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On the nature of bulges in general and of box/peanut bulges in particular: input from N-body simulations
Objects designated as bulges in disc galaxies do not form a homogeneousclass. I distinguish three types: the classical bulges, the propertiesof which are similar to those of ellipticals and which form by collapseor merging; boxy and peanut bulges, which are seen in near-edge-ongalaxies and which are in fact just a part of the bar seen edge-on; and,finally, disc-like bulges, which result from the inflow of (mainly) gasto the centre-most parts, and subsequent star formation. I make adetailed comparison of the properties of boxy and peanut bulges withthose of N-body bars seen edge-on, and answer previously voicedobjections about the links between the two. I also present and analysesimulations where a boxy/peanut feature is present at the same time as aclassical spheroidal bulge, and compare them with observations. Finally,I propose a nomenclature that can help to distinguish between the threetypes of bulges and avoid considerable confusion.
| Ultraluminous X-Ray Sources in Nearby Galaxies from ROSAT High Resolution Imager Observations I. Data Analysis
X-ray observations have revealed in other galaxies a class ofextranuclear X-ray point sources with X-ray luminosities of1039-1041 ergs s-1, exceeding theEddington luminosity for stellar mass X-ray binaries. Theseultraluminous X-ray sources (ULXs) may be powered by intermediate-massblack holes of a few thousand Msolar or stellar mass blackholes with special radiation processes. In this paper, we present asurvey of ULXs in 313 nearby galaxies withD25>1' within 40 Mpc with 467 ROSAT HighResolution Imager (HRI) archival observations. The HRI observations arereduced with uniform procedures, refined by simulations that help definethe point source detection algorithm employed in this survey. A sampleof 562 extragalactic X-ray point sources withLX=1038-1043 ergs s-1 isextracted from 173 survey galaxies, including 106 ULX candidates withinthe D25 isophotes of 63 galaxies and 110 ULX candidatesbetween 1D25 and 2D25 of 64 galaxies, from which aclean sample of 109 ULXs is constructed to minimize the contaminationfrom foreground or background objects. The strong connection betweenULXs and star formation is confirmed based on the striking preference ofULXs to occur in late-type galaxies, especially in star-forming regionssuch as spiral arms. ULXs are variable on timescales over days to yearsand exhibit a variety of long term variability patterns. Theidentifications of ULXs in the clean sample show some ULXs identified assupernovae (remnants), H II regions/nebulae, or young massive stars instar-forming regions, and a few other ULXs identified as old globularclusters. In a subsequent paper, the statistic properties of the surveywill be studied to calculate the occurrence frequencies and luminosityfunctions for ULXs in different types of galaxies to shed light on thenature of these enigmatic sources.
| A wide-field photometric study of the globular cluster system of NGC 4636
Previous smaller-scale studies of the globular cluster system of NGC4636, an elliptical galaxy in the southern part of the Virgo cluster,have revealed an unusually rich globular cluster system. Were-investigate the cluster system of NGC 4636 with wide-field Washingtonphotometry. The globular cluster luminosity function can be followedroughly 1 mag beyond the turn-over magnitude found at {V} =23.31±0.13 for the blue cluster sub-population. This correspondsto a distance modulus of ({m}-{M})=31.24±0.17, 0.4 mag largerthan the distance determined from surface brightness fluctuations. Thehigh specific frequency is confirmed, yet the exact value remainsuncertain because of the uncertain distance: it varies between5.6±1.2 and 8.9±1.2. The globular cluster system has aclearly bimodal color distribution. The color peak positions show noradial dependence and are in good agreement with the values found forother galaxies studied in the same filter system. However, a luminositydependence is found: brighter clusters with an“intermediate” color exist. The clusters exhibit a shallowradial distribution within 7´, represented by a power-law with anexponent of -1.4. Within the same radial interval, the galaxy light hasa distinctly steeper profile. Because of the difference in the clusterand light distribution the specific frequency increases considerablywith radius. At 7´ and 9´ the density profiles of the redand blue clusters, respectively, change strongly: the power-law indicesdecrease to around -5 and become similar to the galaxy profile. Thissteep profile indicates that we reach the outer rim of the clustersystem at approximately 11´. This interpretation is supported bythe fact that in particular the density distribution of the blue clusterpopulation can be well fit by the projection of a truncated power-lawmodel with a core. This feature is seen for the first time in a globularcluster system. While the radial distribution of the cluster and fieldpopulations are rather different, this is not true for the ellipticityof the system: the elongation as well as the position angle of thecluster system agree well with the galaxy light. We compare the radialdistribution of globular clusters with the light profiles for a sampleof elliptical galaxies. The difference observed in NGC 4636 is typicalof an elliptical galaxy of this luminosity. The intrinsic specificfrequency of the blue population is considerably larger than that of thered one.Tables A.1 to A.6 are only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/433/43
| The surface brightness and colour-magnitude relations for Fornax cluster galaxies
We present BVI photometry of 190 galaxies in the central 4 ×3deg2 region of the Fornax cluster observed with the MichiganCurtis Schmidt Telescope. Results from the Fornax Cluster SpectroscopicSurvey (FCSS) and the Flair-II Fornax Surveys have been used to confirmthe membership status of galaxies in the Fornax Cluster Catalogue (FCC).In our catalogue of 213 member galaxies, 92 (43 per cent) have confirmedradial velocities.In this paper, we investigate the surface brightness-magnitude relationfor Fornax cluster galaxies. Particular attention is given to the sampleof cluster dwarfs and the newly discovered ultracompact dwarf galaxies(UCDs) from the FCSS. We examine the reliability of the surfacebrightness-magnitude relation as a method for determining clustermembership and find that at surface brightnesses fainter than 22 magarcsec-2, it fails in its ability to distinguish betweencluster members and barely resolved background galaxies. Cluster membersexhibit a strong surface brightness-magnitude relation. Both elliptical(E) galaxies and dwarf elliptical (dE) galaxies increase in surfacebrightness as luminosity decreases. The UCDs lie off the locus of therelation.B-V and V-I colours are determined for a sample of 113 cluster galaxiesand the colour-magnitude relation is explored for each morphologicaltype. The UCDs lie off the locus of the colour-magnitude relation. Theirmean V-I colours (~1.09) are similar to those of globular clustersassociated with NGC 1399. The location of the UCDs on both surfacebrightness and colour-magnitude plots supports the `galaxy threshing'model for infalling nucleated dwarf elliptical (dE, N) galaxies.
| Measuring Distances and Probing the Unresolved Stellar Populations of Galaxies Using Infrared Surface Brightness Fluctuations
To empirically calibrate the IR surface brightness fluctuation (SBF)distance scale and probe the properties of unresolved stellarpopulations, we measured fluctuations in 65 galaxies using NICMOS on theHubble Space Telescope. The early-type galaxies in this sample includeelliptical and S0 galaxies and spiral bulges in a variety ofenvironments. Absolute fluctuation magnitudes in the F160W (1.6 μm)filter (MF160W) were derived for each galaxy using previouslymeasured I-band SBF and Cepheid variable star distances. F160W SBFs canbe used to measure distances to early-type galaxies with a relativeaccuracy of ~10%, provided that the galaxy color is known to ~0.035 magor better. Near-IR fluctuations can also reveal the properties of themost luminous stellar populations in galaxies. Comparison of F160Wfluctuation magnitudes and optical colors to stellar population modelpredictions suggests that bluer elliptical and S0 galaxies havesignificantly younger populations than redder ones and may also be moremetal-rich. There are no galaxies in this sample with fluctuationmagnitudes consistent with old, metal-poor (t>5 Gyr, [Fe/H]<-0.7)stellar population models. Composite stellar population models implythat bright fluctuations in the bluer galaxies may be the result of anepisode of recent star formation in a fraction of the total mass of agalaxy. Age estimates from the F160W fluctuation magnitudes areconsistent with those measured using the Hβ Balmer-line index. Thetwo types of measurements make use of completely different techniquesand are sensitive to stars in different evolutionary phases. Bothtechniques reveal the presence of intermediate-age stars in theearly-type galaxies of this sample.Based on observations with the NASA/ESA Hubble Space Telescope, obtainedat the Space Telescope Science Institute, which is operated by AURA,Inc., under NASA contract NAS 5-26555.
| 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
| Surface brightness fluctuation distances for dwarf elliptical galaxies in the Fornax cluster
We have obtained deep B and R-band CCD images of eight dwarf elliptical(dE) galaxies in the Fornax cluster using the FORS1 instrument at theVLT in service mode under excellent atmospheric conditions. A total of92 fields distributed over the central regions of the galaxies have beenanalysed to measure local (B-R)0 colours and R-band surfacebrightness fluctuation (SBF) magnitudes /line{m}R. Within agalaxy the observed correlation of (B-R)0 with/line{m}R0 follows closely the predicted slope ofthe colour-fluctuation luminosity relation for composite single-burst,mainly old, metal-poor stellar populations. This allows to determine thedistances of the dEs from simple offset measurements to a typically 9%accuracy. The distance distribution of these genuine cluster dwarfscenters at a mean distance of (m-M)0=31.54+/-0.07 mag, or20.3 +/- 0.7 Mpc, a value that is in best agreement with previous SBFwork on Fornax early-type giants and thus represents a robust estimateof the distance to the Fornax cluster core. The application of thebootstrap resampling technique on the distance data further reveals acluster depth of sigmaint = 1.4{+0.5 atop -0.8} Mpc. We takethis preliminary result as a confirmation of the compact appearance ofFornax in the projection on the sky although the cluster might beslightly more elongated along the line of sight. Combining the newlyderived cluster distance with the cosmological velocity of Fornax of1324+/-41 km s-1 gives a Hubble constant of H0 =65 +/- 4 km s-1 Mpc-1. This value is consistent atthe 95% confidence level with both the most recent result from the teamthat favours a long distance scale and the final value adopted by theHST ``Key Project'' team in their work for the Hubble constant. Finally,we explore the possibility to determine rough metallicities of ourcluster dEs from their (B-R)0 colours via Worthey's stellarpopulation synthesis models. The median metallicities are found in therange from -1.5 to -1 with a concentration around [Fe/H] =-1. Acomparison with spectral line indices results available for threegalaxies shows good agreement. Moreover, the derived metallicities placethe bright Fornax dEs on the extension of the metallicity-luminosityrelation defined by the low luminous Local Group dEs which providesadditional support for the (B-R)0 colour as a usefulmetallicity estimator. The data further suggest an age range between 10and 12 Gyr for the Fornax dwarfs.Based on observations collected at the European Southern Observatory(ESO 68.A-0176).
| 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.
| 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.
| 2D modelling of the light distribution of early-type galaxies in a volume-limited sample - II. Results for real galaxies
In this paper we analyse the results of the two-dimensional (2D) fit ofthe light distribution of 73 early-type galaxies belonging to the Virgoand Fornax clusters, a sample volume- and magnitude-limited down toMB=-17.3, and highly homogeneous. In our previous paper(Paper I) we have presented the adopted 2D models of thesurface-brightness distribution - namely the r1/n and(r1/n+exp) models - we have discussed the main sources oferror affecting the structural parameters, and we have tested theability of the chosen minimization algorithm (MINUIT) in determining thefitting parameters using a sample of artificial galaxies. We show that,with the exception of 11 low-luminosity E galaxies, the best fit of thereal galaxy sample is always achieved with the two-component(r1/n+exp) model. The improvement in the χ2due to the addition of the exponential component is found to bestatistically significant. The best fit is obtained with the exponent nof the generalized r1/n Sersic law different from theclassical de Vaucouleurs value of 4. Nearly 42 per cent of the samplehave n<2, suggesting the presence of exponential `bulges' also inearly-type galaxies. 20 luminous E galaxies are fitted by thetwo-component model, with a small central exponential structure (`disc')and an outer big spheroid with n>4. We believe that this is probablydue to their resolved core. The resulting scalelengths Rh andRe of each component peak approximately at ~1 and ~2kpc,respectively, although with different variances in their distributions.The ratio Re/Rh peaks at ~0.5, a value typical fornormal lenticular galaxies. The first component, represented by ther1/n law, is probably made of two distinct families,`ordinary' and `bright', on the basis of their distribution in theμe-log(Re) plane, a result already suggested byCapaccioli, Caon and D'Onofrio. The bulges of spirals and S0 galaxiesbelong to the `ordinary' family, while the large spheroids of luminous Egalaxies form the `bright' family. The second component, represented bythe exponential law, also shows a wide distribution in theμ0c-log(Rh) plane. Small discs (orcores) have short scalelengths and high central surface brightness,while normal lenticulars and spiral galaxies generally have scalelengthshigher than 0.5kpc and central surface brightness brighter than20magarcsec-2 (in the B band). The scalelengths Reand Rh of the `bulge' and `disc' components are probablycorrelated, indicating that a self-regulating mechanism of galaxyformation may be at work. Alternatively, two regions of theRe-Rh plane are avoided by galaxies due todynamical instability effects. The bulge-to-disc (B/D) ratio seems tovary uniformly along the Hubble sequence, going from late-type spiralsto E galaxies. At the end of the sequence the ratio between the largespheroidal component and the small inner core can reach B/D~100.
| 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 neutral hydrogen content of Fornax cluster galaxies
We present a new set of deep H I observations of member galaxies of theFornax cluster. We detected 35 cluster galaxies in HI. The resulting sample, the most comprehensive to date, is used toinvestigate the distribution of neutral hydrogen in the clustergalaxies. We compare the H I content of the detected cluster galaxieswith that of field galaxies by measuring H I mass-to-light ratios andthe H I deficiency parameter of Solanes et al. (\cite{Sol96}). The meanH I mass-to-light ratio of the cluster galaxies is 0.68+/- 0.15,significantly lower than for a sample of H I-selected field galaxies(1.15+/- 0.10), although not as low as in the Virgocluster (0.45+/- 0.03). In addition, the H I content of twocluster galaxies (NGC 1316C and NGC1326B) appears to have been affected by interactions. The meanH I deficiency for the cluster is 0.38+/-0.09 (for galaxy types T=1-6),significantly greater than for the field sample (0.05+/-0.03). Boththese tests show that Fornax cluster galaxies are HI-deficient compared to field galaxies. The kinematics of the clustergalaxies suggests that the H I deficiency may be caused by ram-pressurestripping of galaxies on orbits that pass close to the cluster core. Wealso derive the most complete B-band Tully - Fisher relation of inclinedspiral galaxies in Fornax. A subcluster in theSouth-West of the main cluster contributes considerably to the scatter.The scatter for galaxies in the main cluster alone is 0.50 mag, which isslightly larger than the intrinsic scatter of 0.4 mag. We use the Tully- Fisher relation to derive a distance modulus ofFornax relative to the Virgocluster of -0.38+/- 0.14 mag. The galaxies in the subclusterare (1.0+/-0.5) mag brighter than the galaxies of the main cluster,indicating that they are situated in the foreground. With their meanvelocity 95 km s-1 higher than that of the main cluster weconclude that the subcluster is falling into the main Fornaxcluster.
| The stellar populations of early-type galaxies in the Fornax cluster
We have measured central line strengths for a magnitude-limited sampleof early-type galaxies in the Fornax cluster, comprising 11 elliptical(E) and 11 lenticular (S0) galaxies, more luminous thanMB=-17. When compared with single-burst stellar populationmodels we find that the centres of Fornax ellipticals follow a locus offixed age and have metallicities varying roughly from half solar totwice solar. The centres of (lower luminosity) lenticular galaxies,however, exhibit a substantial spread to younger luminosity-weightedages, indicating a more extended star formation history. Galaxies withold stellar populations show tight scaling relations between metal-lineindices and the central velocity dispersion. Remarkably also, the Felines are well correlated with σ0. Our detailedanalysis of the stellar populations suggests that these scalingrelations are driven mostly by metallicity. Galaxies with a youngstellar component do generally deviate from the main relation. Inparticular, the lower luminosity S0s show a large spread. Ourconclusions are based on several age/metallicity diagnostic diagrams inthe Lick/IDS system comprising established indices such asMg2 and Hβ as well as new and more sensitive indicessuch as HγA and Fe3, a combination of three prominentFe lines. The inferred difference in the age distribution betweenlenticular and elliptical galaxies is a robust conclusion, as the modelsgenerate consistent relative ages using different age and metallicityindicators, even though the absolute ages remain uncertain. The absoluteage uncertainty is mainly caused by the effects of non-solar abundanceratios which are not yet accounted for by the stellar population models.Furthermore, we find that elliptical galaxies and the bulge of onebright S0 are overabundant in magnesium, where the most luminousgalaxies show the strongest overabundances. The stellar populations ofyoung and faint S0s are consistent with solar abundance ratios or a weakMg underabundance. Two of the faintest lenticular galaxies in our samplehave blue continua and extremely strong Balmer-line absorption,suggesting star formation <2Gyr ago.
| A Database of Cepheid Distance Moduli and Tip of the Red Giant Branch, Globular Cluster Luminosity Function, Planetary Nebula Luminosity Function, and Surface Brightness Fluctuation Data Useful for Distance Determinations
We present a compilation of Cepheid distance moduli and data for foursecondary distance indicators that employ stars in the old stellarpopulations: the planetary nebula luminosity function (PNLF), theglobular cluster luminosity function (GCLF), the tip of the red giantbranch (TRGB), and the surface brightness fluctuation (SBF) method. Thedatabase includes all data published as of 1999 July 15. The mainstrength of this compilation resides in the fact that all data are on aconsistent and homogeneous system: all Cepheid distances are derivedusing the same calibration of the period-luminosity relation, thetreatment of errors is consistent for all indicators, and measurementsthat are not considered reliable are excluded. As such, the database isideal for comparing any of the distance indicators considered, or forderiving a Cepheid calibration to any secondary distance indicator, suchas the Tully-Fisher relation, the Type Ia supernovae, or the fundamentalplane for elliptical galaxies. This task has already been undertaken byFerrarese et al., Sakai et al., Kelson et al., and Gibson et al.Specifically, the database includes (1) Cepheid distances, extinctions,and metallicities; (2) reddened apparent λ5007 Å magnitudesof the PNLF cutoff; (3) reddened apparent magnitudes and colors of theturnover of the GCLF (in both the V and B bands); (4) reddened apparentmagnitudes of the TRGB (in the I band) and V-I colors at 0.5 mag fainterthan the TRGB; and (5) reddened apparent surface brightness fluctuationmagnitudes measured in Kron-Cousin I, K', andKshort, and using the F814W filter with the Hubble SpaceTelescope (HST) WFPC2. In addition, for every galaxy in the database wegive reddening estimates from IRAS/DIRBE as well as H I maps, J2000coordinates, Hubble and T-type morphological classification, apparenttotal magnitude in B, and systemic velocity.
| 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.
| Box- and peanut-shaped bulges. I. Statistics
We present a classification for bulges of a complete sample of ~ 1350edge-on disk galaxies derived from the RC3 (Third Reference Catalogue ofBright Galaxies, de Vaucouleurs et al. \cite{rc3}). A visualclassification of the bulges using the Digitized Sky Survey (DSS) inthree types of b/p bulges or as an elliptical type is presented andsupported by CCD images. NIR observations reveal that dust extinctiondoes almost not influence the shape of bulges. There is no substantialdifference between the shape of bulges in the optical and in the NIR.Our analysis reveals that 45% of all bulges are box- and peanut-shaped(b/p). The frequency of b/p bulges for all morphological types from S0to Sd is > 40%. In particular, this is for the first time that such alarge frequency of b/p bulges is reported for galaxies as late as Sd.The fraction of the observed b/p bulges is large enough to explain theb/p bulges by bars. Partly based on observations collected at ESO/LaSilla (Chile), DSAZ/Calar Alto (Spain), and Lowell Observatory/Flagstaff(AZ/U.S.A.). Tables 6 and 7 are only available in electronic form at CDSvia anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| On the relationship between age and dynamics in elliptical galaxies
Galaxy age estimates (mostly from spectroscopy of the central regions)are now available for many early-type galaxies. In a previous paper weshowed that the offset of galaxies from the fundamental plane depends ongalaxy age. Here, using the same sample of 88 galaxies, we examine thescatter about the Faber-Jackson (FJ) relation, and find that theposition of a galaxy relative to this relation depends on its age. Inparticular, younger ellipticals are systematically brighter inMB and/or have a lower central velocitydispersion (σ0). The mean relation corresponds togalaxies that are ~10Gyr old. We attempt to reproduce the observed trendof the FJ residuals with age using two simple models. The first assumesthat galaxy age is tracing the last major star formation event in anelliptical galaxy. We assume that this starburst was instantaneous,centrally located and involved 10per cent of the galaxy by mass. Thefading of this burst changes the MBcomponent of the FJ residuals, with time. Such a model was verysuccessful at reproducing the B-V and Mg2 evolution reportedin our previous paper, but is unable to reproduce the strength of the FJtrend. A second model is required to describe age-correlated changes ingalaxy dynamics. Following expectations from cosmological simulations,we assume that σ0, for a galaxy of a given mass, scaleswith the epoch of galaxy formation, i.e. with the mean density of theUniverse. Hence recently formed ellipticals have systematically lowervelocity dispersions than do old ellipticals. We find that a combinationof these two models provides a good match to the change in FJ residualswith galaxy age. This suggests that young ellipticals will have subtlydifferent dynamical properties from old ellipticals. We also find thatthere is not a strong relationship between the age of a galaxy and itsluminosity for our sample. This suggests that the tilt of thefundamental plane is not totally driven by age.
| The Southern Sky Redshift Survey
We report redshifts, magnitudes, and morphological classifications for5369 galaxies with m_B <= 15.5 and for 57 galaxies fainter than thislimit, in two regions covering a total of 1.70 sr in the southerncelestial hemisphere. The galaxy catalog is drawn primarily from thelist of nonstellar objects identified in the Hubble Space TelescopeGuide Star Catalog (GSC). The galaxies have positions accurate to ~1"and magnitudes with an rms scatter of ~0.3 mag. We compute magnitudes(m_SSRS2) from the relation between instrumental GSC magnitudes and thephotometry by Lauberts & Valentijn. From a comparison with CCDphotometry, we find that our system is homogeneous across the sky andcorresponds to magnitudes measured at the isophotal level ~26 magarcsec^-2. The precision of the radial velocities is ~40 km s^-1, andthe redshift survey is more than 99% complete to the m_SSRS2 = 15.5 maglimit. This sample is in the direction opposite that of the CfA2; incombination the two surveys provide an important database for studies ofthe properties of galaxies and their large-scale distribution in thenearby universe. Based on observations obtained at Cerro TololoInter-American Observatory, National Optical Astronomy Observatories,operated by the Association of Universities for Research in Astronomy,Inc., under cooperative agreement with the National Science Foundation;Complejo Astronomico El Leoncito, operated under agreement between theConsejo Nacional de Investigaciones Científicas de laRepública Argentina and the National Universities of La Plata,Córdoba, and San Juan; the European Southern Observatory, LaSilla, Chile, partially under the bilateral ESO-ObservatórioNacional agreement; Fred Lawrence Whipple Observatory;Laboratório Nacional de Astrofísica, Brazil; and the SouthAfrican Astronomical Observatory.
| 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
| X-Ray Emission from the Fornax Cluster
We have analyzed the ROSAT PSPC observations of the central region ofthe Fornax cluster, a relatively poor group of galaxies at a distance ofabout 24 Mpc. The brightest X-ray and optical galaxy in the group is NGC1399, an E1 galaxy located near the center of the Fornax cluster. Wecharacterize the hot gas around the galaxy, derived from a 2' to 18'annulus around NGC 1399, as having a mean temperature of 1.30 +/- 0.05keV and a heavy element abundance of 0.6 +/- 0.1 with respect to solarabundance (Fe/H = 4.68 x 10-5 by number). Spatially resolved spectraldata provide both gas temperature and gas abundance profiles extendingto 125 kpc (18') from the galaxy. The temperature distribution, combinedwith the X-ray surface brightness profile, yields an accuratedetermination of the gravitating mass within 125 kpc, which falls in therange (4.3--8.1) x 1012 Mȯ (95% confidence range, includingsystematic uncertainties). If we include the extended optical haloaround NGC 1399, the mass-to-light ratio increases with radius from 33+/- 8 Mȯ/Lȯ at 18 kpc to 70 +/- 22 Mȯ/Lȯ at 110 kpc.We compare the heavy element abundance distribution measured around NGC1399 with that measured around the Virgo galaxy NGC 4472, as well as tomodels for hot coronae. We find that the abundance distribution is ingood agreement with that previously measured for NGC 4472 by Forman etal. in 1993. For both galaxies, the observed abundance profiles requireboth a weak evolution of the type Ia supernova rate with time and apresent epoch rate which agrees with that of Cappellaro et al. Wecompare mass measurements in NGC 1399 to those for M87. The similarityof the optical masses in these systems and their differences in gasmasses and gravitating masses lead us to suggest that the opticalgalaxies formed at an early stage when the central potentials of thesetwo systems were similar. Subsequent infall of gas and dark matter intothe larger, deeper Virgo potential resulted in the greater mass of theVirgo cluster compared to Fornax. We also report on X-ray properties ofthirteen other Fornax galaxies. Eight of these were detected in ROSATimages with luminosities in the 0.2 to 2 keV energy band from 1 x 1039to 1.6 x 1041 ergs s-1. Five galaxies were sufficiently bright to permitspectral analyses and all but one (NGC 1380) had spectra consistent withthermal emission. Two (NGC 1404 and NGC 1387) of the four galaxies withwell-constrained spectral parameters have hot coronae withcharacteristic gas temperatures of about 0.5 keV and iron abundancesless than that found around NGC 1399 and other bright ellipticals. Tomaintain these hot coronae, the absolute magnitudes of these galaxiesmust be brighter than -19. Thus the distance to Fornax must be at least18 Mpc, and, if there are no large peculiar velocities, the Hubbleconstant should be less than 75 km s-1 Mpc-1. Since these galaxies areall members of Fornax, distance uncertainties do not affect therelationship between their optical magnitude and X-ray luminosity.Analysis of the Fornax galaxies supports the contention that the scatterin the X-ray and optical relationship is intrinsic and does not arisesolely from distance uncertainties. For the elliptical galaxy NGC 1404,the X-ray images show that the hot corona is distorted and likely isbeing stripped, indicating infall of the galaxy toward NGC 1399 and thecluster center.
| New aperture photometry for 217 galaxies in the Virgo and Fornax clusters.
We present photo electric multi-aperture photometry in UBVRI of 171 and46 galaxies in the Virgo and Fornax clusters, respectively. Many of thegalaxies have not been observed in at least one of these passbandsbefore. We discuss the reduction and transformation into the Cousinsphotometric system as well as the extinction coefficients obtainedbetween 1990 and 1993.
| 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.
| Interstellar MG II Absorption Lines from Low-Redshift Galaxies
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1995ApJ...448..634B&db_key=AST
| 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.
| Major axis kinematics of 15 early-type galaxies in the Fornax cluster.
Major axis rotation curves and velocity dispersions profiles, extendingout to about one effective radius, are presented for 15 ellipticals andS0's out of the photometric sample of Fornax cluster galaxies studied byCaon et al. (1994). A brief description of the spectroscopic andphotometric characteristics of each galaxy is provided, together with acomparison with previous studies. Six of the nine E's are possiblymisclassified S0's or ellipticals harboring a disk-like component. Twogalaxies (NGC 1399 and 1404) show a hint of counter-rotation. Evidenceis given that the bright and the ordinary families of early-typegalaxies, first introduced by Capaccioli et al. (1992), look distinctalso in term of the anisotropy parameter (V_m_/σ)*.
| On the Shape of the Light Profiles of Early Type Galaxies - Part Two - the - Diagram
We present new evidence against the universality of the de Vaucouleursr^1/4^ law, considered to be the best empirical formula for fitting thelight profiles of elliptical galaxies, through the analysis of theproperties of the (D_n_/A_e_)-<μ>_e_ diagram for avolume-limited sample of early-type galaxies that are members of theVirgo and Fornax clusters. The r^1/4^ law turns out to be only aparticular case of the more general r^1/4^ law, where the exponent m isfound to correlate with the effective radius of the galaxy. We compareour sample of early-type galaxies with that studied by Burstein et al.,and find that the observed differences can be explained in terms ofprocedures and methodologies adopted for measuring the globalphotometric parameters such as total luminosities, effective radii,effective surface brightnesses and D_n_ diameters.
| Galaxy properties in different environments. 1: The sample
This paper presents two galaxy samples, respectively in a high and in alow local density environments, that were generated from the SouthernSky Redshift Survey (SSRS) catalog using objective criteria. Apreliminary comparison of physical properties in these two samplesreveals that galaxies in high-density environments tend to be under ahigher starbursting activity, have a deficiency of the neutral hydrogencontent, present a higher fractional Seyfert population and a higherfraction of barred spirals as well. The present samples are intended tobe used in future spectroscopic observations for more detailedinvestigation.
| 'Global mapping' B-band photometry of a complete sample of Fornax and Virgo early-type galaxies
We present the B-band surface photometry of 19 early-type galaxies ofthe Virgo cluster, and of 28 galaxies of the same morphological typebelonging to the Fornax clusters, obtained through the `global mapping'technique which couples CCD and photographic plates. Taking into account33 galaxies already studied by Caon et al. (1990) with the samemethodology, the Virgo sample of early-type galaxies is now 80% completedown to B_T_=14. The Fornax sample is 95% complete down to B_T_=15. Thegeometric and photometric properties of the total sample of 80 galaxiesare derived measuring accurate light profiles, ellipticities, positionangles and Fourier coefficients of the isophotes. The main sources oferrors of the `global mapping' procedure are reviewed and the effects ofseeing discussed. Global galaxian parameters such as total luminosity,effective radius, and effective surface brightness, are computed for thewhole sample in a homogeneous way. Our goal is to create an unbiased setof data to be used for investigating the process of galaxy formation andevolution.
| General study of group membership. II - Determination of nearby groups
We present a whole sky catalog of nearby groups of galaxies taken fromthe Lyon-Meudon Extragalactic Database. From the 78,000 objects in thedatabase, we extracted a sample of 6392 galaxies, complete up to thelimiting apparent magnitude B0 = 14.0. Moreover, in order to considersolely the galaxies of the local universe, all the selected galaxieshave a known recession velocity smaller than 5500 km/s. Two methods wereused in group construction: a Huchra-Geller (1982) derived percolationmethod and a Tully (1980) derived hierarchical method. Each method gaveus one catalog. These were then compared and synthesized to obtain asingle catalog containing the most reliable groups. There are 485 groupsof a least three members in the final catalog.
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