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The SAURON project - VI. Line strength maps of 48 elliptical and lenticular galaxies
We present absorption line strength maps of 48 representative ellipticaland lenticular galaxies obtained as part of a survey of nearby galaxiesusing our custom-built integral-field spectrograph, SAURON, operating onthe William Herschel Telescope. Using high-quality spectra, spatiallybinned to a constant signal-to-noise ratio, we measure four key age,metallicity and abundance ratio sensitive indices from the Lick/IDSsystem over a two-dimensional field extending up to approximately oneeffective radius. A discussion of calibrations and offsets is given,along with a description of error estimation and nebular emissioncorrection. We modify the classical Fe5270 index to define a new index,Fe5270S, which maximizes the useable spatial coverage ofSAURON. Maps of Hβ, Fe5015, Mgb and Fe5270S arepresented for each galaxy. We use the maps to compute average linestrengths integrated over circular apertures of one-eighth effectiveradius, and compare the resulting relations of index versus velocitydispersion with previous long-slit work. The metal line strength mapsshow generally negative gradients with increasing radius roughlyconsistent with the morphology of the light profiles. Remarkabledeviations from this general trend exist, particularly the Mgb isoindexcontours appear to be flatter than the isophotes of the surfacebrightness for about 40 per cent of our galaxies without significantdust features. Generally, these galaxies exhibit significant rotation.We infer from this that the fast-rotating component features a highermetallicity and/or an increased Mg/Fe ratio as compared to the galaxy asa whole. The Hβ maps are typically flat or show a mild positiveoutwards radial gradient, while a few galaxies show strong central peaksand/or elevated overall Hβ strength likely connected to recent starformation activity. For the most prominent post-starburst galaxies, eventhe metal line strength maps show a reversed gradient.
| The Two-dimensional XMM-Newton Group Survey: z < 0.012 Groups
We present the results of the two-dimensional XMM-Newton Group Survey(2dXGS), an archival study of nearby galaxy groups. In this paper weconsider 11 nearby systems (z<0.012) in Mulchaey et al., which span abroad range in X-ray luminosity from 1040 to 1043ergs s-1. We measure the iron abundance and temperaturedistribution in these systems and derive pressure and entropy maps. Wefind statistically significant evidence for structure in the entropy andpressure of the gas component of seven groups on the 10%-20% level. TheXMM-Newton data for the three groups with best statistics also suggestpatchy metallicity distributions within the central 20-50 kpc of thebrightest group galaxy, probed with 2-10 kpc resolution. This providesinsights into the processes associated with thermalization of thestellar mass loss. Analysis of the global properties of the groupsreveals a subclass of X-ray-faint groups, which are characterized byboth higher entropy and lower pressure. We suggest that the mergerhistory of the central elliptical is responsible for both the source andthe observed thermodynamical properties of the hot gas of theX-ray-faint groups.
| Group, field and isolated early-type galaxies - II. Global trends from nuclear data
We have derived ages, metallicities and enhanced-element ratios[α/Fe] for a sample of 83 early-type galaxies essentially ingroups, the field or isolated objects. The stellar-population propertiesderived for each galaxy correspond to the nuclear re/8aperture extraction. The median age found for Es is 5.8+/-0.6 Gyr andthe average metallicity is +0.37+/-0.03 dex. For S0s, the median age is3.0+/-0.6 Gyr and [Z/H]= 0.53+/-0.04 dex. We compare the distribution ofour galaxies in the Hβ-[MgFe] diagram with Fornax galaxies. Ourelliptical galaxies are 3-4 Gyr younger than Es in the Fornax cluster.We find that the galaxies lie in a plane defined by [Z/H]= 0.99logσ0- 0.46 log(age) - 1.60, or in linear terms Z~σ0× (age) -0.5. More massive (largerσ0) and older galaxies present, on average, large[α/Fe] values, and therefore must have undergone shorterstar-formation time-scales. Comparing group against field/isolatedgalaxies, it is not clear that environment plays an important role indetermining their stellar-population history. In particular, ourisolated galaxies show ages differing by more than 8 Gyr. Finally weexplore our large spectral coverage to derive log(O/H) metallicity fromthe Hα and NIIλ6584 and compare it with model-dependent[Z/H]. We find that the O/H abundances are similar for all galaxies, andwe can interpret it as if most chemical evolution has already finishedin these galaxies.
| Group, field and isolated early-type galaxies - I. Observations and nuclear data
This is the first paper of a series on the investigation of stellarpopulation properties and galaxy evolution of an observationallyhomogeneous sample of early-type galaxies in groups, field and isolatedgalaxies.Here we present high signal-to-noise ratio (S/N) long-slit spectroscopyof 86 nearby elliptical and S0 galaxies. Eight of them are isolated,selected according to a rigorous criterion, which guarantees a genuinelow-density subsample. The present survey has the advantage of coveringa larger wavelength range than normally found in the literature, whichincludes [OIII]λ5007 and Hα, both lines important foremission correction. Among the 86 galaxies with S/N >= 15 (perresolution element, for re/8 central aperture), 57 have theirHβ-index corrected for emission (the average correction is 0.190Åin Hβ) and 42 galaxies reveal [OIII]λ5007 emission,of which 16 also show obvious Hα emission. Most of the galaxies inthe sample do not show obvious signs of disturbances nor tidal featuresin the morphologies, although 11 belong to the Arp catalogue of peculiargalaxies; only three of them (NGC 750, 751 and 3226) seem to be stronglyinteracting. We present the measurement of 25 central line-strengthindices calibrated to the Lick/IDS system. Kinematic information isobtained for the sample. We analyse the line-strength index versusvelocity dispersion relations for our sample of mainly low-densityenvironment galaxies, and compare the slope of the relations withcluster galaxies from the literature. Our main findings are that theindex-σ0 relations presented for low-density regionsare not significantly different from those of cluster E/S0s. The slopeof the index-σ0 relations does not seem to change forearly-type galaxies of different environmental densities, but thescatter of the relations seems larger for group, field and isolatedgalaxies than for cluster galaxies.
| The NGC 5846 Group: Dynamics and the Luminosity Function to MR=-12
We conduct a photometric and spectroscopic survey of a 10deg2 region surrounding the nearby NGC 5846 group ofgalaxies, using the Canada-France-Hawaii and Keck I telescopes to studythe population of dwarf galaxies as faint as MR=-10.Candidates are identified on the basis of quantitative surfacebrightness and qualitative morphological criteria. Spectroscopic followup and a spatial correlation analysis provide the basis for affirminggroup memberships. Altogether, 324 candidates are identified, and 83have spectroscopic membership confirmation. We argue on statisticalgrounds that a total of 251+/-10 galaxies in our sample are groupmembers. The observations, together with archival Sloan Digital SkySurvey, ROSAT, XMM-Newton, and ASCA data, suggest that the giantellipticals NGC 5846 and NGC 5813 are the dominant components ofsubgroups separated by 600 kpc in projection and embedded in a 1.6 Mpcdiameter dynamically evolved halo. The galaxy population isoverwhelmingly early type. The group velocity dispersion is 322 kms-1, its virial mass is 8.4×1013Msolar, and M/LR=320 MsolarL-1solar. The ratio of dwarfs to giants is largecompared with other environments in the Local Supercluster studied, and,correspondingly, the luminosity function is relatively steep, with afaint-end Schechter function slope of αd=-1.3+/-0.1(statistical) +/-0.1 (systematic) at our completeness limit ofMR=-12.
| Companions to Isolated Elliptical Galaxies: Revisiting the Bothun-Sullivan Sample
We investigate the number of physical companion galaxies for a sample ofrelatively isolated elliptical galaxies. The NASA/IPAC ExtragalacticDatabase (NED) has been used to reinvestigate the incidence of satellitegalaxies for a sample of 34 elliptical galaxies, first investigated byBothun & Sullivan using a visual inspection of Palomar Sky Surveyprints out to a projected search radius of 75 kpc. We have repeatedtheir original investigation using data cataloged in NED. Nine of theseelliptical galaxies appear to be members of galaxy clusters; theremaining sample of 25 galaxies reveals an average of +1.0+/-0.5apparent companions per galaxy within a projected search radius of 75kpc, in excess of two equal-area comparison regions displaced by 150-300kpc. This is significantly larger than the +0.12+/-0.42companions/galaxy found by Bothun & Sullivan for the identicalsample. Making use of published radial velocities, mostly availablesince the completion of the Bothun-Sullivan study, identifies thephysical companions and gives a somewhat lower estimate of +0.4companions per elliptical galaxy. This is still 3 times larger than theoriginal statistical study, but given the incomplete and heterogeneousnature of the survey redshifts in NED, it still yields a firm lowerlimit on the number (and identity) of physical companions. An expansionof the search radius out to 300 kpc, again restricted to sampling onlythose objects with known redshifts in NED, gives another lower limit of4.5 physical companions per galaxy. (Excluding five elliptical galaxiesin the Fornax Cluster, this average drops to 3.5 companions perelliptical.) These physical companions are individually identified andlisted, and the ensemble-averaged radial density distribution of theseassociated galaxies is presented. For the ensemble, the radial densitydistribution is found to have a falloff consistent withρ~R-0.5 out to approximately 150 kpc. For non-FornaxCluster companions the falloff continues out to the 300 kpc limit of thesurvey. The velocity dispersion of these companions is found to reach amaximum of 350 km s-1 at around 120 kpc, after which theyfall at a rate consistent with Keplerian falloff. This falloff may thenindicate the detection of a cut-off in the mass-density distribution inthe elliptical galaxies' dark matter halo at ~100 kpc.
| Further clues to the nature of composite LINER/H II galaxies
We have analyzed new, archival and published high resolution radio andX-ray observations of a sample of composite LINER/H II galaxies known toexhibit AGN-like properties. Five of the 16 AGN candidates havemilliarcsecond-scale detections and are found to display a compact, flatspectrum, high brightness temperature radio core, four of which alsoexhibit extended radio emission. Five of the eight AGN candidates withavailable high resolution X-ray observations were found to possess ahard X-ray nuclear source, two of which have no milliarcsecond radiodetection. The combined high resolution radio and X-ray data yield a 50%detection rate of low luminosity AGN among the AGN candidates, whichtranslates into a 12% detection rate for the entire composite LINER/H IIsample. In the sources where the AGN has been unambiguously detected,the ionizing power of the AGN is not sufficient to generate the observedemission lines, unless the hard X-rays are heavily obscured. We attemptto apply a canonical advection-dominated accretion flow (ADAF) and jetmodel to the sample sources in order to explain the observed radio andX-ray emission. While ADAFs may be responsible for the observed emissionin submillijansky radio cores like NGC 7331, they do not appearconsistent with the radio emission observed in the milliarcsecond-scaleradio detected cores; the latter sources are more likely to have anenergetically important contribution from a radio-emitting jet.
| Companions of Bright Barred Shapley-Ames Galaxies
Companion galaxy environment for a subset of 78 bright and nearby barredgalaxies from the Shapley-Ames Catalog is presented. Among the spiralbarred galaxies, there are Seyfert galaxies, galaxies with circumnuclearstructures, galaxies not associated with any large-scale galaxy cloudstructure, galaxies with peculiar disk morphology (crooked arms), andgalaxies with normal disk morphology; the list includes all Hubbletypes. The companion galaxy list includes the number of companiongalaxies within 20 diameters, their Hubble type, and projectedseparation distance. In addition, the companion environment was searchedfor four known active spiral galaxies, three of them are Seyfertgalaxies, namely, NGC 1068, NGC 1097, and NGC 5548, and one is astarburst galaxy, M82. Among the results obtained, it is noted that theonly spiral barred galaxy classified as Seyfert 1 in our list has nocompanions within a projected distance of 20 diameters; six out of 10Seyfert 2 bar galaxies have no companions within 10 diameters, six outof 10 Seyfert 2 galaxies have one or more companions at projectedseparation distances between 10 and 20 diameters; six out of 12 galaxieswith circumnuclear structures have two or more companions within 20diameters.
| 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.
| Redshift-Distance Survey of Early-Type Galaxies. I. The ENEARc Cluster Sample
This paper presents data on the ENEARc subsample of the larger ENEARsurvey of nearby early-type galaxies. The ENEARc galaxies belong toclusters and were specifically chosen to be used for the construction ofa Dn-σ template. The ENEARc sample includes newmeasurements of spectroscopic and photometric parameters (redshift,velocity dispersion, line index Mg2, and the angular diameterdn), as well as data from the literature. New spectroscopicdata are given for 229 cluster early-type galaxies, and new photometryis presented for 348 objects. Repeat and overlap observations withexternal data sets are used to construct a final merged catalogconsisting of 640 early-type galaxies in 28 clusters. Objectivecriteria, based on catalogs of groups of galaxies derived from completeredshift surveys of the nearby universe, are used to assign galaxies toclusters. In a companion paper, these data are used to construct thetemplate Dn-σ distance relation for early-typegalaxies, which has been used to estimate galaxy distances and derivepeculiar velocities for the ENEAR all-sky sample. Based on observationsat Complejo Astronomico El Leoncito, operated under agreement betweenthe Consejo Nacional de Investigaciones Científicas de laRepública Argentina and the National Universities of La Plata,Córdoba, and San Juan; Cerro Tololo Inter-American Observatory,National Optical Astronomical Observatory, which is operated by theAssociation of Universities for Research in Astronomy, Inc., undercooperative agreement with the National Science Foundation; the EuropeanSouthern Observatory (ESO), partially under the ESO-ON agreement; theFred Lawrence Whipple Observatory; the Observatório do Pico dosDias, operated by the Laboratório Nacional de Astrofísicaand the MDM Observatory at Kitt Peak.
| 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.
| Models for the interpretation of CaT and the blue spectral indices in elliptical nuclei
We present a grid of theoretical models where the calculation ofabsorption line spectral indices in both the blue and red wavelengthranges is done with the same evolutionary synthesis code. We havecomputed some of these indices: CaT, Na i, Mg i in the near infrared andMgb, Mg2, Fe52, Fe53, NaD and Hβ , in the blue-visiblerange, for Single Stellar Population (SSP) of 6 different metallicities,(Z=0.0004, 0.001, 0.004, 0.008, 0.02 and 0.05), and ages from 4 Myr to20 Gyr. From the comparison of these evolutionary synthesis models witha compilation of elliptical galaxy data from the literature, we findthat the observed CaT index follows the blue index ratherthan Mg2 as the models predict. If this implies anover-abundance [Mg/Ca] and we take into account the masses of starswhich produce Mg and Ca, these stars could form in a time scale shorterthan 5 Myr from the beginning of the star formation process.Alternatively, an IMF biased towards very massive stars (M> 40Msun) at the early epoch of star formation in ellipticalnuclei has to be assumed. We also suggest to revise the calculation ofthe nucleosynthesis yield of Magnesium. By using the diagnostic diagramCaT-Hβ to disentangle age and metallicity in such populations, weobtain around solar abundances and a sequence of ages between 4 and 16Gyr for the galaxy sample. Complete set of Table~2 is only available inelectronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr(130.79.128.5) or via http://cdsweb.u-strasbg.fr/Abstract.html
| Stellar populations in dwarf elliptical galaxies.
Not Available
| Fundamental plane distances to early-type field galaxies in the South Equatorial Strip. I. The spectroscopic data
Radial velocities and central velocity dispersions are derived for 238E/S0 galaxies from medium-resolution spectroscopy. New spectroscopicdata have been obtained as part of a study of the Fundamental Planedistances and peculiar motions of early-type galaxies in three selecteddirections of the South Equatorial Strip, undertaken in order toinvestigate the reality of large-scale streaming motion; results of thisstudy have been reported in Müller et al. (1998). The new APM SouthEquatorial Strip Catalog (-17fdg 5 < delta < +2fdg 5) was used toselect the sample of field galaxies in three directions: (1) 15h10 -16h10; (2) 20h30 - 21h50; (3) 00h10 - 01h30. The spectra obtained have amedian S/N per Å of 23, an instrumental resolution (FWHM) of ~ 4Å, and the spectrograph resolution (dispersion) is ~ 100 kms-1. The Fourier cross-correlation method was used to derivethe radial velocities and velocity dispersions. The velocity dispersionshave been corrected for the size of the aperture and for the galaxyeffective radius. Comparisons of the derived radial velocities with datafrom the literature show that our values are accurate to 40 kms-1. A comparison with results from Jo rgensen et al. (1995)shows that the derived central velocity dispersion have an rms scatterof 0.036 in log sigma . There is no offset relative to the velocitydispersions of Davies et al. (1987).
| Colour distributions in E-S0 galaxies . IV. Colour data and dust in E's from Nieto's B, R frames
The B-R colours distributions (with R in Cousins's system) have beenmeasured in 44 E classified galaxies in the Local Supercluster, frompairs of frames collected by Nieto and co-workers in 1989-91. These arenearly all from the CFHT, and of sub-arsec resolution. Great attentionhas been given to the effects of unequal PSF's in the B and R framesupon colour distributions near centre; such effects are illustrated frommodel calculations and from pseudo-colours obtained from pairs of framestaken in the same band but with different seeing conditions. Appropriatecorrections were systematically applied in order to derive centralcolours and inner gradients, although still affected by the limitedresolution of the frames. The radial colour distributions have beenmeasured in more detail than usual, considering separately the nearmajor axis and near minor axis regions of the isophotal contours.Azimuthal colour distributions, in rings limited by selected isophotes,were also obtained. Dust ``patterns", i.e. patches, lanes, arcs, ...,have been detected and mapped from the colour distributions. An ad hocdust pattern importance index (or DPII) in a scale of 0 to 3, has beenintroduced to qualify their size and contrast. We have tried to findevidence of a diffuse dust concentration towards the disk, if one isapparent. Positive results (noted by the dd symbol) have been obtainedfor disky E's, whenever the inclination of their disk to the line ofsight is large enough, and eventually also in the small isolated diskssometimes present in both boxy and disky galaxies. The red central peakoccurring in many E-galaxies might be the signature of a centralconcentration of dust, also in cases where this peak is isolated ratherthan embedded in some extensive colour pattern. The properties of thenear centre colour profiles have been related to a classification ofnuclear photometric profiles into ``flat topped" and ``sharply peaked"(equivalent to ``core-like" and ``power-law" in the terminology ofte[Faber et al. 1997).]{fab97} The published here data include thefollowing: . Short descriptions and codes for the characters of the B-Rdistribution of each object, and comparison to the results of recentsurveys. . A table of the mean B-R at the centre and at two selectedisophotes, a ``core colour gradient" and the usual logarithmic gradient.. Maps of near core B-R isochromes and B isophotes for comparison.Images of the B-R colour distribution are made available in electronicform. Based on observations collected at the Canada-France-HawaiiTelescope and at the Observatoire du Pic du Midi.
| An optical and H I study of NGC 5850 - Victim of a high-speed encounter?
We present optical CCD surface photometry and VLA H I observations ofNGC 5850, one of the largest and brightest barred spirals of the innerring variety in the sky. The broadband images reveal numerousmorphological peculiarities, particularly in the spiral arms. Structuralasymmetries are more obvious in H I, the most pronounced being alarge-scale displacement of gas to the west and northwest of thenucleus. Most of the atomic hydrogen is concentrated in the prominentoptical ring and faint spiral arms, with very low H I surface densitiesin the bulge and interarm regions. The H I surface density drops rapidlyoutside the arms, and we find no evidence for either large-scale tidalfeatures or an extended gas disk above 0.05 M(solar)/sq pc. Overall, theintensity-weighted H I velocity field appears fairly regular, yet stillshows clear deviations from circular rotation that we attribute to awarped oval disk and streaming motions across the arms. Radio continuumemission at 20 cm is dominated by a faint bulge component that peaks atthe optical nucleus. The spiral arms are not detected. The absence ofextended X-ray emission throughout the NGC 5846 group and the closesimilarity between NGC 5850's optical and H I morphologies argue againstram pressure stripping through a dense intergalactic medium as the causeof the galaxy's peculiar morphology. We attribute it instead to ahigh-speed encounter with the massive elliptical galaxy NGC 5846.
| 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
| Color distributions in E-S0 galaxies. III. E-objects with ``power-law'' or ``core-like'' central profiles
Measurements of the central red color peak occurring in E-type galaxieshave been obtained from Nieto's CFHT observations in B and R of 39objects. A careful equalization of the PSF of the two frames involved incolor maps and profiles was crucial in achieving significant results,although still affected by limited resolution. The class of the centrallight profile, i.e. ``core-like'' or ``power-law'', was also derived.The well known correlation between the class of central profile and thelarge scale morphology is somewhat improved. The distributions ofcentral red peak amplitudes are obtained separately for the two classesof central profiles, and shown to be quite different; most objects witha core-like center also have a flat central color profile. The model ofSilva & Wise (1996), for the production of broad cores by centrallylocated diffuse dust, is not supported. This is in agreement with recentHST results by Carollo et al. (1997) from a special subsample of objectswith kinematically decoupled cores. Based on observations collected atthe Canada-France-Haw= aii Telescope and at the Observatoire du Pic duMidi
| Color distributions in E-S0 galaxies. I. Frequency and importance of dust patterns for various brands of E classified galaxies
>From the consideration of a sample of color distributions in 67 Eclassified objects of the Local Supercluster, it is found that localdust features are much more frequent and important in disky E's thanboxy E's. The subclass of undeterminate objects, those which cannot beassigned to the diE or boE groups, is intermediate. Subsets of objectsof common properties are considered from the point of view of local dustfeatures occurrence: giant boxy E's; minor boxy E's with rotationalsupport; compact dwarfs; SB0-like E's. It is noted that the detection ofdust features is more than twice less frequent in Virgo clusterellipticals than in the full sample, but the significance of this resultis not clear. Based on observations collected at theCanada-France-Hawaii Telescope and at the Observatoire du Pic du Midi
| Structural Components of NGC 5850.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1997AJ....114.1413P&db_key=AST
| On the Origin of Globular Clusters in Elliptical and cD Galaxies
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1997AJ....113.1652F&db_key=AST
| Hubble Space Telescope Imaging of the Globular Cluster System Around NGC 5846
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1997AJ....113..887F&db_key=AST
| The fundamental plane of early-type galaxies: non-homology of the spatial structure.
Parametrizing their light distribution with a Sersic profile, we showthat the non-homology in the structure of early-type galaxies has ameasurable incidence on their scaling relations. Indeed, the Sersicexponent (i.e., the shape of the photometric profile) correlates withthe residuals to the Fundamental Plane. This correlation is in excellentagreement with the theoretical expectation for isotropic galaxies.Adding together the contributions of: (i) the stellar population, (ii)the rotational support, and (iii) the non-homology, fully accounts forthe tilt of the Fundamental Plane. This supports the hypothesis of aconstant stellar to dynamical mass ratio in the luminous region ofearly-type galaxies. We confirm the existence of relations between theSersic exponent, n, and the effective radius or the absolute magnitude,and we give indications for a saturation of this index for the bright(M_B_<-20) or large (r_e_>6.3kpc) galaxies at a value compatiblewith the de Vaucouleurs law (n=4).
| Extragalactic Globular Clusters. IV. The Data
We have explored the use of absorption line strength indices, measuredfrom integrated globular cluster spectra, to predict mean metallicity inlate-type stellar systems. In previous papers we identified the bestindices for such metallicity calibrations out of ~13 measured in a largesample of galactic and M31 cluster spectra. In this paper we present theindividual measurements of 13 indices and averages of multiplemeasurements, where appropriate. Data are given for 151 M31 globularclusters, 88 galaxies, 22 M33 cluster candidates, 10 M87 clusters, eightM81 globular clusters, three Fornax dwarf galaxy clusters, "standard"stars from the lists of Faber et al., stars in the open cluster NGC 188and, for completeness, other stars observed as candidate globularclusters.
| Accurate sky Subtraction of Long-Slit Spectra: Velocity Dispersions at Sigma(v) = 24.0 Mag/arcsec^2
We describe an observing strategy for obtaining accurate sky subtractionwhen observing with a long-slit spectrograph. The technique is achopping procedure in which the telescope is sequentially moved fromobject to sky on short time scales (~300 s), but instead of reading outthe CCD detector with each exposure, we repeatedly clock the charge onthe chip in the parallel direction in a manner that produces twocomplete exposures (one object+sky, one sky) on each CCD frame. Thebackground subtraction proceeds naturally by differencing these twoexposures. We show that this method provides superior results to moretraditional sky- subtraction methods that rely on measuring the skybrightness at the ends of the slit. We find that we can reach a V-bandsurface brightness of 24 mag arcsec^2^ in about 8 hours of observingtime on the 2.4-meter Hiltner telescope at the Michigan-Dartmouth-MITObservatory. We present some preliminary results obtained with thismethod for the stellar dynamics in the outer envelopes of threeelliptical galaxies (M87, NGC 5846, and IC 1101). We usecross-correlation and Fourier quotient techniques to derive radialvelocity and velocity dispersion profiles. We confirm that the velocitydispersion in the outer envelope of IC 1101 (the central galaxy in Abell2029) rises with distance from the center of the galaxy, as noted byDressler [APJ. 23,659 (1979)].
| 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 Mg/Fe abundance ratio in the nuclei of elliptical and disk galaxies
Results of a spectral investigation of a sample of 100 nearby galaxiesare used to discover that the Mg/Fe abundance ratios in the stellarpopulation of the nuclei of elliptical and disk galaxies are different.Stars in the nuclei of disk galaxies, from SO to Sc, have a solar Mg/Feratio, while the elliptical ones, on the average, exhibit an Mg/Fe ratiogreater than zero. Implications of this discovery for galaxy formationscenarios are discussed.
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