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Outlying H II Regions in H I-Selected Galaxies
We present results from the first systematic search for outlying H IIregions, as part of a sample of 96 emission-line point sources (referredto as ELdots-emission-line dots) derived from the NOAO Survey forIonization in Neutral Gas Galaxies (SINGG). Our automated ELdot findersearches SINGG narrowband and continuum images for high equivalent widthpoint sources outside the optical radius of the target galaxy (>2× r 25 in the R band). Follow-up long-slit spectroscopyand deep Galaxy Evolution Explorer (GALEX) images (exposure time>1000 s) distinguish outlying H II regions from background galaxieswhose strong emission lines ([O III], Hβ, or [O II]) have beenredshifted into the SINGG bandpass. We find that these deep GALEX imagescan serve as a substitute for spectroscopic follow-up because outlying HII regions separate cleanly from background galaxies in color-colorspace. We identify seven SINGG systems with outlying massive starformation that span a large range in Hα luminosities correspondingto a few O stars in the most nearby cases, and unresolved dwarfsatellite companion galaxies in the most distant cases. Six of theseseven systems feature galaxies with nearby companions or interactinggalaxies. Furthermore, our results indicate that some outlying H IIregions are linked to the extended-UV disks discovered by GALEX,representing emission from the most massive O stars among a moreabundant population of lower-mass (or older) star clusters. The overallfrequency of outlying H II regions in this sample of gas-rich galaxiesis 8%-11% when we correct for background emission-line galaxycontamination (~75% of ELdots).
| An Hα Imaging Survey of Galaxies in the Local 11 Mpc Volume
As part of a broader effort to characterize the population ofstar-forming galaxies in the local universe, we have carried out anHα+[N II] imaging survey for an essentially volume-limited sampleof galaxies within 11 Mpc of the Milky Way. This first paper describesthe design of the survey, the observation, data processing, andcalibration procedures, and the characteristics of the galaxy sample.The main product of the paper is a catalog of integrated Hαfluxes, luminosities, and equivalent widths for the galaxies in thesample. We briefly discuss the completeness properties of the survey andcompare the distribution of the sample and its star formation propertiesto other large Hα imaging surveys. These data form the foundationfor a series of follow-up studies of the star formation properties ofthe local volume, and the properties and duty cycles of star formationbursts in dwarf galaxies.
| The Survey for Ionization in Neutral Gas Galaxies. III. Diffuse, Warm Ionized Medium and Escape of Ionizing Radiation
We use the first data release from the SINGG Hα survey of H I-selected galaxies to study the quantitative behavior of the diffuse,warm ionized medium (WIM) across the range of properties represented bythese 109 galaxies. The mean fraction fWIM of diffuse ionizedgas in this sample is 0.59+/-0.19, slightly higher than found inprevious samples. Since lower surface brightness galaxies tend to havehigher fWIM, we believe that most of this difference is dueto selection effects favoring large, optically bright, nearby galaxieswith high star formation rates. As found in previous studies, there isno appreciable correlation with Hubble type or total star formationrate. However, we find that starburst galaxies, defined here by anHα surface brightness >2.5×1039 ergs-1 kpc-2 within the Hα half-light radius,do show much lower fractions of diffuse Hα emission. The causeapparently is not dominated by a lower fraction of field OB stars.However, it is qualitatively consistent with an expected escape ofionizing radiation above a threshold star formation rate, predicted fromour model in which the ISM is shredded by pressure-driven supernovafeedback. The H I gas fractions in the starburst galaxies are alsolower, suggesting that the starbursts are consuming and ionizing all thegas, and thus promoting regions of density-bounded ionization. If true,these effects imply that some amount of Lyman continuum radiation isescaping from most starburst galaxies, and that WIM properties andoutflows from mechanical feedback are likely to be pressure-driven.However, in view of previous studies showing that the escape fraction ofionizing radiation is generally low, it is likely that other factorsalso drive the low fractions of diffuse ionized gas in starbursts.
| The Survey for Ionization in Neutral Gas Galaxies. I. Description and Initial Results
We introduce the Survey for Ionization in Neutral Gas Galaxies (SINGG),a census of star formation in H I-selected galaxies. The survey consistsof Hα and R-band imaging of a sample of 468 galaxies selected fromthe H I Parkes All Sky Survey (HIPASS). The sample spans three decadesin H I mass and is free of many of the biases that affect otherstar-forming galaxy samples. We present the criteria for sampleselection, list the entire sample, discuss our observational techniques,and describe the data reduction and calibration methods. This paperfocuses on 93 SINGG targets whose observations have been fully reducedand analyzed to date. The majority of these show a single emission linegalaxy (ELG). We see multiple ELGs in 13 fields, with up to four ELGs ina single field. All of the targets in this sample are detected inHα, indicating that dormant (non-star-forming) galaxies withMHI>~3×107 Msolar are veryrare. A database of the measured global properties of the ELGs ispresented. The ELG sample spans 4 orders of magnitude in luminosity(Hα and R band), and Hα surface brightness, nearly 3 ordersof magnitude in R surface brightness and nearly 2 orders of magnitude inHα equivalent width (EW). The surface brightness distribution ofour sample is broader than that of the Sloan Digital Sky Survey (SDSS)spectroscopic sample, the EW distribution is broader than prism-selectedsamples, and the morphologies found include all common types ofstar-forming galaxies (e.g., irregular, spiral, blue compact dwarf,starbursts, merging and colliding systems, and even residual starformation in S0 and Sa spirals). Thus, SINGG presents a superior censusof star formation in the local universe suitable for further studiesranging from the analysis of H II regions to determination of the localcosmic star formation rate density.
| The 1000 Brightest HIPASS Galaxies: H I Properties
We present the HIPASS Bright Galaxy Catalog (BGC), which contains the1000 H I brightest galaxies in the southern sky as obtained from the H IParkes All-Sky Survey (HIPASS). The selection of the brightest sourcesis based on their H I peak flux density (Speak>~116 mJy)as measured from the spatially integrated HIPASS spectrum. The derived HI masses range from ~107 to 4×1010Msolar. While the BGC (z<0.03) is complete inSpeak, only a subset of ~500 sources can be consideredcomplete in integrated H I flux density (FHI>~25 Jy kms-1). The HIPASS BGC contains a total of 158 new redshifts.These belong to 91 new sources for which no optical or infraredcounterparts have previously been cataloged, an additional 51 galaxiesfor which no redshifts were previously known, and 16 galaxies for whichthe cataloged optical velocities disagree. Of the 91 newly cataloged BGCsources, only four are definite H I clouds: while three are likelyMagellanic debris with velocities around 400 km s-1, one is atidal cloud associated with the NGC 2442 galaxy group. The remaining 87new BGC sources, the majority of which lie in the zone of avoidance,appear to be galaxies. We identified optical counterparts to all but oneof the 30 new galaxies at Galactic latitudes |b|>10deg.Therefore, the BGC yields no evidence for a population of``free-floating'' intergalactic H I clouds without associated opticalcounterparts. HIPASS provides a clear view of the local large-scalestructure. The dominant features in the sky distribution of the BGC arethe Supergalactic Plane and the Local Void. In addition, one can clearlysee the Centaurus Wall, which connects via the Hydra and Antlia Clustersto the Puppis Filament. Some previously hardly noticable galaxy groupsstand out quite distinctly in the H I sky distribution. Several newstructures, including some not behind the Milky Way, are seen for thefirst time.
| 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.
| Nebular abundances of nearby southern dwarf galaxies
The results of optical spectroscopy of H II regions in a sample ofsouthern dwarf irregulars consisting of five dwarf galaxies in theCentaurus A group, four dwarfs in the Sculptor group, and eightadditional dwarf galaxies are presented. Oxygen abundances are derivedusing the direct method where [O III]lambda 4363 is detected;otherwise, abundances are derived with the bright-line method using theMcGaugh and the Pilyugin calibrations. ESO358-G060 has the lowest oxygenabundance (12+log(O/H) = 7.32) in the sample, which is comparable to thevalue for the second most metal-poor galaxy known (SBS 0335-052). Inall, new oxygen abundances are reported for nine dwarf galaxies; updatedvalues are presented for the remaining galaxies. Derived oxygenabundances are in the range from 3% to 26% of the solar value. Oxygenabundances for dwarfs in the southern sample are consistent with themetallicity-luminosity relationship defined by a control sample of dwarfirregulars with [O III]lambda 4363 abundances and well-measureddistances. However, NGC 5264 appears to have an (upper branch) oxygenabundance approximately two to three times higher than other dwarfs atsimilar luminosities. Nitrogen-to-oxygen and neon-to-oxygen abundanceratios are also reported; in particular, IC 1613 and IC 5152 showelevated nitrogen-to-oxygen ratios for their oxygen abundances.
| The large-scale distribution of neutral hydrogen in the Fornax region
Using data from the HI Parkes All Sky Survey (HIPASS), we have searchedfor neutral hydrogen in galaxies in a region ~25 × 25deg2 centred on NGC 1399, the nominal centre of the Fornaxcluster. Within a velocity search range of 300-3700 km s-1and to a 3σ lower flux limit of ~40 mJy, 110 galaxies with HIemission were detected, one of which is previously uncatalogued. None ofthe detections has early-type morphology. Previously unknown velocitiesfor 14 galaxies have been determined, with a further four velocitymeasurements being significantly dissimilar to published values.Identification of an optical counterpart is relatively unambiguous formore than ~90 per cent of our HI galaxies. The galaxies appear to beembedded in a sheet at the cluster velocity which extends for more than30° across the search area. At the nominal cluster distance of ~20Mpc, this corresponds to an elongated structure more than 10 Mpc inextent. A velocity gradient across the structure is detected, withradial velocities increasing by ~500 km s-1 from south-eastto north-west. The clustering of galaxies evident in optical surveys isonly weakly suggested in the spatial distribution of our HI detections.Of 62 HI detections within a 10° projected radius of the clustercentre, only two are within the core region (projected radius<1°) and less than 30 per cent are within 3.5°, suggesting aconsiderable deficit of HI-rich galaxies in the centre of the cluster.However, relative to the field, there is a 3(+/-1)-fold excess ofHI-rich galaxies in the outer parts of the cluster where galaxies may beinfalling towards the cluster for the first time.
| Properties of Quasar-Galaxy Associations and Gravitational Mesolensing by Halo Objects
A new catalog of 8382 close quasar-galaxy pairs is presented. Thecatalog was composed using published catalogs of quasars and activegalactic nuclei containing 11358 objects, as well as the LEDA catalog ofgalaxies, which contains on the order of 100 thousand objects. Based onthese new data, the dependence of the number of pairs on a=z G /z Q isanalyzed, where z G and z Q are the redshifts of the galaxy and quasar,respectively, revealing an excess of pairs with a<0.1 and a>0.9.This means that the galaxies in pairs are preferably located close toeither the observer or the quasar and avoid intermediate distances alongthe line of sight to the quasar. Computer simulations demonstrate thatit is not possible to explain this number of pairs with the observeddistribution in a as the result of chance positional coincidences with auniform spatial distribution of galaxies. Data on globular clusters showthat the excess of pairs with a<0.1 and a>0.9 is consistent withthe hypothesis that we are observing distant compact objects that arestrongly gravitationally lensed by transparent lenses with a King massdistribution located in the halos of nearby galaxies. The Hubble diagramfor galaxies and quasars is presented. Observational tests of themesolensing hypothesis are formulated.
| Galaxy coordinates. II. Accurate equatorial coordinates for 17298 galaxies
Using images of the Digitized Sky Survey we measured coodinates for17298 galaxies having poorly defined coordinates. As a control, wemeasured with the same method 1522 galaxies having accurate coordinates.The comparison with our own measurements shows that the accuracy of themethod is about 6 arcsec on each axis (RA and DEC).
| The Southern Sky Redshift Survey
We report redshifts, magnitudes, and morphological classifications for5369 galaxies with m_B <= 15.5 and for 57 galaxies fainter than thislimit, in two regions covering a total of 1.70 sr in the southerncelestial hemisphere. The galaxy catalog is drawn primarily from thelist of nonstellar objects identified in the Hubble Space TelescopeGuide Star Catalog (GSC). The galaxies have positions accurate to ~1"and magnitudes with an rms scatter of ~0.3 mag. We compute magnitudes(m_SSRS2) from the relation between instrumental GSC magnitudes and thephotometry by Lauberts & Valentijn. From a comparison with CCDphotometry, we find that our system is homogeneous across the sky andcorresponds to magnitudes measured at the isophotal level ~26 magarcsec^-2. The precision of the radial velocities is ~40 km s^-1, andthe redshift survey is more than 99% complete to the m_SSRS2 = 15.5 maglimit. This sample is in the direction opposite that of the CfA2; incombination the two surveys provide an important database for studies ofthe properties of galaxies and their large-scale distribution in thenearby universe. Based on observations obtained at Cerro TololoInter-American Observatory, National Optical Astronomy Observatories,operated by the Association of Universities for Research in Astronomy,Inc., under cooperative agreement with the National Science Foundation;Complejo Astronomico El Leoncito, operated under agreement between theConsejo Nacional de Investigaciones Científicas de laRepública Argentina and the National Universities of La Plata,Córdoba, and San Juan; the European Southern Observatory, LaSilla, Chile, partially under the bilateral ESO-ObservatórioNacional agreement; Fred Lawrence Whipple Observatory;Laboratório Nacional de Astrofísica, Brazil; and the SouthAfrican Astronomical Observatory.
| An HI survey for protogalaxies in the Centaurus and Fornax galaxy clusters
The results of 21-cm neutral hydrogen survey observations, made usingthe 64-m Parkes telescope, are presented for two 8 deg by 8 deg fields,centred on the Centaurus and Fornax galaxy clusters, and a smaller 1deg.5 field in Eridanus. The purpose of the observations was to searchfor extended Hi clouds with no clear optical counterparts. 31 previouslycatalogued galaxies were detected, with Hi parameters for 16 beinglisted for the first time. One previously uncatalogued dwarf galaxy(`Wombat I', J0341-3851) was found near the Fornax cluster. AustraliaTelescope Compact Array observations give an Hi mass of 8x10^7 Msolarand a diameter of 4kpc for this object, which is also visible on UKSTsurvey plates. However, no clouds with optically invisible counterpartswere detected. We deduce a 99 per cent confidence limit on the total Hidensity of such objects in the cluster and near-cluster environment ofOmega_HI<10^-2h^-1(deltaV/100kms^-1.
| The Catalog of Southern Ringed Galaxies
The Catalog of Southern Ringed Galaxies (CSRG) is a comprehensivecompilation of diameters, axis ratios, relative bar position angles, andmorphologies of inner and outer rings, pseudorings, and lenses in 3692galaxies south of declination -17 deg. The purpose of the catalog is toevaluate the idea that these ring phenomena are related to orbitalresonances with a bar or oval in galaxy potentials. The catalog is basedon visual inspection of most of the 606 fields of the Science ResearchCouncil (SRC) IIIa-J southern sky survey, with the ESO-B, ESO-R, andPalomar Sky surveys used as auxiliaries when needed for overexposed coreregions. The catalog is most complete for SRC fields 1-303 (mostly southof declination -42 deg). In addition to ringed galaxies, a list of 859mostly nonringed galaxies intended for comparison with other catalogs isprovided. Other findings from the CSRG that are not based on statisticsare the identification of intrinsic bar/ring misalignment; bars whichunderfill inner rings; dimpling of R'1pseudorings; pointy, rectangular, or hexagonal inner or outer ringshapes; a peculiar polar-ring-related system; and other extreme examplesof spiral structure and ring morphology.
| Groups of galaxies within 80 Mpc. II - The catalogue of groups and group members
This paper gives a catalog of the groups and associations obtained bymeans of a revised hierarchical algorithm applied to a sample of 4143galaxies with diameters larger than 100 arcsec and redshifts smallerthan 6000 km/s. The 264 groups of galaxies obtained in this way (andwhich contain at least three sample galaxies) are listed, with the looseassociations surrounding them and the individual members of eachaggregate as well; moreover, the location of every entity among 13regions corresponding roughly to superclusters is specified. Finally,1729 galaxies belong to the groups, and 466 to the associations, i.e.,the total fraction of galaxies within the various aggregates amounts to53 percent.
| Southern Sky Redshift Survey - The catalog
The catalog of radial velocities for galaxies which comprise thediameter-limited sample of the Southern Sky Redshift Survey ispresented. It consolidates the data of observations carried out at theLas Campanas Observatory, Observatorio Nacional, and South AfricanAstronomical Observatory. The criteria used for the sample selection aredescribed, as well as the observational procedures and the techniqueutilized to obtain the final radial velocities. The intercomparisonbetween radial velocity measurements from different telescopes indicatesthat the final data base is fairly homogeneous with a typical error ofabout 40 km/s. The sample is at present 90 percent complete, and themissing galaxies are predominantly objects with very low surfacebrightness for which it is very difficult to obtain optical redshifts.
| The surface photometry catalogue of the ESO-Uppsala galaxies
Not Available
| Near-infrared photometry and stellar populations in dwarf elliptical and irregular galaxies
Studies of three different types of dwarf galaxies have been conducted,taking into account low surface brightness (LSB) dwarf irregular (dI)galaxies, dwarf elliptical (dE) galaxies, and blue compact dwarfgalaxies (BCDGs). Near-infrared observations for a large sample of BCDGshave been reported by Thuan (1983). The present paper is concerned withcomplementary near-infrared observations for a large sample of LSB dIand dE galaxies, and, in addition, with a few additional BCDGobservations. In a discussion of dwarf elliptical galaxies, attention isgiven to an infrared color-color diagram, optical-infrared colors andburst ages, and the UVK color plane. Low surface brightness dwarfirregular galaxies and blue compact dwarf galaxies are considered alongwith the possible evolutionary scenarios which may link LSB dIs, BCDGs,and dEs.
| Southern Galaxy Catalogue.
Not Available
| An optical and H I study of late-type low surface brightness galaxies
Neutral hydrogen and optical parameters are presented for 151 galaxiesof low surface brightness selected from UK Schmidt plates. The 21-cm H Iline was detected in 100 of these systems. It is found that the galaxiesshow the same trends of global properties with type as samples of brightgalaxies, while the data are consistent with the low surface brightness(LSB) galaxies being of systematically lower mass than bright galaxiesof the same type and linear dimensions. A constant value of hydrogenmass/(linear dimension)/squared is strongly suggested for LSB and brightgalaxies.
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