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A Spectroscopic and Photometric Study of NGC 2685, the Prototype Polar-Ring Galaxy
We present and analyze spectroscopic and photometric observations forNGC 2685, the prototype polar-ring galaxy. The spectroscopic data wereacquired using the 6 m telescope of the Special AstrophysicalObservatory of the Russian Academy of Sciences with the UAGSspectrograph and a scanning Fabry-Perot interferometer, while thephotometric analysis was based on images from the Hubble Space Telescopearchive. We demonstrate that the subsystem usually called the“inner polar ring” is a highly inhomogeneous gas and dustdisk rotating approximately in the polar plane relative to thegalaxy’s main body. When the self-absorption in the disk is takeninto account, a comparison of its color indices with those from modelcomputations of the color evolution of galaxies results in an age forthe disk of about 1.4 × 109 years, much lower than the previouslyaccepted estimate.
| Radio Continuum Emission in Polar Ring Galaxies
We have used the Very Large Array aperture synthesis telescope toconduct a radio continuum survey of polar ring galaxies, at 20 cm and 6cm. Forty objects were observed at 20 cm with ~=5" resolution. Twenty(50%) of the program sources were detected at 20 cm, down to our 5σ limit of 0.5 mJy beam-1. This detection rate issimilar to those in surveys with comparable sensitivity for early-typegalaxies without polar rings. Sixteen of the objects we detected at 20cm were also observed at 6 cm. We show radio continuum maps for the fiveobjects in our sample that have noticeably extended emission. Ourspatial resolution was sufficient to distinguish emission originating inthe host galaxy from that in the polar ring. The radio morphology of theextended sources, as well as the ratio of radio to far-infrared flux andthe radio spectral indices of our detected sources, indicate that starformation, not nuclear activity, is the dominant source of the radiocontinuum emission in polar ring galaxies. However, the implied starformation rates are modest, and only one of our sample galaxies willconsume its supply of cool gas within 500 Myr.
| 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.
| Polar Ring Galaxies and the Tully-Fisher Relation: Implications for the Dark Halo Shape
We have investigated the Tully-Fisher relation for polar ring galaxies(PRGs), based on near-infrared, optical, and H I data available for asample of these peculiar objects. The total K-band luminosity, whichmainly comes from the central host galaxy, and the measured H I linewidth at 20% of the peak line flux density, which traces the potentialin the polar plane, place most polar rings in the sample far from theTully-Fisher relation defined for spiral galaxies, with many PRGsshowing larger H I line widths than expected for the observed K-bandluminosity. This result is confirmed by a larger sample of objects,based on B-band data. This observational evidence may be related to thedark halo shape and orientation in these systems, which we study bynumerical modeling of PRG formation and dynamics: the larger rotationvelocities observed in PRGs can be explained by a flattened polar halo,aligned with the polar ring.
| Minor-axis velocity gradients in spirals and the case of inner polar disks
We measured the ionized-gas and stellar kinematics along the major andminor axis of a sample of 10 early-type spirals. Much to our surprise wefound a remarkable gas velocity gradient along the minor axis of 8 ofthem. According to the kinematic features observed in their ionized-gasvelocity fields, we divide our sample galaxies in three classes ofobjects. (i) NGC 4984, NGC 7213, and NGC 7377 show an overall velocitycurve along the minor axis without zero-velocity points, out to the lastmeasured radius, which is interpreted as due to the warped structure ofthe gaseous disk. (ii) NGC 3885, NGC 4224, and NGC 4586 arecharacterized by a velocity gradient along both major and minor axis,although non-zero velocities along the minor axis are confined to thecentral regions. Such gas kinematics have been explained as being due tonon-circular motions induced by a triaxial potential. (iii) NGC 2855 andNGC 7049 show a change of slope of the velocity gradient measured alongthe major axis (which is shallower in the center and steeper away fromthe nucleus), as well as non-zero gas velocities in the central regionsof the minor axis. This has been attributed to the presence of akinematically-decoupled gaseous component in orthogonal rotation withrespect to the galaxy disk, namely an inner polar disk. The case andorigin of inner polar disks are discussed and the list of their hostgalaxies is presented.Based on observations carried out at the European Southern Observatory(ESO 62.A-0463 and 63.N-0305).Tables 3 and 4 are 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/cgi-bin/qcat?J/A+A/408/873
| A Chemically Decoupled Nucleus and Inner Polar Ring of the SBb Galaxy NGC 4548
Not Available
| The UZC-SSRS2 Group Catalog
We apply a friends-of-friends algorithm to the combined Updated ZwickyCatalog and Southern Sky Redshift Survey to construct a catalog of 1168groups of galaxies; 411 of these groups have five or more members withinthe redshift survey. The group catalog covers 4.69 sr, and all groupsexceed the number density contrast threshold, δρ/ρ=80. Wedemonstrate that the groups catalog is homogeneous across the twounderlying redshift surveys; the catalog of groups and their membersthus provides a basis for other statistical studies of the large-scaledistribution of groups and their physical properties. The medianphysical properties of the groups are similar to those for groupsderived from independent surveys, including the ESO Key Programme andthe Las Campanas Redshift Survey. We include tables of groups and theirmembers.
| A neutral hydrogen survey of polar ring galaxies. IV. Parkes observations
A total of 33 polar ring galaxies and polar ring galaxy candidates wereobserved in the 21-cm H I line with the 64-m Parkes radio telescope. Theobjects, selected by their optical morphology, are all south ofdeclination -39o and in only 5 of them H I had been reportedpreviously. H I line emission was detected towards 18 objects, though in3 cases the detection may be confused by another galaxy in the telescopebeam, and one is a marginal detection. Eight objects were detected forthe first time in H I, of which 5 did not have previously knownredshifts. Table 1 is also available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/386/140
| Nuclear spectra of polar-ring galaxies
We report the results of spectroscopic observations of eight southernpolar-ring galaxies (PRGs), in the wavelength range 5900-7300Å. Wefind that five out of eight galaxies contain LINERs or Sy nuclei. Takinginto consideration all PRGs with available spectral data, we estimatethat about half of all PRGs and PRG candidates have either LINER orSeyfert nuclei. The observed widths of the [Nii]λ6583 line in thenuclei of early-type PRGs follow the linewidth-absolute luminosityrelation for normal E/S0 galaxies. We found that one of the observedgalaxies - ESO 576-G69 - is a new kinematically-confirmed polar-ringgalaxy with a spiral host.
| Arp 220: A Circumnuclear Polar Ring as an Alternative to a Double Nucleus?
Recent millimeter interferometer observations of Arp 220 have yielded~0.5" resolution images showing two strong concentrations of millimeterradio continuum and CO line emission embedded in a larger molecular gasdisk (r~1 kpc). The interferometer observations also revealed a complexvelocity field with steep velocity gradients across each of the fluxconcentrations of Δv~500 km s-1 within r=0.3". Thedirections of these gradients are not aligned with each other or withthat of the outer gas disk. This led to the conclusion that the twoemission peaks represent either double nuclei with their own gas disks(r~100 pc), which are counterrotating with respect to each other androtate around the dynamical center of the system, or that they are twohot spots within a nuclear molecular gas disk. The overall structure ofthe molecular gas distribution and the corresponding complex velocityfield, however, are highly symmetric, except for the unequalbrightnesses of the two flux concentrations. This fact and similaritiesto the distribution and kinematics of the molecular gas in the central2'' of NGC 1068 motivated us to try describing the Arp 220nucleus as a warped molecular gas disk in which the peaks in the fluxand line width distributions arise as a result of crowding of inclinedcircular orbits. Hubble Space Telescope (HST) images of the dust lanesflaring toward larger radii provide further support for a warped gasdisk. The final model is surprisingly successful in explaining the COline flux distribution, the velocity field, and position-velocitydiagrams across the central flux concentrations. The model represents astrong 90deg warp of the gas orbits out of the principalplane forming a circumnuclear polar ring and reproduces well thestructures in HST near-IR color and continuum maps. The large number ofyoung stars recently formed out of the warped, polar-ring gas impliesthat those stars will have kinematic properties similar to that of themolecular gas. We suggest that the red near-IR source at the center ofthe polar ring is the true nucleus of Arp 220. The success of the modelimplies that the two flux concentrations are not necessarilycounterrotating nuclei, but rather the result of a combination of hotspots and orbit crowding due to the warp. The warp could be a directconsequence of the recent merger event indicated by tidal tails inoptical images.
| A neutral hydrogen survey of polar ring galaxies. III. Nançay observations and comparison with published data
A total of 50 optically selected polar ring galaxies, polar ring galaxycandidates and related objects were observed in the 21-cm H i line withthe Nançay decimetric radio telescope and 31 were detected. Theobjects, selected by their optical morphology, are all north ofdeclination -39o, and generally relatively nearby (V< 8000km s-1) and/or bright (mB< 15.5). The H i linedata are presented for all 74 galaxies observed for the survey with theEffelsberg, Green Bank or Nanç radio telescopes, as well as allother published H i line parameters of these objects. Three objects wereobserved and detected by us at Parkes. A total of 59 objects weredetected. For each object a brief description is given based on aliterature search.
| Magnesium-to-Iron Ratio in Nuclei and Bulges of Disk Galaxies
The results of magnesium-to-iron ratio estimates are presented for thenuclei and central bulges of disk galaxies. A great variety ofbehaviours is found: the nuclei have solar Mg/Fe ratio or areMg-overabundant, the bulges can be more or less Mg-overabundant than thenuclei. But the most bulges have nearly solar Mg/Fe ratios, irrespectiveof their luminosity.
| The Universality of the Fundamental Plane of E and S0 Galaxies: Spectroscopic Data
We present central velocity dispersion measurements for 325 early-typegalaxies in eight clusters and groups of galaxies, including newobservations for 212 galaxies. The clusters and groups are the A262,A1367, Coma (A1656), A2634, Cancer, and Pegasus Clusters and the NGC 383and NGC 507 Groups. The new measurements were derived frommedium-dispersion spectra that cover 600 Å centered on the Mg I btriplet at lambda ~ 5175 Å. Velocity dispersions were measuredusing the Tonry & Davis cross-correlation method, with a typicalaccuracy of 6%. A detailed comparison with other data sources is made.
| The Universality of the Fundamental Plane of E and S0 Galaxies: Sample Definition and I-Band Photometric Data
As part of a project to compare the fundamental plane and Tully-Fisherdistance scales, we present here I-band CCD photometry for 636early-type galaxies in eight clusters and groups of galaxies. These arethe A262, A1367, Coma (A1656), A2634, Cancer and Pegasus Clusters, andthe NGC 383 and NGC 507 Groups. Sample selection, cluster properties,and cluster membership assignment criteria are discussed. We presentphotometric parameters that are used in the fundamental plane relation,the effective radius r_e, and the effective surface brightness mu_e, asderived from a r^1/4 fit to the observed radial photometric profile ofeach galaxy. A comparison with similar data found in the literature forthe Coma Cluster shows that large systematic uncertainties can beintroduced in the measurement of r_e and mu_e by the particular methodused to derive those parameters. However, the particular combination ofthese two parameters that enters in the fundamental plane relation is aquantity that can be measured with high accuracy.
| Environments of Redshift Survey Compact Groups of Galaxies
Redshift survey compact groups (RSCGs) are tight knots of N >= 3galaxies selected from the CfA2+SSRS2 redshift survey. The selection isbased on physical extent and association in redshift space alone. Wemeasured 300 new redshifts of fainter galaxies within 1 h^-1 Mpc of 14RSCGs to explore the relationship between RSCGs and their environments.Thirteen of 14 RSCGs are embedded in overdense regions of redshiftspace. The systems range from a loose group of five members to an Abellcluster. The remaining group, RSCG 64, appears isolated. RSCGs areisolated and distinct from their surroundings to varying degrees, as arethe Hickson compact groups. Among the 13 embedded RSCGs, three aredistinct from their general environments (RSCG 9, RSCG 11, and RSCG 85).
| Catalogue of HI maps of galaxies. I.
A catalogue is presented of galaxies having large-scale observations inthe HI line. This catalogue collects from the literature the informationthat characterizes the observations in the 21-cm line and the way thatthese data were presented by means of maps, graphics and tables, forshowing the distribution and kinematics of the gas. It containsfurthermore a measure of the HI extension that is detected at the levelof the maximum sensitivity reached in the observations. This catalogueis intended as a guide for references on the HI maps published in theliterature from 1953 to 1995 and is the basis for the analysis of thedata presented in Paper II. The catalogue is only available inelectronic form at the CDS via anonymous ftp 130.79.128.5 orhttp://cdsweb.u-strasbg.fr/Abstract.html
| 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
| Central regions of the polar-ring galaxies NGC 2685 and IC 1689
Results of two-dimensional spectroscopy for central parts of polar-ringgalaxies NGC 2685 and IC 1689 are presented. An orthogonality of starand gas rotations is detected. A strong break of absorption-line indexMgb between the nuclei and the inner bulges ("chemically decouplednuclei") and perhaps an intermediate age of the stellar population inthe nucleus of IC 1689 imply secondary star formation bursts in thecenters of the polar-ring galaxies which are possibly related toaccretion events having produced polar rings themselves. Based onobservations collected with the 6m telescope of the SpecialAstrophysical Observatory (SAO) of the Russian Academy of Sciences (RAS)which is operated under the financial support of Science Department ofRussia (registration number 01-43).
| Search for chemically decoupled galactic nuclei with the Multi-Pupil Field Spectrograph of the 6 M telescope.
Not Available
| The visible environment of polar ring galaxies.
A statistical study of the environment around Polar Ring Galaxies ispresented. Two kinds of search are performed: 1) a study of theconcentration and diameters of all the objects surrounding the PolarRings, within a search field 5 times the ring diameter. New magnitudesfor polar ring galaxies are presented. 2) a search, in a wider field,for galaxies of similar size that may have encountered the polar ringhost galaxy in a time of the order of 1Gyr. Differently from the resultsof similar searches in the fields of active galaxies, the environment ofthe Polar Ring Galaxies seems to be similar to that of normal galaxies.This result may give support to the models suggesting long times forformation and evolution of the rings. If the rings are old (and stableor in equilibrium), no traces of the past interaction are expected intheir surroundings. In addition, the formation of massive polar rings,too big to derive from the ingestion of a present-day dwarf galaxy, maybe easily placed in epochs with a higher number of gas-rich galaxies.
| 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.
| IC 1689: S0 galaxy with inner polar disk.
The results of spectroscopic observations of the S0 galaxy IC 1689 aregiven. The radial velocity curves constructed from the measurements ofHα and [NII]λ6583 lines show that in the galaxy interiorthere is a gas disk (r=~3kpc) rotating around the axis placed in themain plane of the galaxy (polar disk). Active star formation occurs inthe outer part of the disk (in the ring). Both Hα and[NII]λ6583 emission lines are observed here. Only collisionallyexcited [NII] radiates in the inner regions of the disk.
| Spectroscopic observations of IC 1689 - a galaxy with an inner polar ring.
Not Available
| Simulation of large-scale gas structures formed in the interaction between galaxies. I. Method and preliminary results
Computer programs developed to study large-scale, transient gasstructures in galaxies are described and test results are given.Gas-dynamic quantities are determined on the basis of athree-dimensional algorithm using so-called "smoothed particlehydrodynamics" (SPH). Preliminary calculations were made to simulate theformation of a gas ring around a spheroidal galaxy when it absorbs alow-mass, gas-rich companion, as well due to gas accretion during theflyby of a spiral galaxy of comparable mass. The evolution of tidal gastails of disk galaxies is investigated.
| Photometric study of polar-ring galaxies. II. IC 1689.
The results are given of detailed surface B,V, and R_c_ photometry of IC1689- a galaxy with an inner polar ring. It is shown that the centralgalaxy is a normal S0-type galaxy with a relatively short and warpedstellar disk. The inner polar ring (its radius is only about 2kpc) hasblue colour (B-V=+0.3, V-R_c_=+0.3) and comparatively high surfacebrightness (μ_B_=~23.2). Comparison of observed surface brightnessesand colours B-V for all single polar rings studied earlier show thatthere is a dependence between these characteristics. We interpret thisdependence as a consequence of the fact that global bursts of starformation may occur (with a burst strength up to 0.15) in many polarrings in the course of their evolution.
| 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.
| New observations and a photographic atlas of polar-ring galaxies
A photographic atlas of polar-ring galaxies and related objects ispresented. The atlas includes kinematically confirmed polar-ringgalaxies (category A), good condidates based on their morphologicalappearance (category B), possible candidates (category C), and possiblyrelated objects (category D). New photometric and kinematic observationsare reported for several galaxies in the catalog, including observationsthat show that UGC 7576 and UGC 9796 ( = II ZW 73) are S0 galaxies withpolar rings. Roughly 0.5 percent of all nearby S0 galaxies appear tohave polar rings. When corrected for various selection effects (e.g.,nonoptimal viewing orientation, possible dimming, or limited lifetime ofthe ring) the percentage increases to about 5 percent of S0 galaxieswhich have, or have had a polar ring.
| A 21 CM survey of the Pisces-Perseus supercluster. IV - Addenda to the declination zone 21.5 deg to 33.5 deg
Using the 305-m Arecibo telescope, 21-cm line data on 472 disk galaxiesin the Pisces-Perseus supercluster have been obtained. Data on galaxiessmaller than 1 arcmin are presented for the declination strips coveredin previous studies (Giovanelli and Haynes, 1985 and Giovanelli et al.,1986). Tables of the 21-cm line data for this region are presented.
| Determination of the relative spectrophotometric gradients of galaxies. IV
Relative spectrophotometric gradients of continua are determined for 195galaxies. The spectra have been obtained with the 70-cm meniscustelescope of the Abastumani Astrophysical Observatory using a 2-degpreobjective prism (the reverse linear dispersion was 1200 A/mm inH-gamma). The gradient values were reduced to the AO spectral class andcorrected for light absorption in the Galaxy.
| H I maps of S0 galaxies with polar rings
VLA maps in the 21 cm line of neutral hydrogen have been obtained forthree S0 galaxies with polar rings, and an upper limit on H I has beenobtained for a fourth system. Polar rings span a continuum, ranging fromthose in which the H I seems to be in a relatively stable configuration,producing stars throughout its extent, to those in which the H I is veryasymmetric, with stars forming only at the inner edge of an H I disk. Adeep CCD image of MGC -5-7-1 shows arcs and filaments, some of whichcoincide with the likewise chaotic H I. If the system formed as theresult of the merger of a gas-rich system with an S0 galaxy, thegas-rich system must have included considerable numbers of stars.
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