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Star Formation Histories of Early-Type Galaxies. I. Higher Order Balmer Lines as Age Indicators
We have obtained blue integrated spectra of 175 nearby early-typegalaxies, covering a wide range in galaxy velocity dispersion andemphasizing those with σ<100 km s-1. Galaxies havebeen observed both in the Virgo Cluster and in lower densityenvironments. The main goals are the evaluation of higher order Balmerlines as age indicators and differences in stellar populations as afunction of mass, environment, and morphology. In this first paper, ouremphasis is on presenting the methods used to characterize the behaviorof the Balmer lines through evolutionary population synthesis models.Lower σ galaxies exhibit a substantially greater intrinsicscatter, in a variety of line-strength indicators, than do higherσ galaxies, with the large intrinsic scatter setting in below aσ of 100 km s-1. Moreover, a greater contrast inscatter is present in the Balmer lines than in the lines of metalfeatures. Evolutionary synthesis modeling of the observed spectralindexes indicates that the strong Balmer lines found primarily among thelow-σ galaxies are caused by young age, rather than by lowmetallicity. Thus we find a trend between the population age and thecentral velocity dispersion, such that low-σ galaxies have youngerluminosity-weighted mean ages. We have repeated this analysis usingseveral different Balmer lines and find consistent results from onespectral indicator to another.
| Spectroscopy of Low Surface Brightness Galaxies with the Hobby-Eberly Telescope
We have obtained low-resolution spectra of 19 red and blue low surfacebrightness (LSB) galaxies, using the Marcario Low-ResolutionSpectrograph on the 9.2 m Hobby-Eberly Telescope. These galaxies form avery heterogeneous class, whose spectra qualitatively resemble those ofhigh surface brightness galaxies covering the full range of spectra seenin galaxies of Hubble types from E to Irr. We use a combination ofemission-line (EW(Hα), [N II] λ6584/Hα) andabsorption-line (Mg b, Hβ, ) based diagnostics toinvestigate the star formation and chemical enrichment histories ofthese galaxies. These are diverse, with some galaxies having lowmetallicity and very young mean stellar ages and other galaxies showingold, supersolar-metallicity stellar populations. In contrast with someprevious studies, which found a strong trend of decreasing metallicitywith decreasing central surface brightness, we find a population ofgalaxies with low surface brightness and near-solar metallicity.Correlations between several of the gas-phase and stellar population ageand metallicity indicators are used to place constraints on plausibleevolutionary scenarios for LSB galaxies. The redshift range spanned bythese galaxies is broad, with radial velocities from 3400 kms-1 to more than 65,000 km s-1. A subset of thesample galaxies have published H I redshifts and gas masses based onobservations with the Arecibo 305 m single-dish radio telescope, whichplace these galaxies far off of the mean Tully-Fisher relation. Our newoptical redshifts do not agree with the published H I redshifts forthese galaxies. Most of the discrepancies can be explained by beamconfusion in the Arecibo observations, causing erroneous H I detectionsfor some of the galaxies.
| A new catalogue of ISM content of normal galaxies
We have compiled a catalogue of the gas content for a sample of 1916galaxies, considered to be a fair representation of ``normality''. Thedefinition of a ``normal'' galaxy adopted in this work implies that wehave purposely excluded from the catalogue galaxies having distortedmorphology (such as interaction bridges, tails or lopsidedness) and/orany signature of peculiar kinematics (such as polar rings,counterrotating disks or other decoupled components). In contrast, wehave included systems hosting active galactic nuclei (AGN) in thecatalogue. This catalogue revises previous compendia on the ISM contentof galaxies published by \citet{bregman} and \citet{casoli}, andcompiles data available in the literature from several small samples ofgalaxies. Masses for warm dust, atomic and molecular gas, as well asX-ray luminosities have been converted to a uniform distance scale takenfrom the Catalogue of Principal Galaxies (PGC). We have used twodifferent normalization factors to explore the variation of the gascontent along the Hubble sequence: the blue luminosity (LB)and the square of linear diameter (D225). Ourcatalogue significantly improves the statistics of previous referencecatalogues and can be used in future studies to define a template ISMcontent for ``normal'' galaxies along the Hubble sequence. The cataloguecan be accessed on-line and is also available at the Centre desDonnées Stellaires (CDS).The catalogue is available in electronic form athttp://dipastro.pd.astro.it/galletta/ismcat and at the CDS via anonymousftp to\ cdsarc.u-strasbg.fr (130.79.128.5) or via\http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/405/5
| New UBVRI color distributions in E-type galaxies. II. Central and mean metallicities color distributions in E-type galaxies. II.
Central and mean metallicities are calculated for a sample of 40early-type galaxies, whose color gradients were reported in a previouspaper (Idiart et al. \cite{Idiart2002}). The present color-metallicitycalibration was derived from a grid of evolutionary models which fit thecolor-magnitude sequence of ellipticals in Coma and Virgo clusters. Themean metallicity gradient derived from our data is (Delta [Fe/H]/Deltalog r) = -0.26 +/- 0.08 and the mean sample average metallicity is<[Fe/H]> = 0.01 +/- 0.11 (rmsd). Central and mean metallicitiesare correlated with the central velocity dispersion, consistent with theinterpretation by metallicity variations of the color-magnitude sequenceand of color gradients. Age effects are also discussed, in particularconcerning the interpretation of the Hβ line strength in thoseobjects.Based partially on data collected at the Observatory of Haute-Provence.}
| Bar Galaxies and Their Environments
The prints of the Palomar Sky Survey, luminosity classifications, andradial velocities were used to assign all northern Shapley-Ames galaxiesto either (1) field, (2) group, or (3) cluster environments. Thisinformation for 930 galaxies shows no evidence for a dependence of barfrequency on galaxy environment. This suggests that the formation of abar in a disk galaxy is mainly determined by the properties of theparent galaxy, rather than by the characteristics of its environment.
| The UZC-SSRS2 Group Catalog
We apply a friends-of-friends algorithm to the combined Updated ZwickyCatalog and Southern Sky Redshift Survey to construct a catalog of 1168groups of galaxies; 411 of these groups have five or more members withinthe redshift survey. The group catalog covers 4.69 sr, and all groupsexceed the number density contrast threshold, δρ/ρ=80. Wedemonstrate that the groups catalog is homogeneous across the twounderlying redshift surveys; the catalog of groups and their membersthus provides a basis for other statistical studies of the large-scaledistribution of groups and their physical properties. The medianphysical properties of the groups are similar to those for groupsderived from independent surveys, including the ESO Key Programme andthe Las Campanas Redshift Survey. We include tables of groups and theirmembers.
| Compact groups in the UZC galaxy sample
Applying an automatic neighbour search algorithm to the 3D UZC galaxycatalogue (Falco et al. \cite{Falco}) we have identified 291 compactgroups (CGs) with radial velocity between 1000 and 10 000 kms-1. The sample is analysed to investigate whether Tripletsdisplay kinematical and morphological characteristics similar to higherorder CGs (Multiplets). It is found that Triplets constitute lowvelocity dispersion structures, have a gas-rich galaxy population andare typically retrieved in sparse environments. Conversely Multipletsshow higher velocity dispersion, include few gas-rich members and aregenerally embedded structures. Evidence hence emerges indicating thatTriplets and Multiplets, though sharing a common scale, correspond todifferent galaxy systems. Triplets are typically field structures whilstMultiplets are mainly subclumps (either temporarily projected orcollapsing) within larger structures. Simulations show that selectioneffects can only partially account for differences, but significantcontamination of Triplets by field galaxy interlopers could eventuallyinduce the observed dependences on multiplicity. Tables 1 and 2 are onlyavailable in electronic at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.125.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/391/35
| New UBVRI colour distributions in E-type galaxies . I. The data
New colour distributions have been derived from wide field UBVRI framesfor 36 northern bright elliptical galaxies and a few lenticulars. Theclassical linear representations of colours against log r were derived,with some improvements in the accuracy of the zero point colours and ofthe gradients. The radial range of significant measurements was enlargedboth towards the galaxy center and towards the outskirts of each object.Thus, the ``central colours'', integrated within a radius of 3\arcsec,and the ``outermost colours'' averaged near the muV =24surface brightness could also be obtained. Some typical deviations ofcolour profiles from linearity are described. Colour-colour relations ofinterest are presented. Very tight correlations are found between theU-V colour and the Mg2 line-index, measured either at theGalaxian center or at the effective radius. Based in part onobservations collected at the Observatoire de Haute-Provence. Tables9-11 plus detailed tables for each object are available in electronicform at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5)or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/383/30
| Deep-Imaging Observations of a Candidate of an Absorbed QSO at z=0.653, AX J131831+3341
The results of deep-imaging observations of a candidate of an absorbedQSO at z=0.653, AX J131831+3341, are presented. AX J131831+3341 wasfound during the course of optical follow-up observations of the ASCALarge Sky Survey, and has an X-ray luminosity of 1045 ergs-1 (2-10 keV), which corresponds to those of QSOs. Itsoptical spectrum shows no significant broad Hβ emission line,suggesting that the object is an absorbed QSO. Deep R and V band imagesreveal the presence of a point-like nucleus and an asymmetric extendedcomponent. The nuclear component has a blue color, and the opticalmagnitude is much fainter than that expected from the observed X-rayflux for typical type-1 AGNs. These photometric properties and thepresence of broad Mg II 2800 { Angstroms} emission can be explainedsimultaneously if the observed nuclear light is dominated by scatterednuclear light, though there is a possibility that the nuclear componentis a slightly absorbed nucleus if its intrinsic X-ray to optical fluxratio is the largest among X-ray selected AGNs. The size of the extendedcomponent, which is thought to be the host galaxy of the QSO, is largerthan those of normal disk galaxies at z=0-0.75, and the absolutemagnitude is similar to those of the brightest host galaxies of QSOs atredshifts smaller than 0.5. The V-R and R-I colors of the component areconsistent with a 1 Gyr-old stellar population model without absorption.
| 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.
| A Test for Large-Scale Systematic Errors in Maps of Galactic Reddening
Accurate maps of Galactic reddening are important for a number ofapplications, such as mapping the peculiar velocity field in the nearbyuniverse. Of particular concern are systematic errors which vary slowlyas a function of position on the sky, as these would induce spuriousbulk flow. We have compared the reddenings of Burstein & Heiles (BH)and those of Schlegel, Finkbeiner, & Davis (SFD) to independentestimates of the reddening, for Galactic latitudes |b|>10^deg. Ourprimary source of Galactic reddening estimates comes from comparing thedifference between the observed B-V colors of early-type galaxies, andthe predicted B-V color determined from the B-V-Mg_2 relation. We havefitted a dipole to the residuals in order to look for large-scalesystematic deviations. There is marginal evidence for a dipolar residualin the comparison between the SFD maps and the observed early-typegalaxy reddenings. If this is due to an error in the SFD maps, then itcan be corrected with a small (13%) multiplicative dipole term. Weargue, however, that this difference is more likely to be due to a small(0.01 mag) systematic error in the measured B-V colors of the early-typegalaxies. This interpretation is supported by a smaller, independentdata set (globular cluster and RR Lyrae stars), which yields a resultinconsistent with the early-type galaxy residual dipole. BH reddeningsare found to have no significant systematic residuals, apart from theknown problem in the region 230^deg
| Arcsecond Positions of UGC Galaxies
We present accurate B1950 and J2000 positions for all confirmed galaxiesin the Uppsala General Catalog (UGC). The positions were measuredvisually from Digitized Sky Survey images with rms uncertaintiesσ<=[(1.2")2+(θ/100)2]1/2,where θ is the major-axis diameter. We compared each galaxymeasured with the original UGC description to ensure high reliability.The full position list is available in the electronic version only.
| The Mass-to-Light Ratio of Binary Galaxies
We report on the mass-to-light ratio determination based on a newlyselected binary galaxy sample, which includes a large number of pairswhose separations exceed a few hundred kpc. The probabilitydistributions of the projected separation and the velocity differencehave been calculated considering the contamination of optical pairs, andthe mass-to-light (M/L) ratio has been determined based on the maximumlikelihood method. The best estimate of the M/L in the B band for 57pairs is found to be 28-36 depending on the orbital parameters and thedistribution of optical pairs (solar unit: H_0=50 km s^-1 Mpc^-1). Thebest estimate of the M/L for 30 pure spiral pairs is found to be 12-16.These results are relatively smaller than those obtained in previousstudies but are consistent with each other within the errors. Althoughthe number of pairs with large separation is significantly increasedcompared with previous samples, the M/L does not show any tendency ofincrease but is found to be almost independent of the separation ofpairs beyond 100 kpc. The constancy of the M/L beyond 100 kpc mayindicate that the typical halo size of spiral galaxies is less than ~100kpc.
| 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.
| 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.
| Groups of galaxies. III. Some empirical characteristics.
Not Available
| 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.
| 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
| An image database. II. Catalogue between δ=-30deg and δ=70deg.
A preliminary list of 68.040 galaxies was built from extraction of35.841 digitized images of the Palomar Sky Survey (Paper I). For eachgalaxy, the basic parameters are obtained: coordinates, diameter, axisratio, total magnitude, position angle. On this preliminary list, weapply severe selection rules to get a catalog of 28.000 galaxies, wellidentified and well documented. For each parameter, a comparison is madewith standard measurements. The accuracy of the raw photometricparameters is quite good despite of the simplicity of the method.Without any local correction, the standard error on the total magnitudeis about 0.5 magnitude up to a total magnitude of B_T_=17. Significantsecondary effects are detected concerning the magnitudes: distance toplate center effect and air-mass effect.
| 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.
| 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.
| Integrated photoelectric magnitudes and color indices of bright galaxies in the Johnson UBV system
The photoelectric total magnitudes and color indices published in theThird Reference Catalogue of Bright Galaxies (RC3) are based on ananalysis of approximately equals 26,000 B, 25,000 B-V, and 17,000 U-Bmultiaperture measurements available up to mid 1987 from nearly 350sources. This paper provides the full details of the analysis andestimates of internal and external errors in the parameters. Thederivation of the parameters is based on techniques described by theVaucouleurs & Corwin (1977) whereby photoelectric multiaperture dataare fitted by mean Hubble-type-dependent curves which describe theintegral of the B-band flux and the typical B-V and U-B integrated colorgradients. A sophisticated analysis of the residuals of thesemeasurements from the curves was made to allow for the random andsystematic errors that effect such data. The result is a homogeneous setof total magnitudes BTA total colors(B-V)T and (U-B)T, and effective colors(B-V)e and (U-B)e for more than 3000 brightgalaxies in RC3.
| Quantitative morphology of E-S0 galaxies. III. Coded and parametric description of 108 galaxies in a complete sample
A survey has been performed of the morphological and photometricproperties of 108 E-S0 galaxies out of a complete sample of 112: thissample is built from the Revised Shapley-Ames Catalogue (RSA, Sandage& Tammann, 1981) keeping objects with δ>-10deg andV_0_<3000km/s, rejecting SB0's and Local Group dwarfs. The data weremainly derived from our CCD observations at Observatoire deHaute-Provence: the camera allowed fields of 4x7 arcmin (or 7x7 for thelast run), the seeing being generally in the 2-3 arcsec FWHM range. Themeasurements include the isophotal analysis according to Carter's(1978), principles,and the photometric profiles along the two main axis.Opposite semi-axis are measured separately to detect asymmetries.Partial results about strongly flattened galaxies were given anddiscussed in Paper I and II of this series (Michard & Marchal, 1993and 1994). The present paper gives in tabular form: - in Table 2a, 2bthe most useful morphological parameters and a coded description of the108 studied objects. This table includes a revised classificationaccording to Hubble types, this being completed by the subclassificationof ellipticals into "boxy", "disky" and "undeterminate". It alsoincludes the classifications of envelope geometry and disk extent, asintroduced in Paper I. - in Table 3a, b the usual photometric globalparameters, also converted to absolute units for future reference. Thetabular data is completed by individual notes for each galaxy, collectedin an Appendix. A discussion of the present data will be presented in aforthcoming Paper IV : it aims at checking the working hypothesis thatgalaxies of both E and S0 Hubble types belong, but for a small minority,to a common population of objects with similar structures.
| Quantitative morphology of E-S0 galaxies IV. Ellipticals and lenticulars as a single population
The geometrical properties of E and S0 galaxies have been intercomparedusing the data collected in Paper III (Michard & Marchal 1994) for108 RSA objects in a complete, luminosity and distance limited, sample.As the apparent flattening (largely an effect of projection along theline of sight), is a determining factor in the segregation between E andS0 objects, the working hypothesis has been made that an important biasis introduced in the recognition of the two classes. It is perhaps aswell to assume that galaxies of both Hubble types belong, but for asmall(?) minority, to a common population of objects with similarstructures. This hypothesis receives strong support from thefrequency-diagrams of the ellipticity ɛ_max_, measured near itsmaximum or at the isophote of surface brightness V=21.5. The diagram forS0's alone cannot be generated by the random projection of any objects:it is clearly biased by the shift to the E type of many S0's of moderateinclination and relatively modest disk. This limits the significance ofthe same diagrams for E galaxies. The noted bias is much reduced if S0'sand disky E's are considered together. Because of the strong outwardsdecrease of the ellipticities in disky E's and in the S0's with non-thinenvelopes (thick disks and spheroidal haloes), the frequency diagrams ofthe ellipticities measured at the classical B=25, or at V=25, do notshow the bias noted above for S0's. The lack of round E's requires thespheroidal components to be faintly triaxial, as recently emphasized byother authors. Our hypothesis is also supported by the overlap of E andS0 galaxies in ad hoc classification schemes of ellipticity profiles andenvelope geometry, and in such correlation diagrams as: - theellipticity in the envelope, i.e. near μ(V)= 25, against theintermediate maximum ellipticity - the extremum of the Carter'scoefficient e_4_ (or a_4_ or c_4_ in other similar works) against themaximum ellipticity - the disk extent, as far as it can be estimatedwithout detailed modeling, against the maximum ellipticity. The"standard" structure of E-S0 objects includes a spheroidal, nearlyoblate component, that cannot be of constant ellipticity: this parameteroften increases outwards from its bulge value, then decreases again inthe envelope. Disks of various brightness and extent, between dominatingand vanishing, are the second essential component. Obviously, theirrelative importance is, together with the dust content, a physicalcriterion involved in the morphological separation between E and S0objects, besides the inclination effect. In the present sample, the diskcannot be detected in nearly half of E classified objects, and isprobably vanishing in about 40% of this class, or circa 17% of the totalof studied early-type objects. This minority contains mostly boxy E'swith non-standard ellipticity profiles, and, as is well known, nosignificant rotational support. From the convergent results ofquantitative morphology and kinematics, the early-type galaxies shouldbe segregated into the majority class of disky fast oblate rotators anda minority class of non-rotating ellipsoids.
| The nature of elongated ellipticals
We have analyzed the isophotal shapes of a sample of 63 elongatedelliptical galaxies, previously classified E4, 5, 6 or 7. We sorted themaccording to their isophotal class, defined by the type of deviationsfrom perfectly elliptical isophotal contours. These deviations areexpected to appear clearly, because of the very favorable orientation ofthese galaxies. We find the following results, after exclusion of 6non-elliptical galaxies: A large percentage (56%) of elongated E's aredisky objects with pointed isophotes, while only 35% have either boxy orirregular isophotes, in equal proportions, and the remaining 6 galaxies(10%) are diffucult to classify. Furthermore, 38% of disky Es's alsoshow slightly boxy spheroids. In almost all the galaxies of the sample,there is an angular range where the deviations are of the disk-type. Thefour galaxies not showing this effect are among the roundest ones in thesample, which suggests that projection effects hide detailed structuresof this kind in many ellipticals. The correlations already reported inthe literature between isophotal class and radio, X-ray emission andkinematical behavior are confirmed. In particular, there is a clear-cutcorrelation between velocity anisotropy and isophotal shape. The mostelongated Hubble types tend to be disky E's. Boxy/irregular E's rarelyexceed ellipticities of 0.45 while the maximum ellipticity of half ofthe disky Es's exceeds this value. These results confirm the dichotomyof E's, which fall roughly into two classes, disky and boxy/irregularellipticals. They also show a physical continuity between disky E's andSO's and suggest that the Hubble types are strongly correlated withdisk-to-bulge ratios throughout the Hubble sequence, even at itsearly-type end (round E's), for which the disk is hidden by orientationeffects Galaxies escaping the correlations are the boxy/irregular Es's,resulting probably from strong merging processes.
| The dependence of the cool matter content on galaxy morphology in galaxies of types E/S0, S0, and SA
Using the material assembled in earlier papers, we examine the manner inwhich the interstellar matter content varies along the Hubble sequencefrom S0 galaxies to Sa galaxies selected from the RSA2 compilation. Forthis we make use of a new and more detailed classification which isdescribed here as applied to these early disk/spiral galaxies. Theprominence of the disk in S0's and the visibility of features (H IIregions) in the Sa's serve as the basis for the subtypes. Three S0categories: subtle, intermediate, and pronounced, and four Sadescriptors: very early, early, intermediate, and late are assigned tothe galaxies. It is found that the total amount of hydrogen (H I + H2)is a function of subtype, being low in the S0's and rising smoothly fromthe early Sa's to the later Sa's. The average surface density ofhydrogen exceeds 3 solar masses/pc-squared only in the latest subtypesof the Sa's. We conclude that the prominence of the disk of a galaxyclosely follows the amount of cool gas which the disk contains.
| Near Infrared Spectral Synthesis in Giant Early Type Galaxies
Not Available
| The origin of inner isophotal twists in elliptical galaxies
The analysis of the projected geometry of 99 elliptical galaxies listedin the Revised Shapley-Ames Catalog of Bright Galaxies reveals that 16of them have inner isophotal twists larger than 20 degrees, which cannotbe attributed to internal dust absorption. For 12 of them, the profilesof the position angle, ellipticity and axisymmetric coefficients of theFourier expansion of their isophotal contours, show features allcorrelated with each other, a result consistent with the assumption thatthese objects are at least two-component systems. Detailed features inthe profiles of these parameters resemble scale-down structures found ina comparison sample of SB0 galaxies, which indicates the presence ofbars generally accompanied with disks. It is suggested that: (a) asignificant fraction of isophotal twists, in relation with changes ofisophotal shapes and internal kinematics, is due to the SB0-like or(more generally) to the two-component nature of many E galaxies, (b)large-scale disks in E's are cold systems formed dissipatively at earlystages in the history of these galaxies and not in recent mergings, (c)there is a strong continuity in morphological properties between S0/SB0sand E's where bars and disks have been unambiguously detected, and (d) asignificant percentage of triaxial systems may not have the form of pureellipsoids.
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