Contents
Images
Upload your image
DSS Images Other Images
Related articles
Nearby early-type galaxies with ionized gas. I. Line-strength indices of the underlying stellar population
With the aim of building a data-set of spectral properties of wellstudied early-type galaxies showing emission lines, we presentintermediate resolution spectra of 50 galaxies in the nearby Universe.The sample, which covers several of the E and S0 morphologicalsub-classes, is biased toward objects that might be expected to haveongoing and recent star formation, at least in small amounts, because ofthe presence of the emission lines. The emission is expected to comefrom the combination of active galactic nuclei and star formationregions within the galaxies. Sample galaxies are located in environmentscorresponding to a broad range of local galaxy densities, althoughpredominantly in low density environments. Our long-slit spectra coverthe 3700-7250 Å wavelength range with a spectral resolution of≈7.6 Å at 5550 Å. The specific aim of this paper, and ourfirst step in the investigation, is to map the underlying galaxy stellarpopulation by measuring, along the slit positioned along the galaxymajor axis, line-strength indices at several, homogeneousgalacto-centric distances. For each object we extracted 7luminosity-weighted apertures (with radii 1.5´´,2.5´´, 10´´, r_e/10, r_e/8, r_e/4 and r_e/2)corrected for the galaxy ellipticity and 4 gradients (0 ≤ r ≤r_e/16, r_e/16 ≤ r ≤ r_e/8, r_e/8 ≤ r ≤ r_e/4 and r_e/4≤ r ≤ r_e/2). For each aperture and gradient we measured 25line-strength indices: 21 of the set defined by the Lick-IDS“standard” system (Trager et al. [CITE], ApJS, 116, 1) and 4introduced by Worthey & Ottaviani ([CITE], ApJS, 111, 377).Line-strength indices have been transformed to the Lick-IDS system.Indices derived then include Hβ, Mg1, Mg2, Mgb, MgFe, Fe5270,Fe5335 commonly used in classic index-index diagrams. The paperintroduces the sample, presents the observations, describes the datareduction procedures, the extraction of apertures and gradients, thedetermination and correction of the line-strength indices, the procedureadopted to transform them into the Lick-IDS System and the proceduresadopted for the emission correction. We finally discuss the comparisonsbetween our dataset and line-strength indices available in theliterature. A significant fraction, about 60%, of galaxies in thepresent sample has one previous measurement in the Lick-IDS system butbasically restricted within the r_e/8 region. Line-strength measuresobtained both from apertures and gradients outside this area and withinthe r_e/8 region, with the present radial mapping, are completely new.Full appendix and Figs. 8 to 13 are only available in electronic form athttp://www.edpsciences.org Full Tables 6, 7, 9 and 10 are only availableat the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) orvia http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/433/497 Based onobservations obtained at the European Southern Observatory, La Silla,Chile (Programs Nr. 60.A-0647 and 61.A-0406).
| Cold Dust in Early-Type Galaxies. I. Observations
We describe far-infrared observations of early-type galaxies selectedfrom the Infrared Space Observatory (ISO) archive. This ratherinhomogeneous sample includes 39 giant elliptical galaxies and 14 S0 (orlater) galaxies. These galaxies were observed with the array photometerPHOT on-board the ISO satellite using a variety of different observingmodes-sparse maps, mini-maps, oversampled maps, and singlepointings-each of which requires different and often rather elaboratephotometric reduction procedures. The ISO background data agree wellwith the COBE-DIRBE results to which we have renormalized ourcalibrations. As a further check, the ISO fluxes from galaxies at 60 and100 μm agree very well with those previously observed with IRAS atthese wavelengths. The spatial resolution of ISO is several timesgreater than that of IRAS, and the ISO observations extend out to 200μm, which views a significantly greater mass of colder dust notassessable to IRAS. Most of the galaxies are essentially point sourcesat ISO resolution, but a few are clearly extended at FIR wavelengthswith image sizes that increase with FIR wavelength. The integratedfar-infrared luminosities do not correlate with optical luminosities,suggesting that the dust may have an external, merger-related origin. Ingeneral, the far-infrared spectral energy distributions can be modeledwith dust at two temperatures, ~43 and ~20 K, which probably representlimits of a continuous range of temperatures. The colder dust componentdominates the total mass of dust, 106-107Msolar, which is typically more than 10 times larger than thedust masses previously estimated for the same galaxies using IRASobservations. For S0 galaxies we find that the optically normalizedfar-infrared luminosity LFIR/LB correlatesstrongly with the mid-infrared luminosityL15μm/LB, but that correlation is weaker forelliptical galaxies.Based on observations with ISO, an ESA project with instruments fundedby ESA Member States (especially the PI countries: France, Germany, theNetherlands, and United Kingdom) and with the participation of ISAS andNASA.
| ATCA HI observations of the peculiar galaxy IC 2554
ATCA HI and radio continuum observations of the peculiar southern galaxyIC 2554 and its surroundings reveal typical signatures of an interactinggalaxy group. We detected a large HI cloud between IC 2554 and theelliptical galaxy NGC 3136B. The gas dynamics in IC 2554 itself, whichis sometimes described as a colliding pair, are surprisingly regular,whereas NGC 3136B was not detected. The HI cloud, which emerges from IC2554 as a large arc-shaped plume, has a size of ~30 kpc, larger thanthat of IC 2554. The total HI mass of the IC 2554 system is ~2 ×109 Msolar, one-third of which resides in the HIcloud. It is possible that tidal interaction between IC 2554 and NGC3136B caused this spectacular HI cloud, but the possibility of IC 2554being a merger remnant is also discussed. We also detected HI gas in thenearby galaxies ESO 092-G009 and RKK 1959 and an associated HI cloud,ATCA J1006-6710. Together they have an HI mass of ~4.6 ×108 Msolar. Another new HI source, ATCAJ1007-6659, with an HI mass of only ~2.2 × 107Msolar was detected roughly between IC 2554 and ESO 092-G009and corresponds to a face-on low surface brightness dwarf galaxy. Starformation is evident only in the galaxy IC 2554 with a rate of ~4Msolar yr-1.
| 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.
| 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.
| Parkes H I observations of galaxies behind the southern Milky Way. I. The Hydra/Antlia region (l~ 266o to 296o)
As part of our program to map the large-scale distribution of galaxiesbehind the Milky Way, we used the Parkes 210 ft (64 m) radio telescopefor pointed \normalsize H \footnotesize I observations of a sample oflow surface-brightness (due to heavy obscuration) spiral galaxiesselected from the deep optical Zone of Avoidance (ZOA) galaxy catalog inthe Hydra/Antlia region (Kraan-Korteweg \cite{Kraan-2000a}). Searching asimultaneous velocity range of either 300 to 5500 km s-1 or300 to 10 500 km s-1 to an rms level of typically 2-4 m Jyresulted in detections in 61 of the 139 pointings, leading to a total of66 detections (an additional detection was made in a reference position,and two other pointings revealed two and four independent signalsrespectively). Except for 2 strong \normalsize H \footnotesize Iemitters identified in the shallow Zone of Avoidance \normalsize H\footnotesize I survey (Henning et al. \cite{Henning}), all \normalsizeH \footnotesize I detections are new. An analysis of the properties ofthe observed and detected galaxies prove that pointed \normalsize H\footnotesize I observations of highly obscured galaxies allow thetracing of a population of nearby, intrinsically large and bright spiralgalaxies that otherwise would not be recovered. The new data identifieda previously unrecognized nearby group at l ~ 287. o5, b ~-9. o5, V ~ 1700 km s-1, the continuation of theHydra/Antlia filament on the opposite side of the Galactic plane, andhelped to delimit a distinct void in the ZOA centered at 2000 kms-1. Tables 1 and 2 are also available in electronic form atthe CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/391/887
| Serendipitous detection of galaxies behind the Milky Way from the DENIS survey
A search has been undertaken at Lyon Observatory to identify, by eye,galaxy candidates at galactic latitudes lower than +/-15 degrees on theDENIS J and K-band images. This paper presents a list of 2028 objectsthat were serendipitously detected throughout the DENIS survey.Cross-identification with galaxy entries in the LEDA Database has beenperformed. Comparison with the second release of the 2MASS survey led toa satisfactory agreement of J band magnitudes (std. dev. = 0.3 mag). Thedistribution of galaxy candidates along the Galactic Plane shows aconcentration near the galactic longitude l=305 deg . As a by product ofthis inspection of J and K images some interesting galactic objects werefound (star clusters and nebulae). Based on observations collected atthe European Southern Observatory, La Silla, Chile. The catalog (Table1) is only available in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.188.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/387/1
| 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.
| A synthesis of data from fundamental plane and surface brightness fluctuation surveys
We perform a series of comparisons between distance-independentphotometric and spectroscopic properties used in the surface brightnessfluctuation (SBF) and fundamental plane (FP) methods of early-typegalaxy distance estimation. The data are taken from two recent surveys:the SBF Survey of Galaxy Distances and the Streaming Motions of AbellClusters (SMAC) FP survey. We derive a relation between(V-I)0 colour and Mg2 index using nearly 200galaxies and discuss implications for Galactic extinction estimates andearly-type galaxy stellar populations. We find that the reddenings fromSchlegel et al. for galaxies with E(B-V)>~0.2mag appear to beoverestimated by 5-10 per cent, but we do not find significant evidencefor large-scale dipole errors in the extinction map. In comparison withstellar population models having solar elemental abundance ratios, thegalaxies in our sample are generally too blue at a given Mg2;we ascribe this to the well-known enhancement of the α-elements inluminous early-type galaxies. We confirm a tight relation betweenstellar velocity dispersion σ and the SBF `fluctuation count'parameter N, which is a luminosity-weighted measure of the total numberof stars in a galaxy. The correlation between N and σ is eventighter than that between Mg2 and σ. Finally, we deriveFP photometric parameters for 280 galaxies from the SBF survey data set.Comparisons with external sources allow us to estimate the errors onthese parameters and derive the correction necessary to bring them on tothe SMAC system. The data are used in a forthcoming paper, whichcompares the distances derived from the FP and SBF methods.
| The SBF Survey of Galaxy Distances. IV. SBF Magnitudes, Colors, and Distances
We report data for I-band surface brightness fluctuation (SBF)magnitudes, (V-I) colors, and distance moduli for 300 galaxies. Thesurvey contains E, S0, and early-type spiral galaxies in the proportionsof 49:42:9 and is essentially complete for E galaxies to Hubblevelocities of 2000 km s-1, with a substantial sampling of Egalaxies out to 4000 km s-1. The median error in distancemodulus is 0.22 mag. We also present two new results from the survey.(1) We compare the mean peculiar flow velocity (bulk flow) implied byour distances with predictions of typical cold dark matter transferfunctions as a function of scale, and we find very good agreement withcold, dark matter cosmologies if the transfer function scale parameterΓ and the power spectrum normalization σ8 arerelated by σ8Γ-0.5~2+/-0.5. Deriveddirectly from velocities, this result is independent of the distributionof galaxies or models for biasing. This modest bulk flow contradictsreports of large-scale, large-amplitude flows in the ~200 Mpc diametervolume surrounding our survey volume. (2) We present adistance-independent measure of absolute galaxy luminosity, N and showhow it correlates with galaxy properties such as color and velocitydispersion, demonstrating its utility for measuring galaxy distancesthrough large and unknown extinction. Observations in part from theMichigan-Dartmouth-MIT (MDM) Observatory.
| The Ratio of α-Elements to Iron in Early-Type Galaxies from TIO and MG2
In order to derive the ratio of α-elements to iron in galaxies, wehave observed the strongest TiO band heads of the γ and γ'systems at 7000-7500 Å in a sample of a dozen early-type galaxies.The equivalent widths of the TiO bands are compared with syntheticspectra for single-aged stellar populations and composite galaxy models,all computed with [α/Fe]=0.0 and +0.3. The same method is alsoapplied to the and Mg2 Lick indices for the samplegalaxies. The results obtained are [Ti/Fe]~[Mg/Fe]~+0.3, indicating aclear enhancement of the α-elements-to-iron ratio for our sampleof early-type galaxies. Based on observations in the Observatóriodo Pico dos Dias, operated by the Laboratório Nacional deAstrofísica/CNPq/MCT, Brazil.
| 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
| A catalog of galaxies behind the Southern Milky Way . I. The Hydra/Antlia extension (l~ 266or - 296or)
A deep optical galaxy search in the southern Milky Way - aimed atreducing the width of the Zone of Avoidance - revealed 3279 galaxycandidates above the diameter limit of D >~ 0.2', of which only 112(3.4%) were previously catalogued. The surveyed region (266o<~ \ell <~ 296o and -10o <~ b <~+8o) lies in the extension of the Hydra and Antlia clusters -where a supercluster is suspected - and in the approximate direction ofthe dipole anisotropy in the Cosmic Microwave Background radiation. Herewe present the optical properties of the unveiled galaxies such aspositions, diameters, magnitudes, morphological types, including adetailed discussion on the quality of these data and the completenesslimits as a function of the foreground dust extinction. For 127 of the227 positional matches in the IRAS PSC, a reliable cross-identificationcould be found. Several distinct overdensities and filaments of galaxiescan be identified that are apparently uncorrelated with the Galacticforeground extinction hence the probable signature of extragalacticlarge-scale structures. This catalog constitutes the first part in aseries of five equally conducted optical searches for galaxies in thesouthern Milky Way (245o <~ \ell <~ 350o).With these surveys, the entire Zone of Avoidance will have been coveredby means of visual inspection. The catalogs build the basis for variousspectroscopic and photometric follow-up programs which eventually willallow a thorough analyse of the galaxy distribution in redshift spaceand the peculiar velocity fields within the Zone of Avoidance, as wellan an improved understanding of the Galactic foreground extinction.Tables 1 and 2 are available in electronic form at the CDS via anonymousftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| 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.
| Far-Infrared Emission from E and E/S0 Galaxies
Early-type galaxies are filled with hot X-ray-emitting gas, but thestudy of the less plentiful cold gaseous component has been morechallenging. Studies of cold material through IRAS 60 and 100 mu mobservations indicated that half of ordinary E and E/S0 galaxies weredetected above the 3 sigma level, indicating that cold gas is common,although no correlation was found between the optical and far-infraredfluxes. Most detections were near the instrumental threshold, and givenan improved understanding of detection confidence, we reconsider the 60and 100 mu m detection rate. After excluding active galactic nuclei,peculiar systems, and background contamination, only 15 nonpeculiar Eand E/S0 galaxies from the RSA catalog are detected above the 98%confidence level, about 12% of the sample. An unusually high percentageof these 15 galaxies possess cold gas (H I CO) and optical emissionlines (H alpha ), supporting the presence of gas cooler than 104 K. The60-100 mu m flux ratios imply a median dust temperature for the sampleof 30 K, with a range of 23-28 K. These detections define the upperenvelope of the optical to far-infrared relationship,F_{{fir}}~F^{0.24+/-0.08}B , showing that optically brightobjects are also brighter in the infrared, although with considerabledispersion. A luminosity correlation is present wthL_{{fir}}~L^{1.65+/-0.28}B , but the dust temperature isuncorrelated with luminosity. The dust masses inferred from thefar-infrared measurements are 1 order of magnitude greater than thosefrom extinction observations, except for the recent merger candidate NGC4125, where they are equal. We suggest that the ratio of thefar-infrared dust mass to the extinction dust mass may be an indicatorof the time since the last spiral-spiral merger. These results arecompared to the model in which most of the dust comes from stellar massloss and the heating is primarily by stellar photons. Models thatcontain large dust grains composed of amorphous carbon plus silicatescome close to reproducing the typical 60-100 mu m flux ratios, thefar-infrared luminosity, and the Lfir-LB relationship.
| 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. 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
| 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.
| Evidence for diffusely distributed dust in elliptical galaxies and its effect on radial colour gradients.
Not Available
| 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.
| Total and effective colors of 501 galaxies in the Cousins VRI photometric system
Total color indices (V-R)T, (V-I)T and effectivecolor indices (V-R)e, (V-I)e in the Cousins VRIphotometric system are presented for 501 mostly normal galaxies. Thecolors are computed using a procedure outlined in the Third ReferenceCatalogue of Bright Galaxies (RC3) whereby standard color curvesapproximated by Laplace-Gauss integrals are fitted to observedphotoelectric multiaperture photometry. 11 sources of such photometrywere used for our analysis, each source being assigned an appropriateweight according to a rigorous analysis of residuals of the data fromthe best-fitting standard color curves. Together with the integrated B-Vand U-B colors provided in RC3, our analysis widens the range ofwavelength of homogeneously defined colors of normal galaxies of allHubble types. We present color-color and color-type relations that canbe modeled to understand the star formation history of galaxies.
| Interstellar matter in Shapley-Ames elliptical galaxies. IV. A diffusely distributed component of dust and its effect on colour gradients.
We have investigated IRAS far-infrared observations of a complete, bluemagnitude limited sample of 56 elliptical galaxies selected from theRevised Shapley-Ames Catalog. Data from a homogeneous optical CCDimaging survey as well as published X-ray data from the EINSTEINsatellite are used to constrain the infrared data. Dust masses asdetermined from the IRAS flux densities are found to be roughly an orderof magnitude higher than those determined from optical extinction valuesof dust lanes and patches, in strong contrast with the situation inspiral galaxies. This "mass discrepancy" is found to be independent ofthe (apparent) inclination of the dust lanes. To resolve this dilemma wepostulate that the majority of the dust in elliptical galaxies exists asa diffusely distributed component of dust which is undetectable atoptical wavelengths. Using observed radial optical surface brightnessprofiles, we have systematically investigated possible heatingmechanisms for the dust within elliptical galaxies. We find that heatingof the dust in elliptical galaxies by the interstellar radiation fieldis generally sufficient to account for the dust temperatures asindicated by the IRAS flux densities. Collisions of dust grains with hotelectrons in elliptical galaxies which are embedded in a hot,X-ray-emitting gas is found to be another effective heating mechanismfor the dust. Employing model calculations which involve the transfer ofstellar radiation in a spherical distribution of stars mixed with adiffuse distribution of dust, we show that the observed infraredluminosities imply total dust optical depths of the postulated diffuselydistributed dust component in the range 0.1<~τ_V_<~0.7 andradial colour gradients 0.03<~{DELTA}(B-I)/{DELTA}log r<~0.25. Theobserved IRAS flux densities can be reproduced within the 1σuncertainties in virtually all ellipticals in this sample by this newlypostulated dust component, diffusely distributed over the inner few kpcof the galaxies, and heated by optical photons and/or hot electrons. Theradial colour gradients implied by the diffuse dust component are foundto be smaller than or equal to the observed colour gradients. Thus, weargue that the effect of dust extinction should be taken seriously inthe interpretation of colour gradients in elliptical galaxies. We showthat the amount of dust observed in luminous elliptical galaxies isgenerally higher than that expected from production by mass loss ofstars within elliptical galaxies and destruction by sputtering in hotgas. This suggests that most of the dust in elliptical galaxiesgenerally has an external origin.
| Interstellar Matter in Elliptical Galaxies - Part Three - Properties of Dust Extinction
We have used multicolour CCD surface photometry of 10 ellipticalgalaxies with large-scale dust lanes or rings to investigate thewavelength dependence of the dust extinction. In general, the extinctioncurves are found to run parallel to the Galactic curve of Rieke &Lebofsky. The ratio of total to selective extinction R_V_ is found torange between 2.1 and 3.3, and is lower on average than the canonicalGalactic value of 3.1, implying that the `large' dust grains - which areresponsible for the extinction of optical light - are generally smallerthan in our Galaxy. We show that systematic effects concerning thelocation of the dust within the galaxy body, which may modify theobserved extinction curves, do not change this conclusion. We haveestimated the dust content of the lanes directly from total extinctionvalues (e.g., A_V_), using the observed grain sizes. Extinctionefficiencies of refractory grains and a grain size distribution aretaken from the literature. The dust masses calculated using the totalextinction values turn out to be up to 35 per cent lower than thosecalculated using the Galactic ratio of neutral hydrogen column densityto E(B - V) colour excess, showing that the effect of smaller `large'grain sizes on the total dust mass is significant. We find that thegalaxies with R_V_ values (and, hence, characteristic grain sizes) thatare smaller than in our Galaxy have smooth, regularly distributed dustlanes, whereas the dust in galaxies with `normal' grain sizes istypically much more irregularly distributed, e.g., in patches. Assumingthat the dust in these galaxies has an external origin, this suggeststhat the observed characteristic dust grain size is determined by thetime elapsed since the dust lane was accreted from outside. Followingthe current theoretical model calculations of formation time-scales ofregular dust lanes and rings in early-type galaxies, we predict thatelliptical galaxies containing regular dust lanes with typical dustmasses of 10^6^ - 10^7^ M_sun_ do not contain hot, X-ray- emitting gas.
| Photometrically distinct nuclei in elliptical and early-type disks galaxies.
Not Available
| Interstellar matter in Shapley-Ames elliptical galaxies. II. The distribution of dust and ionized gas
We present results of deep optical CCD imaging for a complete, opticalmagnitude-limited sample of 56 elliptical galaxies from the RSA catalog.For each galaxy we have obtained broad-band images (in B, V, and I) andnarrow-band images using interference filters isolating theHα+[NII] emission lines to derive the amount and morphology ofdust and ionized gas. Detailed consideration of systematic errors due toeffects of sky background subtraction and removal of stellar continuumlight from the narrow-band images is described. The flux calibration ofthe narrow-band images is performed by deconvolving actually measuredspectral energy distributions with the filter transmission curves. Wealso present optical long-slit spectroscopy to determine the[NII]/Hα intensity ratio of the ionized gas. Dust lanes and/orpatches have been detected in 23 galaxies (41%) from this sample usingboth colour-index images and division by purely elliptical model images.We achieved a detection limit for dust absorption of A_B_~0.02.Accounting for selection effects, the true fraction of ellipticalgalaxies containing dust is estimated to be of order 80%. This detectionrate is comparable to that of the IRAS satellite, and significantlylarger than results of previous optical studies. Ionized gas has beendetected in 32 galaxies (57%). The spectroscopic data confirm thepresence and distribution of ionized gas as seen in the direct imaging.All elliptical galaxies in our sample in which a number of emissionlines is detected show very similar emission-line intensity ratios,which are typical of LINER nuclei. The amounts of detectable dust andionized gas are generally small--of order 10^4^-10^5^Msun_ ofdust and 10^3^-10^4^Msun_ of ionized gas. The dust andionized gas show a wide variety of distributions-extended along eitherthe apparent major axis, or the minor axis, or a skewed axis, indicatingthat triaxiality is in general required as a galaxy figure. In somecases (NGC 1275, NGC 2325, NGC 3136, NGC 3962, NGC 4696, NGC 5018, NGC5044, NGC 5813, IC 1459) the interstellar matter has a patchy orfilamentary distribution, suggestive of a recent interaction event. Thedistributions of dust and ionized gas are consistent with beingphysically associated with each other.
| Interstellar matter in Shapley-Ames elliptical galaxies. I. Multicolour CCD surface photometry
We present accurate CCD surface photometry in Johnson B and V andCousins I for a complete, magnitude-limited sample of 56 ellipticalgalaxies from the RSA catalog. For each galaxy we have determined radialprofiles of surface brightness, B-V and/or B-I colour index,ellipticity, position angle, and the third- and fourth order Fouriercoefficients that describe the deviations of the B, V, and I isophotesfrom perfect ellipses, using a full two-dimensional fitting technique.The present sample contains 13 galaxies for which no previous isophoteanalysis has been published, and 26 without published colour gradients.The radial profiles of the ellipticity, position angle, and the third-and fourth-order Fourier coefficients are found to show considerabledetail. The profiles are mostly similar in all passbands, except incases where dust lanes or patches are present. In this respect, thehigher-order Fourier coefficients turn out to be sensitive diagnostictools for the presence of dust in elliptical galaxies. Isophotaldeviations from ellipses on the level of 0.5-1% are found to be commonin elliptical galaxies. As noted before by others, these deviations aredue to structures that do not necessarily align with the apparent majoror minor axes of the galaxies, advocating the use of both the cosine andsine higher-order terms in correlation studies. We show that fittingouter radial intensity profiles of elliptical galaxies is an excellenttool for determining the sky background for the surface photometry. Thesky values determined from a power-law fit to the outer intensityprofiles are found to be within 0.1% of the sky values at the corners ofpresent-day large CCDs where the contribution of galaxy light isnegligible. The average colour gradients for the sample galaxies in B-Vand B-I are 0.06 and 0.14 mag arcsec^-2^ per decade in radius,respectively. This compares well with colour gradients in ellipticalgalaxies found by others. The small uncertainty introduced by the skybackground determination method applied here results in an averageinternal uncertainty of only ~ 0.01 mag for our colour gradients, whichis significantly better than the results of previous studies. Theprofiles are compared extensively with results from other authors whenavailable. The result is encouraging, especially for the ellipticity andposition angle where we find mean RMS differences of 0.01 and 1.8deg ,respectively. The surface brightness profiles generally agree to within+/- 0.0.5mag.
| UBVRI photoelectric photometry of bright southern early-type galaxies
UBVRI multi-aperture photometry of 207 bright southern galaxies and of72 objects of an additional list is presented. These observations weremade for obtaining the magnitude scale zero-point as an accuratedetermination of the sky background for a two-dimensional photometryprogram concerning these galaxies. We have also inferred the asymptoticmagnitudes, color indices and effective apertures of these objects. Ourresults are in good agreement with those of others authors.
|
Submit a new article
Related links
Submit a new link
Member of following groups:
|
Observation and Astrometry data
Catalogs and designations:
|
