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XMM-Newton Observation of an X-Ray Trail between the Spiral Galaxy NGC 6872 and the Central Elliptical Galaxy NGC 6876 in the Pavo Group
We present XMM-Newton observations of a trail of enhanced X-ray emissionextending along the full 8.7 arcmin ×4' region betweenthe large spiral galaxy NGC 6872 and the dominant elliptical galaxy NGC6876 in the Pavo group, the first known X-ray trail associated with aspiral galaxy in a poor galaxy group and, with a projected length of 90kpc, one of the longest known X-ray trails. The X-ray surface brightnessin the trail region is roughly constant beyond ~20 kpc of NGC 6876 inthe direction of the spiral galaxy. The trail is hotter (~1 keV) thanthe undisturbed Pavo IGM (~0.5 keV) and has low metal abundances (0.2Zsolar). The 0.5-2 keV luminosity of the trail, measuredusing a 67×90 kpc rectangular region, is 6.6×1040ergs s-1. We compare the properties of gas in the trail tothe spectral properties of gas in the spiral galaxy NGC 6872 and in theelliptical galaxy NGC 6876 to constrain its origin. We suggest that theX-ray trail is either IGM gas gravitationally focused into a Bondi-Hoylewake, a thermal mixture of ~60% Pavo IGM gas with ~40% galaxy gas thathas been removed from the spiral galaxy NGC 6872 by turbulent viscousstripping, or both, due to the spiral galaxy's supersonic motion atangle ξ~40deg with respect to the plane of the sky,through the densest region of the Pavo IGM. Assumingξ=40deg and a filling factor η in a cylindrical volumewith radius 33 kpc and projected length 90 kpc, the mean electrondensity and total hot gas mass in the trail are1×10-3η-1/2 cm-3 and1.1×1010η1/2 Msolar,respectively.
| The star cluster population in the tidal tails of NGC 6872
We present a photometric analysis of the rich star cluster population inthe tidal tails of NGC 6872. We find star clusters with ages between1-100 Myr distributed in the tidal tails, while the tails themselveshave an age of less than 150 Myr. Most of the young massive(104 ≤ M/Mȯ ≤ 107)clusters are found in the outer regions of the galactic disk or thetidal tails. The mass distribution of the cluster population can be welldescribed by a power-law of the form N(m) ∝ m-α,where α = 1.85 ± 0.11, in very good agreement with otheryoung cluster populations found in a variety of different environments.We estimate the star formation rate for three separate regions of thegalaxy, and find that the eastern tail is forming stars at ~2 times therate of the western tail and ~5 times the rate of the main body of thegalaxy. By comparing our observations with published N-body models ofthe fate of material in tidal tails in a galaxy cluster potential, wesee that many of these young clusters will be lost into theintergalactic medium. We speculate that this mechanism may also be atwork in larger galaxy clusters such as Fornax, and suggest that theso-called ultra-compact dwarf galaxies could be the most massive starclusters that have formed in the tidal tails of an ancient galacticmerger.
| Stars and Gas in the Large Interacting Galaxy NGC 6872
The luminous barred galaxy NGC 6872 is one of the largest spiralgalaxies known. Star formation occurs all along the arms, which extendover more than 100 kpc. The galaxy experiences tidal perturbations fromthe nearby companion IC 4970 passing by on a low-inclination, progradeorbit. We have mapped the large-scale distribution and kinematics of theatomic gas (HI) in the NGC 6872/IC 4970 system and carried out N-bodysimulations with stars and gas. HI is absent from the central region; onthe other hand, large gas concentrations are found at the tip of thetidal arms, spatially coincident with the blue stellar clusters and withthe peaks of the Hα distribution. We use that remarkable system toinvestigate the evolution of gas and stars in a close progradeencounter, examine the influence of a dark matter halo on the length ofthe tidal tails, and test models of collisionally induced starformation.
| Australia Telescope Compact Array H I observations of the NGC 6845 galaxy group
We present the results of Australia Telescope Compact Array (ATCA) HIline and 20-cm radio continuum observations of the galaxy quartet NGC6845. The HI emission extends over all four galaxies but can only beassociated clearly with the two spiral galaxies, NGC 6845A and B, whichshow signs of strong tidal interaction. We derive a total HI mass of atleast 1.8 × 1010 Msolar, most of which isassociated with NGC 6845A, the largest galaxy of the group. Weinvestigate the tidal interaction between NGC 6845A and B by studyingthe kinematics of distinct HI components and their relation to the knownHII regions. No HI emission is detected from the two lenticulargalaxies, NGC 6845C and D. A previously uncatalogued dwarf galaxy, ATCAJ2001-4659, was detected 4.4 arcmin NE from NGC 6845B and has an HI massof ~5 × 108 Msolar. No HI bridge is visiblebetween the group and its newly detected companion. Extended 20-cm radiocontinuum emission is detected in NGC 6845A and B as well as in thetidal bridge between the two galaxies. We derive star formation rates of15-40 Msolar yr-1.
| Galaxy interactions - poor starburst triggers. III. A study of a complete sample of interacting galaxies
We report on a study of tidally triggered star formation in galaxiesbased on spectroscopic/photometric observations in the optical/near-IRof a magnitude limited sample of 59 systems of interacting and merginggalaxies and a comparison sample of 38 normal isolated galaxies. From astatistical point of view the sample gives us a unique opportunity totrace the effects of tidally induced star formation. In contrast toresults from previous investigations, our global UBV colours do notsupport a significant enhancement of starforming activity in theinteracting/merging galaxies. We also show that, contrary to previousclaims, there is no significantly increased scatter in the colours ofArp galaxies as compared to normal galaxies. We do find support formoderate (a factor of ~ 2-3) increase in star formation in the verycentres of the interacting galaxies of our sample, contributingmarginally to the total luminosity. The interacting and in particularthe merging galaxies are characterized by increased far infrared(hereafter FIR) luminosities and temperatures that weakly correlate withthe central activity. The LFIR/LB ratio however,is remarkably similar in the two samples, indicating that truestarbursts normally are not hiding in the central regions of the FIRluminous cases. The gas mass-to-luminosity ratio in optical-IR ispractically independent of luminosity, lending further support to thepaucity of true massive starburst galaxies triggered byinteractions/mergers. We estimate the frequency of such cases to be ofthe order of ~ 0.1% of the galaxies in an apparent magnitude limitedsample. Our conclusion is that interacting and merging galaxies, fromthe global star formation aspect, generally do not differ dramaticallyfrom scaled up versions of normal, isolated galaxies. No drastic changewith redshift is expected. One consequence is that galaxy formationprobably continued over a long period of time and did not peak at aspecific redshift. The effects of massive starbursts, like blowoutscaused by superwinds and cosmic reionization caused by starburstpopulations would also be less important than what is normally assumed.Based on observations collected at the European Southern Observatory, LaSilla, Chile.
| A Catalog of H I-Selected Galaxies from the South Celestial Cap Region of Sky
The first deep catalog of the H I Parkes All Sky Survey (HIPASS) ispresented, covering the south celestial cap (SCC) region. The SCC areais ~2400 deg2 and covers δ<-62°. The average rmsnoise for the survey is 13 mJy beam-1. Five hundredthirty-six galaxies have been cataloged according to their neutralhydrogen content, including 114 galaxies that have no previous catalogedoptical counterpart. This is the largest sample of galaxies from a blindH I survey to date. Most galaxies in optically unobscured regions of skyhave a visible optical counterpart; however, there is a small populationof low-velocity H I clouds without visible optical counterparts whoseorigins and significance are unclear. The rms accuracy of the HIPASSpositions is found to be 1.9′. The H I mass range of galaxiesdetected is from ~106 to ~1011 Msolar.There are a large number of late-type spiral galaxies in the SCC sample(66%), compared with 30% for optically selected galaxies from the sameregion in the NASA Extragalactic Database. The average ratio of H I massto B luminosity of the sample increases according to optical type, from1.8 Msolar/Lsolar for early types to 3.2Msolar/Lsolar for late-type galaxies. The HI-detected galaxies tend to follow the large-scale structure traced bygalaxies found in optical surveys. From the number of galaxies detectedin this region of sky, we predict the full HIPASS catalog will contain~5000 galaxies, to a peak flux density limit of ~39 mJy (3 σ),although this may be a conservative estimate as two large voids arepresent in the region. The H I mass function for this catalog ispresented in a subsequent paper.
| Galaxies with Rows
The results of a search for galaxies with straight structural elements,usually spiral-arm rows (“rows” in the terminology ofVorontsov-Vel'yaminov), are reported. The list of galaxies that possess(or probably possess) such rows includes about 200 objects, of whichabout 70% are brighter than 14m. On the whole, galaxies with rows makeup 6 8% of all spiral galaxies with well-developed spiral patterns. Mostgalaxies with rows are gas-rich Sbc-Scd spirals. The fraction ofinteracting galaxies among them is appreciably higher than amonggalaxies without rows. Earlier conclusions that, as a rule, the lengthsof rows are similar to their galactocentric distances and that theangles between adjacent rows are concentrated near 120° areconfirmed. It is concluded that the rows must be transient hydrodynamicstructures that develop in normal galaxies.
| HIPASS Detection of an Intergalactic Gas Cloud in the NGC 2442 Group
We report the discovery from the H I Parkes All-Sky Survey (HIPASS) of agas cloud associated with the asymmetric spiral galaxy NGC 2442. Thisobject, designated HIPASS J0731-69, contains ~109Msolar of H I, or nearly one-third as much atomic gas as NGC2442 itself. No optical counterpart to any part of HIPASS J0731-69 hasyet been identified, consistent with the gas being diffuse and itsstreamlike kinematics. If the gas in HIPASS J0731-69 was once part ofNGC 2442, then it was most likely a fairly recent tidal encounter with amoderately massive companion that tore it loose, although thepossibility of ram-pressure stripping cannot be ruled out. Thisdiscovery highlights the potential of the HIPASS data for yielding newclues to the nature of some of the best-known galaxies in the localuniverse.
| Homogenization of the Stellar Population along Late-Type Spiral Galaxies
We present a study of the broadband UBV color profiles for 257 Sbcbarred and nonbarred galaxies, using photoelectric aperture photometrydata from the literature. Using robust statistical methods, we haveestimated the color gradients of the galaxies, as well as the total andbulge mean colors. A comparative photometric study using CCD images wasdone. In our sample, the color gradients are negative (reddish inward)in approximately 59% of the objects, are almost null in 27%, and arepositive in 14%, considering only the face-on galaxies, which representapproximately 51% of the sample. The results do not change, essentially,when we include the edge-on galaxies. As a consequence of this study wehave also found that barred galaxies are overrepresented among theobjects having null or positive gradients, indicating that bars act as amechanism of homogenization of the stellar population. This effect ismore evident in the U-B color index, although it can also be detected inthe B-V color. A correlation between the total and bulge colors wasfound that is a consequence of an underlying correlation between thecolors of bulges and disks found by other authors. Moreover, the meantotal color is the same irrespective of the gradient regime, whilebulges are bluer in galaxies with null or positive gradients, whichindicates an increase of the star formation rate in the central regionsof these objects. We have also made a quantitative evaluation of theamount of extinction in the center of these galaxies. This was doneusing the Wide Field Planetary Camera 2 (WFPC2) and the Near InfraredCamera and Multi-Object Spectrometer (NICMOS) Hubble Space Telescope(HST) archival data, as well as CCD B, V, and I images. We show thatalthough the extinction in the V-band can reach values up to 2 mag inthe central region, it is unlikely that dust plays a fundamental role inglobal color gradients. We found no correlation between color and O/Habundance gradients. This result could suggest that the color gradientsare more sensitive to the age rather than to the metallicity of thestellar population. However, the absence of this correlation may becaused by dust extinction. We discuss this result by considering apicture in which bars are a relatively fast, recurrent phenomenon. Theseresults are not compatible with a pure classical monolithic scenario forbulge and disk formation. On the contrary, they favor a scenario inwhich both these components are evolving in a correlated process inwhich stellar bars play a crucial role. Based partly on observationsmade at the Pico dos Dias Observatory (PDO/LNA-CNPq), Brazil.
| Star Formation Rates in Disk Galaxies and Circumnuclear Starbursts from Cloud Collisions
We invoke star formation triggered by cloud-cloud collisions to explainglobal star formation rates of disk galaxies and circumnuclearstarbursts. Previous theories based on the growth rate of gravitationalperturbations ignore the dynamically important presence of magneticfields. Theories based on triggering by spiral density waves fail toexplain star formation in systems without such waves. Furthermore,observations suggest gas and stellar disk instabilities are decoupled.Following Gammie, Ostriker, & Jog, the cloud collision rate is setby the shear velocity of encounters with initial impact parameters of afew tidal radii, due to differential rotation in the disk. This,together with the effective confinement of cloud orbits to atwo-dimensional plane, enhances the collision rate above that forparticles in a three-dimensional box. We predictΣSFR(R)~ΣgasΩ(1-0.7β). Forconstant circular velocity (β=0), this is in agreement with recentobservations by Kennicutt. Our estimates for the normalization of thisstar formation law, while uncertain, are consistent with the observedstar formation in the Milky Way and starburst galaxies. We predict aB-band Tully-Fisher relation:LB~v7/3circ, also consistent withobservations. As additional tests, we predict enhanced/reduced starformation in regions with relatively high/low shear rates, and lowerstar formation efficiencies in clouds of higher mass.
| Box- and peanut-shaped bulges. I. Statistics
We present a classification for bulges of a complete sample of ~ 1350edge-on disk galaxies derived from the RC3 (Third Reference Catalogue ofBright Galaxies, de Vaucouleurs et al. \cite{rc3}). A visualclassification of the bulges using the Digitized Sky Survey (DSS) inthree types of b/p bulges or as an elliptical type is presented andsupported by CCD images. NIR observations reveal that dust extinctiondoes almost not influence the shape of bulges. There is no substantialdifference between the shape of bulges in the optical and in the NIR.Our analysis reveals that 45% of all bulges are box- and peanut-shaped(b/p). The frequency of b/p bulges for all morphological types from S0to Sd is > 40%. In particular, this is for the first time that such alarge frequency of b/p bulges is reported for galaxies as late as Sd.The fraction of the observed b/p bulges is large enough to explain theb/p bulges by bars. Partly based on observations collected at ESO/LaSilla (Chile), DSAZ/Calar Alto (Spain), and Lowell Observatory/Flagstaff(AZ/U.S.A.). Tables 6 and 7 are only available in electronic form at CDSvia anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| 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.
| NGC 2442: Tidal Encounters and the Evolution of Spiral Galaxies
Using imaging Fabry-Perot data, we study the star-forming properties andkinematics of the nearby barred spiral galaxy NGC 2442. The H alphaemission is very localized along the strong spiral arms of the galaxy,and shows a marked asymmetry between the sharp, well-defined northerntidal arm and the weaker southern arm. The H alpha velocity fieldappears highly distorted, with a rapidly rotating nuclear component. Wefind evidence for strong noncircular motions along the northern arm,coincident with the pronounced dust lane and regions of intense starformation. The strong asymmetries, the disturbed velocity field, and thepresence of a perturbed companion suggest that we are witnessing astrong kinematic response to a close interaction, which hasredistributed the star formation activity throughout the disk of NGC2442. Dynamical modeling of the NGC 2442 system supports this hypothesisand suggests that the regions of strongest star formation are coincidentwith strong shocks occurring along the tidally perturbed northern arm.Despite this strong redistribution of the gas on small scales, thisgalaxy does not show a significant departure from the Tully-Fisherrelation, nor does it appear to be experiencing any strong starburst.Moreover, our models predict that in a few times 108 yr, NGC 2442 willhave recovered from this first tidal encounter and will experienceanother passage---and ultimately a merger---in a few gigayears. Thismerger may provoke stronger, permanent changes in the structuralproperties of the galaxy, depending on the detailed response of thedisk. Given the environment of many disk galaxies, this tidal encountercycle seems likely to be a normal phase of disk galaxy evolution.
| 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
| CO and HI in a southern sample of interacting galaxies. I. The data
Using SEST, the Parkes antenna and the Australia Telescope CompactArray, we have made a survey of the ^12CO(1-0) and HI emission of anoptically-selected sample of ~60 southern interacting and merginggalaxies. In this paper we present the data and determine global massesof neutral gas (in molecular and atomic form) for the observed galaxies.We have detected HI in 26 systems and found that these galaxies haveless than 15% of their gas in molecular form. Figure 3 in its entirelyis only available in electronic form at CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| Evidences of Secular Dynamical Evolution in Disk Galaxies
After a recall of fundamental concepts used in galactic dynamics, wereview observational facts as well as results of orbit theory andnumerical simulations which suggest long-term evolution of galaxies.Dynamical interactions between galaxy constituents (bulges, disks, bars,haloes, dark matter) are discussed and effects of external perturbationson internal structures are examined. We report recent developments onthe connection between dynamical interaction processes and efficiency ofstar formation in galaxies of various morphological types. The Hubblesequence as an evolution sequence is revisited.
| 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.
| 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 Variation of the Scalelengths of Galaxies at Different Wavelengths
We develop model profiles of spiral galaxies with different amounts andgeometries of disc absorption and different bulge sizes. These are usedto investigate whether there are any systematic changes in the profilesof absorbed galaxies at different wavelengths, and whether measurementof the scalelength of disc galaxies at different wavelengths can be usedas a test of whether galaxies are optically thick or thin, Using modelswith realistic geometries where the dust vertical scaleheight is lessthan the stars vertical scaleheight, and including a bulge component, wefind very little difference in the B-band and I- or H-band scalelengths,even for optical depths as high as τ_B_ = 20. When we compare thepredictions of our models to our own data and the data in theliterature, we find that the observational uncertainties are greaterthan the predicted effects, rendering this test of optical depthessentially useless. However, our models do predict subtle trends anddifferences in the surface brightness profiles of galaxies when viewedat different wavelengths. With the increasing availability ofnear-infrared arrays, it should be possible to test whether thesepredicted differences are, in fact, seen.
| 2.1 μm images of the evolved stellar disk and the morphological classification of spiral galaxies
Near-infrared images confirm that the Hubble classification of spiralgalaxies does not constrain the morphology of their stellar PopulationII disk, since galaxies on opposite ends of the spiral sequence candisplay remarkably similar evolved disk morphologies. Thus, the gasdominated Population I component determines the types (a, b, c),decoupled from the Population II. The underlying mass distributionsobserved in the infrared are exceptionally regular, suggesting thatlarge scale spiral structure is principally intrinsic, as argued by themodal theory. Moreover, single arms, bisymmetric arms, lopsidednessand/or bars dominate the old stellar disk. The absence of infraredmultiple-armed structure is attributed to the efficiency of InnerLindblad Resonance absorption in the evolved Population II disk. Theseobservations support a coherent framework for galaxy classificationbased on three parameters: stellar disk "temperature", gas content andactive disk mass.
| Modeling the Spatial Distribution of Star Formation in Interacting Disk Galaxies
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1993ApJ...418...82M&db_key=AST
| The X-ray spectra of galaxies. I - Spectral FITS of individual galaxies and X-ray colors
The X-ray spectra of normal galaxies is investigated systematically byusing the Imaging Proportional Counter (IPC) data in the Einstein databank. In addition to the standard model fitting technique, X-ray colorsare introduced in order to extract spectral information from the fainterX-ray sources. Spectral parameters for 43 galaxies and X-ray colors for127 galaxies are presented.
| An X-ray catalog and atlas of galaxies
An X-ray catalog and atlas of galaxies observed with the EinsteinObservatory imaging instruments (IPC and HRI) are presented. The catalogcomprises 493 galaxies, including targets of pointed observations, andRSA or RC2 galaxies serendipitously included in Einstein fields. A totalof 450 of these galaxies were imaged well within the instrumentalfields, resulting in 238 detections and 2123 sigma upper limits. Theother galaxies were either at the edge of the visible field of view orconfused with other X-ray sources. For these a rough measure of theirX-ray emission is also given. The atlas shows X-ray contour maps ofdetected galaxies superposed on optical photographs and givesazimuthally averaged surface brightness profiles of galaxies detectedwith a high signal-to-noise ratio.
| 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.
| A study of a complete sample of interacting galaxies. I - Presentation of the sample and the UBVRIJHK photometry
An investigation is presented on what effects galaxy-galaxy interactionhas on the properties of the involved galaxies. A magnitude limitedsample of interacting galaxies is presented, together with a controlsample of isolated galaxies. The Cousins UBVRI and Johnson JHKphotometry of all galaxies included in the samples is also presented.
| A catalog of southern groups of galaxies
A catalog of groups of galaxies identified in the southern Galactic capis presented. This catalog was constructed utilizing the group-findingalgorithm developed by Huchra and Geller (1982) to analyze galaxysamples with well-defined selection criteria and complete velocityinformation.
| Galaxy evolution and large-scale structure in the far-infrared. I - IRAS pointed observations
Redshifts for 66 galaxies were obtained from a sample of 93 60-micronsources detected serendipitously in 22 IRAS deep pointed observations,covering a total area of 18.4 sq deg. The flux density limit of thissurvey is 150 mJy, 4 times fainter than the IRAS Point Source Catalog(PSC). The luminosity function is similar in shape with those previouslypublished for samples selected from the PSC, with a median redshift of0.048 for the fainter sample, but shifted to higher space densities.There is evidence that some of the excess number counts in the deepersample can be explained in terms of a large-scale density enhancementbeyond the Pavo-Indus supercluster. In addition, the faintest counts inthe new sample confirm the result of Hacking et al. (1989) that faintIRAS 60-micron source counts lie significantly in excess of anextrapolation of the PSC counts assuming no luminosity or densityevolution.
| Redshifts of galaxies in some southern groups and clusters
A table of redshifts for 67 galaxies in southern groups and clusters ispresented. The galaxies are found in or near Sersic 40/6, A496, Klemola44, 2354-35, Klemola 2, Pavo, Sersic 149/5, Sersic 149/10, 2355-35,0001-36, 0003-35, and 0007-36.
| Southern Galaxy Catalogue.
Not Available
| The very large, interacting galaxy pair IC 5174/75
The interacting galaxy pair IC 5174/75 has drawn attention, due to anangular size for IC 5174 that is disproportionate to its brightness. Apreliminary investigation of this peculiar system is given, based on twoESO Schmidt plates and digital spectra of the two galaxies. At aredshift of 0.036, the system measures about 320 kpc, and the two longouter arms of IC 5174 measure approximately 300 kpc. It is suggestedthat the present morphology of the system is the result of a recentencounter, and may be qualitatively similar to the M51+NGC 5195 systemwhen viewed edge-on despite differences of absolute size.
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