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Photometric structure of polar-ring galaxies
The results of B, V, R surface photometry of three polar-ring galaxies(PRGs) - A 0017+2212, UGC 1198, UGC 4385 - are presented. The data wereacquired at the 6-m telescope of the Special Astrophysical Observatoryof the Russian Academy of Sciences. It was shown that all three galaxiesare peculiar late-type spirals in the state of ongoing interaction ormerging. We discuss available photometric properties of the PRGs withspiral hosts and consider the Tully-Fisher relation for different typesof PRGs. In agreement with Iodice et al. (\cite{Iodice03}), we haveshown that true PRGs demonstrate 1/3 larger maximum rotationvelocities than spiral galaxies of the same luminosity. Peculiar objectswith forming polar structures satisfy, on average, the Tully-Fisherrelation for disk galaxies but with large scatter.
| The Structure and Evolution of M51-Type Galaxies
We discuss the integrated kinematic parameters of 20 M51-type binarygalaxies. A comparison of the orbital masses of the galaxies with thesum of the individual masses suggests that moderately massive dark halossurround bright spiral galaxies. The relative velocities of the galaxiesin binary systems were found to decrease with increasing relativeluminosity of the satellite. We obtained evidence that the Tully-Fisherrelation for binary members could be flatter than that for local fieldgalaxies. An enhanced star formation rate in the binary members may beresponsible for this effect. In most binary systems, the direction ofthe orbital motion of the satellite coincides with the direction of therotation of the main galaxy. Seven candidates for distant M51-typeobjects were found in the Northern and Southern Hubble Deep Fields. Acomparison of this number with the statistics of nearby galaxiesprovides evidence for the rapid evolution of the space density ofM51-type galaxies with redshift z. We assume that M51-type binarysystems could be formed through the capture of a satellite by a massivespiral galaxy. It is also possible that the main galaxy and itssatellite in some of the systems have a common cosmological origin.
| 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
| Near-Infrared photometry in J, H and Kn bands for polar ring galaxies. II. Global properties
We discuss the properties of the host galaxy and ring lightdistributions in the optical and near infrared bands for a sample ofPolar Ring Galaxies (PRGs), presented in Paper I (Iodice et al.\cite{paperI}). The goal of this work is to test different formationscenarios for PRGs, proposed by different authors in the last decades,by comparing their predictions with these new data. The strategy istwofold: i) the integrated colors of the main components in thesesystems are compared with those of standard morphological galaxy types,to investigate whether differences in colors are caused by dustabsorption or difference in stellar populations. We then derived anestimate of the stellar population ages in PRGs, which can be used toset constrains on the dynamical modeling and the time evolution of thesesystems; ii) we analyse the structural parameters of the host galaxy inorder to understand whether this component is a standard early-typesystem as its morphology suggests, and the light distribution in thepolar ring to measure its radial extension. These observational resultsindicate that the global properties of PRGs are better explained bydissipative merging of disks with un-equal masses as proposed by Bekki(1998), rather than the accretion-or stripping-of gas by a pre-existingearly-type galaxy.
| Statistical study of M 51-type galaxies
We present a statistical analysis of a new sample of M 51-type galaxies.Using the MCG and VV catalogues, we selected 32 such binary systems. Wefound that a typical M 51-type pair consists of a bright L*spiral galaxy and a satellite with blue luminosity 1/30-1/3 of theprimary one. The main galaxies in such pairs are often barred and havetwo well-defined spiral arms. M 51-type systems show an enhanced starformation rate (from FIR luminosities). We found a weak dependence ofthe star formation rate of the system on relative luminosity of thecompanion. M 51-type galaxies are relatively frequent: about 1/12 of allpairs are of M 51-type.
| BVRI imaging of M 51-type pairs. II. Bulge and disk parameters
We present decompositions of azimuthally averaged surface brightnessprofiles in optical B, V, R and I-bands for a sample of 40 M 51-typeinteracting galaxies. The profiles were modelled by an exponential diskand a spherical bulge described either by the R1/4 law or byan exponential function. Half of the galaxies were well fitted by bothbulge models, whereas for 35 % the exponential function was a betterchoice. Special care was taken on eliminating superpositions of thecompanion galaxies. The mean B-band central surface brightness mu_0 wasfound to be 21.5 mag arcsec-2, which is near to the valueoriginally found by Freeman (\cite{freeman70}), but the scatter wasfairly large. Galaxy interactions have strongly modified the disks inmany of the galaxies in the sample. For example, six of them hadextremely flat brightness profiles outside the exponential part of thedisk, and many showed significant isophotal twists. Tables 1 to 4 andFigs. 2 to 4 are only available in the electronic version athttp://www.edpsciences.org}
| On the local radio luminosity function of galaxies. II. Environmental dependences among late-type galaxies
Using new extensive radio continuum surveys at 1.4 GHz (FIRST and NVSS),we derive the distribution of the radio/optical and radio/NIR luminosity(RLF) of late-type (Sa-Irr) galaxies (m_p<15.7) in 5 nearby clustersof galaxies: A262, Cancer, A1367, Coma and Virgo. With the aim ofdiscussing possible environmental dependences of the radio properties,we compare these results with those obtained for relatively isolatedobjects in the Coma supercluster. We find that the RLF of Cancer, A262and Virgo are consistent with that of isolated galaxies. Conversely weconfirm earlier claims that galaxies in A1367 and Coma have their radioemissivity enhanced by a factor ~ 5 with respect to isolated objects. Wediscuss this result in the framework of the dynamical pressure sufferedby galaxies in motion through the intra-cluster gas (ram-pressure). Wefind that the radio excess is statistically larger for galaxies in fasttransit motion. This is coherent with the idea that enhanced radiocontinuum activity is associated with magnetic field compression. TheX-ray luminosities and temperatures of Coma and A1367 imply that thesetwo clusters have significantly larger intracluster gas density than theremaining three studied ones, providing a clue for explaining the higherradio continuum luminosities of their galaxies. Multiple systems in theComa supercluster bridge (with projected separations smaller than 300kpc) have radio luminosities significantly larger than isolatedgalaxies. Table~1 is only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html}
| BVRI imaging of M51-type interacting galaxy pairs. I. Data reductions
Deep broad-band BVRI photometry of a sample of 22 closely interactingisolated galaxy pairs is presented. The sample consists of pairs with alarge variety of orbital geometries, but most of them are M51-typepairs: a small companion in the vicinity of a prominent two-armedspiral. This subsample will be later modelled in detail with N-bodysimulations. Nine of the thirteen M51-type pairs show enhanced starformation in the central regions of the companions, detected in B-V orR-I color maps, and only one pair in the nucleus of the main galaxy.This is expected if there is mass transfer from the main galaxy to thecompanion. Some pairs with larger separation, and with more massivecompanions show global instabilities manifesting as strong colorgradients at least in one of the members.
| 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
| Global structure and formation of polar-ring galaxies.
We present an analysis of structural features of all known galaxies withoptical polar rings. We find a clear dichotomy for objects of thispeculiar class. Bulge-dominated S0 galaxies possess only short narrowrings, while disk-dominated objects always have wide extended polarrings. We try by gas dynamical simulations to explain such a segregationby dependence of the ring-forming process on different galaxypotentials. It is found that the total mass captured into the ringduring an encounter of a host-ring system with a gas-rich spiral galaxyof comparable mass exceeds 10^9^Msun_ (or about 10% of allgas in the donor galaxy), which is of the order of that found byobservation. The process of gas to gather into a steady-state ring takesapproximately (7-9)x10^8^years. This time is somewhat shorter for ringsforming around bulge-dominated galaxies. We also present observationalarguments for S0 galaxies with extended rings to be similar to late-typespirals by their photometric properties, while numerical modelling ofthe extended ring formation suggests that these galaxies must possessmassive dark halos as well. In this case, the sizes of the modelledrings turn out large enough (up to 30kpc in diameter), and the timescale for ring formation is prolonged up to several Gyrs.
| Photometric study of polar-ring galaxies. III. Forming rings.
We present the results of detailed surface photometry of NGC 3808B andNGC 6286 - two spiral galaxies with possibly forming ring-likestructures rotating around major axes of the galaxies. The formation ofrings in NGC 3808B and NGC 6286 being accompanied by accretion of matteron galactic disk results in some interesting gasdynamical andstellar-dynamical effects in these galaxies. One can note, for instance,peculiar rotation curve of NGC 3808B gaseous disk; strong infrared andHα emission from the galaxies; bending and flaring stellar disksin both galaxies. Our observations clearly illustrate the possibilitythat polar-ring galaxies may be formed as a result of matter accretionfrom one galaxy to another.
| Kinematics and dark haloes of polar-ring galaxies
We have observed with long slit H alpha spectroscopy 16 polar-ringgalaxies or related objects. From the nuclear spectra, we find thatthese objects have enhanced nuclear activity with respect to normalgalaxies. The objects indentified as forming polar rings now, by gasaccretion, have chaotic velocity fields. One of the objects -UGC 5600-displays counter-rotating features. We also find that the globalstar-formation rate is enhanced in polar-ring galaxies with respect tonormal isolated objects; their star-forming efficiency is comparable tothat of the most strongly interacting samples. In the three settledpolar-rings of our sample, we compared the rotation curves in theequatorial and polar planes. The maximum rotational velocities in thetwo planes are always comparable, although they are not measured at thesame radii. In the two galaxies UGC 7576 and UGC 9796, we build massmodels after fitting luminosity profiles of the bulge, disk and polarrings. We are not able to account for the rotational velocities in thering without adding dark matter, even taking into account the large gasmasses detected. The required amount of dark mass reaches 1.6 and 3 theluminous mass in UGC 7576 and UGC 9796, inside radii of 17 kpc and 21.4kpc respectively. We cannot constrain the 3D shape of the dark halo,since equatorial and polar velocities are not measured at the same radiiin the outer parts. This is a general impossibility in polar-ringsystems, since there cannot exist gas in the outer parts at the sameradii as the ring itself, which is formed out of gas. This unfortunatelyprevents any direct determination of the dark halo flattening in spiralgalaxies.
| Companions' influence on the emission-line rotation curves of galaxies
The sample of members of isolated pairs of galaxies and close binaryinteracting systems - demonstrating a systematic falling of theemission-line rotation curves after the maxima - are considered. It isfound that there is a significant correlation between thecharacteristics of the galaxies' emission-line velocity fields and thespatial distance to the companion. The different factors affecting theinvestigated relationships are discussed.
| Effects of Interactions on the Radio Properties of Non-Seyfert Galaxies
On the basis of radio surveys published in the literature we havecompared the radio properties of samples of relatively isolated spiralgalaxies with LINER- and H II- region-like nuclei (hereafter called Land H galaxies) with corresponding samples of non-Seyfert interactinggalaxies, in order to explore the effects of interactions on their radioproperties. Basically, we have found enhanced total and central radioemission (per light unit) in interacting H galaxies (compared with theirrelatively isolated counterparts) and enhanced central radio emission(per light unit) in interacting L galaxies. Analogous enhancements inthe strength of the total and nuclear Hα emission lines areobserved in interacting galaxies. Furthermore, within a sample ofinteracting galaxies, there appears to be evidence of enhanced total andcentral radio emission (per light unit) in strongly interacting galaxieswhich are likely to have H II-region-like nuclei, compared withmoderately interacting objects of the same nuclear type. Interacting Hgalaxies contain more extended central radio sources than isolatedgalaxies, whereas no difference in this sense is observed in the case ofL galaxies. L galaxies which contain, on average, weaker total andcentral radio sources than the H galaxies have, on average, smallercentral radio sources (of greater radio surface brightness) than the Hgalaxies and follow a less-steep logarithmic radio power-radio sizerelation. As regards the Seyfert galaxies, which are known to becharacterized by powerful central radio emission, we have found thatthey contain, on average, central radio sources of intermediate size,which obey a power-size relation of intermediate steepness (with respectto the L and H galaxies). Thus our statistical study reveals basicstructural differences between the radio properties of the L, H andSeyfert galaxies, and between the effects of interactions on the radioproperties of the three classes of galaxies.
| Recent star formation in interacting galaxies. III - Evidence from mid-infrared photometry
Mid-IR (10 and 20 microns) observations of a sample of interactinggalaxies have been conducted to argue that interactions induce a burstof star formation in the nucleus of one member of the interacting pair.The observations are combined with existing mid-IR data and radio andoptical data. A simple starburst model is used to derive some of thequantitative features of interaction-induced starbursts. It is shownthat the starbursts are unusually efficient in using available gas, andthat the initial mass function is heavily biased toward massive stars.The supernova rate and radio luminosity implied by the model areconsistent with observations. It is concluded that if the observed rateof interactions is representative, interaction-induced starbursts arelikely to have occurred in the evolution of most galaxies.
| Individual and orbital masses of double galaxies
A list is given of individual estimates of the masses of 124 componentsof isolated pairs of galaxies from Turner's catalog for which there arepublished data on the velocity dispersions in the central parts of thegalaxies, on the width of the 21-cm radio line profile, and on theamplitude of the rotation curve of the galaxies. From the comparison ofthe orbital estimates of the mass with the sum of the individual massesof the double galaxies it is concluded that the bulk of the mass of thegalaxies is situated within their standard optical diameter A(25). Theconsidered observational data for the Turner galaxy pairs do not containany arguments for the hypothesis of massive halos. Good agreementbetween the orbital and individual estimates of the mass is observed foralmost circular motions of the galaxies in pairs with mean orbitaleccentricity 0.25.
| The effects of interactions on spiral galaxies. III - A radio continuum survey of galactic nuclei at 1.49 GHz
The radio continuum emission from the central region of a sample ofinteracting spiral galaxies (92 galaxies of which 60 in a completesample) and of a control sample of more isolated spiral galaxies (94)was observed with the Very Large Array at 1.49 GHz. The angularresolution of the observations is about 1.3 arcsec, and the detectionlimits are about 0.6 and 1.5 mJy for point sources and extended sourceswith a half power size of 10 arcsec, respectively. This survey, incombination with published optical spectroscopy, provides the data for adetailed comparison of the central region in interacting and moreisolated spiral galaxies.
| Observations of peculiar galaxies in clusters of galaxies
In the course of a large survey of the radio and optical properties ofcluster spirals, Bothun (1981) could observe a number of galaxies withpeculiar characteristics. The observed galaxies contain some interactingsystems which may provide important test cases in probing the role ofgalaxy-galaxy interactions as a mechanism of gas removal in clusters.The present investigation is concerned with some specific examples ofinteracting/peculiar galaxies, which are illustrated in the atlasprepared by Arp (1966). In general, the considered galaxies do not havethe characteristic signatures of the violent encounters seen in smallgroups and described by Gallagher et al. (1981). However, their samplemay be one in which the interactions are 'interpenetrating' as opposedto the grazing encounters expected to occur in clusters. With regard tothe efficiency of tidal interactions as a gas removal agent, the dataare rather inconclusive.
| Binary galaxie. I. A well-defined statistical sample.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1976ApJ...208...20T&db_key=AST
| 160 interacting galaxies of the M51 class
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