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The Supernova Rate-Velocity Dispersion Relation in the Interstellar Medium
We investigate the relationship between the velocity dispersion of thegas and the supernova (SN) rate and feedback efficiency withthree-dimensional numerical simulations of SN-driven turbulence in theinterstellar medium (ISM). Our simulations aim to explore the constancyof the velocity dispersion profiles in the outer parts of galactic disksat ~6-8 km s-1 and the transition to the starburst regime,i.e., high star formation rates (SFRs) associated with high velocitydispersions. With our fiducial value of the SN feedback efficiency(i.e., ε=0.25, corresponding to an injected energy per SN of0.25×1051 ergs), our results show that (1) SN drivingleads to constant velocity dispersions of σ~6 km s-1for the total gas and σHI~3 km s-1 for the HI gas, independent of the SN rate, for values of the rate between 0.01and 0.5 the Galactic value (ηG) (2) the position of thetransition to the starburst regime (i.e., location of sharp increase inthe velocity dispersion) at around SFR/area~=5×10-3 to10-2 Msolar yr-1 kpc-2observed in the simulations is in good agreement with the transition tothe starburst regime in the observations (e.g., NGC 628 and NGC 6949);(3) for the high SN rates, no H I gas is present in the simulations box;however, for the total gas velocity dispersion, there is good agreementbetween the models and the observations; (4) at the intermediate SNrates (η/ηG~0.5-1), taking into account the thermalbroadening of the H I line helps reach a good agreement in that regimebetween the models and the observations; and (5) forη/ηG<0.5, σ and σHI fallbelow the observed values by a factor of ~2. However, a set ofsimulations with different values of ɛ indicates that, forlarger values of the SN feedback efficiencies, velocity dispersions ofthe H I gas of the order of 5-6 km s-1 can be obtained, incloser agreement with the observations. The fact that forη/ηG<0.5, the H I gas velocity dispersions are afactor of ~2 smaller than the observed values could result from the factthat we might have underestimated the SN feedback efficiency. On theother hand, it might also be an indication that other physical processescouple to the stellar feedback in order to produce the observed level ofturbulence in galactic disks.
| The Effects of Interactions on the Structure and Morphology of Elliptical/Lenticular Galaxies in Pairs
We present a structural and photometric analysis of 42elliptical/lenticular galaxies in E/S0 + S pairs observed in the BVRIcolor bands. The aim of the analysis is to empirically determine theeffects of interactions on the galaxies' morphology, structure, andstellar populations as seen from the CAS parameters (light concentrationC, asymmetry A, and clumpiness S). We further compare these values to acontrol sample of 67 mostly isolated noninteracting E/S0 galaxies. Wefind that the paired E/S0 galaxies occupy more scattered loci in CASspace than noninteracting E/S0s and that the structural effects ofinteractions on E/S0s are minor, in contrast to disk galaxies involvedin interactions. This suggests that observational methods forrecognizing interactions, such the CAS methodology of Conselice, wouldnot detect E/S0s involved in interactions (related to early phases ofthe so-called dry mergers), and that the majority of interactinggalaxies identified at high redshift must be gas-dominated systems.However, we find statistical differences in the asymmetry index whencomparing isolated and interacting E/S0s. On average, paired E/S0galaxies have A-values 2.96+/-0.72 times larger than those ofnoninteracting E/S0s. For the subset of presumably strongly interactingE/S0s, A and S can be several times larger than the typical values ofthe isolated E/S0s. We show that the asymmetries are consistent withseveral internal and external morphological distortions. We concludethat the subsample of interacting E/S0s should be dense, gas-poorgalaxies in systems spanning a wide range of interaction stages, withtypical merging timescales >~0.1-0.5 Gyr. We use the observedphenomenology of this subsample to predict the approximate loci of drypremergers in the CAS parameter space.
| BVRI Surface Photometry of Mixed Morphology Pairs of Galaxies. III. The Third Data Set
This is the third of a series of papers devoted to the study of thephotometric properties of spiral and elliptical galaxies in interactingpairs. We report broad band (BVRI) total magnitudes, as well as surfacebrightness, color and geometric (ɛ = 1 - b/a, PA, anda4/a) profiles for a sample of 10 mixed morphology (E/S0+S)pairs drawn from the Karachentsev Catalogue of Isolate Pairs of Galaxies(KPG). Most of the objects reported here have their photometricparameters derived for the first time. Surface photometry in combinationwith image processing and color diagrams are useful to test andreevaluate the morphological classification of each galaxy in thesepairs. We find 5 true (E+S) pairs in the present sample, 4lenticular-spiral (S0+S) systems and 1 spiral-spiral (S+S) pair. Wefound no clear evidence of a Holmberg effect in our sample of mixedpairs. The existence of a large number of isolated (E+S) pairs (50% in our sample) rises interesting questions for models of galaxyformation.
| Massive black hole remnants of the first stars - II. Optical and X-ray signatures in present-day galactic haloes
The first stars forming in minihaloes at redshifts greater than 20 mayhave been very massive, and could have left behind massive black hole(MBH) remnants. In a previous paper we investigated the hierarchicalmerging of these MBHs and their associated haloes, using asemi-analytical approach consisting of a hierarchical merger treealgorithm and explicit prescriptions for the dynamics of mergedsubstructure inside a larger host halo following a merger. One of theresults was the prediction of a number of MBHs orbiting throughoutpresent-day galactic haloes. In addition, we estimated themass-accretion rate of these MBHs, assuming that they retained aroundthem a core of material from the original haloes in which they formed.On the basis of these estimates, in this paper we determine thebolometric, optical and X-ray luminosity functions for accreting MBHs,using thin-disc and advection-dominated accretion-flow models. Ourpredicted MBH X-ray fluxes are then compared with observations ofultraluminous X-ray sources in galaxies. We find that the slope andnormalization of the predicted X-ray luminosity functions are similar tothose observed, suggesting that MBHs could account for some fraction ofthese sources.
| Redshift-Distance Survey of Early-Type Galaxies: Spectroscopic Data
We present central velocity dispersions and Mg2 line indicesfor an all-sky sample of ~1178 elliptical and S0 galaxies, of which 984had no previous measures. This sample contains the largest set ofhomogeneous spectroscopic data for a uniform sample of ellipticalgalaxies in the nearby universe. These galaxies were observed as part ofthe ENEAR project, designed to study the peculiar motions and internalproperties of the local early-type galaxies. Using 523 repeatedobservations of 317 galaxies obtained during different runs, the dataare brought to a common zero point. These multiple observations, takenduring the many runs and different instrumental setups employed for thisproject, are used to derive statistical corrections to the data and arefound to be relatively small, typically <~5% of the velocitydispersion and 0.01 mag in the Mg2 line strength. Typicalerrors are about 8% in velocity dispersion and 0.01 mag inMg2, in good agreement with values published elsewhere.
| Multiwavelength Insights into Mixed-Morphology Binary Galaxies. I. ISOCAM, ISOPHOT, and Hα Imaging
We present Hα and ISO mid- and far-IR observations for a sample ofmixed-morphology galaxy pairs that reveal both the stellar andnonstellar signatures of the interaction process. A mixed-morphologypair is perhaps the simplest form of galaxy-galaxy interaction becauseit is expected to involve only a single rapidly rotating gas-richcomponent paired with a gas-poor elliptical or lenticular galaxy. Aprimary assumption that we address is whether spirals are the only IRemitter in these mixed (E+S) pairs. Our observations reveal that many ofthe early-type galaxies exhibit weak (low equivalent width) emission, asoften observed in field elliptical galaxies. These are the classicalmixed-morphology pairs. However, some of the early-type components,especially the lenticular galaxies, show evidence for significant starformation, with Hα equivalent widths and 15 μm luminositiescomparable to or exceeding those of their often much larger spiralcompanions. Our sample contains five Seyfert 2 nuclei, of which threecan be described as companions on the end of a spiral arm. The Seyfertnucleus is often accompanied by a starburst region, while other suchcompanions currently show only the starburst component. These pairs areamong the best candidates for direct interaction fuelling of bothstarbursts and active galactic nuclei.Based on observations with the Infrared Space Observatory (ISO), an ESAproject with instruments funded by ESA Member States (especially the PIcountries: France, Germany, the Netherlands and the United Kingdom) withthe participation of ISAS and NASA.
| 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
| 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
| 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.
| 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.
| 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.
| An X-Ray Survey of Galaxies in Pairs
Results are reported from the first survey of X-ray emission fromgalaxies in pairs. The sample consists of 52 pairs of galaxies from theCatalog of Paired Galaxies whose coordinates overlap the ROSAT PositionSensitive Proportional Counter pointed observations. The mean observedlogl_X for early-type pairs is 41.35+/-0.21, while the mean logl_Xpredicted using the l_X-l_b relationship for isolated early-typegalaxies is 42.10+/-0.19. With 95% confidence, the galaxies in pairs areunderluminous in the X-ray, compared with isolated galaxies, for thesame l_b. A significant fraction of the mixed pair sample also appearssimilarly underluminous. A spatial analysis shows that the X-rayemission from pairs of both types typically has an extent of ~10-50 kpc,much smaller than the group intergalactic medium, and thus likelyoriginates from the galaxies. CPG 564, the most X-ray luminousearly-type pair, 4.7x10^42 ergs s^-1, is an exception. The extent of itsX-ray emission, greater than 169 kpc, and HWHM, ~80 kpc, is comparableto that expected from an intergalactic medium. The sample shows only aweak correlation, ~81% confidence, between l_X and l_b, presumably dueto variations in gas content within the galaxies. No correlation betweenl_X and the pair velocity difference (Deltav), separation (Deltar), orfar-infrared luminosity (l_fir) is found, although the detection rate islow, 22%.
| Investigation of Barred Galaxies. V. Surroundings of SB and SA Galaxies
Not Available
| Morphology transformation in pairs of galaxies - the local sample
We present photometric analysis of a local sample of 14 isolated pairsof galaxies. The photometric properties analyzed in the local pairs are:colors, morphology, tidal effects and activity. We verify that closepairs have an excess of early-type galaxies and many elliptical galaxiesin this pairs are, in fact, lenticular galaxies. Many late-pairs in oursample show strong tidal damage and blue star formation regions. Weconclude that pairs of different morphologies may have passed throughdifferent evolution processes which violently transformed theirmorphology. Pairs with at least one early-type component may bedescendents of groups of galaxies. However, late-type pairs are probablylong-lived showing clearly signs of interaction. Some of them could beseen as an early stage of mergers. These photometric databases will beused for future comparison with more distant pairs in order to studygalaxy evolution.
| 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
| An Einstein X-Ray Survey of Optically Selected Galaxies. I. Data
We present the results of a complete Einstein imaging proportionalcounter X-ray survey of optically selected galaxies from theShapley-Ames Catalog, the Uppsala General Catalogue, and the EuropeanSouthern Observatory Catalog. Well-defined optical criteria are used toselect the galaxies, and X-ray fluxes are measured at the opticallydefined positions. The result is a comprehensive list of X-ray detectionand upper limit measurements for 1018 galaxies. Of these, 827 haveeither independent distance estimates or radial velocities. Associatedoptical, redshift, and distance data have been assembled for thesegalaxies, and their distances come from a combination of directlypredicted distances and those predicted from the Faber-Burstein GreatAttractor/Virgocentric infall model. The accuracy of the X-ray fluxeshas been checked in three different ways; all are consistent with thederived X-ray fluxes being of <=0.1 dex accuracy. In particular,there is agreement with previously published X-ray fluxes for galaxiesin common with a 1991 study by Roberts et al. and a 1992 study byFabbiano et al. The data presented here will be used in further studiesto characterize the X-ray output of galaxies of various morphologicaltypes and thus to enable the determination of the major sourcescontributing to the X-ray emission from galaxies.
| Kinematical Observations of a Sample of Binary Galaxies
Not Available
| A survey of the ISM in early-type galaxies. I. The ionized gas.
We present results of a CCD optical imaging survey of the ionized gas in73 luminous elliptical and lenticular galaxies, selected from the RC3catalog to represent a broad variety of X-ray, radio, infrared andkinematical properties. For each galaxy we have used broad-band R imagesand narrow-band images centered at the Hα and [NII] emission linesto derive the luminosity and distribution of the ionized gas. We foundthat a large fraction of E (72%) and S0 (85%) galaxies in our samplecontain ionized gas. The gas morphology appears to be rather smooth formost galaxies; however ~12% of the sample galaxies show a very extendedfilamentary structure. According to the morphology and size of the gasdistribution, the galaxies have been classified into three broad groups,named small disk (SD), regular extended (RE) and filamentary structure(F). The mean diameter of the emitting region ranges between 1 and10kpc; the derived mass of the ionized gas ranges between 10^3^ and10^5^ solar masses. A significant correlation between Hα+[NII] andX-ray luminosities is found for those galaxies (27% of the sample) forwhich we have detected ionized gas and are also listed as X-ray sources.However, there are relatively strong X-ray emitting galaxies for whichwe have not detected Hα+[NII] emission and objects which showemission-lines but are not listed either in the EINSTEIN or in the ROSATdatabases. The distribution of datapoint and upper limits in thisdiagram suggests that galaxies with warm gas are also X-ray emitters,while there are X-ray emitters without measurable Hα+[NII]emission. Similar characteristics are present in the correlation betweenthe infrared luminosity in the 12 μm band and L_Hα+[NII]_;correlations with other infrared wavelengths are weaker. A strongcorrelation was also found between the Hα+[NII] luminosity and theluminosity in the B band inside the region occupied by the line-emittinggas. We use these correlations to discuss the possible mechanismsresponsible for the gas ionization and excitation, analyzing inparticular the role of the post-AGB stars and the thermal conductionfrom the X-ray halo in providing the necessary source of ionization.
| 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 multiparametric analysis of the Einstein sample of early-type galaxies. 1: Luminosity and ISM parameters
We have conducted bivariate and multivariate statistical analysis ofdata measuring the luminosity and interstellar medium of the Einsteinsample of early-type galaxies (presented by Fabbiano, Kim, &Trinchieri 1992). We find a strong nonlinear correlation betweenLB and LX, with a power-law slope of 1.8 +/- 0.1,steepening to 2.0 +/- if we do not consider the Local Group dwarfgalaxies M32 and NGC 205. Considering only galaxies with logLX less than or equal to 40.5, we instead find a slope of 1.0+/- 0.2 (with or without the Local Group dwarfs). Although E and S0galaxies have consistent slopes for their LB-LXrelationships, the mean values of the distribution functions of bothLX and LX/LB for the S0 galaxies arelower than those for the E galaxies at the 2.8 sigma and 3.5 sigmalevels, respectively. We find clear evidence for a correlation betweenLX and the X-ray color C21, defined by Kim,Fabbiano, & Trinchieri (1992b), which indicates that X-rayluminosity is correlated with the spectral shape below 1 keV in thesense that low-LX systems have relatively large contributionsfrom a soft component compared with high-LX systems. We findevidence from our analysis of the 12 micron IRAS data for our samplethat our S0 sample has excess 12 micron emission compared with the Esample, scaled by their optical luminosities. This may be due toemission from dust heated in star-forming regions in S0 disks. Thisinterpretation is reinforced by the existence of a strongL12-L100 correlation for our S0 sample that is notfound for the E galaxies, and by an analysis of optical-IR colors. Wefind steep slopes for power-law relationships between radio luminosityand optical, X-ray, and far-IR (FIR) properties. This last point arguesthat the presence of an FIR-emitting interstellar medium (ISM) inearly-type galaxies is coupled to their ability to generate nonthermalradio continuum, as previously argued by, e.g., Walsh et al. (1989). Wealso find that, for a given L100, galaxies with largerLX/LB tend to be stronger nonthermal radiosources, as originally suggested by Kim & Fabbiano (1990). We notethat, while LB is most strongly correlated withL6, the total radio luminosity, both LX andLX/LB are more strongly correlated with L6CO, the core radio luminosity. These points support the argument(proposed by Fabbiano, Gioia, & Trinchieri 1989) that radio cores inearly-type galaxies are fueled by the hot ISM.
| The Nature of Seyfert 2 Galaxies with Obscured Broad-Line Regions. I. Observations
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1995ApJ...440..565T&db_key=AST
| Gaseous and stellar components in mixed pairs of galaxies. I. The data.
Isolated mixed morphology pairs are composed of an early and a late typegalaxy. They are an ideal laboratory for studying the response of gas toa gravitational instability. We present data from a kinematic andphotometric study of six mixed pairs. High resolution rotation andvelocity dispersion curves, for both gas and stellar components, arepresented. Slit orientations were along the major axis of the spiraland, in most of the cases, along the line connecting the galaxy nuclei.B and V luminosity and geometrical profiles are also presented.Photometric parameters including effective radius and disk scale lengthare also presented. Data on the [N II](6583)/Hα emission lineratio provide a further insight into physical conditions of the gas.Half of the early-type components show lenticular morphology involving awell defined disk. Most late-type components show Grand Design spiralstructure. Rotation curves of both members appear normal along the axesstudied. The nuclear region of NGC 5297 is the single case where thegaseous component shows evidence for an apparent counter rotationrelative to the stellar component, probably due to the presence of abar. There is evidence in the early type member NGC 5953, and possiblyalso in NGC 5296, that the gas component has been acquired from thespiral member of the pair. The gas in these objects is concentrated innuclear star forming regions as deduced from (B-V) color. This may beevidence for mass transfer induced activity (cross-fuelling) in thesepairs. The nuclear gas in NGC 5297, 6962 and E 297-G-8 shows a reversalof the [N II] to Hα emission line intensity ratio. This indicatoralong with the [O III](5007)/Hβ ratio suggests that these nucleishow low level (LINER) activity.
| Numerical simulation of large-scale magnetic-field evolution in spiral galaxies.
The evolution of large-scale magnetic fields in disk galaxies isinvestigated numerically. The gasdynamical simulations in a diskperturbed by spiral or bar potential are incorporated into the kinematiccalculations of induction equations to elucidate the effects ofnon-axisymmetric disk structure on magnetic fields. The effects ofinterstellar turbulence are given as the turbulent diffusion of magneticfields. The usually adopted dynamo mechanism of α-effect is notconsidered in our computations, because it is not obvious about theactual existence of the effect in a galaxy. Our principal concern is toclear how observationally and theoretically well-established gas flowaffects the magnetic-field structure and evolution, without putting alot of artificial parameters in the model. We have found that thedensity-wave streaming motion of gas has a significant influence on thedistribution of magnetic fields: the lines of force are well alignedwith spiral arms due to the compressional and additional shearing flowof gas in these regions. In the inter-arm regions, the field lines havethe finite angles with respect to the imposed arms, because the gaseousstreamlines induced by spiral arms deviate from the orientation ofspiral arms themselves. These properties of magnetic-field orientationacross the arm are well in agreement with the results of radio continuumobservations. All simulation models have resulted in the eventual decayof magnetic energy due to the strong turbulent diffusion. We have alsoexplored the azimuthally periodic function for the coefficient ofturbulent diffusion with the maximum in spiral-arm regions. This isanticipated from the enhancement of turbulence by young OB stars andsupernovae. This effect of non-uniform dissipation gives rise to themodulation of magnetic-field structure and its time evolution. Inparticular, the dissipation rate of magnetic fields can be much smallerthan the usually assumed rate of ~1/10^8^yr^-1^.
| CCD calibration of the magnitude scale for the SSRS2 sample: The equatorial region
In this paper we continue our investigation on the isophotal nature,accuracy, and uniformity of the magnitude system adopted in the SouthernSky Redshift Survey extension (SSRS2). Extending our earlier work, weexamine galaxies in the equatorial region, primarily in the declinationrange delta greater than or equal to -17.5 deg and less than or equal to0 deg, over a large range of right ascension, covering the southern andnorthern Galactic caps. For this purpose, we have obtained CCD isophotalmagnitudes in the B and R bands for 265 galaxies of differentmorphological types. Using the larger sample we confirm our earlierclaim that the mSSRS2 magnitudes are very nearly themagnitude measured within the isophote muB = 26 mag/sqarcsec, with a dispersion of about 0.30 mag. The relative zero-pointoffset between our mSSRS2 magnitudes and the CCD photometryis -0.02 mag from all data we have obtained. However, we detect avariation of the zero-point across different regions of the sky of +/-0.10 mag for regions at large angular separations. We also estimate thatthe zero-point offset between the mSSRS2 and Zwicky systemsis relatively small (approximately 0.10 mag), which should allow us tocombine the data from the SSRS2 and the CfA2 Redshift Survey.
| UBVRI photoelectric photometry of bright southern early-type galaxies
UBVRI multi-aperture photometry of 207 bright southern galaxies and of72 objects of an additional list is presented. These observations weremade for obtaining the magnitude scale zero-point as an accuratedetermination of the sky background for a two-dimensional photometryprogram concerning these galaxies. We have also inferred the asymptoticmagnitudes, color indices and effective apertures of these objects. Ourresults are in good agreement with those of others authors.
| 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.
| Models and observations of starbursts. II - Starbursts in interacting galaxies
Evolutionary models are applied here to starburst galaxies in a sampleof 30 interacting or merged systems in order to determine the durationof the starbursts. The time delay between bursts in both components ofinteracting pairs of disk galaxies is investigated and it is found thatstarbursts in the minor galaxies of these pairs started earlier thanthose in the major galaxies. While strong starbursts are found to beactive for only about 2 x 10 exp 7 yrs, the time delay between thebursts in both components of the interacting pairs can be significantlylarger. Delays of up to 2 x 10 exp 8 yrs are found in the sample. Modelfits show that the mass-to-luminosity ratios of strong centralstarbursts indicate a deficiency of low-mass stars in the starburstinitial mass function. The required low-mass-star deficiency is smallerthan previously believed.
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