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Публикации по объекту
Dark matter in early-type galaxies: dynamical modelling of IC 1459, IC 3370, NGC 3379 and NGC 4105
We analyse long-slit spectra of four early-type galaxies which extendfrom ~1 to 3 effective radii: IC 1459; IC 3370; NGC 3379 and NGC 4105.We have extracted the full line-of-sight velocity distribution (in thecase of NGC 3379 we also used data from the literature), which we modelusing the two-integral approach. Using two-integral modelling, we findno strong evidence for dark haloes, but the fits suggest thatthree-integral modelling is necessary. We also find that the inferredconstant mass-to-light ratio in all the four cases is typical forearly-type galaxies. Finally, we also discuss the constraints on themass-to-light ratio, which can be obtained using X-ray haloes in thecase of IC 1459, NGC 3379 and NGC 4105, and compare the estimated valueswith the predictions from the dynamical modelling.
| Do Observed Metallicity Gradients of Early-Type Galaxies Support a Hybrid Formation Scenario?
We measure radial gradients of the Mg2 index in 15 E-E/S0 and14 S0 galaxies. Our homogeneous data set covers a large range ofinternal stellar velocity dispersions (2.0
| Line-of-Sight Reddening Predictions: Zero Points, Accuracies, the Interstellar Medium, and the Stellar Populations of Elliptical Galaxies
Revised (B-V)0-Mg2 data, which are used to testreddening predictions, are presented for 402 elliptical galaxies. Thesereddening predictions can tell us both what the intrinsic errors are inthis relationship among gE galaxy stellar populations as well as detailsof nearby structure in the interstellar medium (ISM) of our Galaxy, andof the intrinsic errors in reddening predictions. Using least-squaresfits, the explicit 1 σ errors in reddenings predicted by theBurstein-Heiles (BH) method and the Schlegel and coworkers (IR) methodare calculated, as well as the 1 σ observational error in the(B-V)0-Mg2 for gE galaxies. It is found that indirections with E(B-V)<0.100 mag (where most of these galaxies lie),1 σ errors in the IR reddening predictions are 0.006-0.009 mag inE(B-V), those for BH reddening predictions are 0.011 mag, and the 1σ agreement between the two reddening predictions is 0.007 mag.The IR predictions have an accuracy of 0.010-0.011 mag in directionswith E(B-V)>=0.100 mag, significantly better than those of the BHpredictions (0.024-0.025). Both methods yield good evidence thatgas-to-dust variations that vary by a factor of 3, both high and low,exist along many lines of sight in our Galaxy. Both methods also predictmany directions with E(B-V)<0.015 mag, despite the difference in zeropoint that each has assumed. The ~0.02 higher reddening zero point inE(B-V) previously determined by Schlegel and coworkers is confirmed,primarily at the Galactic poles. Independent evidence of reddening atthe north Galactic pole (NGP) is reviewed, with the conclusion thatdirections still exist at the NGP that have E(B-V)<<0.01. Twolines of evidence suggest that IR reddenings are overpredicted indirections with high gas-to-dust ratios. As high gas-to-dust directionsin the ISM also include the Galactic poles, this overprediction is thelikely cause of the E(B-V)~0.02 mag larger IR reddening zero pointrelative to that of BH.
| Redshift-Distance Survey of Early-Type Galaxies: Circular-Aperture Photometry
We present R-band CCD photometry for 1332 early-type galaxies, observedas part of the ENEAR survey of peculiar motions using early-typegalaxies in the nearby universe. Circular apertures are used to tracethe surface brightness profiles, which are then fitted by atwo-component bulge-disk model. From the fits, we obtain the structuralparameters required to estimate galaxy distances using theDn-σ and fundamental plane relations. We find thatabout 12% of the galaxies are well represented by a pure r1/4law, while 87% are best fitted by a two-component model. There are 356repeated observations of 257 galaxies obtained during different runsthat are used to derive statistical corrections and bring the data to acommon system. We also use these repeated observations to estimate ourinternal errors. The accuracy of our measurements are tested by thecomparison of 354 galaxies in common with other authors. Typical errorsin our measurements are 0.011 dex for logDn, 0.064 dex forlogre, 0.086 mag arcsec-2 for<μe>, and 0.09 for mRC,comparable to those estimated by other authors. The photometric datareported here represent one of the largest high-quality and uniformall-sky samples currently available for early-type galaxies in thenearby universe, especially suitable for peculiar motion studies.Based on observations at Cerro Tololo Inter-American Observatory (CTIO),National Optical Astronomy Observatory, which is operated by theAssociation of Universities for Research in Astronomy, Inc., undercooperative agreement with the National Science Foundation (NSF);European Southern Observatory (ESO); Fred Lawrence Whipple Observatory(FLWO); and the MDM Observatory on Kitt Peak.
| On the calibration of the COBE/IRAS dust emission reddening maps
In this work we study the spectral properties (3600-6800 Å) of thenuclear region of early-type galaxies at low (|b|<25deg),intermediate (including surroundings of the Magellanic Clouds) and high(South Polar Cap) Galactic latitudes. We determine the E(B-V) reddeningvalues of the galaxies by matching their continuum distribution withrespect to those of reddening-free spectral galaxy templates withsimilar stellar populations. We also compare the spectroscopic reddeningvalue of each galaxy with that derived from 100 mu m dust emission(E(B-V)FIR) in its line of sight, and we find that there isagreement up to E(B-V)=0.25. Beyond this limit E(B-V)FIRvalues are higher. Taking into account the data up to E(B-V) ~ 0.7, wederive a calibration factor of 0.016 between the spectroscopic E(B-V)values and Schlegel et al.'s (\cite{Schlegel1998}) opacities. Bycombining this result with an AK extinction map built withinten degrees of the Galactic centre using Bulge giants as probes (Dutraet al. \cite{Dutra2003}), we extended the calibration of dust emissionreddening maps to low Galactic latitudes down to |b|=4deg andE(B-V)= 1.6 (AV ~ 5). According to this new calibration, amultiplicative factor of ~0.75 must be applied to the COBE/IRAS dustemission reddening maps.Based on observations made at Complejo Astronómico El Leoncito,which is operated under agreement between the Consejo Nacional deInvestigaciones Científicas y Técnicas de laRepública Argentina and the National Universities of La Pata,Córdoba and San Juan, Argentina.
| 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
| 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.
| Line-strength indices and velocity dispersions for 148 early-type galaxies in different environments
We have derived high quality line-strength indices and velocitydispersions for a sample of 148 early-type galaxies in differentenvironments. The wavelength region covered by the observations (lambda=~ 4600 to 6600 Å) includes the Lick/IDS indices Hβ,Mg1, Mg2, Mgb, Fe5015, Fe5270, Fe5335, Fe5406,Fe5709, Fe5782, NaD, TiO1 and TiO2. The data areintended to address possible differences of the stellar populations ofearly-type galaxies in low- and high-density environments. This paperdescribes the sample properties, explains the data reduction andpresents the complete list of all the measurements. Most galaxies of thesample (85%) had no previous measurements of any Lick/IDS indices andfor 30% of the galaxies we present first-time determinations of theirvelocity dispersions. Special care is taken to identify galaxies withemission lines. We found that 62 per cent of the galaxies in the samplehave emission lines, as measured by the equivalent width of the [OIII]5007Å line, EW[OIII] > 0.3 Å. Tables 5 and 6 are onlyavailable in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/ A+A/395/431. They are also available via ftp atftp.mpe.mpg.de in the directory people/dthomas/Beuing02 or via WWW atftp://ftp.mpe.mpg.de/people/dthomas/Beuing02.
| An elliptical galaxy luminosity function and velocity dispersion sample of relevance for gravitational lensing statistics
We have selected 42 elliptical galaxies from the literature andestimated their velocity dispersions at the effective radius(σRe) and at 0.54 effective radii(σ0.54Re). We find by a dynamical analysisthat the normalized velocity dispersion of the dark halo of anelliptical galaxy σDM is roughlyσRe multiplied by a constant, which isalmost independent of the core radius or the anisotropy parameter ofeach galaxy. Our sample analysis suggests that σDM*lies in the range 178-198 km s-1. The power law relation wefind between the luminosity and the dark matter velocity dispersionmeasured in this way is(L/L*)=(σDM/σDM*)γ,where /γ is between 2 and 3. These results are of interest forstrong gravitational lensing statistics studies. In order to determinethe value of σDM*, we calculateMBT* in the same BT band in whichσDM* has been estimated. We select 131 ellipticalgalaxies as a complete sample set with apparent magnitudes BTbetween 9.26 and 12.19. We find that the luminosity function is wellfitted to the Schechter form, with parametersMBT*=-19.66+5.log10h+/-0.30,/α=0.15+/-0.55, and the normalization constantφ*=(1.34+/-0.30)×10-3h3Mpc-3, with the Hubble constant Ho=100 /h kms-1 Mpc-1. This normalization implies thatmorphology type E galaxies make up (10.8 /+/- 1.2) per cent of allgalaxies.
| 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 LX-σ Relation for Galaxies and Clusters of Galaxies
We demonstrate that individual elliptical galaxies and clusters ofgalaxies form a continuous X-ray luminosity-velocity dispersion(LX-σ) relation. Our samples of 280 clusters and 57galaxies have LX~σ4.4 andLX~σ10, respectively. This unifiedLX-σ relation spans 8 orders of magnitude inLX and is fully consistent with the observed and theoreticalluminosity-temperature scaling laws. Our results support the notion thatgalaxies and clusters of galaxies are the luminous tracers of similardark matter halos.
| Line-of-sight velocity distributions of 53 early-type galaxies
55 long-slit spectra of 53 early-type galaxies were observed at LaSilla/ESO and reduced using standard methods. The line-of-sight velocitydistributions (LOSVDs) were measured using the fourier quotient methodand the fourier fitting method as described by van der Marel et al.(\cite{vdmarel93}). 32% of the examined galaxies contain kinematicallydecoupled stellar omponents, the size of these cores was 0.40 +/- 0.28kpc, in each case the core was smaller than 1 kpc. Analysis of thekinematics reveals in 49% of the sample galaxies the signature of astellar disk component, in 15% this is uncertain. There is evidence thatthe phenomenon of kinematically decoupled components is present in thewhole class of early-type galaxies. Several correlations betweenphotometric and kinematic parameters like the (v/sigma )* vs.epsilon diagram, the anisotropy - luminosity correlation or kappa -spacewere as well examined using measurement results for spectroscopic dataand photometric data out of literature. It is also shown that thosesample galaxies with kinematically decoupled components are more likelyto be found in groups of high density, strengthening the assumption thatsuch components are remnants of merging events. Full Fig. 6 is onlyavailable at http://www.edpsciences.org
| X-ray luminosities for a magnitude-limited sample of early-type galaxies from the ROSAT All-Sky Survey
For a magnitude-limited optical sample (B_T <= 13.5 mag) ofearly-type galaxies, we have derived X-ray luminosities from the ROSATAll-Sky Survey. The results are 101 detections and 192 useful upperlimits in the range from 10^36 to 10^44 erg s^-1. For most of thegalaxies no X-ray data have been available until now. On the basis ofthis sample with its full sky coverage, we find no galaxy with anunusually low flux from discrete emitters. Below log (L_B) ~ 9.2L_⊗ the X-ray emission is compatible with being entirely due todiscrete sources. Above log (L_B) ~ 11.2 L_osolar no galaxy with onlydiscrete emission is found. We further confirm earlier findings that L_xis strongly correlated with L_B. Over the entire data range the slope isfound to be 2.23 (+/- 0.12). We also find a luminosity dependence ofthis correlation. Below log L_x = 40.5 erg s^-1 it is consistent with aslope of 1, as expected from discrete emission. Above this value theslope is close to 2, as expected from gaseous emission. Comparing thedistribution of X-ray luminosities with the models of Ciotti et al.leads to the conclusion that the vast majority of early-type galaxiesare in the wind or outflow phase. Some of the galaxies may have alreadyexperienced the transition to the inflow phase. They show X-rayluminosities in excess of the value predicted by cooling flow modelswith the largest plausible standard supernova rates. A possibleexplanation for these super X-ray-luminous galaxies is suggested by thesmooth transition in the L_x--L_B plane from galaxies to clusters ofgalaxies. Gas connected to the group environment might cause the X-rayoverluminosity.
| Gradients of Absorption-Line Strengths in Elliptical Galaxies
We have restudied line-strength gradients of 80 elliptical galaxies.Typical metallicity gradients of elliptical galaxies areΔ[Fe/H]/Δlogr~=-0.3, which is flatter than the gradientspredicted by monolithic collapse simulations. The metallicity gradientsdo not correlate with any physical properties of galaxies, includingcentral and mean metallicities, central velocity dispersionsσ0, absolute B magnitudes MB, absoluteeffective radii Re, and dynamical masses of galaxies. Byusing the metallicity gradients, we have calculated mean stellarmetallicities for individual ellipticals. Typical mean stellarmetallicities are <[Fe/H]>~=-0.3 and range from<[Fe/H]>~=-0.8 to +0.3, which is contrary to what Gonzalez &Gorgas claimed; the mean metallicities of ellipticals are not universal.The mean metallicities correlate well with σ0 anddynamical masses, though relations for MB and Reinclude significant scatters. We find fundamental planes defined bysurface brightnesses SBe, <[Fe/H]>, and Re(or MB), the scatters of which are much smaller than those ofthe <[Fe/H]>-Re (or <[Fe/H]>-MB)relations. The <[Fe/H]>-logσ0 relation is nearlyparallel to the [Fe/H]0-logσ0 relation butsystematically lower by 0.3 dex; thus the mean metallicities are aboutone-half of the central values. The metallicity-mass relation or,equivalently, the color-magnitude relation of ellipticals holds not onlyfor the central parts of galaxies but also for entire galaxies. Assumingthat Mg2 and Fe1 give [Mg/H] and [Fe/H],respectively, we find <[Mg/Fe]>~=+0.2 in most of ellipticalgalaxies. <[Mg/Fe]> shows no correlation with galaxy mass tracerssuch as σ0, in contrast to what was claimed for thecentral [Mg/Fe]. This can be most naturally explained if the starformation had stopped in elliptical galaxies before the bulk of Type Iasupernovae began to occur. Elliptical galaxies can have significantlydifferent metallicity gradients and <[Fe/H]>, even if they havethe same galaxy mass. This may result from galaxy mergers, but noevidence is found from presently available data to support the sameorigin for metallicity gradients, the scatters around themetallicity-mass relation, and dynamical disturbances. This may suggestthat the scatters have their origin at the formation epoch of 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.
| 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
| The Iron Discrepancy in Elliptical Galaxies after ASCA
We present estimates for the iron content of the stellar and diffusedcomponents of elliptical galaxies, as derived respectively fromintegrated optical spectra and from ASCA X-ray observations. Amacroscopic discrepancy emerges between the expected iron abundances inthe hot interstellar medium (ISM) and what is indicated by the X-rayobservations, especially when allowance is made for the current ironenrichment by Type Ia supernovae. This strong discrepancy, that in someextreme instances may be as large as a factor of ~20, calls intoquestion our current understanding of supernova enrichment and chemicalevolution of galaxies. We discuss several astrophysical implications ofthe inferred low iron abundances in the ISM, including the chemicalevolution of galaxies and clusters of galaxies, the evolution of gasflows in elliptical galaxies, and the heating of the intraclustermedium. Some of the consequences appear hard to accept, and in theattempt to avoid some of the difficulties we explore ways of hiding ordiluting iron in the ISM of ellipticals. None of these possibilitiesappears astrophysically plausible, and we alternatively raise thequestion of the reliability of iron L line diagnostic tools that arecurrently used to infer abundances from X-ray spectra. Variousthin-plasma emission models are shown to give iron abundances that maydiffer significantly, especially at low temperatures (kT <~ 1 keV),when the iron L complex is dominated by iron ions with still many boundelectrons. From a collection of ASCA and other X-ray observatory data,it is shown that current thin-plasma codes tend to give very low ironabundances when the temperature of the objects is below ~1 keV. Suchobjects include various types of binary stars, supernova remnants,starburst galaxies, and AGNs, with the case of galaxy groups beingespecially well documented. We conclude that, besides rethinking thechemical evolution of galaxies, one should also consider the possibilitythat existing thin-plasma models may incorporate inaccurate atomicphysics for the ions responsible for the iron L complex.
| Scale-free dynamical models for galaxies: flattened densities in spherical potentials
This paper presents two families of phase-space distribution functionsthat generate scale-free spheroidal mass densities in scale-freespherical potentials. The assumption of a spherical potential has theadvantage that all integrals of motion are known explicitly. The `caseI' distribution functions are anisotropic generalizations of theflattened f(E,<E1>L_z</E1> model, which theyinclude as a special case. The `case II' distribution functions generateflattened constant-anisotropy models. Free parameters control the radialpower-law slopes of the mass density and potential, the flattening ofthe mass distribution, and the velocity dispersion anisotropy. Themodels can describe the outer parts of galaxies and the density cuspstructure near a central black hole, but also provide general insightinto the dynamical properties of flattened systems. Because of theirsimplicity they provide a useful complementary approach to theconstruction of flattened self-consistent three-integral models forelliptical galaxies. &emspThe dependence of the intrinsic andprojected properties on the model parameters and the inclination isdescribed. The case I models have a larger ratio of rms tangential toradial motion in the equatorial plane than on the symmetry axis, themore so for smaller axial ratios. The case II models have a constantratio of rms tangential to radial motion throughout the system, ascharacterized by Binney's parameter beta. The maximum possible ratio_p/sigma_p of the mean projected line-of-sight velocity and velocitydispersion on the projected major axis always decreases with increasingradial anisotropy. The observed ratio of the rms projected line-of-sightvelocities on the projected major and minor axes of elliptical galaxiesis best fitted by the case II models with beta0. These models alsopredict non-Gaussian velocity profile shapes consistent with existingobservations. &emspThe distribution functions are used to model thegalaxies NGC 2434 (E1) and NGC 3706 (E4), for which stellar kinematicalmeasurements out to two effective radii indicate the presence of darkhaloes. The velocity profile shapes of both galaxies can be well fittedby radially anisotropic case II models with a spherical logarithmicpotential. This contrasts with the f(E,L_z) models studied previously,which require flattened dark haloes to fit the data.
| A radio continuum study of the Magellanic Clouds. IVa. Catalogue of radio sources in the Large Magellanic Cloud at 2.30GHz (λ=13cm).
We present a new catalogue of radio sources in the Large MagellanicCloud (LMC) based on observations at 2.30GHz with the Parkes radiotelescope. A total of 119 sources have been detected. We comparepositions and flux densities of these sources with previously publishedradio results and find no significant positional displacement or fluxdiscrepancies.
| 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.
| Dark matter in elliptical galaxies
We present measurements of the shape of the stellar line-of-sightvelocity distribution out to two effective radii along the major axes ofthe four elliptical galaxies NGC 2434, 2663, 3706, and 5018. Thevelocity dispersion profiles are flat or decline gently with radius. Wecompare the data to the predictions of f = f(E, Lz)axisymmetric models with and without dark matter. Strong tangentialanisotropy is ruled out at large radii. We conclude from ourmeasurements that massive dark halos must be present in three of thefour galaxies, while for the fourth galaxy (NGC 2663) the case isinconclusive.
| Line-strength gradients in the bulge components of NGC 3190 and 1023.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1994MNRAS.271...39S&db_key=AST
| Colours Line Strengths and Stellar Kinematics of NGC2663 and NGC5018
Results of the analysis of broad-band optical images and long-slitspectra of the two elliptical galaxies NGC 2663 and 5018 are presented.Line-strength profiles of Mg_2_, Fe_5270_ and Fe_5335_ have been derivedfor both galaxies, together with rotational velocity and velocitydispersion curves at three and four position angles (PAs) for NGC 2663and 5018, respectively. The measurements extend to about 1.8 effectiveradii for NGC 2663, and to about 3 effective radii for NGC 5018.Axisymmetric dynamical models with distribution function f= f(E, J_z_)(i.e. depending only on the energy E and the angular momentum along thesymmetry axis J_z_) have been fitted to the kinematic profiles of bothgalaxies, to derive information about the intrinsic shapes of theluminous galaxies and the sizes and shapes of possible dark haloes. Inagreement with what has been found for other ellipticals: (i) versus Mg_2_ shows, within both galaxies, a steeper slope than thatshown by galactic nuclei, and (ii) the slope is approximately equal inthe two galaxies and constant within each galaxy (over the whole radialrange, to ~2R_e_). A shift is observed between the two galaxies,implying different [Mg/Fe] abundance ratios. In NGC 2663, the derived[Mg/Fe] abundance ratio is (as is normally found in ellipticals) largerthan solar; its colour [d(B - R )/d log r = - 0.08] and Mg_2_ (dMg_2_/dlog r = - 0.06) gradients are consistent with each other and with achange in metallicity only. The galaxy shows a hint of counter-rotationwithin the innermost 20 arcsec and minor axis rotation. Any oblate orprolate model fitting its kinematics along any two position angles failsto fit the third position angle available, the discrepancy with the databeing a systematic shift. Most probably, this galaxy is a triaxialobject (observed V_rot_/σ~ 0.15 with e~0.3, anisotropy parameterδ >= 0.2-0.3); alternatively, it might be prolate but alwayswith an anisotropic velocity dispersion tensor. In NGC 5018, an almostflat velocity dispersion profile is observed out to the last measuredpoint. Assuming that the galaxy is an axisymmetric rotator, such a flata profile can be reproduced at a confidence level >~ 5 sigma only ifa very massive dark matter halo surrounds the luminous component (M_D_ ~6 M_lum_). A rather strong (B-R) colour gradient is observed in NGC 5018[d(B- R)/dlog r= -0.13], despite its shallow Mg_2_ gradient (dMg_2_/dlogr= - 0.04). Although the whole galaxy is blue, its central (B - R)colour and the observed patchy structure in the (B - R) colour mapsuggest a considerable amount of extinction in its central regions. Ifthe dust follows the Galactic extinction law, at 1550 A one could evenexpect ~2 mag of extinction. This might hide a younger stellarpopulation diluting the Mg_2_ line strength, and might explain the lackof UV flux reported by other authors. The dilution of Mg_2_ would alsoexplain the solar [Mg/Fe] abundance ratio.
| 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.
Not Available
| Kinematical properties of early-type galaxies.
Not Available
| Metallicity Gradients in Early Type Galaxies
Long-slit spectra in the range 4500-6500 A have been obtained for asample of 42 galaxies. Rotation velocities and velocity dispersions,together with radial line strength gradients of Mg_2_, Mg_1_, Hβ,NaD, TiO_1_, TiO_2_ and Fe_5270_, have been measured to, on average,half an effective radius. To a high level of significance, Mg_2_gradients positively correlate with those of Mg_1_ and Na D, but nocorrelation is observed with the other indices. In addition,correlations of Mg_2_ gradients with various physical parameters arestudied. For galaxies smaller than about 10^11^ M_sun_, the Mg_2_gradient increases with increasing mass, but more massive objects showno correlation. In low- mass galaxies, the correlation of Mg_2_gradients with mass suggests dissipative collapse as the mechanismacting during the initial star formation episode. Different formationmechanisms, such as, for example, a less dissipative collapse and/ormerging of smaller systems, are discussed as a means of explaining thelack of correlation at higher masses. Even at low masses, the galacticmass seems not to influence either the position or the slope on theFe_5270_-Mg_2_ plane, abundance ratios within galaxies depending onstill-unidentified parameters.
| IRAS CPC Observations of Galaxies - Part One - Catalog and Atlas
. - We present the results of far-infrared imaging observations of 258regions of 12' x9' each centered on a selected individual galaxy, aclose pair, or a compact group of galaxies mapped at 50 and 100 micronwavelength with the CPC instrument of the IRAS satellite. The CPCinstrument has a significantly better resolution than the IRAS Surveyinstrument at these wavelengths, i.e. a round beam with a FWHM of about80" at 50 microns and 95" at 100 microns, respectively, intended to bematched to the diffraction limit of the telescope at 100 microns. Themaps were made using a new algorithm to correct for gain variations,which gives better results than the one used previously for the imagesmade available on tape in 1985. Of 262 objects observed, 167 and 188were detected at 50 and 100 microns, respectively, about 85% of thegalaxies from the same sample listed as detected by the Surveyinstrument in the IRAS Point Source Catalog. For all 55 galaxiesresolved (i.e. with a FWHM major axis diameter exceeding 1.6 times thebeam FWHM and/or extended lower-level emission) by the CPC we alsopresent the averaged maps at 50 and 100 microns. These 55 objectsinclude 35 for which there are no published maps obtained with the IRASSurvey instrument. We rescaled the flux densities of the published CPCmaps using the more accurate IRAS Survey instrument data, since theabsolute flux density calibration of the CPC is only accurate to about+/-60%. We also present images of a triplet of galaxies associated witha single Survey point source, which were resolved into separate sourcesby the CPC.
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