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The sense of rotation of subhaloes in cosmological dark matter haloes
We present a detailed analysis of the velocity distribution andorientation of orbits of subhaloes in high-resolution cosmologicalsimulations of dark matter haloes. We find a trend for substructure topreferentially revolve in the same direction as the sense of rotation ofthe host halo: there is an excess of prograde satellite haloes.Throughout our suite of nine host haloes (eight cluster-sized objectsand one galactic halo), there are on average 59 per cent of thesatellites corotating with the host. Even when including subhaloes outto five virial radii of the host, the signal still remains pointing outthe relation of the signal to the infall pattern of subhaloes. However,the fraction of prograde satellites weakens to about 53 per cent whenobserving the data along a (random) line of sight and deriving thedistributions in a way an observer would infer them. This decrease inthe observed prograde fraction has its origin in the technique used bythe observer to determine the sense of rotation, which results in apossible misclassification of non-circular orbits. We conclude that theexistence of subhaloes on corotating orbits is another prediction of thecold dark matter structure formation scenario, although there will bedifficulties to verify it observationally. Since the galactic halosimulation gave the same result as the cluster-sized simulations, weassume that the fraction of prograde orbits is independent of the scaleof the system, though more galactic simulations would be necessary toconfirm this.
| The Peculiar Velocities of Satellites of External Disk Galaxies
We analyze the angular distribution and the orbital rotation directionsof a sample of carefully selected satellite galaxies about disk galaxyprimaries extracted from the Sloan Digital Sky Survey (SDSS). Wecomplement this analysis with a theoretical study of these statistics inan N-body simulation of cosmological structure formation set within theΛCDM paradigm under various assumptions for the orientations ofdisk angular momenta. Under the assumption that the angular momenta ofthe disks are aligned with the angular momenta of the inner regions oftheir host dark matter halos, we find that the fraction of simulatedsatellite halos that exhibit prograde motion isfprog~0.55-0.60, with larger satellites more likely to beprograde. In our observational sample, approximately 60% of thesatellites exhibit prograde motion, a result that is broadly consistentwith the simulated sample. Our observational sample of satellitegalaxies shows no evidence for an anisotropic satellite distributionrelative to disk primaries; however, the small sample size does not yetsupport a statistically significant comparison to previous studies ofsatellite anisotropy. Again, this result is broadly consistent with oursimulated sample of satellites under the assumption that disk and haloangular momenta are aligned. However, the small size of ourobservational sample does not yet allow us to distinguish betweenvarious assumptions regarding the orientations of disks in their halos.Finally, we present an assessment of the importance of contamination byinterlopers on the measured prograde and retrograde statistics.
| Probing Halos of Galaxies at Very Large Radii Using Background QSOs
Gaseous halos of nine nearby galaxies (with redshifts cz<6000 kms-1) were probed at large galactocentric radii usingbackground quasars observed with the Hubble Space Telescope Goddard HighResolution Spectrograph and the Space Telescope Imaging Spectrograph.The projected quasar-galaxy separations range from 55 to 387h-175 kpc. Lyα absorption lines weresuccessfully detected in the spectra of five quasars, at impactparameters of up to ~170 h-175 kpc from the centerof the nearby galaxy, and in each case at wavelengths consistent withthe galaxy's redshift. Our observations include the lowest redshiftLyα lines detected to date. H I velocity fields were obtained atthe Very Large Array for three of the galaxies in our sample (in onecase the velocity field was available from the literature) to derivetheir rotation curves. When comparing the inner rotation curves of thegalaxies with the velocity at large radius provided by the Lyαline, it is apparent that it is very difficult to explain the observedLyα velocity as due to gas in an extended rotating disk. In mostcases, one would need to invoke large warps in the outer gas disks andalso thick gas disks to reconcile the observed velocities with thepredicted ones. Indeed, in one case, the Lyα line velocityindicates, in fact, counterrotation with respect to the inner diskrotation. In light of these results, we conclude that in a typicalgalaxy there is no longer detectable atomic gas corotating in anextended disk at radii greater than 35α-1, whereα-1 is the stellar disk exponential scale length. Thecosmic web is the most likely origin for the detected Lyα lines.Our observations confirm the recent Bowen et al. correlation ofequivalent widths with the local volume density of galaxies around thesight line, and the observed equivalent widths of the lines areconsistent with expectations of the cosmic web.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 NAS5-26555.
| Beyond the Galaxy Luminosity Function
With the advent of large-scale surveys (i.e. Legacy Surveys) it is nowpossible to start looking beyond the galaxy luminosity function (LF) tomore detailed statistical representations of the galaxy population, i.emultivariate distributions. In this review I first summarise the currentstate-of-play of the B-band global and cluster LFs and then brieflypresent two promising bivariate distributions: the luminosity-surfacebrightness plane (LSP) and the colour-luminosity plane (CLP). In bothplanes galaxy bulges and galaxy disks form marginally overlapping butdistinct distributions, indicating two key formation/evolutionaryprocesses (presumably merger and accretion). Forward progress in thissubject now requires the routine application of reliable bulge-diskdecomposition codes to allow independent investigation of these two keycomponents.
| Observational Constraints on the Physical Parameters of Dark Matter Halos
After looking at the difference in the mass distribution between massivespiral and dwarf irregular (dIrr) and low surface brightness (LSB)galaxies, the central Dark Matter (DM) concentration (flat vs cuspy) indwarf and LSB galaxies, derived from observations, will be examined. Wewill then present what kind of observational constraints can be put onthe total mass and total extent of DM halos from the studies ofindividual galaxies, small groups, satellites' dynamics and tidal tailsof interacting systems. Finally, we will discuss how limits on thephysical parameters of DM halos could be set by deriving extendedrotation curves beyond the HI radius (r > rHI), usingeither Lyα absorption or Hα emission observations.
| The Properties of Satellite Galaxies in External Systems. II. Photometry and Colors
In this second paper dedicated to the study of satellite galaxies wepresent broadband photometry in the B, V, R, and I filters of 49satellite galaxies orbiting giant isolated spiral galaxies. Firstanalysis of the properties of these objects are presented by means ofcolor-color and color-magnitude diagrams for early- and late-typesatellites. Although we find differences in the slope of the V-I versusMv color magnitude diagram, as a whole, the relations are inagreement with the trends known to date for galaxies of similarmagnitudes in nearby clusters of galaxies. Comparison with the relationsfound for satellites in the Local Group allows us to sample better thebright end of the luminosity function of satellite galaxies and extendsfor brighter objects the validity of the color-magnitude relation foundfor dwarf galaxies in the Local Group. Most of the E/S0 galaxies in oursample show a negative color gradient with values similar to those knownfor early-type galaxies in other environments.
| 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.
| Optical Imaging and Spectroscopy of the Edge-on Sbc Galaxy UGC 10043: Evidence for a Galactic Wind and a Peculiar Triaxial Bulge
We present new optical imaging and spectroscopy of the peculiar, edge-onSbc galaxy UGC 10043. Using the WIYN telescope, we have obtained B, R,and Hα+[NII] images, together with DensePak integral fieldspectroscopic measurements of the stellar Ca II infrared triplet and theHα and [N II] lines from the ionized gas. The imaging observationsshow that the inner bulge of UGC 10043 (a<=7.5") is elongatedperpendicular to the galaxy major axis. At larger r the bulge isophotestwist to become oblate and nearly circular, suggesting the bulge istriaxial. The bulge shows no clear evidence for rotation about eitherits major or minor axis. The inner, southwestern quadrant of the bulgeis girdled by a narrow dust lane parallel to the minor axis; unsharpmasking reveals that this minor-axis dust lane may be part of an innerpolar ring, although we find no unambiguous kinematic evidence oforthogonally rotating material. The stellar disk of UGC 10043 has arather low optical surface brightness [μ(0)R,i~23.2 magarcsec-2], a small scale height (hz=395 pc forD=33.4 Mpc), and a mild integral sign warp. A dusty, inner diskcomponent that appears tilted relative to the outlying disk is alsoseen. The Hα and [N II] emission lines in UGC 10043 resolve intomultiple velocity components, indicating the presence of a large-scalegalactic wind with an outflow velocity of Vout>~104 kms-1. Hα+[NII] imaging reaffirms this picture byrevealing ionized gas extended to |z|~3.5 kpc in the form of a roughlybiconical structure. The [N II]/Hα line intensity ratio increaseswith increasing distance from the plane, reaching values as high as 1.7.Unlike most galaxies with large-scale winds, UGC 10043 has only a modestglobal star formation rate (<~1 Msolar yr-1),implying the wind is powered by a rather feeble central starburst. Wediscuss evolutionary scenarios that could account for both thestructural complexities of UGC 10043 and its large-scale wind. The mostplausible scenarios require a major accretion or merger event at least afew gigayears ago.
| Stellar Kinematics of Boxy Bulges: Large-Scale Bars and Inner Disks
Long-slit stellar kinematic observations were obtained along the majoraxis of 30 edge-on spiral galaxies, 24 with a boxy or peanut-shaped(B/PS) bulge and six with other bulge types for comparison. Such B/PSbulges are identified in at least 45% of highly inclined systems, and agrowing body of theoretical and observational work suggests that theyare the edge-on projection of thickened bars. Profiles of the meanstellar velocity V, the velocity dispersion σ, as well as theasymmetric (h3) and symmetric (h4) deviations froma pure Gaussian are presented for all objects. Comparing these profileswith stellar kinematic bar diagnostics developed from N-bodysimulations, we find bar signatures in 24 of our sample galaxies (80%).Galaxies with a B/PS bulge typically show a double-humped rotation curvewith an intermediate dip or plateau. They also frequently show a ratherflat central velocity dispersion profile accompanied by a secondary peakor plateau, and numerous galaxies have a local central σ minimum(>~40%). The h3 profiles display up to three slopereversals. Most importantly, h3 is normally correlated with Vover the presumed bar length, contrary to expectations from axisymmetricdisks. These characteristic bar signatures strengthen the case for aclose relationship between B/PS bulges and bars and leave little roomfor other explanations of the bulges' shape. We also find thath3 is anticorrelated with V in the very center of mostgalaxies (>~60%), indicating that these objects additionally harborcold and dense decoupled (quasi-) axisymmetric central stellar disks,which may be related to the central light peaks. These central diskscoincide with previously identified star-forming ionized-gas disks(nuclear spirals) in gas-rich systems, and we argue that they formed outof gas accumulated by the bar at its center through inflow. As suggestedby N-body models, the asymmetry of the velocity profile (h3)appears to be a reliable tracer of asymmetries in disks, allowing us todiscriminate between axisymmetric and barred disks seen in projection.B/PS bulges (and thus a large fraction of all bulges) appear to be madeup mostly of disk material, which has acquired a large vertical extentthrough bar-driven vertical instabilities. Their formation is thusprobably dominated by secular evolution processes rather than merging.
| Minor-axis velocity gradients in disk galaxies
We present the ionized-gas kinematics and photometry of a sample of 4spiral galaxies which are characterized by a zero-velocity plateau alongthe major axis and a velocity gradient along the minor axis,respectively. By combining these new kinematical data with thoseavailable in the literature for the ionized-gas component of the S0s andspirals listed in the Revised Shapley-Ames Catalog of Bright Galaxies werealized that about 50% of unbarred galaxies show a remarkable gasvelocity gradient along the optical minor axis. This fraction rises toabout 60% if we include unbarred galaxies with an irregular velocityprofile along the minor axis. This phenomenon is observed all along theHubble sequence of disk galaxies, and it is particularly frequent inearly-type spirals. Since minor-axis velocity gradients are unexpectedif the gas is moving onto circular orbits in a disk coplanar to thestellar one, we conclude that non-circular and off-plane gas motions arenot rare in the inner regions of disk galaxies.Based on observations carried out at the European Southern Observatoryin La Silla (Chile) (ESO 69.B-0706 and 70.B-0338), with the MultipleMirror Telescope which is a joint facility of the SmithsonianInstitution and the University of Arizona, and with the ItalianTelescopio Nazionale Galileo (AOT-5, 3-18) at the Observatorio del Roquede los Muchachos in La Palma (Spain).Table 1 is only available in electronic form athttp://www.edpsciences.org. Table 5 is only available in electronic format 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/416/507
| The column density distribution function at z= 0 from HI selected galaxies
We have measured the column density distribution function, f(NHI), at z= 0 using 21-cm HI emission from galaxies selected from ablind HI survey. f(NH I) is found to be smaller and flatterat z= 0 than indicated by high-redshift measurements of damped Lymanα (DLA) systems, consistent with the predictions of hierarchicalgalaxy formation. The derived DLA number density per unit redshift,dNDLA/dz= 0.058, is in moderate agreement with valuescalculated from low-redshift QSO absorption line studies. We use twodifferent methods to determine the types of galaxies which contributemost to the DLA cross-section: comparing the power-law slope off(NH I) to theoretical predictions and analysingcontributions to dNDLA/dz. We find that comparison of thepower-law slope cannot rule out spiral discs as the dominant galaxy typeresponsible for DLA systems. Analysis of dNDLA/dz however, ismuch more discriminating. We find that galaxies with log MHI< 9.0 make up 34 per cent of dNDLA/dz Irregular andMagellanic types contribute 25 per cent; galaxies with surfacebrightness account for 22 per cent and sub-L* galaxiescontribute 45 per cent to dNDLA/dz. We conclude that a largerange of galaxy types give rise to DLA systems, not just large spiralgalaxies as previously speculated.
| A Survey for H2O Megamasers. III. Monitoring Water Vapor Masers in Active Galaxies
We present single-dish monitoring of the spectra of 13 extragalacticwater megamasers taken over a period of 9 years and a single epoch ofsensitive spectra for seven others. The primary motivation is a searchfor drifting line velocities analogous to those of the systemic featuresin NGC 4258, which are known to result from centripetal acceleration ofgas in an edge-on, subparsec molecular disk. We detect a velocity driftanalogous to that in NGC 4258 in only one source, NGC 2639. Another, themaser source in NGC 1052, exhibits erratic changes in its broad maserprofile over time. Narrow maser features in all of the other diskgalaxies discussed here either remain essentially constant in velocityover the monitoring period or are sufficiently weak or variable inintensity that individual features cannot be traced reliably from oneepoch to the next. In the context of a circumnuclear, molecular diskmodel, our results suggest that either (a) the maser lines seen aresystemic features subject to a much smaller acceleration than present inNGC 4258, presumably because the gas is farther from the nuclear blackhole, or (b) we are detecting ``satellite'' lines for which theacceleration is in the plane of the sky.Our data include the first K-band science observations taken with thenew 100 m Green Bank Telescope (GBT). The GBT data were taken duringtesting and commissioning of several new components and so are subjectto some limitations; nevertheless, they are in most cases the mostsensitive H2O spectra ever taken for each source and cover800 MHz (~=10,800 km s-1) of bandwidth. Many new maserfeatures are detected in these observations. Our data also include atentative and a clear detection of the megamaser in NGC 6240 at epochs ayear and a few months, respectively, prior to the detections reported byHagiwara et al. and Nakai et al.We also report a search for water vapor masers toward the nuclei of 58highly inclined (i>80deg), nearby galaxies. These sourceswere selected to investigate the tendency that H2O megamasersfavor inclined galaxies. None were detected, confirming that megamasersare associated exclusively with active galactic nuclei.
| The 2MASS Large Galaxy Atlas
We present the largest galaxies as seen in the near-infrared (1-2μm), imaged with the Two Micron All Sky Survey (2MASS), ranging inangular size from 1' to 1.5d. We highlight the 100 largest in thesample. The galaxies span all Hubble morphological types, includingelliptical galaxies, normal and barred spirals, and dwarf and peculiarclasses. The 2MASS Large Galaxy Atlas provides the necessary sensitivityand angular resolution to examine in detail morphologies in thenear-infrared, which may be radically different from those in theoptical. Internal structures such as spirals, bulges, warps, rings,bars, and star formation regions are resolved by 2MASS. In addition tolarge mosaic images, the atlas includes astrometric, photometric, andshape global measurements for each galaxy. A comparison of fundamentalmeasures (e.g., surface brightness, Hubble type) is carried out for thesample and compared with the Third Reference Catalogue. We furthershowcase NGC 253 and M51 (NGC 5194/5195) to demonstrate the quality anddepth of the data. The atlas represents the first uniform, all-sky,dust-penetrated view of galaxies of every type, as seen in thenear-infrared wavelength window that is most sensitive to the dominantmass component of galaxies. The images and catalogs are availablethrough the NASA/IPAC Extragalactic Database and Infrared ScienceArchive and are part of the 2MASS Extended Source Catalog.
| 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 catalog of warps in spiral and lenticular galaxies in the Southern hemisphere
A catalog of optical warps of galaxies is presented. This can beconsidered complementary to that reported by Sánchez-Saavedra etal. (\cite{sanchez-saavedra}), with 42 galaxies in the northernhemisphere, and to that by Reshetnikov & Combes(\cite{reshetnikov99}), with 60 optical warps. The limits of the presentcatalog are: logr 25 > 0.60, B_t< 14.5, delta (2000) <0deg, -2.5 < t < 7. Therefore, lenticular galaxies havealso been considered. This catalog lists 150 warped galaxies out of asample of 276 edge-on galaxies and covers the whole southern hemisphere,except the Avoidance Zone. It is therefore very suitable for statisticalstudies of warps. It also provides a source guide for detailedparticular observations. We confirm the large frequency of warpedspirals: nearly all galaxies are warped. The frequency and warp angle donot present important differences for the different types of spirals.However, no lenticular warped galaxy has been found within the specifiedlimits. This finding constitutes an important restriction fortheoretical models.
| Study of the X-Ray Background Spectrum and Its Large-Scale Fluctuation with ASCA
We studied the energy spectrum and the large-scale fluctuation of theX-ray background with the ASCA GIS instrument based on the ASCA MediumSensitivity Survey and Large Sky Survey observations. A total of 91fields with Galactic latitude |b| > 10° were selected with a skycoverage of 50 deg2 and 4.2 Ms of exposure. For each field,non-X-ray events were carefully subtracted and sources brighter than ~ 2× 1013 erg cm-2 s-1 (2-10keV)were eliminated. Spectral fits with a single power-law model for theindividual 0.7-10 keV spectra showed a significant excess below ~ 2keV,which could be expressed by an additional thermal model with kT ~= 0.4keV or a steep power-law model with a photon index ofΓsoft ~= 6. The 0.5-2keV intensities of the softthermal component varied significantly from field to field by 1 σ= 52 +4-5%, and showed a maximum toward theGalactic Center. This component is considered to be entirely Galactic.As for the hard power-law component, an average photon index of 91fields was obtained to be Γhard = 1.412 +/- 0.007 +/-0.025 and the average 2-10keV intensity was calculated asFhardX = (6.38 +/- 0.04 +/- 0.64) ×10-8erg cm-2 s-1 sr-1 (1σ statistical and systematic errors). The Galactic component ismarginally detected in the hard band. The 2-10keV intensities show a 1σ deviation of 6.49+0.56-0.61%, whiledeviation due to the reproducibility of the particle background is 3.2%.The observed deviation can be explained by the Poisson noise of thesource count in the f.o.v. (~ 0.5 deg2), even assuming asingle N-logS relation on the whole s ky. Based on the observedfluctuation and the absolute intensity, an acceptable region of theN-logS relation was derived, showing a consistent feature with therecent Chandra and XMM-Newton results. The fluctuation of the spectralindex was also examined; it implied a large amount of hard sources and asubstantial variation in the intrinsic source spectra(Γs ~= 1.1 +/- 1.0).
| On the mass of M31
Recent work by several groups has established the properties of thedwarf satellites to M31. We reexamine the reported kinematics of thisgroup employing a fresh technique we have developed previously. Bycalculating the distribution of a χ statistic (which we define inthe paper) for the M31 system, we conclude that the total mass (discplus halo) of the primary is unlikely to be as great as that of our ownMilky Way. In fact the χ distribution for M31 indicates that, likeNGC 3992, it does not have a massive halo. In contrast, the analysis ofthe satellites of NGC 1961 and NGC 5084 provides strong evidence formassive haloes surrounding both spiral galaxies.
| The Properties of Satellite Galaxies in External Systems. I. Morphology and Structural Parameters
We present the first results of an ongoing project to study themorphological, kinematical, dynamical, and chemical properties ofsatellite galaxies of external giant spiral galaxies. The sample ofobjects has been selected from the catalog by Zaritsky et al. The paperanalyzes the morphology and structural parameters of a subsample of 60such objects. The satellites span a great variety of morphologies andsurface brightness profiles. About two-thirds of the sample are spiralsand irregulars, the remaining third being early-types. Some casesshowing interaction between pairs of satellites are presented andbriefly discussed.
| 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.
| Survey of the ISM in early-type galaxies. IV. The hot dust component
We present mid-IR photometric properties for a sample of 28 early-typegalaxies observed at 6.75, 9.63 and 15 mu m with the ISOCAM instrumenton board the ISO satellite. We find total mid-IR luminosities in therange (3-42) x 108 Lsun. The spectral energydistributions (SED) of the galaxies were derived using the mid-IR datatogether with previously published UV, optical and near-IR data. TheseSEDs clearly show a mid-IR emission coming from dust heated at T =~ 260K. Dust grains properties are inferred from the mid-IR colors. Themasses of the hot dust component are in the range 10-400Msun. The relationship between the masses derived from mid-IRobservations and those derived from visual extinction are discussed. Thepossible common heating source for the gas and dust is investigatedthrough the correlations between Hα and mid-IR luminosities. Basedon observations with ISO, an ESA project with instruments funded by ESAmember states (especially the PI countries: France, Germany, theNetherlands and the UK) and with participation of ISAS and NASA.
| A catalogue and analysis of X-ray luminosities of early-type galaxies
We present a catalogue of X-ray luminosities for 401 early-typegalaxies, of which 136 are based on newly analysed ROSAT PSPC pointedobservations. The remaining luminosities are taken from the literatureand converted to a common energy band, spectral model and distancescale. Using this sample we fit the LX:LB relationfor early-type galaxies and find a best-fit slope for the catalogue of~2.2. We demonstrate the influence of group-dominant galaxies on the fitand present evidence that the relation is not well modelled by a singlepower-law fit. We also derive estimates of the contribution to galaxyX-ray luminosities from discrete-sources and conclude that they provideLdscr/LB~=29.5ergs-1LBsolar-1. Wecompare this result with luminosities from our catalogue. Lastly, weexamine the influence of environment on galaxy X-ray luminosity and onthe form of the LX:LB relation. We conclude thatalthough environment undoubtedly affects the X-ray properties ofindividual galaxies, particularly those in the centres of groups andclusters, it does not change the nature of whole populations.
| The ASCA Medium Sensitivity Survey (the GIS Catalog Project): Source Catalog
We present the first X-ray source catalog of the ASCA Medium SensitivitySurvey (AMSS, or the GIS catalog project), constructed from data atGalactic latitudes b>10deg observed between 1993 May and 1996December. The catalog utilizes 368 combined fields and contains 1343sources with the detection significance above 5 σ either in thesurvey bands of 0.7-7 keV, 2-10 keV, or 0.7-2 keV, including targetsources. For each source, the ASCA source name, position, a 90% errorradius, count rates in the three bands, detection significances, fluxes,and a hardness ratio are provided. With extensive simulations, wecarefully evaluate the data quality of the catalog. Results fromcross-correlation with other existing catalogs are briefly summarized.
| The visible environment of galaxies with counterrotation
In this paper we present a statistical study of the environments of 49galaxies in which there is gas- or stellar-counterrotation. The numberof possible companions in the field (to apparent magnitude 22), theirsize and concentration were considered. All the statistical parameterswere analysed by means of Kolgomorov-Smirnov tests, using a controlsample of 43 galaxies without counterrotation. From our data, nosignificant differences between the counter-rotating and control samplesappear. This is different to Seyfert or radio-loud galaxies which lie inenvironments with a higher density of companions. On the contrary, if aweak tendency exists, for galaxies with gas counterrotation only, it isdiscovered in regions of space where the large scale density of galaxiesis smaller. Our results tend to disprove the hypothesis thatcounterrotation and polar rings derive from a recent interaction with asmall satellite or a galaxy of similar size. To a first approximation,they seem to follow the idea that all galaxies are born through a mergerprocess of smaller objects occurring very early in their life, or thatthey derive from a continuous, non-traumatic infall of gas that formedstars later. Whatever the special machinery is which producescounterrotation or polar rings instead of a co-planar, co-rotatingdistribution of gas and stars, it seems not to be connected to thepresent galaxy density of their environments.
| Metal Abundances in the Hot Interstellar Medium in Early-Type Galaxies Observed with ASCA
We have analyzed ASCA data of 27 early-type galaxies, and studied theproperties of their X-ray emitting ISM (InterStellar Medium) in detail.We found that overlapping lines and free-bound continuum cause strongcoupling in the derived abundances of various elements. The abundancedetermination is also difficult due to the uncertainties in the Fe-Latomic physics, because the Fe-L lines couple with the O and Ne K-lines.However, when the abundances of alpha -elements are fixed, all of theplasma codes give similar Fe abundances with a scattering of only20-30%. To relax the strong coupling among the elements, we included 20%systematic errors in the Fe-L region of the spectra. Then, in X-rayluminous galaxies, the derived abundance of Fe and alpha -elements bothbecame ~ 1 solar within a factor of 2. This result relaxes the previoussevere discrepancy between the ISM and stellar metallicities. The ISMmetallicity in X-ray fainter galaxies is still uncertain, but we can atleast constrain that the contribution from type-Ia SN to the ISMabundance is lower than in X-ray luminous systems. These resultsstrongly suggest that a large fraction of SN Ia products have escapedinto intergalactic space.
| 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
| Satellites as Probes of the Masses of Spiral Galaxies
We present H I observations and analyses of the kinematics of 24satellite-primary galaxy pairs with projected separations between 4.9and 240 kpc. The satellites have masses of less than 3% of their primaryspirals. Two estimates for the masses of the primaries are available,one from their rotation curves and one from the orbital properties ofthe satellites. Defining chi as the ratio of these two mass estimates,it is a measure of the presence, or absence, of a significant halo. Thechi-distribution for these 24 pairs is presented and the selectioneffects are discussed. Moreover, we show that the chi-distribution ofmore numerous pairs, with projected separations of less than 200 kpc,identified by Zaritsky et al., after adopting selection criteria quitedifferent from ours, is similar to our chi-distribution. We show thatthe observational biases have a negligible effect; the biased andunbiased distributions are essentially identical. In order to understandthis distribution, N-body calculations were executed to simulate thedynamical behavior of relatively low mass satellites orbiting primarydisk galaxies with and without extended halos. The models and the realgalaxies were ``observed'' in the same fashion. In addition, we made apartially analytical analysis of the behavior of orbits in a logarithmicpotential. We find that a ``generic'' model, characterized by a singledisk/halo combination, cannot reproduce the observed P(chi)distribution. However, a simple two-component population of galaxies,composed of not more than 60% with halos and 40% without halos, issuccessful, if galaxies have dimensions of order 200 kpc. If galaxiesare considerably larger with sizes extending to 400 kpc or more, theconstraints become more onerous. No generic model can describe the fullrange of the observed P(chi), particularly if the distribution forr_p<200 kpc is compared with that for r_p>200 kpc. Regardless ofthe mix of orbital eccentricities, neither pure halo, nor canonical(disk and halo masses are comparable within the disk radius) models willwork. A multicomponent approximation to reality can be constructed forwhich the canonical model must be mixed with a small fraction of systemsessentially devoid of a massive dark halo. Only by including thesecomplexities can the full range of P(chi) be modeled with any degree ofsuccess over all radial extents. We show that dynamical friction cannotbe ignored in these explorations and that the average mass of a galaxyis in the range of (1-5)x10^12 M_solar, with a mass-to-luminosity ratioof at most a few hundred. This is insufficient to close the universe.
| The Nature of Boxy/Peanut-Shaped Bulges in Spiral Galaxies
We present a systematic observational study of the relationship betweenbars and boxy/peanut-shaped (B/PS) bulges. We first review and discussproposed mechanisms for their formation, focusing on accretion andbar-buckling scenarios. Using new methods relying on the kinematics ofedge-on disks, we then look for bars in a large sample of edge-on spiralgalaxies with a B/PS bulge and in a smaller control sample of edge-onspirals with more spheroidal bulges. We present position-velocitydiagrams of the ionized gas obtained from optical long-slitspectroscopy. We show that almost all B/PS bulges are due to a thick barviewed edge-on, while only a few extreme cases may be due to theaccretion of external material. This strongly supports the bar-bucklingmechanism for the formation of B/PS bulges. None of the galaxies in thecontrol sample show evidence for a bar, which suggests conversely thatbars are generally B/PS.We consider the effects of dust in the disk ofthe galaxies but conclude that it does not significantly affect ourresults. Unusual emission-line ratios correlating with kinematicalstructures are observed in many objects, and we argue that this isconsistent with the presence of strong bars in the disk of the galaxies.As expected from N-body simulations, the boxy-peanut transition appearsto be related to the viewing angle, but more work is required to derivethe precise orientation of the bars in the bulges. The reliableidentification of bars in edge-on spiral galaxies opens up for the firsttime the possibility of studying observationally the vertical structureof bars.
| The Type IA Supernova 1997BR in ESO 576-G40
The peculiar type Ia supernova SN 1997br in ESO 576-G40 was extensivelyobserved at Beijing Astronomical Observatory and Lick Observatory. Inthis paper, we present and discuss the BVRI photometry and the spectracollected over 3 months, beginning 9 days before maximum brightness. Thelight curves of SN 1997br are similar to those of SN 1991T, with slowdecline rates after the B maximum. Well-sampled data before the Bmaximum show unambiguously that SN 1997br rises more slowly and has awider peak than normal type Ia supernovae. The optical color evolutionof SN 1997br is also similar to that of SN 1991T. We estimate theextinction of SN 1997br to be E(B-V)=0.35+/-0.10 mag by comparing itsBVRI light curves with those of SN 1991T and by measuring the equivalentwidth of interstellar Na I D absorption lines. We have conducted athorough comparison of the spectroscopic evolution of SN 1997br, SN1991T, and SN 1994D. Although SN 1997br is generally very similar to SN1991T, it shows some interesting differences at various epochs. Spectraof SN 1997br seem to indicate an earlier transition to the dominantphase of Fe-peak elements after the B maximum. Si II lines in SN 1997brshow a very short duration after the B maximum. We discuss theimplications of our observations of SN 1997br for models of type Iasupernovae. Specifically, we suggest that some SNe Ia may result fromdecelerated detonations of white dwarfs.
| Bulge-Disk Decomposition of 659 Spiral and Lenticular Galaxy Brightness Profiles
We present one of the largest homogeneous sets of spiral and lenticulargalaxy brightness profile decompositions completed to date. The 659galaxies in our sample have been fitted with a de Vaucouleurs law forthe bulge component and an inner-truncated exponential for the diskcomponent. Of the 659 galaxies in the sample, 620 were successfullyfitted with the chosen fitting functions. The fits are generally welldefined, with more than 90% having rms deviations from the observedprofile of less than 0.35 mag. We find no correlations of fittingquality, as measured by these rms residuals, with either morphologicaltype or inclination. Similarly, the estimated errors of the fittedcoefficients show no significant trends with type or inclination. Thesedecompositions form a useful basis for the study of the lightdistributions of spiral and lenticular galaxies. The object base issufficiently large that well-defined samples of galaxies can be selectedfrom it.
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