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Neutral hydrogen in radio galaxies: Results from nearby, importance for far away
The study of neutral hydrogen emission and absorption in radio galaxiesis giving new and important insights on a variety of phenomena observedin these objects. Such observations are helping to understand the originof the host galaxy, the effects of the interaction between the radio jetand the ISM, the presence of fast gaseous outflows as well asjet-induced star formation. Recent results obtained on these phenomenaare summarized in this review. Although the {H I observationsconcentrate on nearby radio galaxies, the results also have relevancefor the high-z objects as all these phenomena are important, and likelyeven more common, in high-redshift radio sources.
| Timescales of merger, starburst and AGN activity in radio galaxy B2 0648+27
We use neutral hydrogen (H I) and optical spectroscopic observations tocompare the timescales of a merger event, starburst episode andradio-AGN activity in the radio galaxy B2 0648+27. Wedetect a large ring-like structure of H I in emission around theearly-type host galaxy of B2 0648+27 (MH I= 8.5 × 109~Mȯ, diameter = 190 kpc). Weinterpret this as the result of a major merger that occurred ≳1.5Gyr ago. From modelling optical long-slit spectra we find that a youngstellar population of 0.3 Gyr, indicative of a past starburst event,dominates the stellar light throughout the galaxy. The off-set in timebetween the merger event and the starburst activity in B20648+27 suggests that the starburst was triggered in anadvanced stage of the merger, which can be explained if the gas-richprogenitor galaxies contained a bulge. Although the exact age of theradio source remains uncertain, there appears to be a significanttime-delay between the merger/starburst event and the current episode ofradio-AGN activity. We also observe an outflow of emission-line gas inthis system, which is likely related to superwinds driven by the starsthat formed during the starburst event. We argue that the radio galaxyB2 0648+27 is a link in the evolutionary sequencebetween Ultra-Luminous Infrared Galaxies (ULIRGs) and genuine early-typegalaxies.
| Nearby early-type galaxies with ionized gas. II. Line-strength indices for 18 additional galaxies
We previously presented a data-set of line-strength indices for 50early-type galaxies in the nearby Universe. The galaxy sample is biasedtoward galaxies showing emission lines, located in environmentscorresponding to a broad range of local galaxy densities, althoughpredominantly in low density environments. The present addendum enlargesthe above data-set of line-strength indices by analyzing 18 additionalearly-type galaxies (three galaxies, NGC 3607, NGC 5077 and NGC 5898were presented in the previous set). We measured 25 line-strengthindices, defined by the Lick IDS "standard" system (Trager et al. 1998,ApJS, 116, 1; Worthey & Ottaviani 1997, ApJS, 111, 377), for 7luminosity weighted apertures and 4 gradients of each galaxy. Thisaddendum presents the line-strength data-set and compares it with theavailable data in the literature.
| 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.
| Mass-to-light ratio gradients in early-type galaxy haloes
Owing to the fact that the near future should see a rapidly expandingset of probes of the halo masses of individual early-type galaxies, weintroduce a convenient parameter for characterizing the halo masses fromboth observational and theoretical results:∇lΥ, the logarithmic radial gradient of themass-to-light ratio. Using halo density profiles from Λ-cold darkmatter (CDM) simulations, we derive predictions for this gradient forvarious galaxy luminosities and star formation efficienciesɛSF. As a pilot study, we assemble the available∇lΥ data from kinematics in early-type galaxies- representing the first unbiased study of halo masses in a wide rangeof early-type galaxy luminosities - and find a correlation betweenluminosity and ∇lΥ, such that the brightestgalaxies appear the most dark-matter dominated. We find that thegradients in most of the brightest galaxies may fit in well with theΛCDM predictions, but that there is also a population of faintergalaxies whose gradients are so low as to imply an unreasonably highstar formation efficiency ɛSF > 1. This difficultyis eased if dark haloes are not assumed to have the standard ΛCDMprofiles, but lower central concentrations.
| On the Relation between Circular Velocity and Central Velocity Dispersion in High and Low Surface Brightness Galaxies
In order to investigate the correlation between the circular velocityVc and the central velocity dispersion of the spheroidalcomponent σc, we analyzed these quantities for a sampleof 40 high surface brightness (HSB) disk galaxies, eight giant lowsurface brightness (LSB) spiral galaxies, and 24 elliptical galaxiescharacterized by flat rotation curves. Galaxies have been selected tohave a velocity gradient <=2 km s-1 kpc-1 forR>=0.35R25. We used these data to better define theprevious Vc-σc correlation for spiralgalaxies (which turned out to be HSB) and elliptical galaxies,especially at the lower end of the σc values. We findthat the Vc-σc relation is described by alinear law out to velocity dispersions as low as σc~50km s-1, while in previous works a power law was adopted forgalaxies with σc>80 km s-1. Ellipticalgalaxies with Vc based on dynamical models or directlyderived from the H I rotation curves follow the same relation as the HSBgalaxies in the Vc-σc plane. On the otherhand, the LSB galaxies follow a different relation, since most of themshow either higher Vc or lower σc withrespect to the HSB galaxies. This argues against the relevance of baryoncollapse to the radial density profile of the dark matter halos of LSBgalaxies. Moreover, if the Vc-σc relation isequivalent to one between the mass of the dark matter halo and that ofthe supermassive black hole, then these results suggest that the LSBgalaxies host a supermassive black hole (SMBH) with a smaller masscompared to HSB galaxies with an equal dark matter halo. On the otherhand, if the fundamental correlation of SMBH mass is with the halocircular velocity, then LSB galaxies should have larger black holemasses for a given bulge dispersion. Elliptical galaxies withVc derived from H I data and LSB galaxies were not consideredin previous studies.Based on observations made with European Southern Observatory telescopesat the Paranal Observatory under programs 67.B-0283, 69.B-0573, and70.B-0171.
| The photometric properties of isolated early-type galaxies
Isolated galaxies are important because they probe the lowest densityregimes inhabited by galaxies. We define a sample of 36 nearby isolatedearly-type galaxies for further study. Our isolation criteria requirethem to have no comparable-mass neighbours within 2 B-band magnitudes,0.67 Mpc in the plane of the sky and 700 km s-1 in recessionvelocity. New wide-field optical imaging of 10 isolated galaxies withthe Anglo-Australian Telescope confirms their early-type morphology andrelative isolation. We also present imaging of four galaxy groups as acontrol sample. The isolated galaxies are shown to be moregravitationally isolated than the group galaxies. We find that theisolated early-type galaxies have a mean effective colour of(B-R)e= 1.54 +/- 0.14, similar to their high-densitycounterparts. They reveal a similar colour-magnitude relation slope andsmall intrinsic scatter to cluster ellipticals. They also follow theKormendy relation of surface brightness versus size for luminous clustergalaxies. Such properties suggest that the isolated galaxies formed at asimilar epoch to cluster galaxies, such that the bulk of their stars arevery old. However, our galaxy modelling reveals evidence for dust lanes,plumes, shells, boxy and disc isophotes in four out of nine galaxies.Thus at least some isolated galaxies have experienced a recentmerger/accretion event, which may have induced a small burst of starformation. We derive luminosity functions for the isolated galaxies andfind a faint slope of -1.2, which is similar to the `universal' slopefound in a wide variety of environments. We examine the number densitydistribution of galaxies in the field of the isolated galaxies. Only thevery faintest dwarf galaxies (MR>~-15.5) appear to beassociated with the isolated galaxies, whereas anyintermediate-luminosity galaxies appear to lie in the background.Finally, we discuss possible formation scenarios for isolated early-typegalaxies. Early epoch formation and a merger/accretion of galaxies arepossible explanations. The collapse of a large, virialized group is anunlikely explanation, but that of a poor group remains viable.
| A Uniform Database of 2.2-16.5 μm Spectra from the ISOCAM CVF Spectrometer
We present all ISOCAM circular variable filter (CVF) spectra that covermore than one-third of the 2.2-16.5 μm spectral range of theinstrument. The 364 spectra have been classified according to theclassification system of Kraemer et al., as modified by Hodge et al. toaccount for the shorter wavelength range. Prior to classification, thespectra were processed and recalibrated to create a uniform database.Aperture photometry was performed at each wavelength centered on thebrightest position in each image field and the various spectral segmentsmerged into a single spectrum. The aperture was the same for all scalesizes of the images. Since this procedure differs fundamentally fromthat used in the initial ISOCAM calibration, a recalibration of thespectral response of the instrument was required for the aperturephotometry. The recalibrated spectra and the software used to createthem are available to the community on-line via the ISO Data Archive.Several new groups were added to the KSPW system to describe spectrawith no counterparts in either the SWS or PHT-S databases: CA, E/SA,UE/SA, and SSA. The zodiacal dust cloud provides the most commonbackground continuum to the spectral features, visible in almost 40% ofthe processed sources. The most characteristic and ubiquitous spectralfeatures observed in the CVF spectral atlas are those of theunidentified infrared bands (UIR), which are typically attributed toultraviolet-excited fluorescence of large molecules containing aromatichydrocarbons. The UIR features commonly occur superimposed on thezodiacal background (18%) but can also appear in conjunction with otherspectral features, such as fine-structure emission lines or silicateabsorption. In at least 13 of the galaxies observed, the pattern of UIRemission features has been noticeably shifted to longer wavelengths.Based on observations with the Infrared Space Observatory, a EuropeanSpace Agency (ESA) project with instruments funded by ESA Member States(especially the Principal Investigator countries: France, Germany, theNetherlands, and the United Kingdom) and with the participation of theInstitute of Space and Astronautical Science (ISAS) and the NationalAeronautics and Space Administration (NASA).
| The ISOPHOT 170 μm Serendipity Survey II. The catalog of optically identified galaxies%
The ISOPHOT Serendipity Sky Survey strip-scanning measurements covering≈15% of the far-infrared (FIR) sky at 170 μm were searched forcompact sources associated with optically identified galaxies. CompactSerendipity Survey sources with a high signal-to-noise ratio in at leasttwo ISOPHOT C200 detector pixels were selected that have a positionalassociation with a galaxy identification in the NED and/or Simbaddatabases and a galaxy counterpart visible on the Digitized Sky Surveyplates. A catalog with 170 μm fluxes for more than 1900 galaxies hasbeen established, 200 of which were measured several times. The faintest170 μm fluxes reach values just below 0.5 Jy, while the brightest,already somewhat extended galaxies have fluxes up to ≈600 Jy. For thevast majority of listed galaxies, the 170 μm fluxes were measured forthe first time. While most of the galaxies are spirals, about 70 of thesources are classified as ellipticals or lenticulars. This is the onlycurrently available large-scale galaxy catalog containing a sufficientnumber of sources with 170 μm fluxes to allow further statisticalstudies of various FIR properties.Based on observations with ISO, an ESA project with instruments fundedby ESA Member States (especially the PI countries: France, Germany, TheNetherlands and the UK) and with the participation of ISAS and NASA.Members of the Consortium on the ISOPHOT Serendipity Survey (CISS) areMPIA Heidelberg, ESA ISO SOC Villafranca, AIP Potsdam, IPAC Pasadena,Imperial College London.Full Table 4 and Table 6 are only available in electronic form at theCDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/422/39
| Minor-axis velocity gradients in disk galaxies
We present the ionized-gas kinematics and photometry of a sample of 4spiral galaxies which are characterized by a zero-velocity plateau alongthe major axis and a velocity gradient along the minor axis,respectively. By combining these new kinematical data with thoseavailable in the literature for the ionized-gas component of the S0s andspirals listed in the Revised Shapley-Ames Catalog of Bright Galaxies werealized that about 50% of unbarred galaxies show a remarkable gasvelocity gradient along the optical minor axis. This fraction rises toabout 60% if we include unbarred galaxies with an irregular velocityprofile along the minor axis. This phenomenon is observed all along theHubble sequence of disk galaxies, and it is particularly frequent inearly-type spirals. Since minor-axis velocity gradients are unexpectedif the gas is moving onto circular orbits in a disk coplanar to thestellar one, we conclude that non-circular and off-plane gas motions arenot rare in the inner regions of disk galaxies.Based on observations carried out at the European Southern Observatoryin La Silla (Chile) (ESO 69.B-0706 and 70.B-0338), with the MultipleMirror Telescope which is a joint facility of the SmithsonianInstitution and the University of Arizona, and with the ItalianTelescopio Nazionale Galileo (AOT-5, 3-18) at the Observatorio del Roquede los Muchachos in La Palma (Spain).Table 1 is only available in electronic form athttp://www.edpsciences.org. Table 5 is only available in electronic format the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) orvia http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/416/507
| Dust emission in early-type galaxies: The mid-infrared view
We present mid-infrared (MIR) maps for a sample of 18 early-typegalaxies observed at 4.5, 6.7 and 15 μ m with the ISOCAM instrumenton board the ISO satellite with a 6'' spatial resolution. We model theSpectral Energy Distribution (SED) of these galaxies using the stellarevolutionary synthesis model PÉGASE and we derive the MIR excessover the stellar component. We then explore the nature of this excess interms of dust and Polycyclic Aromatic Hydrocarbon molecules (PAHs). Wefind that out of 18 galaxies, 10 show excess at 6.7 μ m (due to thepresence of PAH features) and 14 show excess at 15 μ m (due to thepresence of warm dust). In two galaxies, where a more completewavelength coverage exists, an excess around 9.7 μ m is seen(presumably due to silicate dust emission), while two other galaxies aretotally devoid of dust. We also examine the morphology of the galaxiesin these wavelengths by plotting the azimuthally averaged radialprofiles as well as the MIR color profiles. We find that for themajority of the galaxies the 4.5 μ m emission is well described by ade Vaucouleurs profile. The 6.7 μ m and 15 μ m emission issmoothly distributed throughout the galaxy while only a few galaxiesshow MIR emission which is more concentrated close to the center. Twodwarf galaxies in our sample show patchy distributions of the MIRemission while two other galaxies show edge-on disks. With color-colordiagrams we delineate the regions occupied by late-type and early-typegalaxies. Finally we show that the MIR excess found in strong radiogalaxies like NGC 4486 (M87) can be explained by synchrotron emission.Based on observations with ISO, an ESA project with instruments fundedby ESA Member States (especially the PI countries: France, Germany, TheNetherlands and the UK) and with the participation of ISAS and NASA.Appendix A is only available in electronic form athttp://www.edpsciences.org
| Large-scale HI structures and the origin of radio galaxies
We present the first results of a study aimed to detect large HIstructures in radio galaxies. In two of the three cases presented (ComaA and B2 0648+27), the detection of a large amount of HI distributedover several tens of kpc suggests a major merger as the origin of theobserved system and allows us to infer when this merger must haveoccurred. The situation is less clear for the third object (3C 433). Wepropose an evolutionary sequence for one of the radio galaxies studied.The implications of this study of neutral hydrogen in nearby radiogalaxies for high-/z objects and `normal' (i.e. radio-quiet) ellipticalgalaxies are also discussed.
| 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.
| B2 0648+27: A radio galaxy in a major merger
We present WSRT observations of the neutral hydrogen in the nearby radiogalaxy B2 0648+27. In emission, we detect a very large amount of H I(MH I = 1.1 x 1010 Msun) that isdistributed in a very extended disk, or ring-like structure, of about160 kpc in size. We also detect H I absorption against the central radiocontinuum component. The detection of the H I, its structure andkinematics, give us key information for building a possible evolutionaryscenario. The characteristics of the detected H I are explained as theresult of a major merger event that is likely to have occurred <≈109 yr ago. Interestingly, we find that, when observed inradio continuum at higher resolution, this galaxy has a double lobed,steep spectrum structure of about 1 kpc in size. Thus, despite its lowradio power, B2 0648+27 bears striking similarities with CompactSymmetric Objects, i.e. objects believed to represent the early phase ofradio galaxies (la few thousand yrs old). B2 0648+27 is one of the fewnearby radio galaxies where extended neutral hydrogen has been detectedso far. This, and other recent results, appear however to indicate thatnearby radio galaxies are more often gas rich than commonly assumed. Thephenomena described are likely to be much more common at high redshiftand galaxies like B2 0648+27 may provide valuable information on theevolution of high redshift radio sources.Based on observations with the Westerbork Synthesis Radio Telescope(WSRT) and the Very Large Array (VLA).
| A catalogue and analysis of local galaxy ages and metallicities
We have assembled a catalogue of relative ages, metallicities andabundance ratios for about 150 local galaxies in field, group andcluster environments. The galaxies span morphological types from cD andellipticals, to late-type spirals. Ages and metallicities were estimatedfrom high-quality published spectral line indices using Worthey &Ottaviani (1997) single stellar population evolutionary models. Theidentification of galaxy age as a fourth parameter in the fundamentalplane (Forbes, Ponman & Brown 1998) is confirmed by our largersample of ages. We investigate trends between age and metallicity, andwith other physical parameters of the galaxies, such as ellipticity,luminosity and kinematic anisotropy. We demonstrate the existence of agalaxy age-metallicity relation similar to that seen for local galacticdisc stars, whereby young galaxies have high metallicity, while oldgalaxies span a large range in metallicities. We also investigate theinfluence of environment and morphology on the galaxy age andmetallicity, especially the predictions made by semi-analytichierarchical clustering models (HCM). We confirm that non-clusterellipticals are indeed younger on average than cluster ellipticals aspredicted by the HCM models. However we also find a trend for the moreluminous galaxies to have a higher [Mg/Fe] ratio than the lowerluminosity galaxies, which is opposite to the expectation from HCMmodels.
| Extended H I Disks in Dust Lane Elliptical Galaxies
We present the results of H I observations of five dust lane ellipticalgalaxies with the Australia Telescope Compact Array. Two galaxies (NGC3108 and NGC 1947) are detected, and sensitive upper limits are obtainedfor the other three. In the two detected galaxies, the H I isdistributed in a regular, extended, and warped disklike structure of lowsurface brightness. Adding data from the literature, we find thatseveral more dust lane elliptical galaxies have regular H I structures.This H I is likely to be a remnant of accretions and/or mergers thattook place a considerable time ago and in which a significant fractionof the gas survived to form a disk. The presence of regular H Istructures suggests that some mergers lead to galaxies with extended lowsurface brightness density gas disks. These gas disks will evolve veryslowly, and these elliptical galaxies will remain gas-rich for a longperiod of time. One of the galaxies we observed (NGC 3108) has a verylarge amount of neutral hydrogen(MHI=4.5×109 MsolarMHI/LB~0.09), which is very regularly distributedin an annulus extending to a radius of ~6 Reff. Thekinematics of the H I distribution suggest that the rotation curve ofNGC 3108 is flat out to at least the last observed point. We estimate amass-to-light ratio of M/LB~18Msolar/LB,solar at a radius of ~6Refffrom the center. Several of the galaxies we observed have an unusuallylow gas-to-dust ratio MHI/Mdust, suggesting thattheir cold interstellar medium, if present as expected from the presenceof dust, may be mainly in molecular rather than atomic form. Based onobservations with the Australia Telescope Compact Array (ATCA), which isfunded by the Commonwealth of Australia for operation as a NationalFacility managed by CSIRO.
| Large-scale gas disk around the radio galaxy Coma A
We present WSRT and VLA radio observations of the neutral hydrogen inthe radio galaxy Coma A. We detect extended H I absorption against bothradio lobes of Coma A, at distances of about 30 kpc from the centre.Coma A is the first radio galaxy in which H I is seen in absorption atsuch large distances from the nucleus. The match between the velocitiesof the neutral hydrogen and those of the extended ionized gas suggeststhat they are part of the same disk-like structure of at least 60 kpc indiameter. Most likely, this gas disk is partly ionised by the bulkmotion of the radio lobes expanding into it. The gas mass of this diskis at least 109 Msun. The relatively regularstructure of the gas disk suggests that a merger occurred involving atleast one large gas-rich galaxy, at least a few times 108 yrago. Based on observations with the Westerbork Synthesis Radio Telescope(WSRT) and the Very Large Array (VLA).
| Mid Infrared Colors of Early Type Galaxies
We compare the mid infrared colors of early type galaxies withisochrones that suitably account for the effects of dust in thecircumstellar envelopes of AGB stars. We show that these stars affectsignificantly the integrated colors in the ISO bands. The excess at10μm observed in some early type galaxies combined with the opticalspectrum, is compatible with a 100% old metal rich population. Limits onthe additional young components are: age 0.2 Gyr, mass=0.5% andE(B-V)>=0.5 or age 3 Gyr, mass 10% and E(B-V)>=0.2.
| The gas content of peculiar galaxies: Counterrotators and polar rings
This paper studies the global ISM content in a sample of 104 accretinggalaxies, including counterrotators and polar rings, which spans theentire Hubble sequence. The molecular, atomic and hot gas content ofaccretors is compared to a newly compiled sample of normal galaxies. Wepresent results of a small survey of the J=1-0 line of 12COwith the 15 m SEST telescope on a sample of 11 accretors (10counterrotators and 1 polar ring). The SEST sample is enlarged withpublished data from 48 galaxies, for which observational evidence ofcounterrotation in the gas and/or the stars has been found. Furthermore,the available data on a sample of 46 polar ring galaxies has beencompiled. In order to explore the existence of an evolutionary pathlinking the two families of accretors, the gas content ofcounterrotators and polar rings is compared. It was found that thenormalized content of cold gas (Mgas/LB) in polarrings is ~ 1 order of magnitude higher than the reference value derivedfor normal galaxies. The inferred gas masses are sufficient to stabilizepolar rings through self-gravity. In contrast, it was found that thecold gas content of counterrotators is close to normal for all galaxytypes. Although counterrotators and polar rings probably share a commonorigin, the gas masses estimated here confirm that light gas ringsaccreted by future counterrotators may have evolved faster than theself-gravitating structures of polar rings. In this scenario, thetransformation of atomic into molecular gas could be enhanced near thetransition region between the prograde and the retrograde disks,especially in late-type accretors characterized by a high content ofprimordial gas. This is tentatively confirmed in this work: the measuredH2/HI ratio seems larger in counterrotators than in normal orpolar ring galaxies for types later than S0s. Based on observationscollected at SEST telescope, European Southern Observatory, La Silla,Chile. Table 1 is only available in electronic form athttp://www.edpsciences.org
| HI in early-type galaxies
We summarise the HI properties of early-type galaxies, in particular thedifferences in HI morphologies observed in early-type galaxies ofdifferent luminosities. We find that in low-luminosity early-typegalaxies the HI is almost always in a disk-like structure, with centralsurface densities high enough for star formation to occur. In a fewluminous early-type galaxies the HI is also in a disk or in a ring-likestructure, but in most luminous early-type galaxies the HI has arelatively irregular morphology. The surface densities in the HI disksin luminous early-type galaxies are lower than in the HI disks in low-luminosity early-type galaxies and no large-scale star formation shouldoccur in these disks. We discuss these different HI characteristics inthe context of other properties of early-type galaxies that correlatewith luminosity.
| The Bulge-Disk Orthogonal Decoupling in Galaxies: NGC 4698
The R-band isophotal map of the Sa galaxy NGC 4698 shows that the innerregion of the bulge structure is elongated perpendicularly to the majoraxis of the disk; this is also true for the outer parts of the bulge ifa parametric photometric decomposition is adopted. At the same time, thestellar component is characterized by an inner velocity gradient and acentral zero-velocity plateau along the minor and major axes of thedisk, respectively. This remarkable geometric and kinematic decouplingsuggests that a second event occurred in the formation history of thisgalaxy.
| A Radio Study of the Seyfert Galaxy IC 5063: Evidence for Fast Gas Outflow
We present new radio continuum (8 and 1.4 GHz) and H i 21 cm lineobservations of the Seyfert 2 galaxy IC 5063 (PKS 2048-572), obtainedwith the Australia Telescope Compact Array. The high-resolution 8 GHzimage reveals a linear triple structure ~4" (1.3 kpc) in size. Thissmall-scale radio emission shows a strong morphological association withthe narrow-line region (NLR), the inner part of the opticalemission-line region. It is aligned with the inner dust lane and isoriented perpendicularly to the position angle of the opticalpolarization. We identify the radio nucleus as the central blob of theradio emission. At 21 cm, very broad (~700 km s^-1) H i absorption isobserved against the strong continuum source. This absorption is almostentirely blueshifted, indicating a fast net outflow, but a faint andnarrow redshifted component is also present. In IC 5063 we see clearevidence, both morphological and kinematic, of strong shocks resultingfrom the interaction between the radio plasma and the interstellarmedium (ISM) in the central few kiloparsecs. However, we estimate theenergy flux in the radio plasma to be an order of magnitude smaller thanthe energy flux emitted in emission lines. Thus, although strong shocksassociated with the jet/ISM interaction occur, and could contributelocally to the ionization of the NLR, they are unlikely to accountsolely for the global ionization of the emission-line region,particularly at large distances. The main structure of the H i emissionis a warped disk associated with the system of dust lanes of R ~ 2' (~38kpc, corresponding to ~5 effective radii). The lack of kinematicallydisturbed gas (both neutral and ionized) outside the central fewkiloparsecs, the warped structure of the large-scale disk, and the closemorphological connection between the inner dust lanes and thelarge-scale ionized gas all support the idea that the gas at large radiiis photoionized by the central region, while shadowing effects areimportant in defining its X-shaped morphology. From the kinematics ofthe ionized and neutral gas, we find evidence for a dark halo in IC5063, with properties very similar to those observed in some otherearly-type galaxies. Based on observations made with the AustraliaTelescope Compact Array, which is operated by the CSIRO AustraliaTelescope National Facility.
| A catalogue of Mg_2 indices of galaxies and globular clusters
We present a catalogue of published absorption-line Mg_2 indices ofgalaxies and globular clusters. The catalogue is maintained up-to-datein the HYPERCAT database. The measurements are listed together with thereferences to the articles where the data were published. A codeddescription of the observations is provided. The catalogue gathers 3541measurements for 1491 objects (galaxies or globular clusters) from 55datasets. Compiled raw data for 1060 galaxies are zero-point correctedand transformed to a homogeneous system. Tables 1, 3, and 4 areavailable in electronic form only at the CDS, Strasbourg, via anonymousftp 130.79.128.5. Table 2 is available both in text and electronic form.
| 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 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
| Young tidal dwarf galaxies around the gas-rich disturbed lenticular NGC 5291
NGC 5291 is an early type galaxy at the edge of the cluster Abell 3574which drew the attention because of the unusual high amount of atomicgas ( ~ 5 x 10(10) {M_{\odot}}) found associated to it. The HI isdistributed along a huge and fragmented ring, possibly formed after atidal interaction with a companion galaxy. We present multi-slit opticalspectroscopic observations and optical/near-infrared images of thesystem. We show that NGC 5291 is a LINER galaxy exhibiting severalremnants of previous merging events, in particular a curved dust laneand a counter-rotation of the gas with respect to the stars. The atomichydrogen has undoubtly an external origin and was probably accreted bythe galaxy from a gas-rich object in the cluster. It is unlikely thatthe HI comes from the closest companion of NGC 5291, the so-called``Seashell'' galaxy, which appears to be a fly-by object at a velocitygreater than 400 km s(-1) . We have analyzed the properties of 11optical counterparts to the clumps observed in the HI ring. Thebrightest knots show strong similarities with classical blue compactdwarf galaxies. They are dominated by active star forming regions; theirmost recent starburst is younger than 5 Myr; we did not find evidencesfor the presence of an old underlying stellar population. NGC 5291appears to be a maternity of extremely young objects most probablyforming their first generation of stars. Born in pre-enriched gasclouds, these recycled galaxies have an oxygen abundance which is higherthan BCDGs ({Z_{\odot}}/3 on average) and which departs from theluminosity-metallicity relation observed for typical dwarf and giantgalaxies. We propose this property as a tool to identify tidal dwarfgalaxies (TDGs) among the dwarf galaxy population. Several TDGs in NGC5291 exhibit strong velocity gradients in their ionized gas and mayalready be dynamically independent galaxies. Based on observationscollected at the European Southern Observatory, La Silla, Chile. ESON$^{o
| Cool dense gas in early-type galaxies
CO observations have shown that many lenticular and elliptical galaxiescontain significant amounts of cool dense gas. This review summarizesthe observational results related to the neutral gas phase and presentsa systematic comparison with other interstellar and stellar data. Thediscovery of very dense molecular gas in the nuclear regions ofearly-type galaxies, the possible existence of a dust component neitherseen optically nor in CO, internal inconsistencies of cooling flowscenarios, the origin of the cool gas, the presence of massive stars,aspects of galaxy evolution, and possibilities for future research arediscussed in the light of the new data.
| The HI-rich elliptical galaxy NGC 5266: an old merger remnant?
We present HI images for the dust-lane elliptical galaxy NGC 5266. Thisgalaxy contains more than 10 billion solar masses of HI and our datashow that the neutral hydrogen extends to about 8 arcmin each side ofthe nucleus, or 8 times the optical half-light radius. Surprisingly, theouter HI gas extends almost orthogonal to the optical dust lane. Theoverall HI kinematics can be successfully modeled by assuming that thegas lies in two orthogonal planes: in the plane of the dust lane in thecentral parts and perpendicular to this in the outer regions. The largeamount of neutral gas observed and the HI morphology, suggest that thisobject may have formed from the merger of two gas rich spiral galaxies.If so, it probably represents a relatively old merger remnant since mostof the HI appears settled. The mass-to-light ratio has also been derivedwith evidence for a dark matter halo around this galaxy.
| Ionised hydrogen at large galactocentric distances
We summarize recent attempts to detect warm ionized gas at largegalactocentric distances. This includes searching for gas at the edgesof spirals, in between cluster galaxies, towards extragalactic HIclouds, and towards high velocity clouds and the Magellanic Stream inthe Galaxy. With the exception of extragalactic HI clouds, all of theseexperiments have proved successful. Within each class, we have onlyobserved a handful of objects. It is premature to assess what fractionof the missing baryonic mass fraction might be in the form of ionizedgas. But, in most cases, the detections provide a useful constraint onthe ambient ionizing flux, and in the case of spiral edges, can eventrace dark matter halos out to radii beyond the reach of radiotelescopes.
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