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The Square Kilometre Array: a new probe of cosmic magnetism
Magnetic fields are a fundamental part of many astrophysical phenomena,but the evolution, structure and origin of magnetic fields are stillunresolved problems in physics and astrophysics. When and how were thefirst fields generated? Are present-day magnetic fields the result ofstandard dynamo action, or do they represent rapid or recent fieldamplification through other processes? What role do magnetic fields playin turbulence, cosmic ray acceleration and structure formation? Iexplain how the Square Kilometre Array (SKA), a next-generation radiotelescope, can deliver stunning new data-sets that will address thesecurrently unanswered issues. The foundation for these experiments willbe an all-sky survey of rotation measures, in which Faraday rotationtoward >107 background sources will provide a dense gridfor probing magnetism in the Milky Way, nearby galaxies, and in distantgalaxies, clusters and protogalaxies. Using these data, we can map outthe evolution of magnetized structures from redshifts z > 3 to thepresent, can distinguish between different origins for seed magneticfields in galaxies, and can develop a detailed model of the magneticfield geometry of the intergalactic medium and of the overall Universe.In addition, the SKA will certainly discover new magnetic phenomenabeyond what we can currently predict or imagine.
| The origin and evolution of cosmic magnetism
Magnetism is one of the four fundamental forces. However, the origin ofmagnetic fields in stars, galaxies and clusters is an open problem inastrophysics and fundamental physics. When and how were the first fieldsgenerated? Are present-day magnetic fields a result of dynamo action, ordo they represent persistent primordial magnetism? What role do magneticfields play in turbulence, cosmic ray acceleration and galaxy formation?Here, we demonstrate how the Square Kilometer Array can deliver new datawhich will directly address these currently unanswered issues. Much ofwhat we present is based on an all-sky survey of rotation measures, inwhich Faraday rotation towards >107 background sourceswill provide a dense grid for probing magnetism in the Milky Way, innearby galaxies, and in distant galaxies, clusters and protogalaxies.Using these data, we can map out the evolution of magnetised structuresfrom redshifts z > 3 to the present, can distinguish betweendifferent origins for seed magnetic fields in galaxies, and can developa detailed model of the magnetic field geometry of the intergalacticmedium and of the overall Universe. With the unprecedented capabilitiesof the SKA, the window to the Magnetic Universe can finally be opened.
| Companions of Bright Barred Shapley-Ames Galaxies
Companion galaxy environment for a subset of 78 bright and nearby barredgalaxies from the Shapley-Ames Catalog is presented. Among the spiralbarred galaxies, there are Seyfert galaxies, galaxies with circumnuclearstructures, galaxies not associated with any large-scale galaxy cloudstructure, galaxies with peculiar disk morphology (crooked arms), andgalaxies with normal disk morphology; the list includes all Hubbletypes. The companion galaxy list includes the number of companiongalaxies within 20 diameters, their Hubble type, and projectedseparation distance. In addition, the companion environment was searchedfor four known active spiral galaxies, three of them are Seyfertgalaxies, namely, NGC 1068, NGC 1097, and NGC 5548, and one is astarburst galaxy, M82. Among the results obtained, it is noted that theonly spiral barred galaxy classified as Seyfert 1 in our list has nocompanions within a projected distance of 20 diameters; six out of 10Seyfert 2 bar galaxies have no companions within 10 diameters, six outof 10 Seyfert 2 galaxies have one or more companions at projectedseparation distances between 10 and 20 diameters; six out of 12 galaxieswith circumnuclear structures have two or more companions within 20diameters.
| A new catalogue of ISM content of normal galaxies
We have compiled a catalogue of the gas content for a sample of 1916galaxies, considered to be a fair representation of ``normality''. Thedefinition of a ``normal'' galaxy adopted in this work implies that wehave purposely excluded from the catalogue galaxies having distortedmorphology (such as interaction bridges, tails or lopsidedness) and/orany signature of peculiar kinematics (such as polar rings,counterrotating disks or other decoupled components). In contrast, wehave included systems hosting active galactic nuclei (AGN) in thecatalogue. This catalogue revises previous compendia on the ISM contentof galaxies published by \citet{bregman} and \citet{casoli}, andcompiles data available in the literature from several small samples ofgalaxies. Masses for warm dust, atomic and molecular gas, as well asX-ray luminosities have been converted to a uniform distance scale takenfrom the Catalogue of Principal Galaxies (PGC). We have used twodifferent normalization factors to explore the variation of the gascontent along the Hubble sequence: the blue luminosity (LB)and the square of linear diameter (D225). Ourcatalogue significantly improves the statistics of previous referencecatalogues and can be used in future studies to define a template ISMcontent for ``normal'' galaxies along the Hubble sequence. The cataloguecan be accessed on-line and is also available at the Centre desDonnées Stellaires (CDS).The catalogue is available in electronic form athttp://dipastro.pd.astro.it/galletta/ismcat and at the CDS via anonymousftp to\ cdsarc.u-strasbg.fr (130.79.128.5) or via\http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/405/5
| Environmental effects in galaxies. Molecular gas, star formation, and activity
In order to study whether there is any correlation between nuclearactivities, gas content, and the environment where galaxies reside, wehave obtained optical and millimetric spectra for a well-defined sampleof intermediate Hubble type spirals in dense environments and in thefield. We found that these spirals in dense environments have onaverage: less molecular gas per blue luminosity, a higher atomic gasfraction, lower current star formation rate, and the same star formationefficiency as field galaxies. Although none of these results stands outas a single strong diagnostic given their statistical significance,taken together they indicate a trend for diminished gas content andstar-formation activity in galaxies in high-density environments. Ourresults suggest that galaxies in dense environments have either (i)consumed their molecular gas via star formation in the past or (ii) thatdense environments leads to an inhibition of molecular gas from atomicphase. The similarities in star-formation efficiency of the denseenvironments and field galaxies suggest that the physical processescontroling the formation of stars from the molecular gas are localrather than global. We also found that star formation rate per blueluminosity increases linearly as the total amount of gas increases inLINERs. This result, based on a small sample, suggests that LINERs arepowered by star formation rather than an AGN. Based on observations atthe European Southern Observatory at the 15 m Swedish ESO Submillimetretelescope, SEST, and at the the 1.52 m telescope which is operated underthe ESO-ON agreement.
| Environmental effects in galaxies. The data{
We present optical and millimetric data for 47 intermediate Hubble typespiral galaxies located either in dense environments or in the field. Wecompare correlations between global parameters, such as far-infraredluminosity, blue luminosity, and total molecular gas content, with othersamples of galaxies, including normal galaxies, clusters andultraluminous infrared galaxies. We find that overall our sample is awell-defined subset of these other samples of galaxies. Based onobservations at the European Southern Observatory at the 15 m SwedishESO Submillimetre telescope, SEST, and at the the 1.52 m telescope whichis operated under the ESO-ON agreement. Appendix A is only available inelectronic form at http://www.edpsciences.org
| Supernovae in isolated galaxies, in pairs and in groups of galaxies
In order to investigate the influence of environment on supernova (SN)production, we have performed a statistical investigation of the SNediscovered in isolated galaxies, in pairs and in groups of galaxies. 22SNe in 18 isolated galaxies, 48 SNe in 40 galaxy members of 37 pairs and211 SNe in 170 galaxy members of 116 groups have been selected andstudied. We found that the radial distributions of core-collapse SNe ingalaxies located in different environments are similar, and consistentwith those reported by Bartunov, Makarova & Tsvetkov. SNe discoveredin pairs do not favour a particular direction with respect to thecompanion galaxy. Also, the azimuthal distributions inside the hostmembers of galaxy groups are consistent with being isotropics. The factthat SNe are more frequent in the brighter components of the pairs andgroups is expected from the dependence of the SN rates on the galaxyluminosity. There is an indication that the SN rate is higher in galaxypairs compared with that in groups. This can be related to the enhancedstar formation rate in strongly interacting systems. It is concludedthat, with the possible exception of strongly interacting systems, theparent galaxy environment has no direct influence on SN production.
| X-Ray Measurements of the Field and Particle Energy Distributions in the West Lobe of the Radio Galaxy NGC 1316 (Fornax A)
A follow-up X-ray study was made of the west lobe of the radio galaxyFornax A (NGC 1316) that was based on new ASCA observations made in 1997for 98 ks and that incorporated the previous observation in 1994 for 39ks. The 0.7-10 keV spectrum of the emission can be described by a powerlaw with an energy index of 0.74+/-0.10, which agrees with thesynchrotron radio index of 0.9+/-0.2. Therefore, the X-rays arereconfirmed to arise via the inverse Compton scattering of the cosmicmicrowave photons, as Kaneda et al. and Feigelson et al. concluded. Thesurface brightness of the inverse Compton X-rays exhibits a relativelyflat distribution over the west lobe, indicative of an approximatelyspherical emissivity distribution with a radius of ~11' (75 kpc). Incontrast, the 1.4 GHz radio image by Ekers et al. exhibits arim-brightened surface brightness, consistent with a shell-likeemissivity distribution whose inner and outer boundaries are 4' and 11',respectively. These morphological differences between radio and X-rayssuggest that the relativistic electrons are distributed homogeneouslyover the lobe volume, whereas the magnetic field is amplified toward thelobe rim region.
| Atomic and molecular gas in the merger galaxy NGC 1316 (Fornax A) and its environment
We present and interpret observations of atomic and molecular gas towardthe southern elliptical galaxy NGC 1316 (Fornax A), a strong double-loberadio source with a disturbed optical morphology that includes numerousshells and loops. The 12CO(1-0), 12CO(2-1), and Hiobservations were made with SEST and the VLA. CO emission correspondingto a total molecular hydrogen mass of ~ 5 x 108Msun was detected towards the central position as well asnorthwest and southeast of the nucleus in the regions of the dustpatches. The origin of that gas is likely external and due to accretionof one or several small gas-rich galaxies. Hi was not detected in thecentral region of NGC 1316, but ~ 2 x 107 Msun ofatomic gas was found towards the giant Hii region discovered bySchweizer (1980) located 6{farcm }7 (or 36.2 kpc) from the nucleus. Hiwas also found at three other locations in the outer part of NGC 1316.The Hi distributions and kinematics of the two nearby spiral companionsof NGC 1316, NGC 1317 (a barred galaxy to the north) and NGC 1310 (tothe west) could be studied. Both galaxies have unusually small Hi disksthat may have been affected by ram-pressure stripping.
| The neutral hydrogen content of Fornax cluster galaxies
We present a new set of deep H I observations of member galaxies of theFornax cluster. We detected 35 cluster galaxies in HI. The resulting sample, the most comprehensive to date, is used toinvestigate the distribution of neutral hydrogen in the clustergalaxies. We compare the H I content of the detected cluster galaxieswith that of field galaxies by measuring H I mass-to-light ratios andthe H I deficiency parameter of Solanes et al. (\cite{Sol96}). The meanH I mass-to-light ratio of the cluster galaxies is 0.68+/- 0.15,significantly lower than for a sample of H I-selected field galaxies(1.15+/- 0.10), although not as low as in the Virgocluster (0.45+/- 0.03). In addition, the H I content of twocluster galaxies (NGC 1316C and NGC1326B) appears to have been affected by interactions. The meanH I deficiency for the cluster is 0.38+/-0.09 (for galaxy types T=1-6),significantly greater than for the field sample (0.05+/-0.03). Boththese tests show that Fornax cluster galaxies are HI-deficient compared to field galaxies. The kinematics of the clustergalaxies suggests that the H I deficiency may be caused by ram-pressurestripping of galaxies on orbits that pass close to the cluster core. Wealso derive the most complete B-band Tully - Fisher relation of inclinedspiral galaxies in Fornax. A subcluster in theSouth-West of the main cluster contributes considerably to the scatter.The scatter for galaxies in the main cluster alone is 0.50 mag, which isslightly larger than the intrinsic scatter of 0.4 mag. We use the Tully- Fisher relation to derive a distance modulus ofFornax relative to the Virgocluster of -0.38+/- 0.14 mag. The galaxies in the subclusterare (1.0+/-0.5) mag brighter than the galaxies of the main cluster,indicating that they are situated in the foreground. With their meanvelocity 95 km s-1 higher than that of the main cluster weconclude that the subcluster is falling into the main Fornaxcluster.
| 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.
| Very Wide Galaxy Pairs of the Northern and Southern Sky
We present highly accurate observations of the 21 cm line of hydrogen ingalaxies made at the Arecibo and Parkes Observatories. The galaxiesobserved have been identified, through rigorous selection criteriaapplied to the CfA and SSRS catalogs, as being members of pairs withprojected separations of up to 1.5 Mpc (H0 = 75 km s-1 Mpc-1). Theseobservations form the completion of the Chengalur-Nordgren galaxy pairsample with data previously published by Chengalur, Nordgren andcolleagues. The new selection criteria used in this paper are anextension to larger projected separations of the criteria usedpreviously. Forty-nine new galaxies are observed, while H I is detectedin 41 of them. With the addition of these galaxies, the completed samplehas highly accurate H I velocities for a total of 219 galaxies.
| 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.
| Total magnitude, radius, colour indices, colour gradients and photometric type of galaxies
We present a catalogue of aperture photometry of galaxies, in UBVRI,assembled from three different origins: (i) an update of the catalogueof Buta et al. (1995) (ii) published photometric profiles and (iii)aperture photometry performed on CCD images. We explored different setsof growth curves to fit these data: (i) The Sersic law, (ii) The net ofgrowth curves used for the preparation of the RC3 and (iii) A linearinterpolation between the de Vaucouleurs (r(1/4) ) and exponential laws.Finally we adopted the latter solution. Fitting these growth curves, wederive (1) the total magnitude, (2) the effective radius, (3) the colourindices and (4) gradients and (5) the photometric type of 5169 galaxies.The photometric type is defined to statistically match the revisedmorphologic type and parametrizes the shape of the growth curve. It iscoded from -9, for very concentrated galaxies, to +10, for diffusegalaxies. Based in part on observations collected at the Haute-ProvenceObservatory.
| A catalogue of spatially resolved kinematics of galaxies: Bibliography
We present a catalogue of galaxies for which spatially resolved data ontheir internal kinematics have been published; there is no a priorirestriction regarding their morphological type. The catalogue lists thereferences to the articles where the data are published, as well as acoded description of these data: observed emission or absorption lines,velocity or velocity dispersion, radial profile or 2D field, positionangle. Tables 1, 2, and 3 are proposed in electronic form only, and areavailable from the CDS, via anonymous ftp to cdsarc.u-strasbg.fr (to130.79.128.5) or via http://cdsweb.u-strasbg.fr/Abstract.html
| An Einstein X-Ray Survey of Optically Selected Galaxies. I. Data
We present the results of a complete Einstein imaging proportionalcounter X-ray survey of optically selected galaxies from theShapley-Ames Catalog, the Uppsala General Catalogue, and the EuropeanSouthern Observatory Catalog. Well-defined optical criteria are used toselect the galaxies, and X-ray fluxes are measured at the opticallydefined positions. The result is a comprehensive list of X-ray detectionand upper limit measurements for 1018 galaxies. Of these, 827 haveeither independent distance estimates or radial velocities. Associatedoptical, redshift, and distance data have been assembled for thesegalaxies, and their distances come from a combination of directlypredicted distances and those predicted from the Faber-Burstein GreatAttractor/Virgocentric infall model. The accuracy of the X-ray fluxeshas been checked in three different ways; all are consistent with thederived X-ray fluxes being of <=0.1 dex accuracy. In particular,there is agreement with previously published X-ray fluxes for galaxiesin common with a 1991 study by Roberts et al. and a 1992 study byFabbiano et al. The data presented here will be used in further studiesto characterize the X-ray output of galaxies of various morphologicaltypes and thus to enable the determination of the major sourcescontributing to the X-ray emission from galaxies.
| Optical Rotation Curves and Linewidths for Tully-Fisher Applications
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1997AJ....114.2402C&db_key=AST
| The I band Tully-Fisher relation for cluster galaxies: data presentation.
Observational parameters which can be used for redshift-independentdistance determination using the Tully-Fisher (TF) technique are givenfor \ntot spiral galaxies in the fields of 24 clusters or groups. I bandphotometry for the full sample was either obtained by us or compiledfrom published literature. Rotational velocities are derived either from21 cm spectra or optical emission line long-slit spectra, and convertedto a homogeneous scale. In addition to presenting the data, a discussionof the various sources of error on TF parameters is introduced, and thecriteria for the assignment of membership to each cluster are given.
| Scaleheights of 486 southern spiral galaxies and some statistical correlation
Based on Peng's method (1988), we obtain scaleheights of 486 southernspiral galaxies, the images of which are taken from the Digitized SkySurvey at Xinglong Station of Beijing Astronomical Observatory. Thefitted spiral arms of 70 galaxies are compared with their images to gettheir optimum inclinations. The scaleheights of other 416 ones arelisted in Table A1 in Appendix. After compiling and analyzing the data,we find some statistical correlations. The most interesting results arethat a flatter galaxy is bluer and looks brighter, and galaxies becomeflatter along the Hubble sequence Sab -- Scd. Based on photographic dataof the National Geographic Society -- Palomar Observatory Sky Survey(NGS-POSS) obtained using the Oschin Telescope Palomar Mountain. TheNGS-POSS was funded by a grant from the National Geographic Society tothe California Institute of Technology. The plates were processed intothe present compressed digital form with their permission. The DigitizedSky Survey was produced at the Space Telescope Science Institute underUS Government grant NAG W-2166. Table A1 is available in electronic fromonly, via anonymous ftp 130.79.128.5 orhttp://cdsweb.u-strasbg.fr/Abstract.html
| Parameters of 2447 Southern Spiral Galaxies for Use in the Tully-Fisher Relation
I-band luminosities, rotational velocities, and redshifts of 1092 spiralgalaxies have been measured by CCD photometry and Hα spectroscopyusing the 1 m and 2.3 m telescopes at Siding Spring Observatory,respectively. The results are tabulated. Luminosity profiles andHα rotation curves are given for the galaxies. When these resultsare combined with similar data for 1355 spiral galaxies publishedpreviously (Mathewson, Ford, & Buchhorn, hereafter Paper I), itprovides a large, uniform, and unique data set with which to measure,via the Tully-Fisher relation, the peculiar velocities of galaxies inthe local universe to a distance of 11,000 km s^-1^ (Mathewson &Ford). Taking advantage of the opportunity for publishing this data inmachine-readable form, in the CD-ROM, we have also included similar datafor the 1355 galaxies in Paper I.
| 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.
| Rotation Curves of 967 Spiral Galaxies
We present the rotation curves of 967 southern spiral galaxies, obtainedby deprojecting and folding the raw Hα data originally publishedby Mathewson, Ford, & Buchhorn (1992). For 900 objects, we alsopresent, in figures and tables, the rotation curves smoothed on scalescorresponding to 5%-20% of the optical size; of these, 80 meet objectiveexcellence criteria and are suitable for individual detailed massmodeling, while 820, individually less compelling mainly because of themoderate statistics and/or limited extension, are suitable forstatistical studies. The remaining 67 curves suffer from severeasymmetries, small statistics, and large internal scatter that maylargely limit their use in galaxy structure studies. The deprojectedfolded curves, the smoothed curves, and various related quantities areavailable via anonymous ftp at galileo.sissa.it in the directory/users/ftp/pub/psrot.
| 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.
| Extragalactic Ionized Hydrogen in the Fornax Cluster
The radio galaxy Fornax A is well known for its giant radio lobes whichextend almost a degree (~300 kpc) across the sky. Fomalont et al. haveshown that these lobes are linearly polarized on the largest scales,although the western lobe is highly depolarized in discrete, resolvedregions. The depolarized regions indicate the presence of ionized gas(Faraday screen) along the line of sight to the western lobe. We havenow detected the warm gas at H alpha using a Fabry-Perot interferometerin a way that allows us to reach very low surface brightness levels(<10-19 erg cm-2 s-1 arcsec-2). The radial velocity of the ionizedgas (1610 km s-1) places it in the Fornax cluster at a projected radiusof 1.0 Mpc. The gas is spread over a region 10 kpc in diameter and hasan ionized mass of 6 x 107 f-0.5 Mȯ (where f is the volume fillingfactor). For the inferred column density of electrons (~2.6 x 1020 f-0.5cm-2) and in light of the H I upper limits (<4 x 1019 cm-2), thecloud has to be mostly ionized. Possible sources of ionization arelarge-scale shocks or a putative hot component which confines the radiolobes. The high line-of-sight magnetic field strength (B|| ~ 0.3--1.3 muG) deduced from the rotation measure (~20 rad m-2) and energyequipartition suggests that the cloud may have undergone significantturbulent heating from secondary shocks. The predicted bounds on thefraction of neutral material (10-6--10-1) indicates that this may be thefirst example of a spatially resolved, extragalactic ionized cloud. Suchobjects are thought to be responsible for some of the Ly alphaabsorption lines observed in the spectra of quasars.
| Integrated photoelectric magnitudes and color indices of bright galaxies in the Johnson UBV system
The photoelectric total magnitudes and color indices published in theThird Reference Catalogue of Bright Galaxies (RC3) are based on ananalysis of approximately equals 26,000 B, 25,000 B-V, and 17,000 U-Bmultiaperture measurements available up to mid 1987 from nearly 350sources. This paper provides the full details of the analysis andestimates of internal and external errors in the parameters. Thederivation of the parameters is based on techniques described by theVaucouleurs & Corwin (1977) whereby photoelectric multiaperture dataare fitted by mean Hubble-type-dependent curves which describe theintegral of the B-band flux and the typical B-V and U-B integrated colorgradients. A sophisticated analysis of the residuals of thesemeasurements from the curves was made to allow for the random andsystematic errors that effect such data. The result is a homogeneous setof total magnitudes BTA total colors(B-V)T and (U-B)T, and effective colors(B-V)e and (U-B)e for more than 3000 brightgalaxies in RC3.
| The CO and HI emission of spiral and lenticular galaxies in the Fornax cluster.
We present a ^12^CO(1-0) and HI survey of the spirals and lenticulars inthe nearby southern cluster of galaxies Fornax. We have not found anyevidence for a strong HI deficiency in this cluster, which shows weakX-ray emission. However, three lenticular galaxies located near thecluster centre, NGC 1380, NGC 1386 and NGC 1387, present some HIdeficiency with an HI content respectively 50, 25 and 16 times timeslower than expected. On the other hand, the CO emission of Fornaxgalaxies is weak in general and we have clear detections of only 11galaxies out of 21 observed. We have found that on the average, lessthan 10 percent of the gas in these galaxies is in the molecular phase,if the CO to H_2_ conversion factor has the same value as in our galaxy.We have compared these results with those of other extragalactic surveysand found that such low H_2_ contents are characteristic of samples thatare not selected on a far-infrared criterion. In particular the nearbygalaxies surveyed by Sage (1993a, b) also have a low CO emission,although to a lesser level. The low molecular gas content of Fornaxgalaxies is consistent with their low star formation activity suggestedby their low far-infrared and nonthermal radiocontinuum emissions. Wehave made optical spectroscopical observations of the two CO-poorHI-rich spirals NGC 1350 and 1425 and have found that those galaxieshave weak Hα emission. We have also mapped the CO(1-0) and (2-1)emission of the interacting spiral NGC 1532. The CO distribution showstwo maxima at 7kpc radius, compatible with the presence of a molecularring. As most of Fornax spirals NGC 1532 is very poor in molecular gassince it contains about 30 times less H_2_ than HI.
| Galaxy properties in different environments. 1: The sample
This paper presents two galaxy samples, respectively in a high and in alow local density environments, that were generated from the SouthernSky Redshift Survey (SSRS) catalog using objective criteria. Apreliminary comparison of physical properties in these two samplesreveals that galaxies in high-density environments tend to be under ahigher starbursting activity, have a deficiency of the neutral hydrogencontent, present a higher fractional Seyfert population and a higherfraction of barred spirals as well. The present samples are intended tobe used in future spectroscopic observations for more detailedinvestigation.
| Galaxy properties in different environments. 2: Star formation in bulges of late-type spirals
The star formation history in the nucleus of late spiral galaxies iscompared between a sample in a high galaxy density medium (HDS) and acontrol sample (CS) of isolated galaxies. We have observed 20 HDS and 18CS galaxies from a larger list generated by the application of agroup-finding algorithm to the SSRS survey. Using equivalent widths ofabsorption lines and the continuum distribution, we determined thenuclear stellar population types, from those dominated by old populationto those containing star formation bursts of different ages andintensities. The HDS and CS stellar population type histograms aresimilar, suggesting that environmental influences, at least for thepresent sample, do not affect substantially the nuclear stellarpopulation. However, the nuclear emission lines indicate that, in theBPT diagnostic diagrams, there is an excess of HDS galaxies locatedwithin or close to the active galactic nuclei (AGN) loci. For six HDSand two CS galaxies, it was possible to determine oxygen (O/H) andnitrogen (N/H) abundances. The samples present similar O/H values, butin the CS galaxies the N/O ratio is lower at equal galaxy luminosity.
| 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.
| A southern sky survey of the peculiar velocities of 1355 spiral galaxies
The paper presents data from photometric and spectroscopic observationsof 1355 southern spiral galaxies and uses them to determine theirdistances and peculiar velocities via the Tully-Fisher (TF) relation.I-band CCD surface photometry was carried out using the 1-m and 3.9-mtelescopes at Siding Spring Observatory. H-alpha rotation curves for 965galaxies and 551 H I profiles are presented. The physical parameters,photometric and velocity data, distances, and peculiar velocities of thegalaxies are presented in tabular form. The mean distance, systemicvelocity, and average peculiar velocity of 24 clusters in the sample aregiven. TF diagrams are presented for each cluster.
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