeearly-type galaxies. The active galaxies are low-power radio galaxieswith Fanaroff & Riley type I or I/II radio jets. We focus on (a) thecomparison of the dust distributions in the active and quiescent galaxysamples; and (b) the relation between the radio jet and dustorientations. Our main observational conclusions are: (i) in line withprevious studies, the dust detection rate is higher in radio-jetgalaxies than in non radio-jet galaxies; (ii) radio galaxies contain ahigher fraction of regular dust “ellipses” compared toquiescent galaxies which contain more often irregular dustdistributions; (iii) the morphology, size and orientation of dustellipses and lanes in quiescent early-types and active early-types withkpc-scale radio jets is very similar; (iv) dust ellipses are alignedwith the major axis of the galaxy, dust lanes do not show a preferredalignment except for large (>kpc) dust lanes which are aligned withthe minor axis of the galaxy; and (v) as projected on the sky, jets donot show a preferred orientation relative to the galaxy major axis (andhence dust ellipses), but jets are preferentially perpendicular to dustlanes. We show that the dust ellipses are consistent with being nearlycircular thin disks viewed at random viewing angles. The lanes arelikely warped dust structures, which may be in the process of settlingdown to become regular disks or are being perturbed by anon-gravitational force. We use the observed dust-jet orientations toconstrain the three-dimensional angle θDJ between jetand dust. For dust-lane galaxies, the jet is approximately perpendicularto the dust structure, while for dust-ellipse galaxies there is a muchwider distribution of θDJ. We discuss two scenariosthat could explain the dust/jet/galaxy orientation dichotomy. If lanesare indeed settling, then the jet orientation apparently is roughlyaligned with the angular momentum of the dust before it settles. Iflanes are perturbed by a jet-related force, it appears that it causesthe dust to move out of its equilibrium plane in the galaxy into a planewhich is perpendicular to the jet.
| Stacking Searches for Gamma-Ray Emission above 100 MeV from Radio and Seyfert Galaxies
The EGRET telescope on board Compton Gamma Ray Observatory detected morethan 60 sources of high-energy gamma radiation associated with activegalactic nuclei (AGNs). All but one of those belong to the blazarsubclass; the only exception is the nearby radio galaxy Centaurus A.Since there is no obvious reason other than proximity to expect Cen A tobe the only nonblazar AGN emitting in high-energy gamma rays, we haveutilized the ``stacking'' technique to search for emission above 100 MeVfrom two nonblazar AGN subclasses, radio galaxies and Seyfert galaxies.Maps of gamma-ray counts, exposure, and diffuse background have beencreated, then co-added in varying numbers based on sorts by redshift, 5GHz flux density, and optical brightness, and finally tested forgamma-ray emission. No detection significance greater than 2 σ hasbeen found for any subclass, sorting parameter, or number of objectsco-added. Monte Carlo simulations have also been performed to validatethe technique and estimate the significance of the results.
| Properties of isolated disk galaxies
We present a new sample of northern isolated galaxies, which are definedby the physical criterion that they were not affected by other galaxiesin their evolution during the last few Gyr. To find them we used thelogarithmic ratio, f, between inner and tidal forces acting upon thecandidate galaxy by a possible perturber. The analysis of thedistribution of the f-values for the galaxies in the Coma cluster leadus to adopt the criterion f ≤ -4.5 for isolated galaxies. Thecandidates were chosen from the CfA catalog of galaxies within thevolume defined by cz ≤5000 km s-1, galactic latitudehigher than 40o and declination ≥-2.5o. Theselection of the sample, based on redshift values (when available),magnitudes and sizes of the candidate galaxies and possible perturberspresent in the same field is discussed. The final list of selectedisolated galaxies includes 203 objects from the initial 1706. The listcontains only truly isolated galaxies in the sense defined, but it is byno means complete, since all the galaxies with possible companions underthe f-criterion but with unknown redshift were discarded. We alsoselected a sample of perturbed galaxies comprised of all the diskgalaxies from the initial list with companions (with known redshift)satisfying f ≥ -2 and \Delta(cz) ≤500 km s-1; a totalof 130 objects. The statistical comparison of both samples showssignificant differences in morphology, sizes, masses, luminosities andcolor indices. Confirming previous results, we found that late spiral,Sc-type galaxies are, in particular, more frequent among isolatedgalaxies, whereas Lenticular galaxies are more abundant among perturbedgalaxies. Isolated systems appear to be smaller, less luminous and bluerthan interacting objects. We also found that bars are twice as frequentamong perturbed galaxies compared to isolated galaxies, in particularfor early Spirals and Lenticulars. The perturbed galaxies have higherLFIR/LB and Mmol/LB ratios,but the atomic gas content is similar for the two samples. The analysisof the luminosity-size and mass-luminosity relations shows similartrends for both families, the main difference being the almost totalabsence of big, bright and massive galaxies among the family of isolatedsystems, together with the almost total absence of small, faint and lowmass galaxies among the perturbed systems. All these aspects indicatethat the evolution induced by interactions with neighbors would proceedfrom late, small, faint and low mass Spirals to earlier, bigger, moreluminous and more massive spiral and lenticular galaxies, producing atthe same time a larger fraction of barred galaxies but preserving thesame relations between global parameters. The properties we found forour sample of isolated galaxies appear similar to those of high redshiftgalaxies, suggesting that the present-day isolated galaxies could bequietly evolved, unused building blocks surviving in low densityenvironments.Tables \ref{t1} and \ref{t2} are only available in electronic form athttp://www.edpsciences.org
| Space Telescope Imaging Spectrograph Spectroscopy of the Emission-Line Gas in the Nuclei of Nearby FR-I Galaxies
We present the results of the analysis of a set of medium-resolutionspectra, obtained by the Space Telescope Imaging Spectrograph on boardthe Hubble Space Telescope, of the emission-line gas present in thenuclei of a complete sample of 21 nearby, early-type galaxies with radiojets (the UGC FR-I Sample). For each galaxy nucleus we presentspectroscopic data in the region of Hα and the derived kinematics.We find that in 67% of the nuclei the gas appears to be rotating and,with one exception, the cases where rotation is not seen are eitherface-on or have complex central morphologies. We find that in 62% of thenuclei the fit to the central spectrum is improved by the inclusion of abroad component. The broad components have a mean velocity dispersion of1349+/-345 km s-1 and are redshifted from the narrow linecomponents (assuming an origin in Hα) by 486+/-443 kms-1.Based on observations with the NASA/ESA Hubble Space Telescope, obtainedat the Space Telescope Science Institute, which is operated by theAssociation of Universities for Research in Astronomy, Inc., under NASAcontract NAS 5-26555.
| Redshift-Distance Survey of Early-Type Galaxies: Spectroscopic Data
We present central velocity dispersions and Mg2 line indicesfor an all-sky sample of ~1178 elliptical and S0 galaxies, of which 984had no previous measures. This sample contains the largest set ofhomogeneous spectroscopic data for a uniform sample of ellipticalgalaxies in the nearby universe. These galaxies were observed as part ofthe ENEAR project, designed to study the peculiar motions and internalproperties of the local early-type galaxies. Using 523 repeatedobservations of 317 galaxies obtained during different runs, the dataare brought to a common zero point. These multiple observations, takenduring the many runs and different instrumental setups employed for thisproject, are used to derive statistical corrections to the data and arefound to be relatively small, typically <~5% of the velocitydispersion and 0.01 mag in the Mg2 line strength. Typicalerrors are about 8% in velocity dispersion and 0.01 mag inMg2, in good agreement with values published elsewhere.
| Redshift-Distance Survey of Early-Type Galaxies: Circular-Aperture Photometry
We present R-band CCD photometry for 1332 early-type galaxies, observedas part of the ENEAR survey of peculiar motions using early-typegalaxies in the nearby universe. Circular apertures are used to tracethe surface brightness profiles, which are then fitted by atwo-component bulge-disk model. From the fits, we obtain the structuralparameters required to estimate galaxy distances using theDn-σ and fundamental plane relations. We find thatabout 12% of the galaxies are well represented by a pure r1/4law, while 87% are best fitted by a two-component model. There are 356repeated observations of 257 galaxies obtained during different runsthat are used to derive statistical corrections and bring the data to acommon system. We also use these repeated observations to estimate ourinternal errors. The accuracy of our measurements are tested by thecomparison of 354 galaxies in common with other authors. Typical errorsin our measurements are 0.011 dex for logDn, 0.064 dex forlogre, 0.086 mag arcsec-2 for<μe>, and 0.09 for mRC,comparable to those estimated by other authors. The photometric datareported here represent one of the largest high-quality and uniformall-sky samples currently available for early-type galaxies in thenearby universe, especially suitable for peculiar motion studies.Based on observations at Cerro Tololo Inter-American Observatory (CTIO),National Optical Astronomy Observatory, which is operated by theAssociation of Universities for Research in Astronomy, Inc., undercooperative agreement with the National Science Foundation (NSF);European Southern Observatory (ESO); Fred Lawrence Whipple Observatory(FLWO); and the MDM Observatory on Kitt Peak.
| A new catalogue of ISM content of normal galaxies
We have compiled a catalogue of the gas content for a sample of 1916galaxies, considered to be a fair representation of ``normality''. Thedefinition of a ``normal'' galaxy adopted in this work implies that wehave purposely excluded from the catalogue galaxies having distortedmorphology (such as interaction bridges, tails or lopsidedness) and/orany signature of peculiar kinematics (such as polar rings,counterrotating disks or other decoupled components). In contrast, wehave included systems hosting active galactic nuclei (AGN) in thecatalogue. This catalogue revises previous compendia on the ISM contentof galaxies published by \citet{bregman} and \citet{casoli}, andcompiles data available in the literature from several small samples ofgalaxies. Masses for warm dust, atomic and molecular gas, as well asX-ray luminosities have been converted to a uniform distance scale takenfrom the Catalogue of Principal Galaxies (PGC). We have used twodifferent normalization factors to explore the variation of the gascontent along the Hubble sequence: the blue luminosity (LB)and the square of linear diameter (D225). Ourcatalogue significantly improves the statistics of previous referencecatalogues and can be used in future studies to define a template ISMcontent for ``normal'' galaxies along the Hubble sequence. The cataloguecan be accessed on-line and is also available at the Centre desDonnées Stellaires (CDS).The catalogue is available in electronic form athttp://dipastro.pd.astro.it/galletta/ismcat and at the CDS via anonymousftp to\ cdsarc.u-strasbg.fr (130.79.128.5) or via\http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/405/5
| Core Radio and Optical Emission in the Nuclei of nearby FR I Radio Galaxies
In this paper we analyze the relation between radio, optical continuumand Hα+[N II] emission from the cores of a sample of 21 nearbyFanaroff and Riley type I galaxies as observed with the VLBA and HST.The emission arises inside the inner tens of parsecs of the galaxies.Core radio emission is observed in 19/20 galaxies, optical corecontinuum emission is detected in 12/21 galaxies and Hα+[N II]core emission is detected in 20/21 galaxies. We confirm the recentlydetected linear correlation between radio and optical core emission inFR I galaxies and show that both core emissions also correlate withcentral Hα+[N II] emission. The tight correlations between radio,optical, and Hα+[N II] core emission constrain the bulk Lorentzfactor to γ~2-5 and γ<~2 for a continuous jet and a jetconsisting of discrete blobs, respectively, assuming jet-viewing anglesin the range 30°-90°. Radio and optical core emissions arelikely to be synchrotron radiation from the inner jet, possibly with asignificant contribution from emission by an accretion disk and/or flow.Elliptical galaxies with LINER nuclei without large-scale radio jetsseem to follow the core emission correlations found in FR I galaxies.This suggests that the central engines could be very similar for the twoclasses of active galactic nuclei. Based on observations with theNASA/ESA Hubble 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.
| The UZC-SSRS2 Group Catalog
We apply a friends-of-friends algorithm to the combined Updated ZwickyCatalog and Southern Sky Redshift Survey to construct a catalog of 1168groups of galaxies; 411 of these groups have five or more members withinthe redshift survey. The group catalog covers 4.69 sr, and all groupsexceed the number density contrast threshold, δρ/ρ=80. Wedemonstrate that the groups catalog is homogeneous across the twounderlying redshift surveys; the catalog of groups and their membersthus provides a basis for other statistical studies of the large-scaledistribution of groups and their physical properties. The medianphysical properties of the groups are similar to those for groupsderived from independent surveys, including the ESO Key Programme andthe Las Campanas Redshift Survey. We include tables of groups and theirmembers.
| A new list of extra-galactic radio jets
A catalogue of extra-galactic jets is very useful both in observationaland theoretical studies of active galaxies. With the use of new powerfulradio instruments, the detailed structures of very compact or weak radiosources are investigated observationally and many new radio jets aredetected. In this paper, we give a list of 661 radio sources withdetected radio jets known to us prior to the end of December 2000. Allreferences are collected for the observations of jets in radio, IR,optical, UV and X-ray wave-bands. Table 1 and references to Table 1 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/381/757
| 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.
| VLBA Observations of a Sample of Nearby FR I Radio Galaxies
We observed 17 nearby low-luminosity FR I radio galaxies using the NRAOVery Long Baseline Array (VLBA) at 1.67 GHz, as part of amultiwavelength study of a complete sample of 21 sources selected byradio flux density from the Uppsala General Catalogue of Galaxies. Wedetected radio emission from all 17 galaxies. At a FWHM resolution of~10×4 mas, five galaxies show only an unresolved radio core, 10galaxies show core-jet structures, and two galaxies show twin-jetstructures. Comparing these VLBA images with images previously obtainedwith the NRAO VLA, we find that all detected VLBA jets are well alignedon parsec scales with the VLA jets on kiloparsec scales and that thejet-to-counterjet surface brightness ratios, or the sidedness, decreasessystematically with increasing distance along the jet. We attribute thesidedness to the Doppler boosting effect and its decline to thedeceleration of the jets. We show that a distribution of Lorentz factorcentered near Γ=5 can reproduce our VLBA detection statistics forcore, core-jet, and twin-jet sources. We also note that the luminosityper unit length, Lj, of the VLBA jets drops quickly withdistance, r, along the jet, approximately asLj~r-2.0. We discuss three different mechanisms toexplain this jet fading: (1) the decrease of Doppler boosting due to jetdeceleration, (2) synchrotron losses, and (3) expansion losses inconstant velocity but adiabatically spreading jets. Mechanisms (1) and(2) are inconsistent with the observations, while mechanism (3) isconsistent with the observations provided the magnetic field lines inthe jets are aligned perpendicular to the jet axis. This implies thatthe deceleration of the jets required by the unified scheme does notoccur on the tens of parsec scales but must occur on larger scales.
| 1.65 μm (H-band) surface photometry of galaxies. III. observations of 558 galaxies with the TIRGO 1.5 m telescope
We present near-infrared H-band (1.65 μm ) surface photometry of 558galaxies in the Coma Supercluster and in the Virgo cluster. This dataset, obtained with the Arcetri NICMOS3 camera ARNICA mounted on theGornergrat Infrared Telescope, is aimed at complementing, withobservations of mostly early-type objects, our NIR survey of spiralgalaxies in these regions, presented in previous papers of this series.Magnitudes at the optical radius, total magnitudes, isophotal radii andlight concentration indices are derived. We confirm the existence of apositive correlation between the near-infrared concentration index andthe galaxy H-band luminosity Based on observations taken at TIRGO(Gornergrat, Switzerland). TIRGO is operated by CAISMI-CNR, Arcetri,Firenze, Italy. Tables 1 and 2 are only available in electronic form atthe CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| 1.65 μm (H-band) surface photometry of galaxies. V. Profile decomposition of 1157 galaxies
We present near-infrared H-band (1.65 μm) surface brightness profiledecomposition for 1157 galaxies in five nearby clusters of galaxies:Coma, A1367, Virgo, A262 and Cancer, and in the bridge between Coma andA1367 in the ``Great Wall". The optically selected (mpg≤16.0) sample is representative of all Hubble types, from E to Irr+BCD,except dE and of significantly different environments, spanning fromisolated regions to rich clusters of galaxies. We model the surfacebrightness profiles with a de Vaucouleurs r1/4 law (dV), withan exponential disk law (E), or with a combination of the two (B+D).From the fitted quantities we derive the H band effective surfacebrightness (μe) and radius (re) of each component, theasymptotic magnitude HT and the light concentration indexC31. We find that: i) Less than 50% of the Ellipticalgalaxies have pure dV profiles. The majority of E to Sb galaxies is bestrepresented by a B+D profile. All Scd to BCD galaxies have pureexponential profiles. ii) The type of decomposition is a strong functionof the total H band luminosity (mass), independent of the Hubbleclassification: the fraction of pure exponential decompositionsdecreases with increasing luminosity, that of B+D increases withluminosity. Pure dV profiles are absent in the low luminosity rangeLH<1010 L\odot and become dominantabove 1011 L\odot . Based on observations taken atTIRGO, Gornergrat, Switzerland (operated by CAISMI-CNR, Arcetri,Firenze, Italy) and at the Calar Alto Observatory (operated by theMax-Planck-Institut für Astronomie (Heidelberg) jointly with theSpanish National Commission for Astronomy). Table 2 and Figs. 2, 3, 4are available in their entirety only in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| Investigation of galaxies in and near the cluster A1185
Results of optical, radio, and submillimeter studies of the nearbygalaxy cluster A1185 are presented. Coordinates have been obtained for115 galaxies that are either cluster members or field galaxies in thedirection of A1185. Radio spectra for a number of galaxies in thiscluster have been derived using observations on the RATAN-600 radiotelescope at 2.7, 3.9, 7.6, 13, and 31 cm, together with data publishedin other studies. At the cluster center, some of the galaxies haveeither flat or inverted spectra. The vast majority of the galaxiesdisplay a uniform brightness distribution; i.e., they do not show anysigns of structure. Sixty-four percent of the galaxies are elliptical,and 31% are spherical. The total number of blue galaxies is 22%.
| 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.
| Detailed Surface Photometry of Dwarf Elliptical and Dwarf S0 Galaxies in the Virgo Cluster
We analyze new V-band images of 14 dwarf S0 galaxies and 10 dwarfelliptical galaxies in the Virgo Cluster, in combination with R-bandimages of 70 dwarf elliptical galaxies from an earlier paper. We computethe intensity-weighted mean ellipticity, the mean deviations fromelliptical isophotes, and a newly defined parameter to measure isophotaltwists. We also fit each major-axis profile to a power lawSigma(a)~exp[-(a/a_s)^n], where n is allowed to vary. Consistent withother studies of the Virgo dwarf ellipticals, we find that the profileshapes for the entire sample is strongly peaked near n=1 (exponentialprofiles) and that no galaxies have n=1/4 (de Vaucouleurs profile). Thefaintest galaxies all have nearly exponential profiles, while thebrighter ones on average have n<1. The correlation betweenellipticity and the boxy/disky parameter is similar to that of largeelliptical galaxies, suggesting that dwarfs may also be divided into twogroups with differing internal dynamics. The Virgo dEs also show agreater degree of isophotal twisting than more luminous ellipticalgalaxies. There does not seem to be any combination of parameters fromthe surface photometry that statistically correlates with the dE/dS0designation: in particular, the dS0 galaxies do not, on average, havemore pointed (disky) isophotes than the dEs.
| Hubble Space Telescope Observations of Nearby Radio-Loud Early-Type Galaxies
We present and analyze Hubble Space Telescope (HST) WFPC2 broad- andnarrowband observations of the central regions of 19 nearby radio-loudearly-type galaxies. Together with two more galaxies, they form acomplete sample of Fanaroff and Riley Type I galaxies. We obtained V-and I-band images and narrowband images centered on the Hα+[N II]emission lines. We use archival data for six galaxies. We describe thedata reduction, give isophotal fits, and analyze the centralemission-line gas and dust distributions. Our main conclusions are thefollowing. Although obscuration by dust inhibits a direct determinationof central cusp slopes, the data suggest that most but not all galaxieshave shallow cores. Dust is detected in all but two galaxies. There area wide variety of central dust morphologies, ranging from central disksto lanes and irregular distributions. The analysis suggests that thedifference between disks and lanes is intrinsic and not due to differentviewing angles. Central emission-line gas is detected in all galaxies.Extended low surface brightness emission is always associated with thedust features. In a subsequent paper we will present a detailed analysisof the relation between these central properties and the nuclearactivity.
| The 3-D structure of the Coma-A 1367 supercluster: Optical spectroscopy of 102 galaxies
Optical spectroscopy of 117 CGCG galaxies, 102 of which are projected inthe direction of the Coma-A 1367 supercluster, is reported. These newmeasurements, added to those found in the literature, bring to 1068 thenumber of CGCG galaxies in this region with available redshift, out of atotal of 1085 objects with m_p<= 15.7. We use these data to infer the3-D structure of the Coma supercluster. Based on observations obtainedwith the Loiano telescope belonging to the University of Bologna, Italy,and with the G. Haro telescope of the INAOE, Mexico.
| On the local radio luminosity function of galaxies. II. Environmental dependences among late-type galaxies
Using new extensive radio continuum surveys at 1.4 GHz (FIRST and NVSS),we derive the distribution of the radio/optical and radio/NIR luminosity(RLF) of late-type (Sa-Irr) galaxies (m_p<15.7) in 5 nearby clustersof galaxies: A262, Cancer, A1367, Coma and Virgo. With the aim ofdiscussing possible environmental dependences of the radio properties,we compare these results with those obtained for relatively isolatedobjects in the Coma supercluster. We find that the RLF of Cancer, A262and Virgo are consistent with that of isolated galaxies. Conversely weconfirm earlier claims that galaxies in A1367 and Coma have their radioemissivity enhanced by a factor ~ 5 with respect to isolated objects. Wediscuss this result in the framework of the dynamical pressure sufferedby galaxies in motion through the intra-cluster gas (ram-pressure). Wefind that the radio excess is statistically larger for galaxies in fasttransit motion. This is coherent with the idea that enhanced radiocontinuum activity is associated with magnetic field compression. TheX-ray luminosities and temperatures of Coma and A1367 imply that thesetwo clusters have significantly larger intracluster gas density than theremaining three studied ones, providing a clue for explaining the higherradio continuum luminosities of their galaxies. Multiple systems in theComa supercluster bridge (with projected separations smaller than 300kpc) have radio luminosities significantly larger than isolatedgalaxies. Table~1 is 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/Abstract.html}
| Tidally induced star formation in Abell 1367
Our principal aim is to compare global star formation rates betweencluster galaxies and field galaxies in order to clarify environmentalinfluence on star formation. We use an objective prism technique tosurvey over 200 Zwicky catalogue (CGCG) galaxies within ~2 deg.5 ofAbell 1367 for Hα emission. After a brief discussion of the surveycharacteristics, we consider first the dependence of Hα detection onHubble type, galaxy disturbance and the presence of a bar. As expected,we rarely detect early-type galaxies and consequently restrict furtherdiscussion to spirals (type S0/a and later), of which we detect ~35percent in Hα. We find that an extremely valuable distinction to makeis between galaxies with diffuse Hα and galaxies with compactHα. There is a very significant tendency for galaxies with compactHα emission to be disturbed, and there may be a weak tendency forthem to be barred. Neither of these tendencies is found for galaxieswith diffuse Hα emission. We infer that compact emission resultsfrom tidally induced star formation, while diffuse emission results frommore normal disc star formation. After considering field contamination,we adopt as a `predominantly cluster' sample the spiral populationinside 0.5 r_A; a `predominantly field' sample outside 0.5 r_A; and a`pure field' sample outside 1.5 r_A. We consistently find a much largerfraction of spirals detected with compact Hα in the cluster samplecompared to the field samples (e.g. 38 versus 0per cent detected incluster and `pure field' samples, chi^2 significance 3.6sigma). Thisincreased fraction detected in the cluster is found for early-, mid- andlate-type spirals separately. No such cluster/field differences arefound for galaxies with diffuse Hα emission. We conclude that tidalperturbations are more common in the cluster than in the field, leadingto a higher incidence of compact tidally triggered star formation. Bycombining information on galaxy disturbance, galaxy companions, and thelocation of galaxies within the cluster, we have tried to identify theorigin of the tidal perturbations. We find strong evidence thatnear-neighbour interaction plays a significant role in triggering starformation. However, we also find candidate objects near the cluster corewhich may be perturbed by the overall cluster tidal field, and candidateobjects which may be influenced by a higher speed `harassment'interaction between galaxies.
| Groups of galaxies. III. Some empirical characteristics.
Not Available
| 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
| A Minnesota Automated Plate Scanner Catalog of Galaxies behind the Virgo Cluster and toward Its Antipode
We present a catalog of 1268 galaxies, essentially complete to B <=17.0, found by scanning glass copies of several fields of the originalPalomar Sky Survey using the Minnesota Automated Plate Scanner in itsisodensitometric mode (as opposed to the threshold densitometric modeused in the APS Catalog of the POSS I). In addition to the differentscanning mode, we have employed a different star-galaxy separationmethod and have visually inspected POSS prints to verify that each imageremaining in the catalog is nonstellar. The scanned fields aredistributed generally in two areas, one around the outskirts of theVirgo Cluster, the other toward the antipode of the cluster (but stillin the northern celestial hemisphere). The catalog gives the position ofthe center of each galaxy; estimates of the blue and red magnitudeswithin the outermost threshold crossing and of the blue magnitudeextrapolated to zero surface brightness; and the blue and red diametersof four ellipses fitted to the four threshold crossings (approximately23.8,23.6,23.2, and 22.7 mag arcsec 2 in blue, and 22.5,22.4,21.5, and21.2 mag arcsec^-2^ in red), and the ellipticities of those fourellipses. The catalog has served as a base from which to draw targetsfor a Tully-Fisher study of the Virgocentric infall velocity of theLocal Group.
| The Effects of Dust on Broadband Color Gradients in Elliptical Galaxies
In order to examine the possibility that dust effects cause colorgradients in elliptical galaxies, we have constructed a set ofelliptical galaxy models spanning a wide range of dust properties,including mass, spatial distribution, and spectral properties. Thesemodels are spherically symmetric and include the effects of scattering.We have calculated the emergent broadband colors from the far-UV bandsthrough K. These results were then compared with the color propertiesfor a sample of 52 galaxies taken from the literature. In the optical,we can reproduce the magnitude, morphology, and color gradient ratios[i.e., {DELTA}U - R)/{DELTA}(B - R)] observed in many of the galaxies.The best fits are found for distributions with ρ_d_ ~ r^-1^ andτT ~ 1, which corresponds to dust masses on the order of 10^6^M_sun_ within the central 10-30 kpc. More condensed dust profiles alsoproduce strong color gradients, but only in the central regions (r <0.5 kpc). For many of the objects in this sample, the implied dustmasses are in reasonable agreement with the dust masses inferred fromIRAS observations, although a number of objects require significantlyhigher dust masses than their IRAS observations imply if their colorproperties are to be attributed solely to reddening by dust. Our modelssuggest that a simple dusty elliptical galaxy scenario can reproduce themagnitude, morphology, and ratios of observed broadband color gradientsin many ellipticals. We find that currently available color gradientmeasurements are consistent with our model results but that thesemeasurements are not precise enough in many objects to provide tightconstraints on the models. Extended dust distributions will greatlycomplicate the interpretation of all broadband data. Any broadbandanalysis hindered by age-metallicity degeneracy will also be hindered bydust effects. In effect, all broadband observations of ellipticalgalaxies may be age-metallicity-dust degenerate. We also consider theeffects of dust on several global relationships in ellipticals, such asthe color-magnitude relation and various distance indicators.
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