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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
| Principal component analysis of International Ultraviolet Explorer galaxy spectra
We analyse the UV spectral energy distribution of a sample of normalgalaxies listed in the International Ultraviolet Explorer (IUE) NewlyExtracted Spectra (INES) Guide No. 2 - Normal Galaxies using a principalcomponent analysis. The sample consists of the IUE short-wavelength (SW)spectra of the central regions of 118 galaxies, where the IUE apertureincluded more than 1 per cent of the galaxy size. The principalcomponents are associated with the main components observed in theultraviolet (UV) spectra of galaxies. The first component, accountingfor the largest source of diversity, may be associated with the UVcontinuum emission. The second component represents the UV contributionof an underlying evolved stellar population. The third component issensitive to the amount of activity in the central regions of galaxiesand measures the strength of star-formation events.In all the samples analysed here, the principal component representativeof star-forming activity accounts for a significant percentage of thevariance. The fractional contribution to the spectral energydistribution (SED) by the evolved stars and by the young population aresimilar.Projecting the SEDs on to their eigenspectra, we find that none of thecoefficients of the principal components can outline an internalcorrelation or can correlate with the optical morphological types. In asubsample of 43 galaxies, consisting of almost only compact and BCDgalaxies, the third principal component defines a sequence related tothe degree of starburst activity of the galaxy.
| Are interactions the primary triggers of star formation in dwarf galaxies?
We investigate the assumption that the trigger of star formation indwarf galaxies is interactions with other galaxies, in the context of asearch for a `primary' trigger of a first generation of stars. This iscosmologically relevant because the galaxy formation process consistsnot only of the accumulation of gas in a gravitational potential wellbut also of the triggering of star formation in this gas mass, and alsobecause some high-z potentially primeval galaxy blocks look like nearbystar-forming dwarf galaxies. We review theoretical ideas proposed toaccount for the tidal interaction triggering mechanism and present aseries of observational tests of this assumption using published data.We also show results of a search in the vicinity of a composite sampleof 96 dwarf late-type galaxies for interaction candidates showing starformation. The small number of possible perturbing galaxies identifiedin the neighbourhood of our sample galaxies, along with similar findingsfrom other studies, supports the view that tidal interactions may not berelevant as primary triggers of star formation. We conclude thatinteractions between galaxies may explain some forms of star formationtriggering, perhaps in central regions of large galaxies, but they donot seem to be significant for dwarf galaxies and, by inference, forfirst-time galaxies forming at high redshifts. Intuitive reasoning,based on an analogy with stellar dynamics, shows that conditions forprimary star formation triggering may occur in gas masses oscillating ina dark-matter gravitational potential. We propose this mechanism as aplausible primary trigger scenario, which would be worth investigatingtheoretically.
| Neutral Hydrogen Mapping of Virgo Cluster Blue Compact Dwarf Galaxies
A new installment of neutral hydrogen mappings of blue compact dwarf(BCD) galaxies, as defined by optical morphology, in and near the VirgoCluster is presented. The primary motivation was to search for outlyingclouds of H I as potential interactive triggers of enhanced starformation, and therefore the mapped galaxies were selected for large H Imass, large optical diameter, and large velocity profile width.Approximately half the sample proved to have one or more small, lowcolumn density, star-free companion clouds, either detached or appearingas an appendage in our maps, at a resolution on the order of 4 kpc.Comparison is made with a sample of similarly mapped field BCD galaxiesdrawn from the literature; however, the Virgo Cluster sample of mappedBCDs is still too small for conclusive comparisons to be made. We found,on the one hand, little or no evidence for ram-pressure stripping nor,on the other, for extremely extended low column density H I envelopes.The H I rotation curves in most cases rise approximately linearly andslowly, as far out as we can trace the gas.
| 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.
| Hα surface photometry of galaxies in the Virgo cluster. IV. The current star formation in nearby clusters of galaxies
Hα +[NII] imaging observations of 369 late-type (spiral) galaxiesin the Virgo cluster and in the Coma/A1367 supercluster are analyzed,covering 3 rich nearby clusters (A1367, Coma and Virgo) and nearlyisolated galaxies in the Great-Wall. They constitute an opticallyselected sample (mp<16.0) observed with ~ 60 %completeness. These observations provide us with the current(T<107 yrs) star formation properties of galaxies that westudy as a function of the clustercentric projected distances (Theta ).The expected decrease of the star formation rate (SFR), as traced by theHα EW, with decreasing Theta is found only when galaxies brighterthan Mp ~ -19.5 are considered. Fainter objects show no orreverse trends. We also include in our analysis Near Infrared data,providing information on the old (T>109 yrs) stars. Puttogether, the young and the old stellar indicators give the ratio ofcurrently formed stars over the stars formed in the past, or``birthrate'' parameter b. For the considered galaxies we also determinethe ``global gas content'' combining HI with CO observations. We definethe ``gas deficiency'' parameter as the logarithmic difference betweenthe gas content of isolated galaxies of a given Hubble type and themeasured gas content. For the isolated objects we find that b decreaseswith increasing NIR luminosity. In other words less massive galaxies arecurrently forming stars at a higher rate than their giant counterpartswhich experienced most of their star formation activity at earliercosmological epochs. The gas-deficient objects, primarily members of theVirgo cluster, have a birthrate significantly lower than the isolatedobjects with normal gas content and of similar NIR luminosity. Thisindicates that the current star formation is regulated by the gaseouscontent of spirals. Whatever mechanism (most plausibly ram-pressurestripping) is responsible for the pattern of gas deficiency observed inspiral galaxies members of rich clusters, it also produces the observedquenching of the current star formation. A significant fraction of gas``healthy'' (i.e. with a gas deficiency parameter less than 0.4) andcurrently star forming galaxies is unexpectedly found projected near thecenter of the Virgo cluster. Their average Tully-Fisher distance isfound approximately one magnitude further away (muo = 31.77)than the distance of their gas-deficient counterparts (muo =30.85), suggesting that the gas healthy objects belong to a cloudprojected onto the cluster center, but in fact lying a few Mpc behindVirgo, thus unaffected by the dense IGM of the cluster. Based onobservations taken at the Observatorio Astronómico Nacional(Mexico), the OHP (France), Calar Alto and NOT (Spain) observatories.Table \ref{tab4} is only available in electronic form athttp://www.edpsciences.org
| Studies of galaxies in voids. I. H I observations of Blue Compact Galaxies
We present here results of studies of the properties of galaxies locatedin very low density environments. We observed 26 blue compact galaxies(BCGs) from the Second Byurakan (SBS) and Case surveys located in voidswith the radial velocities Vhel <~ 11 000 kms-1, two BCGs in the void behind the Virgo cluster and 11BCGs in denser environments. H I fluxes and profile widths, as well asestimates of total H I masses, are presented for the 27 detectedgalaxies (of which 6 are in three galaxy pairs and are not resolved bythe radiotelescope beam). Preliminary comparisons of void BCGs withsimilar objects from intermediate density regions - in the general fieldand the Local Supercluster (sub-samples of BCGs in the SBS zone) and inthe dense environment of the Virgo Cluster (a BCD sample) - areperformed using the hydrogen-to-blue-luminosity ratio M(ion{H}i)/LB. We find that for the same blue luminosity, forMB > -18.0m, BCGs in lower density environment have onaverage more H I. The slope beta of the M(ion {H}i)/LBvarpropto Lbeta for BCGs shows a trend of steepening withdecreasing bright galaxy density, being very close to zero for thedensest environment considered here and reaching beta = -0.4 for voids.
| 1.65 μm (H-band) surface photometry of galaxies. VII. Dwarf galaxies in the Virgo Cluster
We present near-infrared H-band (1.65 μm) observations and surfacebrightness profile decompositions for 75 faint (13.5 <~ mp<~ 18.5) galaxies, primarily taken among dwarf Ellipticals members ofthe Virgo cluster, with some Centaurus Cluster members, a BCD and twopeculiar galaxies taken as fillers. We model their surface brightnessprofiles with a de Vaucouleurs (D), exponential (E), mixed (bulge+diskor M) or truncated (T) law, and we derive for each galaxy the H bandeffective surface brightness (μe) and effective radius(re), the asymptotic total magnitude HT and thelight concentration index C31, defined as the ratio betweenthe radii that enclose 75% and 25% of the total light HT. Fora subsample we compare the NIR surface photometry with similar datataken in the B and V bands, and we give the B-H and B-V color profiles.Combining the present data with those previously obtained by our group(1157 objects) we analyze the NIR properties of a nearly completesample, representative of galaxies of all morphological types, spanning4 decades in luminosity. We confirm our earlier claim that the presenceof cusps and extended haloes in the light profiles (C31>5)is a strong, non-linear function of the total luminosity. We also findthat: i) among dE and dS0 galaxies D profiles are absent; 50% of thedecompositions are of type M, the remaining being of type E or T. ii)Less than 50% of the giant elliptical galaxies have pure D profiles, themajority being represented by M profiles. iii) Most giant galaxies (fromelliptical to Sb) have M profiles. iv) Most of late type spirals (Scd toBCD) have either E or T profiles. v) The type of decomposition is astrong function of the total H band luminosity, independent of theHubble classification: the fraction of type E decompositions decreaseswith increasing luminosity, while those of type M increase withluminosity. Pure D profiles are absent in the low luminosity rangeLH<1010 Lsolar and become dominantabove 1011 Lsolar, while T profiles are presentonly among low luminosity galaxies. vi) We find that dE-peculiargalaxies have structural parameters indistinguishable from those oflate-type dwarfs, thus they might represent the missing link between dEsand dIs. Based on observations taken with the ESO/NTT (ESO program64.N-0288), with the Telescopio Nazionale Galileo (TNG) operated on theisland of La Palma by the Centro Galileo Galilei of the CNAA at theSpanish Observatorio del Roque de los Muchachos of the IAC, with the SanPedro Martir 2.1~m telescope of the Observatorio Astronomico Nacional(OAN, Mexico), and with the OHP 1.2~m telescope, operated by the FrenchCNRS.
| The second Kiso Survey for ultraviolet-excess galaxies. II.
Not Available
| Lopsidedness in dwarf irregular galaxies
We quantify the amplitude of the lopsidedness, the azimuthal angularasymmetry index and the concentration of star-forming regions, asrepresented by the distribution of the Hα emission, in a sample of78 late-type irregular galaxies. We bin the observed galaxies into twogroups representing blue compact galaxies (BCDs) andlow-surface-brightness dwarf galaxies (LSBs). The light distribution isanalysed with a novel algorithm, which allows detection of details inthe light distribution pattern. We find that while the asymmetry of theunderlying continuum light, representing the older stellar generations,is relatively small, the Hα emission is very asymmetric and iscorrelated in position angle with the continuum light. We show that theconcentration of continuum light is correlated with the Hαconcentration; this implies that the young star formation has the samespatial properties as the older stellar populations, but that theseproperties are more strongly expressed by the young stars. We test amodel of random star formation over the extent of a galaxy by simulatingHii regions in artificial dwarf galaxies. A galaxy is traced by assumingred star clusters distributed on an underlying exponential disc ofradius twice the scalelength. The disc is allowed to change in apparentmagnitude, scaleradius, position angle and ellipticity. We compare theasymmetry-concentration distribution predicted by the simulations withthe real observed distribution; we find that only LSBs match thedistribution predicted by the model. The reason is that, independentlyof the number of Hii regions, LSBs show no particular location of Hiiregions, whereas BCDs show current star formation activity restrictedvery much to the central parts of the galaxies. A consideration of theproperties of the continuum light leads to the conclusion that most ofLSBs can be approximated by exponential discs of radius twice theirscalelength; BCDs call, however, for much more concentrated underlyingsystems, with smaller scalelengths than assumed in the simulations. Theimplication is that random star formation over the full extent of agalaxy may be generated in LSB dwarf irregular galaxies but not in BCDgalaxies.
| 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.
| Late-type dwarf irregular galaxies in the Virgo cluster - I. H alpha and red continuum data
We present H alpha and red continuum observations for a sample oflate-type low surface brightness (LSB) dwarf irregular galaxies,consisting of all the ImIV and V galaxies with m_B<= 17.2 in theVirgo cluster, and compare them with similar data for a representativesample of high surface brightness (HSB) dwarf irregular galaxies, alsoin the Virgo cluster. Line fluxes and equivalent widths are listed forindividual HII regions, and total H alpha emission is measured for theentire galaxy. Although significant line emission originates in the HIIregions that we have identified, it does not make up the entire H alphaoutput of all galaxies. For those objects in the LSB sample withHα emission, we find typical star formation rates (SFRs) from6.9x10^-3 to as high as 4.3x10^-2 M_solar yr^-1. This is, on average,one order of magnitude weaker than for HSB objects, although the SFRsoverlap. On average, ~2 HII regions are detected per LSB galaxy, for atotal of 38 HII regions among 17 galaxies with Hα emission. TheHII regions are smaller and fainter than in HSB galaxies in the sameVirgo cluster environment, have Hα line equivalent widths about 50per cent of those in HSBs, and cover similar fractions of the galaxies.When more than one HII region is present in a galaxy, we observe astrong intensity difference between the brightest and the secondbrightest HII regions. The line-emitting regions of LSB galaxies arepreferentially located at the periphery of the galaxy, while in HSBsthey tend to be central. The Hα line strength of an HII region iscorrelated with the red continuum light underneath the region; thisholds for both LSBs and HSBs. We do not identify fundamental differencesin the star formation properties of the LSB and HSB dwarf galaxies thatwe have studied, and we infer that these galaxies must be similar, withthe difference being the intensity of the present star formation burst.
| Ultraviolet spectral properties of magellanic and non-magellanic irregulars, H BT II and starburst galaxies
This paper presents the results of a stellar population analysisperformed on nearby (V_R<=5 000 km s^{-1}) star-forming galaxies,comprising magellanic and non-magellanic irregulars, H Ii and starburstgalaxies observed with the IUE satellite. Before any comparison ofgalaxy spectra, we have formed subsets according to absolute magnitudeand morphological classification. Subsequently, we have coadded thespectra within each subset into groups of similar spectral properties inthe UV. As a consequence, high signal-to-noise ratio templates have beenobtained, and information on spectral features can now be extracted andanalysed. Seven groups resulted from this procedure: the magellanicirregulars (including H Ii galaxies) produced two different bluespectral groups; the non-magellanic irregulars could be grouped into twospectral groups with rather peculiar properties; and the luminousstarbursts produced one flat and two blue template spectra. Theirstellar populations are analysed by means of a population synthesisalgorithm based on star cluster spectral components. The syntheticspectra reproduce the observed ones successfully (except thenon-magellanic irregular groups) both in terms of continuum distributionand spectral features. The synthesis flux fractions of different agegroups were transformed into mass fractions, allowing inferences on thestar formation histories. Young stellar populations (age <500 Myrs)are the main flux contributors; in a few cases the intermediate agepopulation (age~1 M_B-2 Myrs) is important, while the old bulgepopulation contributes at most with ~2 % of the lambda2646 Angstromsflux in the case of starburst galaxies, and is negligible in themagellanic irregulars. We also study the reddening values and theextinction law: an SMC-like extinction law is appropriate for all cases.Based upon data collected with the International Ultraviolet Explorer(IUE) Satellite, supported by NASA, SERC and ESA.
| Morphology of star formation regions in irregular galaxies
The location of HII regions, which indicates the locus of present starformation in galaxies, is analysed for a large collection of 110irregular galaxies (Irr) imaged in Hα and nearby continuum. Theanalysis is primarily by visual inspection, although a two-dimensionalquantitative measure is also employed. The two different analyses yieldessentially identical results. HII regions appear preferentially at theedges of the light distribution, predominantly on one side of thegalaxy, contrary to what is expected from stochastic self-propagatingstar formation scenarios. This peculiar distribution of star-formingregions cannot be explained by a scenario of star formation triggered byan interaction with extragalactic gas, or by a strong one-armed spiralpattern.
| Late-type dwarf galaxies in the Virgo cluster - II. Star formation properties
We study star-formation-inducing mechanisms in galaxies throughmultiwavelength measurements of a sample of dwarf galaxies in the Virgocluster described in Paper I. Our main goal is to test howstar-formation-inducing mechanisms depend on several parameters of thegalaxies, such as morphological type and hydrogen content. We derive thestar formation rate and star formation histories of the galaxies, andcheck their dependence on other parameters. Comparison of the samplegalaxies with population synthesis models shows that these objects havesignificantly lower metallicity than the solar value. The colours cangenerally be explained as a combination of two different stellarpopulations: a young (3-20 Myr) metal-poor population which representsthe stars currently forming presumably in a starburst, and an older(0.1-1 Gyr) population of previous stellar generations. There isevidence that the older stellar population was also formed in astarburst. This is consistent with the explanation that star formationin this type of objects takes place in short bursts followed by longquiescent periods. No significant correlation is found between the starformation properties of the sample galaxies and their hydrogen content.Apparently, when star formation occurs in bursts, other parametersinfluence the star formation properties more significantly than theamount of atomic hydrogen. No correlation is found between the projectedVirgocentric distance and the rate of star formation in the galaxies,suggesting that tidal interactions are not significant in triggeringstar formation in cluster dwarf galaxies.
| Late-type dwarf galaxies in the Virgo cluster - I. The samples
We selected samples of late-type dwarf galaxies in the Virgo clusterwith HI information. The galaxies were observed at the Wise Observatoryusing several broad-band and Hα bandpasses. UV measurements werecarried out with the IUE Observatory from VILSPA, and with the FAUSTshuttle-borne UV telescope. We describe the observations in detail,paying particular attention to the determination of measurement errors,and present the observational results together with published data andfar-infrared information from IRAS. The sample will be analysed insubsequent papers, in order to study star formation mechanisms ingalaxies.
| Arecibo H i Mapping of a Large Sample of Dwarf Irregular Galaxies
Neutral hydrogen mapping of 70 dwarf irregular (Sm, Im, and BCD)galaxies is reported, with position-velocity contour maps (and a fewcontour maps in R.A. and decl.) presented for those resolved by theArecibo beam. The galaxies were selected either from the Virgo ClusterCatalog, from similarly identified field galaxies, or from a distance-limited sample within the Arecibo declination range. We do not find anyisolated dwarfs with a larger H I to optical radius ratio than DDO 154;the "protogalaxy" H I 1225+01 of Giovanelli & Haynes continues to bea unique object among dwarfs that have been mapped in H I. For alldwarfs with significant rotation, we are able to determine the sense ofthe spin. For a number of better resolved dwarfs, we are able todetermine rotation curves, in most cases extending well beyond the lastmeasured point in available synthesis array maps. Correlations among theseveral measures of galaxy size and mass are studied; in a companionpaper we combine these data with those for the set of all availablemapped dwarf irregular galaxies and for mapped spirals spanning asimilar range of redshifts to investigate variations in Tully-Fisherrelations and in surface densities as functions of galaxy size andluminosity or mass.
| A Minnesota Automated Plate Scanner Catalog of Galaxies behind the Virgo Cluster and toward Its Antipode
We present a catalog of 1268 galaxies, essentially complete to B <=17.0, found by scanning glass copies of several fields of the originalPalomar Sky Survey using the Minnesota Automated Plate Scanner in itsisodensitometric mode (as opposed to the threshold densitometric modeused in the APS Catalog of the POSS I). In addition to the differentscanning mode, we have employed a different star-galaxy separationmethod and have visually inspected POSS prints to verify that each imageremaining in the catalog is nonstellar. The scanned fields aredistributed generally in two areas, one around the outskirts of theVirgo Cluster, the other toward the antipode of the cluster (but stillin the northern celestial hemisphere). The catalog gives the position ofthe center of each galaxy; estimates of the blue and red magnitudeswithin the outermost threshold crossing and of the blue magnitudeextrapolated to zero surface brightness; and the blue and red diametersof four ellipses fitted to the four threshold crossings (approximately23.8,23.6,23.2, and 22.7 mag arcsec 2 in blue, and 22.5,22.4,21.5, and21.2 mag arcsec^-2^ in red), and the ellipticities of those fourellipses. The catalog has served as a base from which to draw targetsfor a Tully-Fisher study of the Virgocentric infall velocity of theLocal Group.
| 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 kinematics of the Virgo cluster revisited
The paper updates the velocity data of Virgo cluster galaxies andreconsiders the kinematic structure of the Virgo cluster. New velocitiesare given for 144 galaxies listed in the Virgo Cluster Catalog (VCC).Improved velocities are given for another 131 VCC galaxies. The Virgocluster is disentangled from its surrounding clouds of galaxies, and thelikely members of each of these clouds are listed. The velocitydistribution of dwarf elliptical cluster members is found to be highlyasymmetric. This phenomenon is interpreted as evidence for the imminentmerging of two subclusters in the core region, which points to thedynamical youth of the Virgo cluster. The mean heliocentric velocity ofthe Virgo cluster is estimated at 1050 +/- 35 km/s.
| The Virgo cluster as a test for quantization of extragalactic redshifts
Tifft's (1972, 1977) hypothesis that redshifts are partially quantizedwith a periodicity in the range 70-75 km/s is tested for samples ofbright spiral and dwarf irregular galaxies with accurate H I redshiftsin the region of the Virgo cluster. The heliocentric redshifts arecorrected for solar motion, first by adopting an estimate of the sun'smotion with respect to the centroid of the Local Group, and then byallowing the solar velocity vector to vary in direction over the wholesky. Power spectrum analyses of the corrected redshifts are used tosearch for a significant periodicity in the prescribed range 70-75 km/s.No such periodicity is found for the dwarf irregulars, but there is apossible periodicity of about 71.1 km/s for the bright spirals. In afurther exploratory study, the sample of 112 spirals is divided upaccording to environment. The spirals in high-density regions of thecluster show no quantization, whereas those in low-density regionsappear to be partially quantized in intervals of about 71.0 km/s.
| KISO survey for ultraviolet-excess galaxies. IX
A set of identification charts is presented for UV-excess galaxiesdetected on multicolor plates for ten survey fields. The charts are partof the Kiso UV galaxy catalog (Takase and Miyauchi-Isobe, 1988). Thisset of charts brings the total number of objects in the catalog to 583,covering a 300-sq deg sky area down to a photographic magnitude of about18. The parameters presented include morphological classifications,image sizes, and degree of UV-excess.
| Neutral hydrogen detection survey of dwarf galaxies. II - Faint Virgo dwarfs and a field sample
Neutral hydrogen spectra are presented for 53 faint dwarf galaxies inVirgo, completing the Arecibo survey of all late-type dwarfs in theVirgo Cluster Catalog, and for 42 dwarf galaxies from the field sampleof Binggeli et al. (1989). For detected galaxies, heliocentricvelocities, profile widths, and single-beam fluxes are tabulated. Thefield sample has been used to investigate the field luminosity functionand the clustering of dwarf galaxies vis-a-vis bright galaxies.
| Spectrophotometrical study of the blue compact dwarf galaxies in the Virgo cluster.
Not Available
| IRAS observations of galaxies in the Virgo cluster area
IRAS data on 196 galaxies in the area of the Virgo Cluster arepresented. The data derive from combining all available surveyobservations for each object and therefore achieve greater sensitivitythan the IRAS Point Source Catalog (PSC). The enhanced sensitivityallows 78 galaxies to be detected at 12 microns, 82 at 25 microns, 139at 60 microns, and 135 at 100 microns, compared to 16, 23, 88, and 95detections listed in the PSC. From the blue compact dwarf galaxy sample,23 and 19 objects are detected at 60 and 100 microns, compared to threeand two detections listed in the PSC. The emission in three close pairsof galaxies which are reported as single sources in the PSC areseparated here. These statistics demonstrate the importance andpotential of a detailed examination of IRAS data, especially forpossibly resolved sources and, in particular, for galaxies out toredshifts of 0.008 or galaxies with D(25) of 3 arcmin or greater.
| H I detection survey of a complete magnitude-limited sample of dwarf irregular galaxies in the Virgo Cluster area
New single-beam Arecibo H I observations of 298 late-type galaxies inthe Virgo Cluster drawn mostly from the new catalog of Binggeli,Sandage, and Tammann (1985) are presented. Two hundred seventeen ofthese constitute a magnitude-limited 'complete sample' of such galaxies,types Sdm through Im and BCD. Sixty-one percent of this 'completesample' was detected, greatly enhancing the store of redshifts and H Imasses for such galaxies in the Virgo Cluster. For detected galaxies,heliocentric velocities, 50 percent profile widths, and single-beamfluxes are presented. For those that escaped detection, upper limits arecomputed to the flux appropriate to the redshift range (-600 to +3000km/s).
| Studies of the Virgo Cluster. II - A catalog of 2096 galaxies in the Virgo Cluster area.
The present catalog of 2096 galaxies within an area of about 140 sq degapproximately centered on the Virgo cluster should be an essentiallycomplete listing of all certain and possible cluster members,independent of morphological type. Cluster membership is essentiallydecided by galaxy morphology; for giants and the rare class of highsurface brightness dwarfs, membership rests on velocity data. While 1277of the catalog entries are considered members of the Virgo cluster, 574are possible members and 245 appear to be background Zwicky galaxies.Major-to-minor axis ratios are given for all galaxies brighter than B(T)= 18, as well as for many fainter ones.
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