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Optical spectroscopy for a sample of southern binary galaxies
Aims.This work is part of a joint observational program aiming to getphotometric and spectroscopic information on southern pairs of galaxies.We present optical long-slit spectroscopic data on 80 probablecomponents of pairs, 61 of them collected with a spectral resolution of3.4 Å, and 19 with 12 Å. Nevertheless, our analysis takesinto account 53 components of pairs with better spectral resolution, as8 of these target galaxies actually belong to optical pairs. For thesample with better resolution, the covered wavelength range is 5724≤ λ ≤ 7036 Å. The spectroscopic and photometricinformation is gathered for an analysis relating galaxy morphologies totheir spectra. Methods: .We use Hα +[NII] and Hα equivalent widths as star formationtracers for the central region of our sample galaxies, and we classifythe spectra according to the emission lines' relative strength bylooking at their behavior. Results: . Some of our sample galaxiesexhibit high central star formation, most of them belonging to closepairs. However, not all galaxies' components of close pairs show thisbehavior. This may be a clue that besides interaction, other agents canstimulate central emission in binary galaxies. We suggest an enhancementin the number of galaxies with peculiar spectra (probably Seyferts) inour binary sample, when compared to isolated galaxies. Our dataindicates that the morphological types of interacting galaxies arerelated to their spectral characteristics, as almost all early-typegalaxies of our sample do not exhibit central optical emission. We notethat the star formation activity is most likely to take place in bothpairs' components, with a slightly higher mean strength for the lessbright component of the pair. It is interesting to point out that mostspirals exhibiting a strong HII emission line spectra present either abar or a peculiarity, but on a general basis we do not find anenhancement of star formation in our interaction sample.
| 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.
| FLASH redshift survey - I. Observations and catalogue
The FLAIR Shapley-Hydra (FLASH) redshift survey catalogue consists of4613 galaxies brighter than bJ= 16.7 (corrected for Galacticextinction) over a 700-deg2 region of sky in the generaldirection of the Local Group motion. The survey region is a70°× 10° strip spanning the sky from the ShapleySupercluster to the Hydra cluster, and contains 3141 galaxies withmeasured redshifts. Designed to explore the effect of the galaxyconcentrations in this direction (in particular the Supergalactic planeand the Shapley Supercluster) upon the Local Group motion, the 68 percent completeness allows us to sample the large-scale structure betterthan similar sparsely-sampled surveys. The survey region does notoverlap with the areas covered by ongoing wide-angle (Sloan or 2dF)complete redshift surveys. In this paper, the first in a series, wedescribe the observation and data reduction procedures, the analysis forthe redshift errors and survey completeness, and present the surveydata.
| 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
| 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
| Radial velocities and spectrophotometric properties of southern binary galaxies
We present spectrophotometry of a sample of 26 Southern binary galaxies17 pairs were confirmed to be physically associated with typicalseparation of 136 h^{-1} kpc. Pairs with velocity difference Delta v>= 600 km s^{-1} are probably not physically bound. A comparison withfield galaxies suggests that galaxies in pairs tend to have a youngerpopulation probably stimulated by tidal interaction. No correlationbetween the young population and projected separation was found. Table 1is also available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr(130.79.128.5) or via http://cdsweb.u-strasbg.fr/Abs tract.html
| 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.
| Candidates for a southern extension of the Karachentsev catalogue of isolated pairs of galaxies.
Not Available
| 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.
| On the external origin for dust in elliptical galaxies
Large samples of elliptical galaxies, observed at high signal-to-noiseratio with CCDs, are used with ADDSCAN 100 micron fluxes from IRAS toexamine evidence for the external origin of dust in these galaxies. Foursmall sets of galaxies are picked which show features stronglyindicative of a merger, that is, infalling H I gas, extensive dustlanes, and kinematically peculiar cores and shells. Though somecounterexamples exist, it is shown that the dust and isophotalproperties are consistent with the current merger model for thesegalaxies.
| The supergalactic plane redshift survey
Redshift measurements, about 1000 of which are new, are presented for1314 galaxies in a survey toward the apex of the large-scale streamingflow for ellipticals. The velocity histogram shows that the excess ingalaxy number counts in this area is due to a substantial concentrationof galaxies with discrete peaks at V about 3000 km/s and V about 4500km/s. After correction for the sampling function, the centroid of thedensity distribution is found to be near V about 4500 km/s.Normalization to the more extensive SSRS survey, which was selected bythe same criteria, shows that the region studied contains a considerableoverdensity of galaxies from 2000 to 6000 km/s. This result is in goodagreement with the 'great attractor' model suggested by Lynden-Bell etal. (1988) which attributes the peculiar motions of elliptical galaxiesover a large region of space to an extensive mass overdensity whichincludes the Hydra-Centaurus and Pavo-Indus superclusters. The centroidof the density enhancement is also consistent with new data by Dresslerand Faber (1990) of peculiar motions of elliptical and spiral galaxies,both of which show a zero crossing of the Hubble line at approximately4500-5000 km/s.
| The plane W(Na I) X W(Mg I) - Effects of interstellar Na I in a sample of southern galaxies
Galaxy spectra from a subsample of the Southern Sky Redshift Survey databank were used to study the equivalent width plane for the lines Na Ilambda 5893 A vs Mg I lambda 5175 A. An estimate of how important thecontribution of the interstellar gas for the sodium line is compared tothat of the stellar population. The sample is made up of galaxies withmorphological types from E to Sc and are distributed up to radialvelocities of 25,000 km/s, most of them smaller than 15,000 km/s. Mostearly type galaxies with dust lanes, particularly nearly edge-on So's,present an enhancement of the Na I line. Inclined spiral galaxies tendto present enhanced Na I with respect to face-on spirals. This tendency,previously found in a smaller sample of galaxies limited to V equal toor less than 6000 km/s, is now confirmed for more distant ones. In thelarge velocity sample it shows the global bulge rather than the verynucleus; the persistence of the effect suggests that the scale height ofthe gas layer in the central disk can reach a considerable fraction ofthe bulge radius.
| A wide angle redshift survey of the Hydra-Centaurus region
Spectroscopic observations of 266 galaxies in the Hya-Cen region arereported. Redshift data obtained at 350-700 nm with dispersion 21 nm/mmusing the UNIT spectrograph and RPCS detector on the 1.9-m RadcliffeReflector telescope at SAO during March 1985, May 1986, and March 1987are presented in tables and graphs and briefly characterized. It isshown that the Hya supercluster is separated from the Cen superclusterby a large void at right ascension 11 h 40 min, declination -35 deg, andradial velocity 5200 km/sec; a bridge of galaxies at velocity about 3200km/sec connects the two superclusters.
| Properties of elliptical galaxies with dust lanes
The new galactic class of elliptical galaxies with dust lanes ischaracterized by an elliptical stellar body crossed along the minor axisby a dust lane. Ninety objects are presently listed as dust laneellipticals. In this paper, the morphological, statistical, kinematical,and photometric properties of these galaxies are described. The natureof the warps seen in the dust lanes in some of the galaxies isaddressed.
| The Centaurus-Hydra supercluster region. II
In this paper, 139 redshifts obtained in the region of theCentaurus-Hydra supercluster are presented. These data, combined withthe radial velocities reported in an earlier paper, are used in apreliminary investigation of the spatial distribution of galaxies in thesurroundings of the Centaurus cluster. Attention is focused on twoparticular regions of the sky for which we have nearly complete redshiftsamples of galaxies brighter than blue magnitude 15.0. From the analysisof the spatial distribution of galaxies in these two regions, it isfound that the system of galaxies associated with the Centaurus clusterextends northeastward, and that the complexes of Centaurus and Hydra maywell be considered as separate superclusters.
| A catalog of dusty elliptical galaxies
A catalog of about 100 dusty elliptical galaxies and some relatedobjects is presented. A morphological classification system is proposed,and the observed dust lane characteristics of some of the individualgalaxies are described. The properties of the galaxies are discussed,including the distribution of morphological types, their radioproperties, radio source orientation, neutral hydrogen, kinematics anddynamics, and relationship to other types of peculiar galaxies.
| Unusually strong reddening in the dusty elliptical IC 4320
Electronographic surface photometry in five wavebands has been used todetermine the reddening law for the dust lane in the elliptical galaxyIC 4320 in the wavelength range 428-653 nm. The extinction varieslinearly with inverse wavelength with a ratio of total to selectiveextinction R = 1.9, implying that the dust grains are smaller than inthe Galaxy. This could be due to a different formation mechanism, or mayresult from gradual destruction of the dust in the time since it waslast replenished by star formation - a period of approximately 500million yr is required. This may provide a means of dating these dustlane systems.
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