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Optical and Near-Infrared Color Profiles in Nearby Early-Type Galaxies and the Implied Age and Metallicity Gradients
We present results of an age and metallicity gradient analysis inferredfrom both optical and near-infrared surface photometry. The analysis isbased on a sample of 36 nearby early-type galaxies, obtained from theEarly Data Release of the Sloan Digital Sky Survey and the Two MicronAll Sky Survey. Surface brightness profiles were derived in each bandand used to study the color gradients of the galaxies. Using simplestellar population models with both optical and near-infrared colors, wemay interpret the color gradients in terms of age and metallicitygradients of galaxies. UsinggZ≡dlogZmet/dlogR andgA=dlog(age)/dlogR to represent the metallicity and agegradients, we found a median value of gZ=-0.25+/-0.03 for themetallicity gradient, with a dispersionσgZ=0.19+/-0.02. The corresponding valuesfor the age gradients were gA=0.02+/-0.04 andσgA=0.25+/-0.03. These results are in goodagreement with recent observational results, as well as with recentsimulations that suggest that both monolithic collapse and major mergershave played important roles in the formation of early-type galaxies. Ourresults demonstrate the potential of using multi-wave band colorsobtained from current and future optical and infrared surveys inconstraining the age and metallicity gradients of early-type 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
| Radio sources in the 2dF Galaxy Redshift Survey - II. Local radio luminosity functions for AGN and star-forming galaxies at 1.4 GHz
We have cross-matched the 1.4-GHz NRAO VLA Sky Survey (NVSS) with thefirst 210 fields observed in the 2dF Galaxy Redshift Survey (2dFGRS),covering an effective area of 325deg2 (about 20 per cent ofthe final 2dFGRS area). This yields a set of optical spectra of 912candidate NVSS counterparts, of which we identify 757 as genuine radioidentifications - the largest and most homogeneous set of radio sourcespectra ever obtained. The 2dFGRS radio sources span the redshift rangez=0.005 to 0.438, and are a mixture of active galaxies (60 per cent) andstar-forming galaxies (40 per cent). About 25 per cent of the 2dFGRSradio sources are spatially resolved by NVSS, and the sample includesthree giant radio galaxies with projected linear size greater than 1Mpc.The high quality of the 2dF spectra means we can usually distinguishunambiguously between AGN and star-forming galaxies. We make a newdetermination of the local radio luminosity function at 1.4GHz for bothactive and star-forming galaxies, and derive a local star formationdensity of 0.022+/-0.004Msolaryr-1Mpc-3(H0=50kms-1Mpc-1).
| 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 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.
| An extragalactic database. I - The Catalogue of Principal Galaxies
The Catalogue of Principal Galaxies is described, which lists equatorialcoordinates (for the equinoxes 1950 and 2000) and cross-identificationsfor 73,197 galaxies. The 40,932 coordinates have standard deviationssmaller than 10 arcsec. A total of 131,601 names from the 38 most commonsources are listed. In addition, mean data for each object are givenwhen available: 49,102 morphological descriptions, 52,954 apparent majorand minor axes, 67,116 apparent magnitudes, 20,046 radial velocities and24,361 position angles. This information was used for facilitatingproper identification. Finally, distribution options are explained.
| A morphological effect in pairs of elliptical galaxies
A morphological signature of gravitational interaction has been found ina sample of 50 close pairs of elliptical galaxies. The halos of bothgalaxies in five, and possibly more, pairs are off-center and thisoffset is symmetric with respect to the center of the pair. Among thephysical mechanisms that could be responsible for this morphologicaleffect, the displacement of the nucleus with respect to the halo in eachgalaxy or the formation of an asymmetric tidal bulge are the mostlikely. The observation of this effect should provide constraints on theinternal dynamics of elliptical galaxies, as well as on the dynamics ofpairs.
| Individual and orbital masses of double galaxies
A list is given of individual estimates of the masses of 124 componentsof isolated pairs of galaxies from Turner's catalog for which there arepublished data on the velocity dispersions in the central parts of thegalaxies, on the width of the 21-cm radio line profile, and on theamplitude of the rotation curve of the galaxies. From the comparison ofthe orbital estimates of the mass with the sum of the individual massesof the double galaxies it is concluded that the bulk of the mass of thegalaxies is situated within their standard optical diameter A(25). Theconsidered observational data for the Turner galaxy pairs do not containany arguments for the hypothesis of massive halos. Good agreementbetween the orbital and individual estimates of the mass is observed foralmost circular motions of the galaxies in pairs with mean orbitaleccentricity 0.25.
| A catalog of stellar velocity dispersions. I - Compilation and standard galaxies
A catalog of central stellar velocity dispersion measurements ispresented, current through June 1984. The catalog includes 1096measurements of 725 galaxies. A set of 51 standard galaxies is definedwhich consists of galaxies with at least three reliable, concordantmeasurements. It is suggested that future studies observed some of thesestandard galaxies in the course of their observations so that differentstudies can be normalized to the same system. Previous studies arecompared with the derived standards to determine relative accuracies andto compute scale factors where necessary.
| An observational study of the dynamics of binary galaxies
The single velocity measurement rms error value in the present set ofradial velocities for all galaxies in the Turner (1976) catalog of 156binary systems is estimated t be 29 km/sec. Typical velocity differencesare very small, with half of the 55 systems in the subsample of isolatedspiral-spiral pairs (the most reliable set of 'pure' binaries) havingmeasured velocity differences of less than 75 km/sec. By means of MonteCarlo simulations of scale-free ensembles of binary galaxies, it ispossible to show that the present data's independence of eitherluminosity or projected separation is inconsistent both with thehypothesis that the mass of binary systems increases linearly withluminosity, and that galaxies in pairs may effectively be treated aspoint masses. The data favor models in which galaxies interact through aquasi-isothermal potential only weakly depending on luminosity.
| Double galaxy investigations. I - Observations
Redshift information from 240 A/mm spectrograms is presented for 370double arcsec galaxy systems from the Karachentsev (1972) catalog,including all pairs in that catalog with separation less than 80 arcsec.An extensive error discussion utilizing internal and external (21 cm)comparisons provides calibration of systematic error and determines theuncertainty for a typical high weight optical redshift to be plus orminus 65 km/sec. Internal differential redshifts within single spectrausing common lines achieve accuracies of 18-30 km/sec, depending uponseparation, and are available for about 200 pairs. Extensive informationon emission and other properties is also provided.
| Binary galaxie. I. A well-defined statistical sample.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1976ApJ...208...20T&db_key=AST
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