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|Nearby early-type galaxies with ionized gas. I. Line-strength indices of the underlying stellar population|
With the aim of building a data-set of spectral properties of wellstudied early-type galaxies showing emission lines, we presentintermediate resolution spectra of 50 galaxies in the nearby Universe.The sample, which covers several of the E and S0 morphologicalsub-classes, is biased toward objects that might be expected to haveongoing and recent star formation, at least in small amounts, because ofthe presence of the emission lines. The emission is expected to comefrom the combination of active galactic nuclei and star formationregions within the galaxies. Sample galaxies are located in environmentscorresponding to a broad range of local galaxy densities, althoughpredominantly in low density environments. Our long-slit spectra coverthe 3700-7250 Å wavelength range with a spectral resolution of≈7.6 Å at 5550 Å. The specific aim of this paper, and ourfirst step in the investigation, is to map the underlying galaxy stellarpopulation by measuring, along the slit positioned along the galaxymajor axis, line-strength indices at several, homogeneousgalacto-centric distances. For each object we extracted 7luminosity-weighted apertures (with radii 1.5´´,2.5´´, 10´´, r_e/10, r_e/8, r_e/4 and r_e/2)corrected for the galaxy ellipticity and 4 gradients (0 ≤ r ≤r_e/16, r_e/16 ≤ r ≤ r_e/8, r_e/8 ≤ r ≤ r_e/4 and r_e/4≤ r ≤ r_e/2). For each aperture and gradient we measured 25line-strength indices: 21 of the set defined by the Lick-IDS“standard” system (Trager et al. [CITE], ApJS, 116, 1) and 4introduced by Worthey & Ottaviani ([CITE], ApJS, 111, 377).Line-strength indices have been transformed to the Lick-IDS system.Indices derived then include Hβ, Mg1, Mg2, Mgb, MgFe, Fe5270,Fe5335 commonly used in classic index-index diagrams. The paperintroduces the sample, presents the observations, describes the datareduction procedures, the extraction of apertures and gradients, thedetermination and correction of the line-strength indices, the procedureadopted to transform them into the Lick-IDS System and the proceduresadopted for the emission correction. We finally discuss the comparisonsbetween our dataset and line-strength indices available in theliterature. A significant fraction, about 60%, of galaxies in thepresent sample has one previous measurement in the Lick-IDS system butbasically restricted within the r_e/8 region. Line-strength measuresobtained both from apertures and gradients outside this area and withinthe r_e/8 region, with the present radial mapping, are completely new.Full appendix and Figs. 8 to 13 are only available in electronic form athttp://www.edpsciences.org Full Tables 6, 7, 9 and 10 are only availableat the CDS via anonymous ftp to cdsarc.u-strasbg.fr (184.108.40.206) orvia http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/433/497 Based onobservations obtained at the European Southern Observatory, La Silla,Chile (Programs Nr. 60.A-0647 and 61.A-0406).
|BUDDA: A New Two-dimensional Bulge/Disk Decomposition Code for Detailed Structural Analysis of Galaxies|
We present BUDDA (Bulge/Disk Decomposition Analysis), a new code devotedto perform a two-dimensional bulge/disk decomposition directly from theimages of galaxies. The bulge component is fitted with a generalizedSérsic profile, whereas disks have an exponential profile. Noother components are included. Bars and other substructures, likelenses, rings, inner bars, and inner disks, are studied with theresidual images obtained through the subtraction of bulges and disksfrom the original images. This means that a detailed structural analysisof galaxies may be performed with a small number of parameters, andsubstructures may be directly studied with no a priori assumptions. Ashas been already shown by several studies, two-dimensional fitting ismuch more reliable than one-dimensional profile fitting. Moreover, ourcode has been thoroughly tested with artificial data, and we demonstrateit to be an accurate tool for determining structural parameters ofgalaxies. We also show that our code is useful in various kinds ofstudies, including galaxies of, e.g., different morphological types, andinclinations, which also may be observed at different spatialresolutions. Thus, the code has a broader range of potentialapplications than most of the previous codes, which are developed totackle specific problems. To illustrate its usefulness, we present theresults obtained with a sample of 51 mostly early-type galaxies (butcovering the whole Hubble sequence). These results show some of theapplications in which the code may be used: the determination ofparameters for fundamental plane and structural studies, quantitativemorphological classification of galaxies, and the identification andstudy of hidden substructures. We have determined the structuralparameters of the galaxies in our sample and found many examples ofhidden inner disks in ellipticals, secondary bars, nuclear rings anddust lanes in lenticulars and spirals, and also wrong morphologicalclassification cases. We now make BUDDA generally available to theastronomical community.Based on observations made at the Pico dos Dias Observatory(PDO/LNA-CNPq), Brazil.
|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 (220.127.116.11) 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 (18.104.22.168) orvia http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/416/507
|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.
|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.
|A catalogue and analysis of X-ray luminosities of early-type galaxies|
We 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.
|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
|Nearby Optical Galaxies: Selection of the Sample and Identification of Groups|
In this paper we describe the Nearby Optical Galaxy (NOG) sample, whichis a complete, distance-limited (cz<=6000 km s-1) andmagnitude-limited (B<=14) sample of ~7000 optical galaxies. Thesample covers 2/3 (8.27 sr) of the sky (|b|>20deg) andappears to have a good completeness in redshift (97%). We select thesample on the basis of homogenized corrected total blue magnitudes inorder to minimize systematic effects in galaxy sampling. We identify thegroups in this sample by means of both the hierarchical and thepercolation ``friends-of-friends'' methods. The resulting catalogs ofloose groups appear to be similar and are among the largest catalogs ofgroups currently available. Most of the NOG galaxies (~60%) are found tobe members of galaxy pairs (~580 pairs for a total of ~15% of objects)or groups with at least three members (~500 groups for a total of ~45%of objects). About 40% of galaxies are left ungrouped (field galaxies).We illustrate the main features of the NOG galaxy distribution. Comparedto previous optical and IRAS galaxy samples, the NOG provides a densersampling of the galaxy distribution in the nearby universe. Given itslarge sky coverage, the identification of groups, and its high-densitysampling, the NOG is suited to the analysis of the galaxy density fieldof the nearby universe, especially on small scales.
|Face-on Galaxies NGC 524 and NGC 6340: Chemically Decoupled Nuclei and Inclined Circumnuclear Disks|
The central regions of the early-type disk galaxies NGC 524 and NGC 6340have been investigated with the Multipupil Field Spectrograph at the 6 mtelescope of the Special Astrophysical Observatory of the RussianAcademy of Sciences. We confirm the existence of chemically distinctstellar nuclei in these galaxies, which had been claimed earlier. Themetallicity differences that we have found between the nuclei and thebulges, 0.5-1.0 kpc from the centers, reach 0.5-0.6 dex. Both nuclei aremagnesium overabundant, but the bulges have different magnesium-to-ironratios: it is solar in NGC 6340 and the same as the nuclear one in NGC524. Kinematical and morphological analyses reveal the existence ofinclined central disks in these galaxies. In NGC 524 the central diskconsists of stars, dust, and ionized gas; its extension may be as largeas up to R~3 kpc, and it is inclined by some 20° to the globalgalactic plane. In NGC 6340 only a gaseous polar disk is detected, theextension of which does not exceed R~500 pc.
|Galaxy coordinates. II. Accurate equatorial coordinates for 17298 galaxies|
Using images of the Digitized Sky Survey we measured coodinates for17298 galaxies having poorly defined coordinates. As a control, wemeasured with the same method 1522 galaxies having accurate coordinates.The comparison with our own measurements shows that the accuracy of themethod is about 6 arcsec on each axis (RA and DEC).
|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 22.214.171.124. Table 2 is available both in text and electronic form.
|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 (to126.96.36.199) or via http://cdsweb.u-strasbg.fr/Abstract.html
|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.
|Molecular gas in polar-ring galaxies|
We present CO J=1-->0 observations (lambda=2.6 mm) of 10 polar-ringgalaxies, chosen from the Polar Ring Catalogue; we infer masses of H_2ranging from 7x10^7 to 2x10^10 Msolar, with an average of about 1x10^9Msolar. These H_2 masses are greater than the average molecular mass ofan early-type galaxy; we previously found similar results for a sampleof minor-axis dust-lane ellipticals. In the cases where we can estimatethe gas mass in the polar ring, including the H i masses fromliterature, they are high enough to allow self-gravitation to stabilizethe rings. This means that the ages of the rings may be >=1 Gyr.Indeed, the gas masses are often greater than those of most dwarfgalaxies: this would make it unlikely that the polar rings result fromthe recent accretion of a single gas-rich dwarf. A survey of the fieldsaround our sample galaxies shows in all but one case the presence of atleast one companion with either a similar redshift or similar bluemagnitude; these companions are close enough to have encountered thepolar-ring galaxy in <1 Gyr. The companion galaxies may be the sourceof the detected gas, through tidal stripping.
|An Einstein X-Ray Survey of Optically Selected Galaxies. I. Data|
We present the results of a complete Einstein imaging proportionalcounter X-ray survey of optically selected galaxies from theShapley-Ames Catalog, the Uppsala General Catalogue, and the EuropeanSouthern Observatory Catalog. Well-defined optical criteria are used toselect the galaxies, and X-ray fluxes are measured at the opticallydefined positions. The result is a comprehensive list of X-ray detectionand upper limit measurements for 1018 galaxies. Of these, 827 haveeither independent distance estimates or radial velocities. Associatedoptical, redshift, and distance data have been assembled for thesegalaxies, and their distances come from a combination of directlypredicted distances and those predicted from the Faber-Burstein GreatAttractor/Virgocentric infall model. The accuracy of the X-ray fluxeshas been checked in three different ways; all are consistent with thederived X-ray fluxes being of <=0.1 dex accuracy. In particular,there is agreement with previously published X-ray fluxes for galaxiesin common with a 1991 study by Roberts et al. and a 1992 study byFabbiano et al. The data presented here will be used in further studiesto characterize the X-ray output of galaxies of various morphologicaltypes and thus to enable the determination of the major sourcescontributing to the X-ray emission from galaxies.
|The distribution of ionised gas in early-type galaxies.|
|Ultraviolet properties of early-type galaxies.|
We analyse the UV properties of early-type galaxies from their UVspectra in the IUE library, including both normal and active nuclei. Weco-added the spectra, and hence the objects into groups of similarspectral properties in the UV, also taking into account their propertiesin the visible/near-infrared ranges. Although, owing to the presence ofa residual fixed pattern noise, IUE data cannot be improved byco-addition as expected for spectra containing only random noise, thisprocedure still provided spectra of higher signal/noise ratio than inprevious studies, often based on individual spectra and therefromderived colour indices. Thanks to the co-adding procedure, informationon spectral features can now be assessed. The red stellar populationgroups exhibit a far-UV flux at different levels. The higher ones denotethe presence of the UV turnup, which possibly exhibits absorptionfeatures, at least as detected through the IUE aperture. As to the bluestellar population groups and/or AGNs, we have carried out simplesyntheses with UV star cluster templates and galaxy spectra in order toinfer the properties such as burst ages and contamination by an activenucleus. It has been possible to derive information on the extinctionlaw affecting some internally reddened galaxies; there are cases wherethe presence of the λ2200 A absorption feature suggests areddening law similar to the Galactic one, and others without theλ2200A feature, suggesting that it is rather an SMC type lawwhich applies, then.
|The fundamental plane of early-type galaxies: stellar populations and mass-to-light ratio.|
We analyse the residuals to the fundamental plane (FP) of ellipticalgalaxies as a function of stellar-population indicators; these are basedon the line-strength parameter Mg_2_ and on UBVRI broad-band colors, andare partly derived from new observations. The effect of the stellarpopulations accounts for approximately half the observed variation ofthe mass-to-light ratio responsible for the FP tilt. The residual tiltcan be explained by the contribution of two additional effects: thedependence of the rotational support, and possibly that of the spatialstructure, on the luminosity. We conclude to a constancy of thedynamical-to-stellar mass ratio. This probably extends to globularclusters as well, but the dominant factor would be here the luminositydependence of the structure rather than that of the stellar population.This result also implies a constancy of the fraction of dark matter overall the scalelength covered by stellar systems. Our compilation ofinternal stellar kinematics of galaxies is appended.
|K'-Band Dust Albedo from Observations of Galaxies|
A relationship between the dust albedos in the V-band and the K'-bandcan be obtained by analyzing the relative strengths of dust attenuationin the respective bands in dusty late-type galaxies (Witt et al. 1994,ApJ 427, 227). We secured V- and K'-band images of three galaxies whichexhibit a highly symmetric light distribution in K' but displayexceptionally asymmetric dust attenuation in V: NGC 1546 (Sc(s) III),NGC 1947 (SO_3(0)pec), and NGC 3521 (Sbc(s) II). Differences inV-surface brightness and in V-K' color between diagonally symmetriclocations on the galaxy images were analyzed, using galactic radiativetransfer models which incorporate both absorption and multiplescattering (Witt, Thronson, & Capuano 1992, ApJ 393, 611). Assuminga V-albedo for the dust a_v=0.6, the resulting K'-albedo values for thethree galaxies are 0.63, 0.66, and 0.53, respectively. This confirmsearlier results, showing the K'-band dust albedo to be well in excess ofthe value of 0.2 predicted by the MNR model. Thus, the upper limit ofthe size distribution of grains must extend to at least 1mu m.
|A multiparametric analysis of the Einstein sample of early-type galaxies. 1: Luminosity and ISM parameters|
We have conducted bivariate and multivariate statistical analysis ofdata measuring the luminosity and interstellar medium of the Einsteinsample of early-type galaxies (presented by Fabbiano, Kim, &Trinchieri 1992). We find a strong nonlinear correlation betweenLB and LX, with a power-law slope of 1.8 +/- 0.1,steepening to 2.0 +/- if we do not consider the Local Group dwarfgalaxies M32 and NGC 205. Considering only galaxies with logLX less than or equal to 40.5, we instead find a slope of 1.0+/- 0.2 (with or without the Local Group dwarfs). Although E and S0galaxies have consistent slopes for their LB-LXrelationships, the mean values of the distribution functions of bothLX and LX/LB for the S0 galaxies arelower than those for the E galaxies at the 2.8 sigma and 3.5 sigmalevels, respectively. We find clear evidence for a correlation betweenLX and the X-ray color C21, defined by Kim,Fabbiano, & Trinchieri (1992b), which indicates that X-rayluminosity is correlated with the spectral shape below 1 keV in thesense that low-LX systems have relatively large contributionsfrom a soft component compared with high-LX systems. We findevidence from our analysis of the 12 micron IRAS data for our samplethat our S0 sample has excess 12 micron emission compared with the Esample, scaled by their optical luminosities. This may be due toemission from dust heated in star-forming regions in S0 disks. Thisinterpretation is reinforced by the existence of a strongL12-L100 correlation for our S0 sample that is notfound for the E galaxies, and by an analysis of optical-IR colors. Wefind steep slopes for power-law relationships between radio luminosityand optical, X-ray, and far-IR (FIR) properties. This last point arguesthat the presence of an FIR-emitting interstellar medium (ISM) inearly-type galaxies is coupled to their ability to generate nonthermalradio continuum, as previously argued by, e.g., Walsh et al. (1989). Wealso find that, for a given L100, galaxies with largerLX/LB tend to be stronger nonthermal radiosources, as originally suggested by Kim & Fabbiano (1990). We notethat, while LB is most strongly correlated withL6, the total radio luminosity, both LX andLX/LB are more strongly correlated with L6CO, the core radio luminosity. These points support the argument(proposed by Fabbiano, Gioia, & Trinchieri 1989) that radio cores inearly-type galaxies are fueled by the hot ISM.
|The Peculiar HI Kinematics of the Wolf-Rayet Starburst Galaxy NGC 5253|
We report the discovery of a peculiar H I velocity field in the nearbyamorphous dwarf starburst galaxy NGC 5253 which indicates that the bulkof the neutral atomic gas rotates about the galaxy's optical major axis.There is also weak evidence for a second H I dynamical componentrotating about the optical minor axis. We estimate the dynamical mass at3 x 108/sin2 i Mȯ. The gasdynamics in NGC 5253 are vaguelyreminiscent of what is seen in polar ring galaxies and dust laneellipticals, but the large gas mass fraction (~0.6 for i = 50 deg),young starburst population, irregular optical morphology, lack of astellar ring, and lack of stellar rotation (<= 7 km s-1) areinconsistent with either type of object. NGC 5253's unique gasdynamicsand current star formation activity may be either (1) the result of aninteraction with the nearby spiral M83 ~109 yr ago or (2) due to thedisruption and accretion of a gas-rich companion on a highly inclinedorbit. A combination of wide-field, high-sensitivity H I mapping and newoptical spectra measuring the stellar kinematics along the minor axiscould discriminate between these two possible interaction scenarios andconstrain the original, preinteraction nature of NGC 5253. It ispossible that NGC 5253 will later develop into a polar ring galaxy andthat we are observing it during its period of ring formation.
|Integrated photoelectric magnitudes and color indices of bright galaxies in the Johnson UBV system|
The photoelectric total magnitudes and color indices published in theThird Reference Catalogue of Bright Galaxies (RC3) are based on ananalysis of approximately equals 26,000 B, 25,000 B-V, and 17,000 U-Bmultiaperture measurements available up to mid 1987 from nearly 350sources. This paper provides the full details of the analysis andestimates of internal and external errors in the parameters. Thederivation of the parameters is based on techniques described by theVaucouleurs & Corwin (1977) whereby photoelectric multiaperture dataare fitted by mean Hubble-type-dependent curves which describe theintegral of the B-band flux and the typical B-V and U-B integrated colorgradients. A sophisticated analysis of the residuals of thesemeasurements from the curves was made to allow for the random andsystematic errors that effect such data. The result is a homogeneous setof total magnitudes BTA total colors(B-V)T and (U-B)T, and effective colors(B-V)e and (U-B)e for more than 3000 brightgalaxies in RC3.
|The molecular cloud content of early-type galaxies. V. CO in elliptical galaxies.|
A survey of CO emission in 29 far-IR selected elliptical galaxiesresulted in 16 detections, of which 3 remain tentative. The moleculargas masses range from 2x10^6^Msun_ to1x10^9^Msun_, and appear to be unrelated to the underlyingstellar population. This suggests an external origin of the gas. Most ofthe elliptical galaxies with a molecular gas component have agas-to-dust mass ratio of ~700, where dust masses are derived from theIRAS fluxes, but some appear to have a ratio as low as 50. A smallapparent gas-to-dust mass ratio is also found for some late-typegalaxies, and is correlated with a low dust temperature. We suggest thata large part of the far-infrared emission from these galaxies (bothearly- and late-types) comes from dust associated with the atomic gascomponent rather than star forming regions associated with the moleculargas, and that they contain a cold dust component. Low excitationtemperatures for CO transitions in galaxies with cold dust could lead toan underestimate of the molecular gas mass by a factor of 5. The averageM_H_2__/M_HI_ ratio for the elliptical galaxies is 2-5 times lower thanfor normal spiral galaxies. Field ellipticals appear more likely tocontain an observable molecular gas component than those ellipticalsresiding in groups and clusters.
|Interstellar Matter in Elliptical Galaxies - Part Three - Properties of Dust Extinction|
We have used multicolour CCD surface photometry of 10 ellipticalgalaxies with large-scale dust lanes or rings to investigate thewavelength dependence of the dust extinction. In general, the extinctioncurves are found to run parallel to the Galactic curve of Rieke &Lebofsky. The ratio of total to selective extinction R_V_ is found torange between 2.1 and 3.3, and is lower on average than the canonicalGalactic value of 3.1, implying that the `large' dust grains - which areresponsible for the extinction of optical light - are generally smallerthan in our Galaxy. We show that systematic effects concerning thelocation of the dust within the galaxy body, which may modify theobserved extinction curves, do not change this conclusion. We haveestimated the dust content of the lanes directly from total extinctionvalues (e.g., A_V_), using the observed grain sizes. Extinctionefficiencies of refractory grains and a grain size distribution aretaken from the literature. The dust masses calculated using the totalextinction values turn out to be up to 35 per cent lower than thosecalculated using the Galactic ratio of neutral hydrogen column densityto E(B - V) colour excess, showing that the effect of smaller `large'grain sizes on the total dust mass is significant. We find that thegalaxies with R_V_ values (and, hence, characteristic grain sizes) thatare smaller than in our Galaxy have smooth, regularly distributed dustlanes, whereas the dust in galaxies with `normal' grain sizes istypically much more irregularly distributed, e.g., in patches. Assumingthat the dust in these galaxies has an external origin, this suggeststhat the observed characteristic dust grain size is determined by thetime elapsed since the dust lane was accreted from outside. Followingthe current theoretical model calculations of formation time-scales ofregular dust lanes and rings in early-type galaxies, we predict thatelliptical galaxies containing regular dust lanes with typical dustmasses of 10^6^ - 10^7^ M_sun_ do not contain hot, X-ray- emitting gas.
|Parsecscale Radio Cores in Early Type Galaxies|
We find compact (<0.03 arcsec) radio-continuum cores in about 70 percent of radio-emitting elliptical and S0 galaxies over a wide range intotal radio power (10^21^-,10^26^ W Hz^-1^ at 5 GHz). The cores usuallyhave a flat or rising spectrum between 2.3 and 8.4 GHz, with a medianspectral index of + 0.3. Even at low luminosities, the radio emissionfrom most elliptical galaxies appears to be powered by a parsec-scale`engine' like those in classical radio galaxies and quasars. The coreand total radio power are related (P_core_ is proportional toP_total_^0.7^ on average), and the parsec-scale cores of radio galaxiesare typically one hundred times more powerful than those in `normal'giant elliptical galaxies.
|Photometrically distinct nuclei in elliptical and early-type disks galaxies.|
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