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The structure of elliptical galaxies in the Virgo cluster. Results from the INT Wide Field Survey
We report on a complete CCD imaging survey of 226 elliptical galaxies inthe North-East quadrant of the Virgo cluster, representative of theproperties of giant and dwarf elliptical galaxies in this cluster. Wefit their radial light profiles with the Sersic r1/n model oflight distribution. We confirm the result of Graham & Guzman(\cite{Graham03}, AJ, 125, 2936) that the apparent dichotomy between Eand dE galaxies in the luminosity-< μ>e plane nolonger appears when other structural parameters are considered and canbe entirely attributed to the onset of ``core'' galaxies atBT -20.5 mag. When ``core'' galaxies are notconsidered, E and dE form a unique family with n linearly increasingwith the luminosity. For 90 galaxies we analyze the B-I color indices,both in the nuclear and in the outer regions. Both indices are bluertoward fainter luminosities. We find also that the outer color gradientsdo not show any significant correlation with the luminosity. The scatterin all color indicators increases significantly toward lowerluminosities, e.g. galaxies fainter than BT -15 have aB-I spread > 0.5 mag.Table 2, Figs. 13 and 14 are only available in electronic form athttp://www.edpsciences.org
| Completing H I observations of galaxies in the Virgo cluster
High sensitivity (rms noise 0.5 mJy) 21-cm H I line observationswere made of 33 galaxies in the Virgo cluster, using the refurbishedArecibo telescope, which resulted in the detection of 12 objects. Thesedata, combined with the measurements available from the literature,provide the first set of H I data that is complete for all 355 late-type(Sa-Im-BCD) galaxies in the Virgo cluster with mp ≤ 18.0mag. The Virgo cluster H I mass function (HIMF) that was derived forthis optically selected galaxy sample is in agreement with the HIMFderived for the Virgo cluster from the blind HIJASS H I survey and isinconsistent with the Field HIMF. This indicates that both in this richcluster and in the general field, neutral hydrogen is primarilyassociated with late-type galaxies, with marginal contributions fromearly-type galaxies and isolated H I clouds. The inconsistency betweenthe cluster and the field HIMF derives primarily from the difference inthe optical luminosity function of late-type galaxies in the twoenvironments, combined with the HI deficiency that is known to occur ingalaxies in rich clusters.Tables \ref{t1, \ref{sample_dat} and Appendix A are only available inelectronic form at http://www.edpsciences.org
| Star Formation Properties of a Large Sample of Irregular Galaxies
We present the results of Hα imaging of a large sample ofirregular galaxies. Our sample includes 94 galaxies with morphologicalclassifications of Im, 26 blue compact dwarfs (BCDs), and 20 Sm systems.The sample spans a large range in galactic parameters, includingintegrated absolute magnitude (MV of -9 to -19), averagesurface brightness (20-27 mag arcsec-2), current starformation activity (0-1.3 Msolar yr-1kpc-2), and relative gas content(0.02-5Msolar/LB). The Hα images were usedto measure the integrated star formation rates, determine the extents ofstar formation in the disks, and compare azimuthally averaged radialprofiles of current star formation to older starlight. The integratedstar formation rates of Im galaxies normalized to the physical size ofthe galaxy span a range of a factor of 104 with 10% Imgalaxies and one Sm system having no measurable star formation at thepresent time. The BCDs fall, on average, at the high star formation rateend of the range. We find no correlation between star formation activityand proximity to other cataloged galaxies. Two galaxies located in voidsare similar in properties to the Sm group in our sample. The H IIregions in these galaxies are most often found within the Holmbergradius RH, although in a few systems H II regions are tracedas far as 1.7RH. Similarly, most of the star formation isfound within three disk scale lengths RD, but in somegalaxies H II regions are traced as far as 6RD. A comparisonof Hα surface photometry with V-band surface photometry shows thatthe two approximately follow each other with radius in Sm galaxies, butin most BCDs there is an excess of Hα emission in the centers thatdrops with radius. In approximately half of the Im galaxies Hα andV correspond well, and in the rest there are small to large differencesin the relative rate of falloff with radius. The cases with stronggradients in the LHα/LV ratios and with highcentral star formation rate densities, which include most of the BCDs,require a significant fraction of their gas to migrate to the center inthe last gigayear. We discuss possible torques that could have causedthis without leaving an obvious signature, including dark matter barsand past interactions or mergers with small galaxies or H I clouds.There is now a substantial amount of evidence for these processes amongmany surveys of BCDs. We note that such gas migration will also increasethe local pressure and possibly enhance the formation of massive denseclusters but conclude that the star formation process itself does notappear to differ much among BCD, Im, and Sm types. In particular, thereis evidence in the distribution function for Hα surface brightnessthat the turbulent Mach numbers are all about the same in these systems.This follows from the Hα distribution functions corrected forexponential disk gradients, which are log-normal with a nearly constantdispersion. Thus, the influence of shock-triggered star formation isapparently no greater in BCDs than in Im and Sm types.
| Globular Clusters as Candidates for Gravitational Lenses to Explain Quasar-Galaxy Associations
We argue that globular clusters (GCs) are good candidates forgravitational lenses in explaining quasar-galaxy associations. Thecatalog of associations (Bukhmastova 2001) compiled from the LEDAcatalog of galaxies (Paturel 1997) and from the catalog of quasars(Veron-Cetty and Veron 1998) is used. Based on the new catalog, we showthat one might expect an increased number of GCs around irregulargalaxies of types 9 and 10 from the hypothesis that distant compactsources are gravitationally lensed by GCs in the halos of foregroundgalaxies. The King model is used to determine the central surfacedensities of 135 GCs in the Milky Way. The distribution of GCs incentral surface density was found to be lognormal.
| The Three-dimensional Structure of the Virgo Cluster Region from Tully-Fisher and H I Data
The distances and H I contents of 161 spiral galaxies in the region ofthe Virgo cluster are used to gain insight into the complicatedstructure of this galaxy system. Special attention has been paid to theinvestigation of the suggestion presented in an earlier work that someperipheral Virgo groups may contain strongly gas-deficient spiralgalaxies. The three-dimensional galaxy distribution has been inferredfrom quality distance estimates obtained by averaging distance modulibased on the Tully-Fisher relationship taken from eight published datasets previously homogenized, resulting in a relation with a dispersionof 0.41 mag. Previous findings that the spiral distribution issubstantially more elongated along the line of sight than in the planeof the sky are confirmed by the current data. In addition, an importanteast-west disparity in this effect has been detected. The overallwidth-to-depth ratio of the Virgo cluster region is about 1:4, with themost distant objects concentrated in the western half. The filamentarystructure of the spiral population and its orientation are alsoreflected by the H I-deficient objects alone. The H I deficiency patternshows a central enhancement extending from ~16 to 22 Mpc inline-of-sight distance; most of this enhancement arises from galaxiesthat belong to the Virgo cluster proper. However, significant gasdeficiencies are also detected outside the main body of the cluster in aprobable group of galaxies at line-of-sight distances ~25-30 Mpc, lyingin the region dominated by the southern edge of the M49 subcluster andclouds W' and W, as well as in various foreground galaxies. In the Virgoregion, the H I content of the galaxies then is not a straightforwardindicator of cluster membership.
| 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.
| The Spatial Distributions of H II Regions in Irregular Galaxies
CCD Hα and V-band images were used to examine the distributions ofstar-forming regions in 34 irregular galaxies, 28 of which are normalIm's and six of which are blue compact dwarf (BCD)/starburst irregulars.The V-band images were used to determine the center, position angle, andinclination of the galaxies. The Hα images were used to trace thestar formation through H II regions. H II region distributions in theplane of the galaxies were compared to turnovers in the rotation curves,the sizes of the galaxies, and locations relative to stellar bars. Theoverall symmetry and concentration of the H II distributions were alsodetermined. The H II regions are concentrated toward the inner halves of88% of the galaxies. Furthermore, most of the H II regions and complexesare located within R25, the radius at a B surface brightnessof 25 mag arcsec-2, as well as within the part of the galaxythat is rotating as a solid body. Most giant H II regions and complexesare even more centrally concentrated than the bulk of the H II regionsand there is otherwise no preferred location. There are no obviousdifferences in the distribution of H II regions in BCDs and starburstgalaxies relative to that of typical irregulars. However, in oneBCD/starburst galaxy there are H II complexes located well beyond theturnover in the rotation curve, indicating that not all galaxies withintense star formation are unusually centrally concentrated. Finally,the overall distribution of H II regions is symmetrical in most of thegalaxies. Some of the irregular galaxies in our sample have normalrotation curves, while others show no measurable ordered rotation. Mostof the galaxies that do not have measurable rotation have lower starformation rates, while those with measurable rotation velocities extendto higher star formation rates. In addition, the degree of centralconcentration of H II regions is low in the galaxies with no measurableordered rotation, and the galaxies with the fastest Vrot,maxhave among the highest central concentrations of H II regions.
| Arcsecond Positions of UGC Galaxies
We present accurate B1950 and J2000 positions for all confirmed galaxiesin the Uppsala General Catalog (UGC). The positions were measuredvisually from Digitized Sky Survey images with rms uncertaintiesσ<=[(1.2")2+(θ/100)2]1/2,where θ is the major-axis diameter. We compared each galaxymeasured with the original UGC description to ensure high reliability.The full position list is available in the electronic version only.
| The Luminosity Functions and Size Distributions of H II Regions in Irregular Galaxies
CCD Hα images were used to study the properties of H II regions in29 normal Im galaxies and six blue compact dwarf/starburst irregulars.The Hα emission line fluxes were measured and used to constructluminosity functions for each galaxy. For most galaxies, the luminosityfunction is well represented by a power law. Only two of the 29 Imgalaxies have supergiant H II regions, which is probably a result of thesmall size and small total numbers of H II regions in irregulargalaxies. BCDs and starburst galaxies, on the other hand, do not alwayshave supergiant H II regions but may have them even if only a fewregions are present. Comparison of the cumulative composite H IIluminosity function with that of spiral galaxies shows that theirregulars in our sample do not have an unusually large population ofsupergiant H II regions relative to the galactic luminosity. Thus, thesegalaxies will not suffer a disproportionate amount of disruption by theconcentration of massive stars within such regions. However, inBCD/starburst galaxies there is an excess of H II regions withluminosities greater than 10^38 ergs s^-1 compared to Im and Sc galaxiesrelative to the luminosities of the host galaxies. Most of the H IIregion luminosity in normal Im galaxies comes from small regions andthat in BCD/starburst galaxies from moderately large regions. Over 80%of the H II region luminosity in irregulars is found in complexes of HII regions typically with summed luminosities equivalent to <=10Orion nebulae. Two types of luminosity functions were observed: thosethat exhibit turnover and those that do not. Those that do exhibitturnover have an average slope of -1.5+/-0.1, and those that do notexhibit turnover tend to be complete to fainter levels, have lower upperluminosity cutoffs, have fewer H II regions, and have shallower slopesof -1.0+/-0.1. If the luminosity function is universal for a galaxytype, this difference suggests the possibility of a break in theluminosity function corresponding to H II regions ionized by singlestars and H II regions ionized by clusters of stars. However, we cannotexclude the possibility that the two groups of galaxies are different interms of their global star formation properties. Diameters of H IIregions were also measured and diameter distributions were constructedfor each of the galaxies. The diameter distribution was fitted with anexponential and the characteristic diameter D_0 was measured for eachgalaxy, although this fit did not characterize the distribution verywell in most galaxies. The weak correlation between D_0 and the absoluteblue magnitude of the galaxy suggested by others is confirmed to be veryweak.
| Emission-Line Spectroscopy of H II Regions in Irregular and Blue Compact Dwarf Galaxies
We present reddenings and abundances of 189 H II regions measured from203 emission-line spectra in a sample of 65 irregular (Im), blue compactdwarf (BCD), and Sm galaxies. In most of these spectra we measure [OIII] lambda5007, Hβ, [N II] lambda6584, and [S II]lambdalambda6717, 6731; in 24 spectra we measure [O II] lambda3727 andin five we measure [O III] lambda4363. The internal reddenings of thegalaxies are used to determine whether redder irregular galaxies arealso dustier than bluer irregulars. We find that the range in opticalbroadband colors among Im galaxies is most likely dominated bydifferences in the contributions of the massive star population or theeffects of abundances, while the range in colors of BCDs does showevidence consistent with a contribution from dustiness. We use theabundances to confirm that our sample of BCD galaxies, selected to becomparable to Im systems in other global properties, are also comparablein abundances and, hence, evolutionary status. Finally, we explorerelationships between abundances and other global galactic propertiesand find few convincing correlations. However, bluer galaxies tend to bemore metal-poor. There is a slight trend of higher relative gas contentwith lower abundances among the BCD sample, but not in the Im sample.The difference could be due to a difference in gas distributions and thefraction of total gas that is actively participating in the chemicalevolution of the galaxy. In addition, our BCD, but not our Im, sample ofgalaxies are consistent by themselves with the galacticluminosity-metallicity relationship determined by others, but the Imsample is consistent with the general trend seen over a large baselinewhen combined with spiral galaxies. However, the scatter is large.
| The Virgo Cluster Distance from 21 Centimeter Line Widths
The distance of the Virgo cluster is derived in the B band from the 21cm line width-absolute magnitude relation. This relation is calibratedusing 18 spirals with Cepheid distances, mainly from the Hubble SpaceTelescope. The calibration is applied to a complete sample ofnonpeculiar spirals with i > 45 deg lying within the optical (n = 49)or X-ray (n = 35) contour of the cluster, resulting in a mean clusterdistance of (m - M)0 = 31.58 +/- 0.24 mag (external error), or 20.7 +/-2.4 Mpc. The mean distance of subcluster A is 0.46 +/- 0.18 mag smallerthan that of subcluster B, but the individual distances of the membersof the two substructures show considerable overlap. Cluster spirals with30 deg < i < 45 deg yield distances almost as good as those ofmore inclined galaxies. H I-truncated galaxies are overluminous by 0.8mag at a given line width. The distance modulus is corrected by -0.07mag for the fact that cluster members have lower H I surface fluxes andare redder in (B-I) at a given line width than the (field) calibrators.Different sources for the B magnitudes and line widths have littleeffect on the resulting distance. Different precepts for the internalabsorption correction change the result by no more than +/-0.17 mag. Theindividual distances of the cluster members do not show any dependenceon recession velocity, inclination, Hubble type, or line width. Thedependence on apparent magnitude reflects the considerable depth effectof the cluster. The adopted distance is in good agreement withindependent distance determinations of the cluster. Combining thecluster distance with the corrected cluster velocity of 1142 +/- 61 kms-1 gives H0 = 55 +/- 7 km s-1 Mpc-1 (external error). If the Virgocluster distance is inserted into the tight Hubble diagram of clustersout to 11,000 km s-1 using relative distances to the Virgo cluster, oneobtains a global value of H0 = 57 +/- 7 km s-1 Mpc-1.
| 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.
| 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.
| Study of the Virgo Cluster Using the B-Band Tully-Fisher Relation
The distances to spiral galaxies of the Virgo cluster are estimatedusing the B-band Tully-Fisher (TF) relation, and the three-dimensionalstructure of the cluster is studied. The analysis is made for a completespiral sample taken from the Virgo Cluster catalog of Binggeli, Sandage,& Tammann. The sample contains virtually all spiral galaxies down toM_{BT}=-15 mag at 40 Mpc. A careful examination is made ofthe selection effect and errors of the data. We estimate distance to 181galaxies, among which distances to 89 galaxies are reasonably accurate.We compare these distances to those obtained by other authors on agalaxy-by-galaxy basis. We find reasonable consistency of theTully-Fisher distance among various authors. In particular, it is foundthat the discrepancy in the distance among the different analyses withdifferent data is about 15%, when good H I and photometric data areavailable. We clarify that the different results on the Virgo distanceamong authors arise from the choice of the sample and interpretation ofthe data. We confirm that the Tully-Fisher relation for the Virgocluster shows an unusually large scatter sigma = 0.67 mag, compared tothat for other clusters. We conclude that this scatter is not due to theintrinsic dispersion of the Tully-Fisher relation, but due to a largedepth effect of the Virgo cluster, which we estimate to be extended from12 Mpc to 30 Mpc. The distribution of H I--deficient galaxies isconcentrated at around 14--20 Mpc, indicating the presence of a core atthis distance, and this agrees with the distance estimated for M87 andother elliptical galaxies with other methods. We show also that thespatial number density of spiral galaxies takes a peak at this distance,while a simple average of all spiral galaxy distances gives 20 Mpc. Thefact that the velocity dispersion of galaxies takes a maximum at 14--18Mpc lends an additional support for the distance to the core. Thesefeatures cannot be understood if the large scatter of the TF relation ismerely due to the intrinsic dispersion. The structure of the VirgoCluster we infer from the Tully-Fisher analysis looks like a filamentwhich is familiar to us in a late phase of structure formation in thepancake collapse in hierarchical clustering simulations. This Virgofilament lies almost along the line of sight, and this is the originthat has led a number of authors to much confusion in the Virgo distancedeterminations. We show that the M87 subcluster is located around 15--18Mpc, and it consists mainly of early-type type spiral galaxies inaddition to elliptical and S0 galaxies. There are very few late-typespiral galaxies in this subcluster. The spiral rich M49 subclusterconsists of a mixture of all types of spiral galaxies and is located atabout 22 Mpc. The two other known clouds, W and M, are located at about30--40 Mpc and undergo infall toward the core. The M cloud contains fewearly type spirals. We cannot discriminate, however, whether thesesubclusters or clouds are isolated aggregates or merely parts offilamentary structure. Finally, we infer the Hubble constant to be 82+/- 10 km s-1 Mpc-1.
| On the Size and Formation Mechanism of Star Complexes in Sm, Im, and BCD Galaxies
The diameters D_c_ of the largest star-forming complexes in 67Magellanic spiral and irregular galaxies and 16 blue compact dwarf (BCD)galaxies are found to scale approximately with the square root of thegalaxy luminosity for each type, i.e., smaller galaxies haveproportionately smaller star-forming regions. This is the same relationas for the largest complexes in bright spiral galaxies found previously,although Sm/Im galaxies have complexes that, on average, are a factor of2 larger than the extrapolation for spiral galaxies at the same absolutemagnitude, and the BCD galaxies have complexes that are ~2 times largerthan those typical of the Sm/Im galaxies at the same absolute magnitude.These results are consistent with the interpretation that the largestcomplexes form at the gravitational length scale in a marginally stableinterstellar medium with a nearly constant velocity dispersion c ~ 5-10km s^-1^. The luminosity scaling is then the result of higher averagetotal densities in smaller galaxies compared with the outer regions ofgiant spirals. This total density correlation is shown using published HI line widths and optical galaxy sizes. The implication of these resultsis that star formation begins when the ratio of the gas density ρ tothe total density (gas + stars + dark matter) exceeds several tenths. Ifstar formation lasts for a time scaling with (Grho_)^-1/2^ ~D_c_/c, then the main morphological differences between star formationin galaxies of various sizes can be explained: large galaxies have largestar complexes that form groups of OB associations slowly for up to 50Myr; small galaxies have small complexes (in terms of absolute size)that form dense associations quickly, in bursts spanning less than 5Myr.
| Extended LY alpha -absorbing Halos around Nearby Galaxies
In order to establish the Lyα absorption cross section ofpresent-day galaxies, we have identified 38 galaxies with z = 0-0.08that lie within 40-500 h^-1^ kpc of the line of sight to a QSO observedwith the Faint Object Spectrograph aboard the Hubble Space Telescope(HST). Including three galaxies in the field of 3C 273 investigated byprevious authors, we find that nine of 41 galaxies have associatedLyα absorption. If the identified Lyα absorption systems aregenuinely associated with the galaxies, then the covering factor of gasaround galaxies remains roughly constant at ~40% between 100 and 300h^-1^ kpc. Beyond 300 h^-1^ kpc, the incidence of absorption dropssharply. We conclude that (1) nearby galaxies do not possessLyα-absorbing halos beyond 300 h^-1^ kpc in radius and (2) thecovering factor of present-day galaxies between 50 and 300 h^-1^ kpc is44% at an equivalent width limit of W >= 0.3 A. For the nine galaxieswith associated Lyα absorption lines, differences in the galaxiessystemic velocities and the velocity of the absorption line, {DELTA}v,range over +/- 300 km s^-1^, consistent with the distribution found atredshifts > 0.1 by Lanzetta et al. and Le Brun, Bergeron, &Boisse. Values of {DELTA}v spanning several hundred km s^-1^ areprobably real for some of the QSO-galaxy pairs, however, and do notsimply arise from errors in measuring cz_gal_ or cz_abs_. This suggeststhat the absorbing clouds are kinematically tied to the galaxy disks andthat the distribution of {DELTA}v may arise because of the effects ofgalaxy inclination. We find no evidence for a correlation betweenLyα equivalent width and galaxy line-of-sight separation, whichweakens the argument that the identified galaxies are directlyassociated with the Lyα lines. Also, we find that absorption doesnot arise only from bright galaxies, since there are several examples inwhich low-luminosity galaxies apparently cause absorption. Yet we showthat the absorbing halos around galaxies cannot be independent of galaxyluminosity because if all low- redshift galaxies were surrounded byextended halos, the number of Lyα absorption systems found in HSTspectra would be much larger than has recently been determined. Thisresult leads us to question whether the galaxies are actuallyresponsible for the Lyα absorption lines or whether theassociation in redshift is fortuitous. Our results support the picturesuggested by others that Lyα lines arise in filaments or sheetsthat connect and contain the overdense regions that galaxies inhabit.This conclusion, however, remains at odds with the results of Lanzettaet al., who find that Lyα systems are more intimately linked withgalaxies. It may be, therefore, that we are seeing an evolution of theway in which Ly& lines associate with galaxies over the last fewbillion years. We suggest that at least some of the Lyα cloudsthat are not associated with galaxies at z ~ 0.5 have been slowlymerging with galaxies over time, creating larger but less uniform gasdistributions around the galaxies we see today.
| 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.
| Surface photometry of spiral galaxies in the Virgo cluster region
Photographic surface photometry is carried out for 246 spiral galaxiesin the Virgo cluster region north of declination + 5 deg. The samplecontains all spiral galaxies of 'certain' and 'possible' Virgo membersin the Virgo Cluster Catalogue of Binggeli, Sandage, & Tammann. Thesample also includes those galaxies which were used in the Tully-Fisheranalyses of the Virgo cluster given in the literature. A catalog ispresented for positions, B-band total magnitudes and inclinations forthese galaxies, and they are compared with the data given in previousstudies.
| Chemical Evolution of the Galactic Disk: Evidence for a Gradient Perpendicular to the Galactic Plane
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1995AJ....110.2813P&db_key=AST
| The UV properties of normal galaxies. III. Standard luminosity profiles and total magnitudes.
In the previous papers of this series we collected and reduced to thesame system all the available photometric data obtained in theultraviolet (UV) range for normal (i.e. non active) galaxies. Here weuse these data to derive standard UV luminosity profiles for threemorphological bins (E/S0; Sa/Sb; Sc/Sd) and extrapolated totalmagnitudes for almost 400 galaxies. We find that: 1) the UV growthcurves are well matched by the B-band revised standard luminosityprofiles, once a proper shift in the effective radius is applied, and 2)the UV light in early-type galaxies is more centrally concentrated thanthe visible light.
| The UV properties of normal galaxies. II. The ``non-IUE'' data.
In the last decade several satellite and balloon borne experiments havecollected a large number of ultraviolet fluxes of normal galaxiesmeasured through apertures of various sizes and shapes. We havehomogenized this data set by deriving scale corrections with respect toIUE. In a forthcoming paper these data will be used to derive standardluminosity profiles and total magnitudes.
| Global properties of dwarf galaxies. I. Galaxy sample and IRAS infrared flux-densities
We have selected a sample of 278 dwarf galaxies for which at least Bmagnitudes and preferably also optical colour information are available.For those galaxies that have no previously published IRAS fluxes, wehave used the IRAS database to extract fluxes or upper limits tosensitivity levels significantly better than those of the IRAS PointSource Catalog. New IRAS data include 79 galaxies detected in at leastone band, and 66 galaxies with good upper limits. In total, about 60% ofall dwarf galaxies in the sample now have been detected at 60/100μm.
| Global properties of dwarf galaxies II. Colours and luminosities
We have used a previously determined sample of 278 dwarf galaxies formost of which B magnitudes, optical colours, HI fluxes and IRASflux-densities are known, in order to derive luminosities, colours andsurface brightnesses. Dwarf galaxy properties are compared to those of acontrol sample of 228 larger spiral galaxies. The dwarf galaxies have onaverage higher 60/100μm flux ratios and lower 12/25μm flux ratiosthan the spiral galaxies, indicating that the contribution of `cirrus'to the infrared emission from dwarf galaxies is relativelyinsignificant. In the dwarf galaxies, the 60/100μm flux ratioincreases with increasing optical blueness; spiral galaxies show theopposite. Dwarf galaxies with a low optical surface brightness have low100μm/HI ratios, but the converse is not true. Galaxies with high100μm/HI ratios (indicative of high dust-to-gas ratios) also havehigh FIR/B ratios as well as high 60/100μm flux-density ratios.Although this is true for both spiral and dwarf galaxies, at given100μm/HI ratios the dwarf galaxies have both a lower FIR/B ratio anda higher 60/100μm flux-density ratio. This result is of importance inthe interpretation of FIR/B - 60/100μm diagrams in terms of starformation activity.
| Distribution of the spin vectors of the disk galaxies of the Virgo cluster. I. The catalogue of 310 disk galaxies in the Virgo area.
Not Available
| 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.
| Dwarf galaxies in the Virgo cluster. II - Photometric techniques and basic data
Results are presented of photographic surface photometry carried out for305 (mostly dwarf) galaxies in the Virgo cluster, in which the galaxyimages were digitized on 14 of the 67 du Pont plates used for the Virgocluster survey. Azimuthally averaged surface brightness profiles areshown for all galaxies. The following model-free photometric parametersare derived and listed for each galaxy: total apparent blue magnitude,mean effective radius and surface brightness, and various isophotalradii, ellipticity, and position angle. Most galaxies were fitted by anexponential form and/or a King model profile. The best-fittingparameters, including the 'nuclear' (central residual) magnitudes fordE+dS0 galaxies, are listed.
| Abell 154 and Virgo - Pilot study for H I observations of distant clusters of galaxies
As a test of procedures required to study the H I contents of spiralgalaxies in distant clusters of galaxies, the cluster Abell 154 has beenobserved from Arecibo. Fourteen candidate detections were found in tworegions of the cluster comprising about 10 percent of the cluster area.These results are compared in detail with those expected for theexhaustively studied Virgo cluster displaced to the distance of A 154.Most of the candidate detections are likely to be the combined profilesof two or more spiral galaxies, many of them too faint to appear on thelist of morphological types classified by Dressler (1980). Any attemptto identify these H I signals with known bright spirals is problematicat best. The A 154 profiles are systematically broader than expected forVirgo, but a crude application of the Tully-Fisher correlation indicatesthat they are still consistent with available photometric data. Whilethe H I deficiency in Virgo would still be apparent at the A 154distance, no significant evidence is found for H I deficiency in A 154.
| The extragalactic distance scale. II - The unbiased distance to the Virgo Cluster from the B-band Tully-Fisher relation
The behavior of the B-band Tully-Fisher (TF) relation with respect tothe observational biases and parameter uncertainties is studied from analmost complete sample of spiral galaxies belonging to the VirgoCluster. The strong influence of the limiting apparent magnitude whenusing the direct TF relation is confirmed. A distance modulus of 31.4 +or - 0.2 is found along with a corresponding H(0) = 68 + or - 8km/s/Mpc, assuming a cosmological velocity of the cluster V = 1300 + or- 100 km/s. The Virgo S and S-prime clouds are shown to lie atsignificantly different distances. Different distance moduli found byother authors are explained.
| H I observations in the Virgo cluster area. III - All 'member' spirals
H I observations of 141 spiral galaxies in and around the Virgo Clusterare reported, with major-axis mapping for 65 of them. Heliocentricvelocities, profile widths, and H I fluxes are given for all detectedgalaxies. Spin orientations are given for mapped galaxies and H Idiameters for those sufficiently resolved by the 3.2 arcmin beam. Mappedgalaxy spectra are shown as contour plates of position versus velocity;central beam spectra are shown for the remainder. The distributions ofspin orientations are briefly analyzed and shown to be essentiallyrandom. The distributions of H I luminosity are presented along withindicative dynamical mass for the spirals and a synthesized H Idistribution for the cluster as a whole.
| A statistical study of luminosity profiles of galaxies using spheroid-disk composite models
Structural parameters of spheroids and disks are presented for ahomogeneous sample of 167 galaxies of all morphological types, andsystematic properties and interplay of the spheroid and disk areexplored using a new technique to derive the structural parameters fromthe observed luminosity distribution. The luminosity distributions ofmost of the galaxies, including all of the elliptics, can be wellapproximated by two-component models, with the rest approximated byone-component disk models. Spheroids of disk galaxies are on averageless luminous in absolute magnitude and have both fainterbrightness-scale parameter and larger length-scale parameter than thoseof elliptics. Spheroid parameters of S0 galaxies are intermediatebetween those of elliptics and spirals.
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