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From tidal dwarf galaxies to satellite galaxies
The current popular cosmological models have granted the population ofdwarf satellite galaxies a key role: their number, location, and massesconstrain both the distribution of dark matter and the physicalevolution of their hosts. In the past years, there has been increasingobservational evidence that objects with masses of dwarf galaxies canform in the tidal tails of colliding galaxies, as well as speculationsthat they could become satellite-like galaxies orbiting around theirprogenitors and thus be cosmologically important. Yet, whether theso-called "Tidal Dwarf Galaxy" (TDG) candidates are really long-livedobjects and not transient features only present in young interactingsystems is still largely an open question to which numerical simulationsmay give precise answers. We present here a set of 96 N-body simulationsof colliding galaxies with various mass ratios and encounter geometries,including gas dynamics and star formation. We study the formation andlong-term evolution of their TDG candidates. Among the 593 substructuresinitially identified in tidal tails, about 75% fall back onto theirprogenitor or are disrupted in a few 108 years. The remaining25% become long-lived bound objects that typically survive more than 2Gyr with masses above 108 Mȯ. Theselong-lived, satellite-like objects, are found to form in massive gaseousaccumulations originally located in the outermost regions of the tidaltails. Studying the statistical properties of the simulated TDGs, weinfer several basic properties that dwarf galaxies should meet to have apossible tidal origin and apply these criteria to the Local Groupdwarfs. We further found that the presence of TDGs would foster theanisotropy observed in the distribution of classical satellite galaxiesaround their host. Identifying the conditions fulfilled by interactingsystems that were able to form long-lived tidal dwarfs - a spiralmerging with a galaxy between 1/4 and 8 times its mass, on a progradeorbit, with an orbital plane inclined up to 40 degrees to the disk plane- and estimating their fraction as a function of redshift, we roughlyestimate their contribution to the overall population of dwarfs. Weconclude that a small but significant fraction of them - a few percent -could be of tidal origin. This number may be underestimated inparticular environments such as the vicinity of early-type galaxies orin groups.
| The scaling relation of early-type galaxies in clusters. II. Spectroscopic data for galaxies in eight nearby clusters
Aims.We present low and intermediate resolution spectroscopic datacollected for 152 early type galaxies in 8 nearby clusters with z ≤0.10. Methods: .We use low resolution data to produce the redshiftand the K-correction for each galaxy, as well as to give their overallspectral energy distribution and some spectral indicators, including the4000 Å break, the Mg2 strength and the NaD equivalent width. Wehave also obtained higher resolution data for early type galaxies inthree of the clusters, to determine their central velocity dispersion. Results: .The effect of the resolution on the measured parametersis discussed. Conclusions: .A new accurate systemic redshift andvelocity dispersion is presented for four of the surveyed clusters, A98,A3125, A3330, and DC2103-39. We have found that the K-correction valuesfor E/S0 bright galaxies in the given nearby clusters are very similar.We also find that the distribution of the line indicators significantlydiffers from cluster to cluster.
| Orientation and size of the `Z' in X-shaped radio galaxies
Some X-shaped radio galaxies show a Z-symmetric morphology in the lessluminous secondary lobes. Within the scenario of a merger between twogalaxies, each hosting a supermassive black hole in its centre, thisstructure has been explained before. As the smaller galaxy spiralstowards the common centre, it releases gas to the interstellar medium ofthe larger active galaxy. The ram pressure of this streaming gas willbend the lobes of the pre-merger jet into a Z-shape. After the blackholes have merged, the jet propagates in a new direction that is alignedwith the angular momentum of the binary black hole. In this paper wedeproject the pre- and post-merger jets. Taking into account theexpected angles between the jet pairs and with the assumption that theirdirections are uncorrelated, we show that one of three possibleorientations of the jets with respect to the line of sight is morelikely than the others. This actually depends on the distance where thebending occurs. Another result of our deprojection is that the streaminggas bends the jet into a Z-shape in a range between about 30 and 100 kpcdistance to the centre of the primary galaxy. We confirm this finding bycomparing our predictions for the properties of the rotational velocityfield and its radius with observations and numerical simulations ofmerging galaxies. Thus, our results support the merger scenario asexplanation for X- and Z-shaped radio galaxies with the jet pointingalong the former axis of orbital angular momentum of the binary.
| New photometric and spectroscopic observations of the Seyfert galaxy Mrk 315
We present new important results about the intermediate-type Seyfertgalaxy Mrk 315, recently observed through optical imaging andintegral-field spectroscopy. Broad-band images were used to study themorphology of the host galaxy, narrow-band Hα images to trace thestar-forming regions, and middle-band [OIII] images to evidence thedistribution of the highly ionized gas. Some extended emission regionswere isolated and their physical properties studied by means offlux-calibrated spectra. High-resolution spectroscopy was used toseparate different kinematic components in the velocity fields of gasand stars. Some peculiar features characterize this apparentlyundisturbed and moderately isolated active galaxy. Such features,already investigated by other authors, are re-analysed and discussed inthe light of these new observations. The most relevant results weobtained are: the multitiers structure of the disc; the presence of aquasi-ring of regions with star formation much higher than previousclaims; a secondary nucleus confirmed by a stellar componentkinematically decoupled by the main galaxy; a new hypothesis about thecontroversial nature of the long filament, initially described as hookshaped, and more likely made of two independent filaments caused byinteraction events between the main galaxy and two dwarf companions.
| The giant star forming halo associated with the radio galaxy PKS 1932-46
We report the discovery of a giant (~160 kpc) knotty extended emissionline nebula associated with the radio galaxy PKS 1932-46 at z= 0.23. The2-d long slit spectra, obtained with VLT-FORS2 at a large angle(~63°) to the radio source axis, shows that the nebula extends wellbeyond the radio structure and the ionization cones of the activenucleus. This is one of the largest ionized nebulae yet detected arounda radio galaxy at any redshift. The analysis of the ionization,morphological and kinematic properties of the knots suggests that theseare star-forming objects, probably compact HII galaxies. We propose thatthe giant structure is a star forming halo associated with the debris ofthe merger that triggered the activity. This study reinforces the viewthat radio galaxies are activated by major mergers which also triggersubstantial star formation. The star formation activity can extend onthe scale of a galaxy group, beyond the old stellar halo of the hostgalaxy.
| The peculiar galaxy Mkn 298 revisited with integral field spectroscopy
Spectroscopic and imaging data of the peculiar galaxy Mkn 298 arepresented. Narrow-band Hα and broad-band R images are used tostudy the star formation rate in the galaxy and its morphology, which istypical of a merging system. Long-slit and integral field spectra areused to assess the kinematics of gas and stars, and the nature of theionizing source at different distances from the nucleus. In particular,the nucleus of Mkn 298 is characterized by peculiar line ratios: [NII]λ6583/Hα is typical of H II-like regions, while [OI]λ6300/Hα could indicate the presence of an activegalactic nucleus. We show that models where a shock component is addedto photoionization from a starburst allow us to reproduce the observedline ratios. Mkn 298 is thus most likely a star-forming galaxy, ratherthan a galaxy hosting an active nucleus.Based on data obtained at the 2.2m and NTT telescopes of ESO-la Silla(Chile), at the 2.2m telescope of DSAZ-Calar Alto (Spain), and at the 6mtelescope of SAO (Russia).
| A Tidal Dwarf Galaxy in the Hercules Cluster?
A candidate Tidal Dwarf Galaxy, ce-61, was identified in the mergersystem IC 1182 in the Hercules supercluster. The multi-wavelength datawe obtained so far do not prove, however, that it is kinematicallydetached from the IC 1182 system and gravitationally bound.
| Hα Kinematics of Tidal Tails in Interacting Systems: Projection Effects and Dark Matter in TDGs
Several interacting systems exhibit at the tip of their long tidal tailsmassive condensations of atomic hydrogen, which may be the progenitorsof Tidal Dwarf Galaxies. Because, quite often, these tails are observededge-on, projection effects have been claimed to account for the largeHI column densities measured there. Here we show that determining thevelocity field all along the tidal features, one may disentangleprojection effects along the line of view from real bound structures.Due to its large field of view, high spectral and 2D spatialresolutions, Fabry-Perot observations of the ionized gas are welladapted to detect a kinematical signature of either streaming motionsalong a bent tidal tail or of infalling/rotating material associatedwith a forming TDG. Spectroscopic observations also allow to measure thedynamical masses of the TDGs that are already relaxed and check theirdark matter content.
| A Green Bank Telescope Search for Water Masers in Nearby Active Galactic Nuclei
Using the Green Bank Telescope, we have conducted a survey for 1.3 cmwater maser emission toward the nuclei of nearby active galaxies, themost sensitive large survey for H2O masers to date. Among 145galaxies observed, maser emission was newly detected in 11 sources andconfirmed in one other. Our survey targeted nearby (v<12,000 kms-1), mainly type 2 active galactic nuclei (AGNs) north ofδ=-20deg and includes a few additional sources as well.We find that more than one-third of Seyfert 2 galaxies have strong maseremission, although the detection rate declines beyond v~5000 kms-1 because of sensitivity limits. Two of the masersdiscovered during this survey are found in unexpected hosts: NGC 4151(Seyfert 1.5) and NGC 2782 (starburst). We discuss the possiblerelations between the large X-ray column to NGC 4151 and a possiblehidden AGN in NGC 2782 to the detected masers. Four of the masersdiscovered here, NGC 591, NGC 4388, NGC 5728, and NGC 6323, havehigh-velocity lines symmetrically spaced about the systemic velocity, alikely signature of molecular gas in a nuclear accretion disk. The masersource in NGC 6323, in particular, reveals the classic spectrum of a``disk maser'' represented by three distinct groups of Dopplercomponents. Future single-dish and VLBI observations of these fourgalaxies could provide a measurement of the distance to each galaxy andof the Hubble constant, independent of standard candle calibrations.
| M/L, Hα Rotation Curves, and H I Gas Measurements for 329 Nearby Cluster and Field Spirals. II. Evidence for Galaxy Infall
We have conducted a study of optical and H I properties of spiralgalaxies (size, luminosity, Hα flux distribution, circularvelocity, and H I gas mass) to explore the role of gas stripping as adriver of morphological evolution in clusters. We find a strongcorrelation between the spiral and S0 fractions within clusters, and thespiral fraction scales tightly with cluster X-ray gas luminosity. Weexplore young star formation and identify spirals that are (1)asymmetric, with truncated Hα emission and H I gas reservoirs onthe leading edge of the disk, on a first pass through the denseintracluster medium in the cores of rich clusters; (2) strongly H Ideficient and stripped, with star formation confined to the inner 5h-1 kpc and 3 disk scale lengths; or (3) reddened, extremelyH I deficient, and quenched, where star formation has been halted acrossthe entire disk. We propose that these spirals are in successive stagesof morphological transformation, between infalling field spirals andcluster S0's, and that the process that acts to remove the H I gasreservoir suppresses new star formation on a similarly fast timescale.These data suggest that gas stripping plays a significant role inmorphological transformation and rapid truncation of star formationacross the disk.
| M/L, Hα Rotation Curves, and H I Measurements for 329 Nearby Cluster and Field Spirals. I. Data
A survey of 329 nearby galaxies (redshift z<0.045) has been conductedto study the distribution of mass and light within spiral galaxies overa range of environments. The 18 observed clusters and groups span arange of richness, density, and X-ray temperature and are supplementedby a set of 30 isolated field galaxies. Optical spectroscopy taken withthe 200 inch (5 m) Hale Telescope provides separately resolved Hαand [N II] major-axis rotation curves for the complete set of galaxies,which are analyzed to yield velocity widths and profile shapes, extents,and gradients. H I line profiles provide an independent velocity widthmeasurement and a measure of H I gas mass and distribution. I-bandimages are used to deconvolve profiles into disk and bulge components,to determine global luminosities and ellipticities, and to checkmorphological classification. These data are combined to form a unifieddata set ideal for the study of the effects of environment upon galaxyevolution.
| Kinematics of tidal tails in interacting galaxies: Tidal dwarf galaxies and projection effects
The kinematics of tidal tails in colliding galaxies has been studied viaFabry-Pérot observations of the Hα emission. With theirlarge field of view and high spatial resolution, the Fabry-Pérotdata allow us to probe simultaneously, in 2D, two kinematical featuresof the tidal ionized gas: large-scale velocity gradients due tostreaming motions along the tails, and small-scale motions related tothe internal dynamics of giant HII regions within the tails. In severalinteracting systems, massive (109 Mȯ)condensations of HI, CO and stars are observed in the outer regions oftails. Whether they are genuine accumulations of matter or not is stilldebated. Indeed a part of the tidal tail may be aligned with theline-of-sight, and the associated projection effect may result inapparent accumulations of matter that does not exist in the 3D space.Using numerical simulations, we show that studying the large-scalekinematics of tails, it is possible to know whether these accumulationsof matter are the result of projection effects or not. We conclude thatseveral ones (Arp 105-South, Arp 242, NGC 7252, and NGC 5291-North) aregenuine accumulations of matter. We also study the small-scale motionsinside these regions: several small-scale velocity gradients areidentified with projected values as large as 50-100 km s-1accross the observed HII regions. In the case of NGC 5291-North, thespatial resolution of our observations is sufficient to detail thevelocity field; we show that this system is rotating andself-gravitating, and discuss its dark matter content. TheFabry-Pérot observations have thus enabled us to prove that some109 Mȯ condensations of matter are realstructures, and are kinematically decoupled from the rest of the tail.Such massive and self-gravitating objects are the progenitors of theso-called ``Tidal Dwarf Galaxies''.Based on observations collected at the European Southern Observatory, LaSilla, Chile and at the Canada-France-Hawaii Observatory, Hawaii, USA.Appendix is only available in electronic form athttp://www.edpsciences.org
| The gas content of peculiar galaxies: Strongly interacting systems
A study of the gas content in 1038 interacting galaxies, essentiallyselected from Arp, Arp & Madore, Vorontsov-Velyaminov catalogues andsome of the published literature, is presented here. The data on theinterstellar medium have been extracted from a number of sources in theliterature and compared with a sample of 1916 normal galaxies. The meanvalues for each of the different ISM tracers (FIR, 21 cm, CO lines,X-ray) have been estimated by means of survival analysis techniques, inorder to take into account the presence of upper limits. From the datait appears that interacting galaxies have a higher gas content thannormal ones. Galaxies classified as ellipticals have both a dust and gascontent one order of magnitude higher than normal. Spirals have in mostpart a normal dust and HI content but an higher molecular gas mass. TheX-ray luminosity also appears higher than that of normal galaxies ofsame morphological type, both including or excluding AGNs. We consideredthe alternative possibilities that the molecular gas excess may derivefrom the existence of tidal torques which produce gas infall from thesurrounding regions or from a different metallicity which affects the Xconversion factor between the observed CO line luminosity and the H_2calculated mass. According to our tests, it appears that interactinggalaxies possess a higher molecular mass than normal galaxies but with asimilar star formation efficiency.Table 1 is only available in electronic form at the CDS via anonymousftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/422/941
| The peculiar galaxy IC 1182: An ongoing merger?
High resolution broad and narrow band images and long slit spectroscopyof the peculiar galaxy IC 1182 are presented. The analysis of the broadband images reveals a distorted morphology with a large, heavilyobscured disk-like structure and several knots in the central region.Galactic material, some of it in the form of two slender tails, isdetected well beyond the main body of the galaxy. The second, faintertail and several knots are reported here for the first time. The galaxyhas color indices of an early type object except U-B, which issignificantly bluer than what is typical for this kind of galaxy.The narrow band images centered on different emission lines show thatthe galaxy is a very powerful emitter. Most of the knots detected in thecentral region and in the prominent tail emerging eastward from thegalaxy are very luminous in Hα, and have typical sizes about 1 kpc(FWHM). The emission in the main lines extends all over the galaxy, withplumes and arc-like structures seen in Hα at large distances fromthe center. The observed, uncorrected Hα flux corresponds to atotal luminosity of 3.51 × 1041 erg s-1,about 3 times that of the starburst galaxy Arp 220. We have found thatthe internal extinction deduced from the observed Balmer decrement ishigh all along the slit, with EB-V≈ 1, so the correctedSFR could amount to 90 Mȯ per year. On this basis IC1182 is found to be a very powerful starburst galaxy. Surprisingly, thesource is not in the IRAS Point Source Catalogue.The emission knots detected in the central region of the galaxy haveline ratios that place them close to the border of the region occupiedby active nuclei in the diagnostic diagrams. Using the best determineddiagnostic ratio, [O III]/Hβ vs. [N II]/Hα, they can still beclassified as extreme HII-like regions. We notice that the same kind ofline ratios are also measured at different places in the galaxy, addingto the idea that the nuclear line ratios can be explained in terms ofstellar photoionization. The metallicity we have measured for theionized gas in the two brightest central knots is low, 0.1Zȯ and 0.06 Zȯ respectively, and theirmeasured helium abundance is also lower than solar.In the main body of the galaxy, besides the reported knots, thedistribution of the ionized gas resembles that of an inclined disk about12 kpc in size. The spectroscopic data show however a complex rotationpattern. We interpret them as corresponding to two identifiable diskgalaxies with observed rotation amplitudes of 200 km s-1 and100 km s-1 respectively. The stellar absorption linesdetected in the bigger system do not show any clear rotation pattern.The data presented here indicate that IC 1182 is a high luminositystarburst system. Its global properties and peculiarities can beunderstood as corresponding to two systems that can still be recognized,in the process of merging, with two tidal tails emerging from thecentral region of the galaxy. In the main tail there are severalcandidates forming tidal dwarf galaxies. The measured low metallicity ofthe ionized gas, together with the low amplitude of one of the systems,suggests that the process involves a late-type, gas-rich spiral galaxythat is supplying most of the gas to the system.Based on data obtained with the Nordic Optical telescope (La Palma,Spain) with ALFOSC. Also based on observations obtained with FORS1 atthe ESO Very Large Telescope (Paranal, Chile), and on observationscollected with DFOSC at the D1.54 m telescope at the European SouthernObservatory (La Silla, Chile).
| Radio emission from AGN detected by the VLA FIRST survey
Using the most recent (April 2003) version of the VLA FIRST survey radiocatalog, we have searched for radio emission from >2800 AGN takenfrom the most recent (2001) version of the Veron-Cetty and Veron AGNcatalog. These AGN lie in the 9033 square degrees of sky alreadycovered by the VLA FIRST survey. Our work has resulted in positivedetection of radio emission from 775 AGN of which 214 are new detectionsat radio wavelengths.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/416/35
| Optically bright active galactic nuclei in the ROSAT-Faint source catalogue
To build a large, optically bright, X-ray selected AGN sample we havecorrelated the ROSAT-FSC catalogue of X-ray sources with the USNOcatalogue limited to objects brighter than O=16.5 and then with the APSdatabase. Each of the 3212 coincidences was classified using theslitless Hamburg spectra. 493 objects were found to be extended and 2719starlike. Using both the extended objects and the galaxies known frompublished catalogues we built up a sample of 185 galaxies withO_APS<17.0 mag, which are high-probability counterparts of RASS-FSCX-ray sources. 130 galaxies have a redshift from the literature and foranother 34 we obtained new spectra. The fraction of Seyfert galaxies inthis sample is 20%. To select a corresponding sample of 144high-probability counterparts among the starlike sources we searched forvery blue objects in an APS-based color-magnitude diagram. Forty-onewere already known AGN and for another 91 objects we obtained newspectra, yielding 42 new AGN, increasing their number in the sample to83. This confirms that surveys of bright QSOs are still significantlyincomplete. On the other hand we find that, at a flux limit of 0.02count s-1 and at this magnitude, only 40% of all QSOs aredetected by ROSAT.Tables 2, 3 and 4 are only available in electronic form athttp://www.edpsciences.org
| The peculiar galaxy IC 1182: an ongoing merger?
High resolution broad band images, and long slit spectroscopy of thepeculiar galaxy IC 1182 are presented. The broad band images show adistorted morphology with a heavily obscured central region, multiplecentral knots and two jet-like structures extending well beyond the mainbody of the galaxy. The second jet and several knots are reported herefor the first time. The data presented suggest that IC 1182 is a verypowerful star-burst system, comparable to Arp 220. The overall aspectand the peculiarities can be explained in term of a merging processstill going on. The low metallicity would suggest that the processinvolves a gas rich galaxy, or that it is accompanied by accretion offresh gas from the neighborhood.
| A study of H I-selected galaxies in the Hercules cluster
The present study focuses on a sample of 22 galaxies detected in theblind VLA H I survey of the Hercules cluster by Dickey (\cite{Dickey),18 of which were selected on an H I line width smaller than 270 kms-1 and 4 others with only tentative optical counterparts inthe Palomar Sky Survey. Sensitive single-dish H I line spectra wereobtained for 20 of them, and for one the VLA detection was notconfirmed. Optical surface photometry has been carried out for 10objects, for 8 of which optical spectroscopy was obtained as well. Basedon various criteria, we classify two sample galaxies (ce-143 and ne-204)as genuine dwarfs whereas the remaining sample objects are found to beintrinsically luminous galaxies. For those objects investigated inoptical wavelengths we determine properties similar to those of activelystar-forming galaxies, and find that approximately one half of them hasproperties intermediate between those of dwarf galaxies andlow-luminosity disc galaxies. No optical redshifts could be determinedfor two of the galaxies (sw-103 and sw-194) and their physicalassociation with the H I clouds detected at their positions thereforeremains uncertain. A particularly interesting object in our sample isthe Tidal Dwarf Galaxy candidate ce-061 in the galaxy merger IC 1182.Appendix A and Figs. \ref{ce042} to \ref{sw222} are only available inelectronic form at http://www.edpsciences.org
| Non-confirmation of reported HI clouds without optical counterparts in the Hercules cluster
21 cm H I line observations were made with the Arecibo Gregoriantelescope of 9 H I clouds in the Hercules Cluster which were reported astentative detections in a VLA H I study of the cluster (Dickey\cite{Dickey97}) and for which our deep CCD imaging failed to find anyoptical counterparts. No sensitive observations could be made of one ofthese (sw-174) due to the presence of a close-by strong continuumsource. The other 8 tentative H I detections were not confirmed by theArecibo H I measurements. The CCD images did reveal faint, low surfacebrightness counterparts near the centres of two other VLA H I sourcesinvisible on the Palomar Sky Survey, sw-103 and sw-194.
| Mass loss from galaxies: feeding the IGM, recycling in the IGM
As a result of internal processes or environmental effects likeram-pressure stripping or collisions, galaxies lose a significant partof their stellar and gaseous content. Whereas the impact of suchstripping on galaxy evolution has been well studied, much less attentionhas been given to the fate of the expelled material in the intergalacticor intra cluster medium (IGM/ICM). Observational evidence exists showingthat a fraction of the injected matter is actually recycled to form anew generation of galaxies, such as the Tidal Dwarf Galaxies discoverednear numerous interacting systems. Using a set of multiwavelength data,we are now able to roughly analyze the processes pertaining to theirformation: from an instability in the HI clouds, through the formationof molecular gas, and to the onset of star formation.
| 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.
| The scaling relations of early-type galaxies in clusters. I. Surface photometry in seven nearby clusters
This is the first paper of a series investigating the scaling relationsof early-type galaxies in clusters. Here we illustrate the multi-bandimagery and the image reduction and calibration procedures relative tothe whole sample of 22 clusters at 0.05 <~ z <~ 0.25. We alsopresent detailed surface photometry of 312 early-type galaxies in 7clusters in the first redshift bin, z ≈0.025-0.075. We give for eachgalaxy the complete set of luminosity and geometrical profiles, and anumber of global, photometric and morphological parameters. They havebeen evaluated taking into account the effects of seeing. Internalconsistency checks and comparisons with data in the literature confirmthe quality of our analysis. These data, together with the spectroscopicones presented in the second paper of the series, will provide the localcalibration of the scaling relations. Tables 6, 7a-7g, the colour printsof Figs. 12a-12g AND Figs. 13a-13g are only available in electronic format http://www.edpsciences.com. The complete set of profiles is availableupon request from the authors. Tables 7a-7g are also available inelectronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr(130.79.188.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/387/26
| Abundant molecular gas in tidal dwarf galaxies: On-going galaxy formation
We investigate the process of galaxy formation as can be observed in theonly currently forming galaxies - the so-called Tidal Dwarf Galaxies,hereafter TDGs - through observations of the molecular gas detected viaits CO (Carbon Monoxide) emission. These objects are formed of materialtorn off of the outer parts of a spiral disk due to tidal forces in acollision between two massive galaxies. Molecular gas is a key elementin the galaxy formation process, providing the link between a cloud ofgas and a bona fide galaxy. We have detected CO in 8 TDGs (two of themhave already been published in Braine et al. 2000, hereafter Paper I),with an overall detection rate of 80%, showing that molecular gas isabundant in TDGs, up to a few 108 Msun. The COemission coincides both spatially and kinematically with the HIemission, indicating that the molecular gas forms from the atomichydrogen where the HI column density is high. A possible trend of moreevolved TDGs having greater molecular gas masses is observed, in accordwith the transformation of HI into H2. Although TDGs sharemany of the properties of small irregulars, their CO luminosity is muchgreater (factor ~ 100) than that of standard dwarf galaxies ofcomparable luminosity. This is most likely a consequence of the highermetallicity (gtrsim 1/3 solar) of TDGs which makes CO a good tracer ofmolecular gas. This allows us to study star formation in environmentsordinarily inaccessible due to the extreme difficulty of measuring themolecular gas mass. The star formation efficiency, measured by the COluminosity per Hα flux, is the same in TDGs and full-sizedspirals. CO is likely the best tracer of the dynamics of these objectsbecause some fraction of the HI near the TDGs may be part of the tidaltail and not bound to the TDG. Although uncertainties are large forindividual objects, as the geometry is unknown, our sample is now ofeight detected objects and we find that the ``dynamical" masses of TDGs,estimated from the CO line widths, seem not to be greater than the``visible" masses (HI + H2 + a stellar component). Althoughhigher spatial resolution CO (and HI) observations would help reduce theuncertainties, we find that TDGs require no dark matter, which wouldmake them the only galaxy-sized systems where this is the case. Darkmatter in spirals should then be in a halo and not a rotating disk. Mostdwarf galaxies are dark matter-rich, implying that they are not of tidalorigin. We provide strong evidence that TDGs are self-gravitatingentities, implying that we are witnessing the ensemble of processes ingalaxy formation: concentration of large amounts of gas in a boundobject, condensation of the gas, which is atomic at this point, to formmolecular gas and the subsequent star formation from the dense molecularcomponent.
| The integral field spectroscopy (IFS) as a tool for investigating the nature of active galactic nuclei.
Not Available
| MKN 298: an AGN hidden by starbursts.
Not Available
| 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.
| Seeking the Local Convergence Depth. IV. Tully-Fisher Observations of 35 Abell Clusters
We present Tully-Fisher observations for 35 rich Abell clusters ofgalaxies. Results from I-band photometry and optical rotation curve workconstitute the bulk of this paper. This is the third such datainstallment of an all-sky survey of 52 clusters in the distance range~50 to 200 h^-1 Mpc. The complete data set provides the basis fordetermining an accurate Tully-Fisher template relation and forestimating the amplitude and direction of the local bulk flow on a 100h^-1 Mpc scale.
| The I-Band Tully-Fisher Relation for SC Galaxies: 21 Centimeter H I Line Data
A compilation of 21 cm line spectral parameters specifically designedfor application of the Tully-Fisher (TF) distance method is presentedfor 1201 spiral galaxies, primarily field Sc galaxies, for which opticalI-band photometric imaging is also available. New H I line spectra havebeen obtained for 881 galaxies. For an additional 320 galaxies, spectraavailable in a digital archive have been reexamined to allow applicationof a single algorithm for the derivation of the TF velocity widthparameter. A velocity width algorithm is used that provides a robustmeasurement of rotational velocity and permits an estimate of the erroron that width taking into account the effects of instrumental broadeningand signal-to-noise. The digital data are used to establish regressionrelations between measurements of velocity widths using other commonprescriptions so that comparable widths can be derived throughconversion of values published in the literature. The uniform H I linewidths presented here provide the rotational velocity measurement to beused in deriving peculiar velocities via the TF method.
| The I-Band Tully-Fisher Relation for SC Galaxies: Optical Imaging Data
Properties derived from the analysis of photometric I-band imagingobservations are presented for 1727 inclined spiral galaxies, mostly oftypes Sbc and Sc. The reduction, parameter extraction, and errorestimation procedures are discussed in detail. The asymptotic behaviorof the magnitude curve of growth and the radial variation in ellipticityand position angle are used in combination with the linearity of thesurface brightness falloff to fit the disk portion of the profile. TotalI-band magnitudes are calculated by extrapolating the detected surfacebrightness profile to a radius of eight disk scale lengths. Errors inthe magnitudes, typically ~0.04 mag, are dominated by uncertainties inthe sky subtraction and disk-fitting procedures. Comparison is made withthe similar imaging database of Mathewson, Ford, & Buchhorn, both aspresented originally by those authors and after reanalyzing theirdigital reduction files using identical disk-fitting procedures. Directcomparison is made of profile details for 292 galaxies observed incommon. Although some differences occur, good agreement is found,proving that the two data sets can be used in combination with onlyminor accommodation of those differences. The compilation of opticalproperties presented here is optimized for use in applications of theTully-Fisher relation as a secondary distance indicator in studies ofthe local peculiar velocity field.
| A Hubble Space Telescope Imaging Survey of Nearby Active Galactic Nuclei
We have obtained WFPC2 images of 256 of the nearest (z <= 0.035)Seyfert 1, Seyfert 2, and starburst galaxies. Our 500 s broadband(F606W) exposures reveal much fine-scale structure in the centers ofthese galaxies, including dust lanes and patches, bars, rings, wisps,and filaments, and tidal features such as warps and tails. Most of thisfine structure cannot be detected in ground-based images. We haveassigned qualitative classifications for these morphological featuresand a Hubble type for the inner region of each galaxy, and we have alsomeasured quantitative information such as 0."18 and 0."92 aperturemagnitudes, position angles, and ellipticities, where possible. There islittle direct evidence for unusually high rates of interaction in theSeyfert galaxies. Slightly less than 10% of all the galaxies show tidalfeatures or multiple nuclei. The incidence of inner starburst rings isabout 10% in both classes of Seyfert galaxies. In contrast, galaxieswith H II region emission-line spectra appear substantially moreirregular and clumpy because of their much higher rates of current starformation per unit of galactic mass. The presence of an unresolvedcentral continuum source in our Hubble Space Telescope images is avirtually perfect indicator of a Seyfert 1 nucleus as seen byground-based spectroscopy. Fifty-two percent of these Seyfert 1 pointsources are saturated in our images; we use their wings to estimatemagnitudes ranging from 15.8 to 18.5. The converse is not universallytrue, however, as over one-third of Seyferts with direct spectroscopicevidence for broad Balmer wings show no nuclear point source. These 34resolved Seyfert 1's have fainter nonstellar nuclei, which appear to bemore extinguished by dust absorption. Like the Seyfert 2's, they havecentral surface brightnesses consistent with those expected for thebulges of normal galaxies. The rates for the occurrences of bars inSeyfert 1's and 2's and non-Seyferts are the same. We found onesignificant morphological difference between the host galaxies ofSeyfert 1 and Seyfert 2 nuclei. The Seyfert 2 galaxies are significantlymore likely to show nuclear dust absorption, especially in lanes andpatches that are irregular or reach close to the nucleus. A few simpletests show that the difference cannot be explained by different averageredshifts or selection techniques. It is confirmed by our galaxymorphology classifications, which show that Seyfert 1 nuclei reside inearlier type galaxies than Seyfert 2 nuclei. If, as we believe, this isan intrinsic difference in host galaxy properties, it undermines one ofthe postulates of the strong unification hypothesis for Seyfertgalaxies, that they merely appear different because of the orientationof their central engine. The excess galactic dust we see in Seyfert 2'smay cause substantial absorption that obscures their hypothesized broademission line regions and central nonstellar continua. This galacticdust could produce much of the absorption in Seyfert 2 nuclei that hadinstead been attributed to a thick dusty accretion torus forming theouter part of the central engine.
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