WIKISKY.ORG
 Home Getting Started To Survive in the Universe News@Sky Astro Photo The Collection Forum Blog New! FAQ Press Login

# NGC 3073

Contents

### Images

DSS Images   Other Images

### Related articles

 The Second Byurakan Survey. General CatalogueThe Second Byurakan Survey (SBS) General Catalogue is presented. TheSBS, a continuation of the Markarian survey reaching fainter limitingmagnitudes, is the first survey which combines the search of galaxiesand QSOs. A total area of 991OS#square;degrees of the Northern sky wascovered with the use of three objective prisms in combination withSchott filters. The limited magnitude on the best plates reached B ~19.5.The General Catalogue consists of 3563 objects presented in two parts: aCatalogue of galaxies (1863 objects) and one of stellar objects (1700objects). The Catalogue of SBS AGN consists of 761 objects (155 SyG, 596QSOs, and 10 BLLac). Multi-wavelength data are presented for 1438 SBSobjects identified with X-ray, IRAS and FIRST sources.Spectrophotometric observations obtained over 26 years are available for3132 objects. Redshifts were measured for ~ 2100 extragalactic objects.Spectral classification is presented for ~ 2970 objects. The majority ofthe data is presented here for the first time. The Catalogue presentsnew large homogeneous deep representative complete samples of brightQSOs, AGNs, and faint UVX galaxies in the Northern sky. The SBS sampleis found to be complete at 70% for galaxies and ~ 85% for AGN/QSOs withB ≤ 17.5. Galactic WindsGalactic winds are the primary mechanism by which energy and metals arerecycled in galaxies and are deposited into the intergalactic medium.New observations are revealing the ubiquity of this process,particularly at high redshift. We describe the physics behind thesewinds, discuss the observational evidence for them in nearbystar-forming and active galaxies and in the high-redshift universe, andconsider the implications of energetic winds for the formation andevolution of galaxies and the intergalactic medium. To inspire futureresearch, we conclude with a set of observational and theoreticalchallenges. Ultraluminous X-Ray Sources in Nearby Galaxies from ROSAT High Resolution Imager Observations I. Data AnalysisX-ray observations have revealed in other galaxies a class ofextranuclear X-ray point sources with X-ray luminosities of1039-1041 ergs s-1, exceeding theEddington luminosity for stellar mass X-ray binaries. Theseultraluminous X-ray sources (ULXs) may be powered by intermediate-massblack holes of a few thousand Msolar or stellar mass blackholes with special radiation processes. In this paper, we present asurvey of ULXs in 313 nearby galaxies withD25>1' within 40 Mpc with 467 ROSAT HighResolution Imager (HRI) archival observations. The HRI observations arereduced with uniform procedures, refined by simulations that help definethe point source detection algorithm employed in this survey. A sampleof 562 extragalactic X-ray point sources withLX=1038-1043 ergs s-1 isextracted from 173 survey galaxies, including 106 ULX candidates withinthe D25 isophotes of 63 galaxies and 110 ULX candidatesbetween 1D25 and 2D25 of 64 galaxies, from which aclean sample of 109 ULXs is constructed to minimize the contaminationfrom foreground or background objects. The strong connection betweenULXs and star formation is confirmed based on the striking preference ofULXs to occur in late-type galaxies, especially in star-forming regionssuch as spiral arms. ULXs are variable on timescales over days to yearsand exhibit a variety of long term variability patterns. Theidentifications of ULXs in the clean sample show some ULXs identified assupernovae (remnants), H II regions/nebulae, or young massive stars instar-forming regions, and a few other ULXs identified as old globularclusters. In a subsequent paper, the statistic properties of the surveywill be studied to calculate the occurrence frequencies and luminosityfunctions for ULXs in different types of galaxies to shed light on thenature of these enigmatic sources. Starbursting nuclear CO disks of early-type spiral galaxiesWe have initiated the first CO interferometer survey of early-typespiral galaxies (S0-Sab). We observed five early-type spiral galaxieswith HII nuclei (indicating circumnuclear starburst activities). Theseobservations indicate gas masses for the central kiloparsec of 1{-}5%of the dynamical masses. Such low gas mass fractions suggest thatlarge-scale gravitational instability in the gas is unlikely to be thedriving cause for the starburst activities. We estimated Toomre Q valuesand found that these galaxies have Q>1 (mostly >3) within thecentral kiloparsec, indicating that the gas disks are globallygravitationally stable. From the brightness temperatures of the COemission we estimated the area filling factor of the gas disks withinthe central kiloparsec to be about 0.05. This small value indicates theexistence of lumpy structure, i.e. molecular clouds, in theglobally-gravitationally stable disks. The typical surface density ofthe molecular clouds is as high as 3000 {Mȯ} {pc}-2. In the light of these new observations, we reconsiderthe nature of the Toomre Q criterion, and conclude that the Toomre Qparameter from CO observations indicates neither star formation normolecular cloud formation. This argument should be valid not only forthe circumnuclear disks but also for any region in galactic disks. Wetentatively explore an alternative model as an initiating mechanism ofstar formation. Cloud-cloud collisions might account for the active starformation. A High Spatial Resolution X-Ray and Hα Study of Hot Gas in the Halos of Star-forming Disk Galaxies. I. Spatial and Spectral Properties of the Diffuse X-Ray EmissionWe present arcsecond resolution Chandra X-ray and ground-based opticalHα imaging of a sample of 10 edge-on star-forming disk galaxies(seven starburst and three normal'' spiral galaxies), a sample thatcovers the full range of star formation intensity found in diskgalaxies. The X-ray observations make use of the unprecedented spatialresolution of the Chandra X-ray observatory to more robustly than beforeremove X-ray emission from point sources and hence obtain the X-rayproperties of the diffuse thermal emission alone. We have combined theX-ray observations with existing, comparable-resolution, ground-basedHα and R-band imaging and present a mini-atlas of images on acommon spatial and surface brightness scale to aid cross-comparison. Ingeneral, the morphology of the extraplanar diffuse X-ray emission isvery similar to the extraplanar Hα filaments and arcs, on bothsmall and large scales (scales of tens of parsecs and kiloparsecs,respectively). The most spectacular cases of this are found in NGC 1482(for which we provide the first published X-ray observation) and NGC3079. We provide a variety of quantitative measures of how the spectralhardness and surface brightness of the diffuse X-ray emission varieswith increasing height z above the plane of each galaxy. Of the eightgalaxies in which diffuse X-ray emitting halos are found (the starburstsand the normal spiral NGC 891), significant spatial variation in thespectral properties of the extraplanar emission (|z|>=2 kpc) is onlyfound in two cases: NGC 3628 and NGC 4631. In general, the verticaldistribution of the halo-region X-ray surface brightness is bestdescribed as an exponential, with the observed scale heights of thesample galaxies lying in the range Heff~2-4 kpc. The presenceof extraplanar X-ray emission is always associated with the presence ofextraplanar optical line emission of similar vertical extent. No X-rayemission was detected from the halos of the two low-mass normal spiralgalaxies NGC 6503 and NGC 4244. Active galactic nuclei, where present,appear to play no role in powering or shaping the outflows from thestarburst galaxies in this sample. The Chandra ACIS X-ray spectra ofextraplanar emission from all these galaxies can be fitted with a commontwo-temperature spectral model with an enhanced α-to-iron elementratio. This is consistent with the origin of the X-ray emitting gasbeing either metal-enriched merged SN ejecta or shock-heated ambienthalo or disk material with moderate levels of metal depletion onto dust.Our favored model is that SN feedback in the disks of star-forminggalaxies create, via blow-out and venting of hot gas from the disk,tenuous exponential atmospheres of density scale heightHg~4-8 kpc. The soft thermal X-ray emission observed in thehalos of the starburst galaxies is either this preexisting halo medium,which has been swept up and shock-heated by the starburst-driven wind,or wind material compressed near the walls of the outflow by reverseshocks within the wind. In either case, the X-ray emission provides uswith a powerful probe of the properties of gaseous halos aroundstar-forming disk galaxies. A High Spatial Resolution X-Ray and Hα Study of Hot Gas in the Halos of Star-forming Disk Galaxies. II. Quantifying Supernova FeedbackWe investigate how the empirical properties of hot X-ray-emitting gas ina sample of seven starburst and three normal edge-on spiral galaxies (asample that covers the full range of star formation intensity found indisk galaxies) correlate with the size, mass, star formation rate, andstar formation intensity in the host galaxies. From this analysis weinvestigate various aspects of mechanical energy feedback''-the returnof energy to the interstellar medium from massive star supernovae andstellar winds-on galactic scales. The X-ray observations make use of theunprecedented spatial resolution of the Chandra X-Ray Observatory toremove X-ray emission from point sources more accurately than in anyprevious study and hence obtain the X-ray properties of the diffusethermal emission alone. Intriguingly, the diffuse X-ray properties ofthe normal spirals (in both their disks and halos) fall whereextrapolation of the trends from the starburst galaxies with superwindswould predict. We demonstrate, using a variety of multiwavelength starformation rate and intensity indicators, that the luminosity of diffuseX-ray emission in the disk (and, where detected, in the halo) isdirectly proportional to the rate of mechanical energy feedback frommassive stars in the host galaxies. Accretion of gas from theintergalactic medium (IGM) does not appear to be a significantcontributor to the diffuse X-ray emission in this sample. Nevertheless,with only three nonstarburst normal spiral galaxies it is hard toexclude an accretion-based origin for extraplanar diffuse X-ray emissionaround normal star-forming galaxies. Larger galaxies tend to have moreextended X-ray-emitting halos, but galaxy mass appears to play no rolein determining the properties of the disk or extraplanar X-ray-emittingplasma. The combination of these luminosity and size correlations leadsto a correlation between the surface brightness of the diffuse X-rayemission and the mean star formation rate per unit area in the disk(calculated from the far-infrared luminosity and the optical size of thegalaxy, LFIR/D225). Furtherobservational work of this form will allow empirical constraints to bemade on the critical star formation rate per unit disk area necessary toblow hot gas out of the disk into the halo. We show that a minorgeneralization of standard superbubble theory directly predicts acritical star formation rate per unit area for superbubble blowout fromthe disk and by extension for superwinds to blow out of the gaseoushalos of their host galaxy. At present there are a variety of poorlyknown parameters in this theory that complicate comparison betweenobservation and theory, making it impossible to assess the quantitativeaccuracy of standard superbubble blowout theory. We argue that thecrucial spatial region around a galaxy that controls whether gas instarburst-driven superwinds will escape into the IGM is not the outerhalo ~100 kpc from the host galaxy, but the inner few halo scaleheights, within ~20 kpc of the galaxy plane. Given the properties of thegaseous halos we observe, superwind outflows from disk galaxies of massM~1010-1011 Msolar should still ejectsome fraction of their material into the IGM. Galaxy Interaction and the Starburst-Seyfert ConnectionGalaxy interactions are studied in terms of the starburst-Seyfertconnection. The starburst requires a high rate of gas supply. Since theefficiency for supplying the gas is high in a galaxy interaction,although the companion is not necessarily discernible, Seyfert galaxieswith circumnuclear starbursts are expected to be interacting. Since thelarge amounts of circumnuclear gas and dust obscure the broad-lineregion, they are expected to be observed as Seyfert 2 galaxies. Theactive galactic nucleus itself does not require a high rate of gassupply. Seyfert galaxies without circumnuclear starbursts are notnecessarily expected to be interacting even at the highest luminosities.They are not necessarily expected to evolve from Seyfert galaxies withcircumnuclear starbursts. We derive these and other theoreticalexpectations and confirm them with statistics on observational data ofmagnitude-limited samples of Seyfert galaxies. Starburst-Driven Galactic WindsIn this contribution I summarize our current knowledge of the nature andsignificance of starburst-driven galactic winds (superwinds'').Superwinds are complex multiphase outflows of cool, warm, and hot gas,dust, and magnetized relativistic plasma. The observationalmanifestations of superwinds result from the hydrodynamical interactionbetween the primary energy-carrying wind fluid and the ambientinterstellar medium. Superwinds are ubiquitous in galaxies in which theglobal star-formation rate per unit area exceeds roughly 10^-1 M[scriptstyle sun ]yr-1 kpc^-2. This criterion is met by local starburstsand the high-z Lyman Break galaxies. Several independent datasets andtechniques imply that the total mass and energy outflow rates in asuperwind are comparable to the starburst's star-formation-rate andmechanical energy injection rate, respectively. Outflow speeds ininterstellar matter entrained in the wind range from ~ 10^2 to 10^3km/s, but the primary wind fluid itself may reach velocities as high as~ 3000 km s-1. The available X-ray and far-UV (FUSE) data imply thatradiative losses in superwinds are not significant. Superwinds may haveestablished the mass-metallicity relation in ellipticals and bulges,polluted the present-day inter-galactic medium to a metallicity of ~10 to 30% solar, heated the inter-galactic medium, and ejected enoughdust into the inter-galactic medium to have observable consequences. Redshift-Distance Survey of Early-Type Galaxies: Circular-Aperture PhotometryWe 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 galaxiesWe 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 Tightly Correlated X-Ray/Hα-emitting Filaments in the Superbubble and Large-Scale Superwind of NGC 3079Using Chandra and HST, we show that X-ray and Hα filaments thatform the 1.3 kpc diameter superbubble of NGC 3079 have strikinglysimilar patterns at ~0.8" resolution. This tight optical line/X-raymatch seems to arise from cool disk gas that has been driven by thewind, with X-rays being emitted from upstream, standoff bow shocks or byconductive cooling at the cloud/wind interfaces. We find that the softX-ray plasma has thermal and kinetic energiesETH~2×1056η0.5Xergs andEKE~5×1054η0.5Xergs, where ηX is the filling factor of the X-ray gas andmay be small; these are comparable to the energies of the opticalline-emitting gas if ηX is large. Hydrodynamicalsimulations reproduce the observations well using a disk-mass loadedsuperwind. X-rays are also seen from the base of the radio counterbubblewhich is obscured optically by the galaxy disk and from the nucleus(whose spectrum shows the Fe Kα line at 6 keV as well as gasabsorbed by a moderate neutral hydrogen column). The superbubble issurrounded by a fainter conical halo of X-ray emission that fills thearea delineated by high-angle, Hα-emitting filaments, supportingour previous assertion that these filaments form the contactdiscontinuity/shock between galaxy gas and shocked wind. This X-rayemission is not significantly edge brightened, indicating a partiallyfilled volume of warm gas within the shocked wind, not a shell ofconductively heated gas. About 40" (3 kpc) above the galaxy disk, anX-ray arc may partially close above the bubble, but the northeastquadrant remains open at the surface brightness attained by Chandra,consistent with the notion that the superwind reaches into at least thegalaxy halo. Nobeyama Millimeter Array CO (J=1-0) Observations of the Hα/Radio Lobe Galaxy NGC 3079: Gas Dynamics in a Weak Bar Potential and Central Massive CoreWe present 12CO (1-0) observations in the central 4.5 kpc(1') of the Hα/radio lobe galaxy NGC 3079 with the NobeyamaMillimeter Array. The molecular gas shows four components: a main disk,spiral arms, a nuclear disk, and a nuclear core. The main disk extendsalong the galaxy major axis. We detected its central 2 kpc radius, whileits full extent is beyond our spatial coverage. Molecular gas issmoothly distributed in the main disk, having a gas mass of5×109 Msolar within the central ~2 kpcradius. The spiral arms are superimposed on the main disk. Abruptvelocity changes of up to ~200 km s-1 are observed along thespiral arms in S-shaped twists of isovelocity contours and doublevelocity-peaked features on the spectra. The nuclear disk with ~600 pcradius appears in position-velocity (PV) diagrams, having an intenseconcentration of molecular gas. Its appearance on PV diagrams isindicative of oval motions of the gas, rather than circular. The nucleardisk and spiral arms form the so-called figure-of-eight pattern on a PVdiagram. The nuclear core is more compact than our current resolution(2''=150 pc) and has a gas mass of 3×108Msolar within the central 150 pc. Although it is unresolved,the nuclear core shows a very high velocity ~200 km s-1 evenat the radius of ~100 pc on the PV diagram. We propose a model that NGC3079 contains a weak bar. The weak bar model explains the observedfeatures of the main disk, spiral arms, and nuclear disk. The main diskand spiral arms result from gaseous x1-orbits and associatedcrowding, respectively. The nuclear disk arises from gaseousx2-orbits. The gas concentration in the nuclear disk could beexplained by the expected gas-fueling mechanism: the gas onx1-orbits flows along spiral arms (or offset shocks),colliding with the gas on x2-orbits, and accumulating ontothe nuclear disk. Assuming that the gas moves nearly along the spiralarms that run perpendicular to the line of sight, the pattern speed ofthe bar is estimated to be 55+/-10 km s-1 kpc-1.The high velocity of the nuclear core cannot be explained by our modelfor a bar. Thus we attribute it to a central massive core with adynamical mass of 109 Msolar within the central100 pc. This mass is 3 orders of magnitude more massive than that of acentral black hole in this galaxy. Kinematical data on early-type galaxies. VI.We present the result of spectroscopic observations of a sample of 73galaxies, completing the database published in this series of articles.The sample contains mostly low-luminosity early-type objects, includingfour dwarfs of the Local Group (in particular, deep spectra of NGC 205),15 dEs or dS0s in the Virgo cluster, and UGC 05442, a spheroidal dwarfof the M 81 group. We have measured the central velocity dispersion forall but one object, and determined the major-axis rotation andvelocity-dispersion profiles for 59 objects. For the current sample ofdiffuse (or dwarf) elliptical galaxies, we have compared stellarrotation to velocity dispersion; the analysis suggests that theseobjects may be nearly rotationally flattened, and therefore thatanisotropy may be less important than previously thought. Based onobservations collected at the Observatoire de Haute-Provence. Table 1 isalso, and Tables 2 and 4 only, available in electronic form at the CDSvia anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/384/371 A catalogue and analysis of X-ray luminosities of early-type galaxiesWe present a catalogue of X-ray luminosities for 401 early-typegalaxies, of which 136 are based on newly analysed ROSAT PSPC pointedobservations. The remaining luminosities are taken from the literatureand converted to a common energy band, spectral model and distancescale. Using this sample we fit the LX:LB relationfor early-type galaxies and find a best-fit slope for the catalogue of~2.2. We demonstrate the influence of group-dominant galaxies on the fitand present evidence that the relation is not well modelled by a singlepower-law fit. We also derive estimates of the contribution to galaxyX-ray luminosities from discrete-sources and conclude that they provideLdscr/LB~=29.5ergs-1LBsolar-1. Wecompare this result with luminosities from our catalogue. Lastly, weexamine the influence of environment on galaxy X-ray luminosity and onthe form of the LX:LB relation. We conclude thatalthough environment undoubtedly affects the X-ray properties ofindividual galaxies, particularly those in the centres of groups andclusters, it does not change the nature of whole populations. A synthesis of data from fundamental plane and surface brightness fluctuation surveysWe perform a series of comparisons between distance-independentphotometric and spectroscopic properties used in the surface brightnessfluctuation (SBF) and fundamental plane (FP) methods of early-typegalaxy distance estimation. The data are taken from two recent surveys:the SBF Survey of Galaxy Distances and the Streaming Motions of AbellClusters (SMAC) FP survey. We derive a relation between(V-I)0 colour and Mg2 index using nearly 200galaxies and discuss implications for Galactic extinction estimates andearly-type galaxy stellar populations. We find that the reddenings fromSchlegel et al. for galaxies with E(B-V)>~0.2mag appear to beoverestimated by 5-10 per cent, but we do not find significant evidencefor large-scale dipole errors in the extinction map. In comparison withstellar population models having solar elemental abundance ratios, thegalaxies in our sample are generally too blue at a given Mg2;we ascribe this to the well-known enhancement of the α-elements inluminous early-type galaxies. We confirm a tight relation betweenstellar velocity dispersion σ and the SBF fluctuation count'parameter N, which is a luminosity-weighted measure of the total numberof stars in a galaxy. The correlation between N and σ is eventighter than that between Mg2 and σ. Finally, we deriveFP photometric parameters for 280 galaxies from the SBF survey data set.Comparisons with external sources allow us to estimate the errors onthese parameters and derive the correction necessary to bring them on tothe SMAC system. The data are used in a forthcoming paper, whichcompares the distances derived from the FP and SBF methods. The SBF Survey of Galaxy Distances. IV. SBF Magnitudes, Colors, and DistancesWe report data for I-band surface brightness fluctuation (SBF)magnitudes, (V-I) colors, and distance moduli for 300 galaxies. Thesurvey contains E, S0, and early-type spiral galaxies in the proportionsof 49:42:9 and is essentially complete for E galaxies to Hubblevelocities of 2000 km s-1, with a substantial sampling of Egalaxies out to 4000 km s-1. The median error in distancemodulus is 0.22 mag. We also present two new results from the survey.(1) We compare the mean peculiar flow velocity (bulk flow) implied byour distances with predictions of typical cold dark matter transferfunctions as a function of scale, and we find very good agreement withcold, dark matter cosmologies if the transfer function scale parameterΓ and the power spectrum normalization σ8 arerelated by σ8Γ-0.5~2+/-0.5. Deriveddirectly from velocities, this result is independent of the distributionof galaxies or models for biasing. This modest bulk flow contradictsreports of large-scale, large-amplitude flows in the ~200 Mpc diametervolume surrounding our survey volume. (2) We present adistance-independent measure of absolute galaxy luminosity, N and showhow it correlates with galaxy properties such as color and velocitydispersion, demonstrating its utility for measuring galaxy distancesthrough large and unknown extinction. Observations in part from theMichigan-Dartmouth-MIT (MDM) Observatory. A ROSAT High Resolution Imager survey of bright nearby galaxiesWe use the extensive public archive of ROSAT High Resolution Imager(HRI) observations to carry out a statistical investigation of the X-rayproperties of nearby galaxies. Specifically we focus on the sample of486 bright (BT<=12.5) northern galaxies studied by Ho,Filippenko and Sargent (HFS) in the context of their exploration of theoptical spectroscopic properties of nearby galactic nuclei. Over 20percent of HFS galaxies are encompassed in ROSAT HRI fields of reasonable(>=10ks) exposure. The X-ray sources detected within the opticalextent of each galaxy are categorized as either nuclear or non-nuclear,depending on whether the source is positioned within or outside a25-arcsec radius circle centred on the optical nucleus. A nuclear X-raysource is detected in over 70per cent of the galaxies harbouring eithera Seyfert or LINER nucleus, compared with a detection rate of only~40per cent in less active systems. The correlation of the Hαluminosity with nuclear X-ray luminosity previously observed in QSOs andbright Seyfert 1 galaxies appears to extend down into the regime ofultra-low luminosity(LX~1038-1040ergs-1) activegalactic nuclei (AGN). The inferred accretion rates for this sample oflow-luminosity AGN are significantly sub-Eddington. In total, 142non-nuclear sources were detected. In combination with published datafor M31, this leads to a luminosity distribution (normalized to anoptical blue luminosity of 1010Lsolar) for thediscrete X-ray source population in spiral galaxies of the formdN/dL38 = (1.0 ± 0.2)L-1.838where L38 is the X-ray luminosity in units of1038ergs-1. The implied LXLBratio is ~1.1×1039ergs-1(1010Lsolar)-1. The nature ofthe substantial number of superluminous' non-nuclear objects detectedin the survey is discussed. Nearby Optical Galaxies: Selection of the Sample and Identification of GroupsIn 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. Far-Infrared ISO Maps of Active GalaxiesFar-IR Infrared Space Observatory (ISO) maps of four Seyfert galaxiesare presented and compared with their optical counterpart images. Thefar-IR maps resemble the optical images of these galaxies when degradedto the ISO resolution. The spatial extension of the far-IR maps is alsocomparable to the optical extension of these objects, an indication ofthe extended nature of their far-IR emission. The 90 μm intensityprofiles of these galaxies show that there is a disk componentnoticeable in the far IR. NGC 3079 shows a 90 μm halo extending farout of the galaxy plane. NGC 4051 shows a dark molecular cloud whosefar-IR output could be as large as that of the active nucleus itself,demonstrating that very bright IR sources other than the active nucleusmay be responsible for a large fraction of the far-IR emission in someSeyfert galaxies. Based on observations made with ISO, an ESA projectwith instruments funded by ESA member states (especially the PIcountries: France, Germany, the Netherlands, and the United Kingdom) andwith the participation of ISAS and NASA. The Neutral Hydrogen Distribution in Merging Galaxies: Differences between Stellar and Gaseous Tidal MorphologiesAs part of several H I synthesis-mapping studies of merging galaxies, wehave mapped the tidal gas in the three disk-disk merger systems Arp 157(NGC 520), Arp 220, and Arp 299 (NGC 3690). These systems differ fromthe majority of the mergers mapped in H I in that their stellar andgaseous tidal features do not coincide. In particular, they exhibitlarge stellar tidal features with little if any accompanying neutral gasand large gas-rich tidal features with little if any accompanyingstarlight. On smaller scales, there are striking anticorrelations inwhich the gaseous and stellar tidal features appear to cross. We exploreseveral possible causes for these differences, including dustobscuration, ram pressure stripping, and ionization effects. No singleexplanation can account for all of the observed differences. The factthat each of these systems shows evidence for a starburst-drivensuperwind expanding in the direction of the most strikinganticorrelations leads us to suggest that the superwind is primarilyresponsible for the observed differences, either by sweeping thefeatures clear of gas via ram pressure or by excavating a clearsightline toward the starburst and allowing UV photons to ionize regionsof the tails. If this suggestion is correct, only systems hosting agalactic superwind and experiencing a high-inclination encountergeometry (such that tidal gas is lifted high above the starburstregions) should exhibit such extreme differences between their H I andoptical tidal morphologies. Accurate optical positions for 2978 objects from the Second Byurakan Survey (SBS) with the Digitized Sky SurveyOptical positions of 2978 objects listed in the Second Byurakan Survey(SBS) were obtained using the Digitized Sky Survey (DSS), and are givenwith an rms uncertainty ~ 1 arcsec in each coordinate. Tables 1 and 2are only available in electronic form at the CDS via anonymous ftp130.79.128.5 or via http://cdsweb.u-strasbg.fr/Abstract.html X-ray luminosities for a magnitude-limited sample of early-type galaxies from the ROSAT All-Sky SurveyFor a magnitude-limited optical sample (B_T <= 13.5 mag) ofearly-type galaxies, we have derived X-ray luminosities from the ROSATAll-Sky Survey. The results are 101 detections and 192 useful upperlimits in the range from 10^36 to 10^44 erg s^-1. For most of thegalaxies no X-ray data have been available until now. On the basis ofthis sample with its full sky coverage, we find no galaxy with anunusually low flux from discrete emitters. Below log (L_B) ~ 9.2L_⊗ the X-ray emission is compatible with being entirely due todiscrete sources. Above log (L_B) ~ 11.2 L_osolar no galaxy with onlydiscrete emission is found. We further confirm earlier findings that L_xis strongly correlated with L_B. Over the entire data range the slope isfound to be 2.23 (+/- 0.12). We also find a luminosity dependence ofthis correlation. Below log L_x = 40.5 erg s^-1 it is consistent with aslope of 1, as expected from discrete emission. Above this value theslope is close to 2, as expected from gaseous emission. Comparing thedistribution of X-ray luminosities with the models of Ciotti et al.leads to the conclusion that the vast majority of early-type galaxiesare in the wind or outflow phase. Some of the galaxies may have alreadyexperienced the transition to the inflow phase. They show X-rayluminosities in excess of the value predicted by cooling flow modelswith the largest plausible standard supernova rates. A possibleexplanation for these super X-ray-luminous galaxies is suggested by thesmooth transition in the L_x--L_B plane from galaxies to clusters ofgalaxies. Gas connected to the group environment might cause the X-rayoverluminosity. Arcsecond Positions of UGC GalaxiesWe 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. A Kinematic Link Between Boxy Bulges, Stellar Bars, and Nuclear Activity in NGC 3079 and NGC 4388We present direct kinematic evidence for bar streaming motions in twoactive galaxies with boxy stellar bulges. The Hawaii Imaging Fabry-PerotInterferometer was used on the 3.6 m Canada-France-Hawaii Telescope andthe University of Hawaii 2.2 m telescope to derive the two-dimensionalvelocity field of the line-emitting gas in the disks of the Sc galaxyNGC 3079 and the Sb galaxy NGC 4388. In contrast to previous work basedon long-slit data, the detection of the bar potential from theFabry-Perot data does not rely on the existence of inner Lindbladresonances or strong bar-induced shocks. Simple kinematic models thatapproximate the intrinsic gas orbits as nonintersecting, inclinedelliptical annuli that conserve angular momentum characterize theobserved velocity fields. In NGC 3079, bar streaming motions withmoderately eccentric orbits (e=b/a~0.7) aligned along P.A.=130 degintrinsic to the disk (P.A.=97 deg on the sky) are detected out toRb=3.6 kpc. The orbits become increasingly circular beyondthat radius (e=1 at Rd~6 kpc). The best model for NGC 4388includes highly eccentric orbits (e~0.3) for Rb<~1.5 kpc,which are aligned along P.A.=135 deg intrinsic to the disk (P.A.=100 degon the sky). The observed spiral arms'' are produced by having theorbits become increasingly circular from the ends of the bar to the edgeof the disk (Rd~5 kpc) and the intrinsic bar position angleshifting from 135 deg to 90 deg. Box-shaped bulges in both NGC 3079 andNGC 4388 are confirmed using new near-infrared images to reduce dustobscuration. Morphological analysis of starlight in these galaxies iscombined with the gas kinematics derived from the Fabry-Perot spectra totest evolutionary models of stellar bars that involve transitory, boxybulges and to quantify the importance of such bars in fueling activenuclei. Our data support the evolutionary bar models but fail to proveconvincingly that the stellar bars in NGC 3079 and NGC 4388 directlytrigger or sustain the nuclear activity. Groups of galaxies. III. Some empirical characteristics.Not Available Catalogue of HI maps of galaxies. II. Analysis of the dataWe use some of the maps of the catalogue presented in Paper I to providesome evidence for global conditions that must be fulfilled by thegalaxies to have extended hydrogen. For this purpose, we tried to findpossible connections between the HI gas extension and other propertiesof the galaxies (morphological type, surface brightness, gas density,etc.). With isophotal hydrogen diameters of a large sample, we couldobserve that optically smaller galaxies seem to have greater relative HIextensions. By means of the relation with the apparent HI surfacedensity, we found an expression that should provide a rough estimate ofthe gas extension. With respect to the dependence on morphological type,we could not find any significant correlation either for the real HIsurface density or the relative gas extension. Nevertheless, whereas forspiral and irregular galaxies the real HI surface density exhibits abroad range of values, the values are rather lower for elliptical and S0galaxies. Table 1 is also available in electronic form at the CDS viaanonymous ftp 130.79.128.5 or viahttp://cdsweb.u-strasbg.fr/Abstract.html 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 galaxiesWe 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. NGC 3079: X-ray emission from the nuclear super-bubble and haloWe report the results of the spatial and spectral analysis of the ROSATHRI and PSPC observations of the edge-on spiral galaxy NGC 3079. Wedetected several sources in the field of NGC 3079 with both PSPC andHRI, and complex emission from the inner 5' around NGC 3079. We haveidentified possible counterparts for several of the sources outside NGC3079 by comparison with optical plates and catalogues. The X-rayemission from NGC 3079 has a L_X = 3x 10(40) erg s(-1) and can beresolved into the following three components: \begin{itemize} Extendedemission in the innermost region, with L_X = 1x 10(40) erg s(-1) ,coincident with the super-bubble seen in optical images. The activenucleus may contribute to the emission as a point source. Emission fromthe disk of the galaxy, with L_X = 7x 10(39) erg s(-1) , that can bepartly resolved by the HRI in 3 point-like sources with luminosities of~ 6 x 10(38) erg s(-1) each. Very soft X-shaped emission from the halo,with L_X = 6x 10(39) erg s(-1) , extending to a diameter of 27 kpc. TheX-ray luminosity of NGC 3079 is higher by a factor of 10 compared toother galaxies of similar optical luminosity and we argue that this maybe caused by the presence of an AGN rather than by starburst activity.The influence of the AGN on the companion galaxies in the NGC 3079 groupare discussed. The obscured circumnuclear region of the outflow galaxy NGC 3079Images of the central region of the almost edge-on Sc galaxy NGC 3079 inthe J, H and K-bands and in the v=1{->}0 S(1) line of molecularhydrogen are presented. The inner few kiloparsecs of NGC 3079 exhibit alarge range of near-infrared colours caused by varying contributionsfrom direct and scattered stellar light, emission from hot dust andextinction gradients. Our results show that interpretation of theobserved light distribution requires high-resolution imaging in order toseparate the different effects of these contributions. The central 1''(87 pc) of NGC 3079 suffers a peak extinction AV ~ mg 6. Itsextremely red near-infrared colours require the additional presence ofhot dust, radiating at temperatures close to 1000 K. The least reddenedeastern parts of the bulge require either a contribution of 20% of lightin the J-band from a younger population in a stellar bar or acontribution of 20-30% from scattered starlight; scattered light from anuclear source would require a less likely emission spectrum S_ν~nufor that source. The nucleus is surrounded by a disk of dense molecularmaterial, extending out to a radius of about 300 pc and with a centralcavity. Bright H_2 emission and emission from hot dust mark the hole inthe CO distribution and trace the inner edge of the dense molecular diskat a radius of 120 pc. Less dense molecular gas and cooler dust extendout to radii of about 2 kpc. In the inner few hundred parsecs of NGC3079, ion {H}i spin temperatures appear to be well below 275 K and theCO-to-H2 conversion factor has at most 5% of the Galacticvalue. An underabundance of H2 with respect to CO isconsistent with theoretical predictions for environments subjected todissociative shocks, where reformation of H2 is impeded byhigh dust grain temperatures. The overall molecular gas content of NGC3079 is normal for a late-type galaxy.
Submit a new article