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The fundamental plane of isolated early-type galaxies
Here we present new measurements of effective radii, surfacebrightnesses and internal velocity dispersions for 23 isolatedearly-type galaxies. The photometric properties are derived from newmulticolour imaging of ten galaxies, whereas the central kinematics forseven galaxies are taken from forthcoming work by Hau & Forbes.These are supplemented with data from the literature. We reproduce thecolour-magnitude and Kormendy relations and strengthen the result of therecent work of Reda et al. that isolated galaxies follow the samephotometric relations as galaxies in high-density environments. We alsofind that some isolated galaxies reveal fine structure indicative of arecent merger, while others appear undisturbed. We examine theFundamental Plane both in the traditional Re,μe, σ space and also in κ space. Most isolatedgalaxies follow the same Fundamental Plane tilt and scatter for galaxiesin high-density environments. However, a few galaxies notably deviatefrom the Plane in the sense of having smaller M/L ratios. This can beunderstood in terms of their younger stellar populations, which arepresumably induced by a gaseous merger. Overall, isolated galaxies havesimilar properties to those in groups and clusters with a slightenhancement in the frequency of recent mergers/interactions.
| 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 Sample of Field Ellipticals
Using well-defined selection criteria derived from Zaritsky et al.applied to the LEDA galaxy catalog, we have constructed a sample ofelliptical galaxies that can be taken to lie in the field. Such criteriacan easily be applied to theoretical simulations for direct comparisonwith observations. The variation of the number of ``isolated''ellipticals with selection criteria is also investigated. A preliminarystudy of the environment of the field ellipticals shows that, in themean, they are surrounded by a population of dwarf galaxies, out toprojected radii of at least 500 kpc, with a radial density profile ofr-0.6+/-0.2 and a luminosity function slope of α~-1.8.The results are compared and contrasted to the satellite populationaround isolated spiral galaxies.
| A new catalogue of ISM content of normal galaxies
We have compiled a catalogue of the gas content for a sample of 1916galaxies, considered to be a fair representation of ``normality''. Thedefinition of a ``normal'' galaxy adopted in this work implies that wehave purposely excluded from the catalogue galaxies having distortedmorphology (such as interaction bridges, tails or lopsidedness) and/orany signature of peculiar kinematics (such as polar rings,counterrotating disks or other decoupled components). In contrast, wehave included systems hosting active galactic nuclei (AGN) in thecatalogue. This catalogue revises previous compendia on the ISM contentof galaxies published by \citet{bregman} and \citet{casoli}, andcompiles data available in the literature from several small samples ofgalaxies. Masses for warm dust, atomic and molecular gas, as well asX-ray luminosities have been converted to a uniform distance scale takenfrom the Catalogue of Principal Galaxies (PGC). We have used twodifferent normalization factors to explore the variation of the gascontent along the Hubble sequence: the blue luminosity (LB)and the square of linear diameter (D225). Ourcatalogue significantly improves the statistics of previous referencecatalogues and can be used in future studies to define a template ISMcontent for ``normal'' galaxies along the Hubble sequence. The cataloguecan be accessed on-line and is also available at the Centre desDonnées Stellaires (CDS).The catalogue is available in electronic form athttp://dipastro.pd.astro.it/galletta/ismcat and at the CDS via anonymousftp to\ cdsarc.u-strasbg.fr (130.79.128.5) or via\http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/405/5
| 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.
| E+A Galaxies in the Near-Infrared: Broadband Photometry
This paper presents near-IR photometry of a selected sample of southernhemisphere E+A galaxies. The sample includes 50 galaxies from nearby(z~0.05) and distant (z~0.3) clusters, as well as E+A galaxies from thefield (z~0.1). Observations include 13 normal early-type galaxies fromthe field and from clusters to be compared with the E+A sample. Thephotometry includes J, H, and Ks apparent magnitudes andcolors. Observed colors are obtained from the apparent total magnitudesand compared with those of the GISSEL96 spectrophotometric models ofgalaxy evolution. There is an overall agreement between integratedcolors of models and observed ones, for both the E+A galaxies located inclusters and those in the field, at z<~0.1. However, largedifferences between colors predicted from models and those observed inE+A galaxies located in clusters at z~0.3 are found. We also computerest-frame colors for all the galaxies using two different sets ofK-corrections and obtain average colors for all the samples. This workinvestigates systematic properties of the E+A sample as a function ofits environment. Results seem to indicate that cluster E+A galaxies (atlow redshift) are bluer than field E+A galaxies at z~0.1. Even thisconclusion does not depend on whether we use comoving or rest-framecolors or on the models used to obtain rest-frame colors; the differenceis not significant enough, considering color dispersions between thesamples. If the differences are real, they could imply a differentstellar content for the E+A galaxies located in the field compared withthose located in the cluster E+A galaxies.
| 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.
| 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.
| 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.
| A Catalog of Stellar Velocity Dispersions. II. 1994 Update
A catalog of central velocity dispersion measurements is presented,current through 1993 September. The catalog includes 2474 measurementsof 1563 galaxies. A standard set of 86 galaxies is defined, consistingof galaxies with at least three reliable, concordant measurements. It issuggested that future studies observe some of these standard galaxies sothat different studies can be normalized to a consistent system. Allmeasurements are reduced to a normalized system using these standards.
| 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.
| New velocity dispersions and photometry for E and S0 galaxies in the great attractor
New spectroscopy and photometry have been obtained for 136 ellipticaland S0 galaxies in the direction of the large-scale streaming flowattributed to the great attractor. Measurements of central velocitydispersion (sigma), total B magnitudes B(T), the photometric parameterDn, and the absorption-line index Mg2 are presented. Both internal andexternal comparisons indicate that measurements of log sigma areaccurate to 0.05 dex, B(T) to 0.15 mag, Dn to 0.015 dex, and Mg2 to0.017 mag. These data have been used by Dressler and Faber (1990) toestimate distances for these galaxies via the Dn-sigma relation. It isshown in this paper that the Dn-Mg2 relation also predicts the sametrends of peculiar velocity with distance, but with less accuracy. Therelative accuracy of other distance indicators for elliptical galaxiesis also discussed.
| Low-luminosity radio sources in early-type galaxies
A sensitive radio continuum survey of 114 nearby E and S0 galaxies hasbeen made to search for weak sources. The radio detection rate is 42percent, with a flux limit of 0.8 mJy at 5 GHz. By deriving the radioluminosity function for a complete sample, it is shown that most brightearly-type galaxies have low-luminosity nonthermal radio sources.Galaxies of similar optical luminosity vary widely in radio luminosity,but a characteristic radio power rises roughly as the optical luminositysquared. S0 galaxies have weaker radio sources on average thanelliptical galaxies, but this can be explained by the low luminosity ofmost S0 bulges relative to ellipticals. No correlation is found betweenradio power and axial ratio for galaxies with radio luminosities below10 to the 23rd W/Hz.
| On the relationship between radio emission and optical properties in early-type galaxies
To study the origin of radio activity in early-type galaxies, thepossible dependence of their radio emission on basic optical parameters,such as the absolute magnitude, the central velocity dispersion sigma,and the mean surface brightness mu is explored. A sample of 743 E and SOgalaxies is used which is based on three independent radio surveys ofoptically selected galaxies with virtually complete information onmagnitudes, morphological types, redshift distances, diameters, andradio fluxes. For both E and SO galaxies, only the absolute magnitudeappears to be directly related to the radio activity, while sigma and mudo not. Also, a significant dependence of the apparent flattening onradio power is confirmed for E galaxies. Some relevant implications ofthese results are discussed.
| Ionized gas in elliptical and S0 galaxies. I - A survey for H-alpha and forbidden N II emission
A spectroscopic survey of a large sample of southern E and S0 galaxiesin order to detect ionized gas in the nuclei is reported. The strongestline in the 6000-7000 A range was nearly always forbidden N II 6584 A,followed by H-alpha and forbidden S II 6716, 6731 A. Identical detectionrates of about 50 percent were obtained for the forbidden N II line inboth E and S0 galaxies. The mass of ionized gas in early-type galaxieswas very small, with values typically in the range 1000-10,000 solarmasses. The relative emission-line strengths in virtually every casewere indistinguishable from those of LINER nuclei. The observed valuesof the forbidden N II 6584 A/H-alpha ratios fell mostly between one andthree and seem correlated with galaxy absolute magnitude. The existenceof such a correlation may be indicative of metallicity differences.
| Southern Galaxy Catalogue.
Not Available
| Radio and optical observations of a complete sample of E and SO galaxies. III. A radio continuum survey at 2.7 and 5.0 GHz.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1984AJ.....89...53S&db_key=AST
| Radio and optical observations of a complete sample of E and SO galaxies. II. UBV aperture photometry.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1984AJ.....89...34S&db_key=AST
| Radio and optical observations of a complete sample of E and S0 galaxies. I - Radial velocities. II - UBV aperture photometry. III - A radio continuum survey at 2.7 and 5.0 GHz
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1984AJ.....89...23S&db_key=AST
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