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Neutral Hydrogen in the Polar Ring Galaxy UGC 9796
We have used the Very Large Array to observe the polar ring galaxy UGC9796 (II Zw 73; PRC A-06) in the 21 cm line of neutral hydrogen. All theneutral gas in this galaxy is associated with the polar ring. Ourobservations show that ~=5×109 Msolar of H Irotates in a plane projected about 25° from perpendicular to theequatorial plane of the early-type host galaxy, consistent with earlierobservations in the Hα line. The outermost gas appears to bendaway from the minor axis of the host system, in the same sense as thestellar ring. UGC 9796 is in a very gas-rich environment: our 21 cmimages show five gas-rich companion galaxies in the same field within100 km s-1, with a total of ~=2×1010Msolar between them. However, we see no H I streamersconnecting the systems or any other evidence for an ongoing interactionbetween UGC 9796 and its companions.
| Principal component analysis of International Ultraviolet Explorer galaxy spectra
We analyse the UV spectral energy distribution of a sample of normalgalaxies listed in the International Ultraviolet Explorer (IUE) NewlyExtracted Spectra (INES) Guide No. 2 - Normal Galaxies using a principalcomponent analysis. The sample consists of the IUE short-wavelength (SW)spectra of the central regions of 118 galaxies, where the IUE apertureincluded more than 1 per cent of the galaxy size. The principalcomponents are associated with the main components observed in theultraviolet (UV) spectra of galaxies. The first component, accountingfor the largest source of diversity, may be associated with the UVcontinuum emission. The second component represents the UV contributionof an underlying evolved stellar population. The third component issensitive to the amount of activity in the central regions of galaxiesand measures the strength of star-formation events.In all the samples analysed here, the principal component representativeof star-forming activity accounts for a significant percentage of thevariance. The fractional contribution to the spectral energydistribution (SED) by the evolved stars and by the young population aresimilar.Projecting the SEDs on to their eigenspectra, we find that none of thecoefficients of the principal components can outline an internalcorrelation or can correlate with the optical morphological types. In asubsample of 43 galaxies, consisting of almost only compact and BCDgalaxies, the third principal component defines a sequence related tothe degree of starburst activity of the galaxy.
| 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.
| 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.
| The gas content of peculiar galaxies: Counterrotators and polar rings
This paper studies the global ISM content in a sample of 104 accretinggalaxies, including counterrotators and polar rings, which spans theentire Hubble sequence. The molecular, atomic and hot gas content ofaccretors is compared to a newly compiled sample of normal galaxies. Wepresent results of a small survey of the J=1-0 line of 12COwith the 15 m SEST telescope on a sample of 11 accretors (10counterrotators and 1 polar ring). The SEST sample is enlarged withpublished data from 48 galaxies, for which observational evidence ofcounterrotation in the gas and/or the stars has been found. Furthermore,the available data on a sample of 46 polar ring galaxies has beencompiled. In order to explore the existence of an evolutionary pathlinking the two families of accretors, the gas content ofcounterrotators and polar rings is compared. It was found that thenormalized content of cold gas (Mgas/LB) in polarrings is ~ 1 order of magnitude higher than the reference value derivedfor normal galaxies. The inferred gas masses are sufficient to stabilizepolar rings through self-gravity. In contrast, it was found that thecold gas content of counterrotators is close to normal for all galaxytypes. Although counterrotators and polar rings probably share a commonorigin, the gas masses estimated here confirm that light gas ringsaccreted by future counterrotators may have evolved faster than theself-gravitating structures of polar rings. In this scenario, thetransformation of atomic into molecular gas could be enhanced near thetransition region between the prograde and the retrograde disks,especially in late-type accretors characterized by a high content ofprimordial gas. This is tentatively confirmed in this work: the measuredH2/HI ratio seems larger in counterrotators than in normal orpolar ring galaxies for types later than S0s. Based on observationscollected at SEST telescope, European Southern Observatory, La Silla,Chile. Table 1 is only available in electronic form athttp://www.edpsciences.org
| 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.
| 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.
| Kinematics of the local universe. VII. New 21-cm line measurements of 2112 galaxies
This paper presents 2112 new 21-cm neutral hydrogen line measurementscarried out with the meridian transit Nan\c cay radiotelescope. Amongthese data we give also 213 new radial velocities which complement thoselisted in three previous papers of this series. These new measurements,together with the HI data collected in LEDA, put to 6 700 the number ofgalaxies with 21-cm line width, radial velocity, and apparent diameterin the so-called KLUN sample. Figure 5 and Appendices A and B forcorresponding comments are available in electronic form at thehttp://www.edpsciences.com
| On the morphology of peculiar ring galaxies
It is proposed that peculiar ring galaxies can be divided into fiveprincipal types according to the morphology of the ring and bulge, basedon the visual inspection of 489 selected objects. Those objects havebeen named ``peculiar'' following the ``Catalogue of Southern PeculiarGalaxies and Associations'' by \cite[Arp & Madore (1986]{am6}) Table2 with its notes is only available electronically via anonymous ftp130.79.128.5 or http://cdsweb.u-strasbg.fr.
| Cool dense gas in early-type galaxies
CO observations have shown that many lenticular and elliptical galaxiescontain significant amounts of cool dense gas. This review summarizesthe observational results related to the neutral gas phase and presentsa systematic comparison with other interstellar and stellar data. Thediscovery of very dense molecular gas in the nuclear regions ofearly-type galaxies, the possible existence of a dust component neitherseen optically nor in CO, internal inconsistencies of cooling flowscenarios, the origin of the cool gas, the presence of massive stars,aspects of galaxy evolution, and possibilities for future research arediscussed in the light of the new data.
| 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.
| An HI survey of polar ring galaxies. II. The Effelsberg sample.
We present the results of a neutral hydrogen survey conducted with the100-m radiotelescope at Effelsberg of 44 northern objects in thepolar-ring galaxy atlas of Whitmore et al. (1990AJ....100.1489W). Theseobservations were performed to complement the Green Bank observations ofpolar-ring galaxies (Paper I, 1994AJ....107...99R). We detected 29 ofthese above our detection limit of a few mJy. The relative content ofneutral hydrogen (M_HI_/L_B_) of the early-type galaxies (E, S0) in thissample is significantly higher than for galaxies of the samemorphological types from comparison samples, i.e. for ellipticalgalaxies M_HI_/L_B_=0.17+/-0.09 and for S0 galaxiesM_HI_/L_B_=0.75+/-0.13 which is about 6 times the mean value from thecomparison samples for the same morphological types.
| Polar rings as probes of the intrinsic shape of dark matter halos.
Not Available
| Dust and infrared imaging of polar ring galaxies
Not Available
| Absolute Magnitudes and Kinematics of RR Lyrae Stars via Statistical Parallax
The absolute magnitude of the RR Lyrae stars is integral in determiningthe distances to the old stellar systems in our Galaxy and to otherLocal Group galaxies, and in determining the ages of the Galacticglobular clusters. We present new estimates of the RR Lyrae starabsolute magnitude as a function of metal abundance, based on a new setof statistical parallax solutions. This analysis is an improvement overprevious works for several reasons: (1) it relies mainly on new absoluteproper motions from the Lick Northern Proper Motion Survey, which are ofuniformly high quality. (2) new metal abundances and radial velocitiesare employed; the former are of particularly high quality anduniformity. (3) the improved metallicities, combined with kinematicanalyses, allow us for the first time to properly separate thick--diskand halo stars; these populations must be treated separately for thesolutions to be valid, and (4) over 200 stars are used in this analysis(>20% have thick disk kinematics), significantly more than inprevious solutions. We discuss the kinematic properties of the local RRLyrae stars, and briefly discuss our absolute magnitude results withregard to the distances and ages of some RR Lyrae-bearing populations.
| Self-gravitating polar rings in axisymmetric and triaxial galaxy potentials
A number of early galaxies show a polar ring of gas, dust, and starslying roughly perpendicular to the apparent major axis of the centralgalaxy. Here, we study the dynamics of a self-gravitating annulus ofmatter which is inclined to the principal planes of a triaxial galacticpotential tumbling about its short axis. In a steadily precessingequilibrium state, the precession rate of the ring in the potential mustbe equal to the tumbling speed of the triaxial figure. As in an oblategalaxy, both stable and unstable equilibria exist: in the tumblingtriaxial potential, there are stable equilibria bending toward theequator, if the ring is light, and toward the pole, at higher ring mass.The former are similar to the `anomalous retrograde orbits,' while thelatter resemble the stable equilibria for a self-gravitating ring in anoblate potential. We follow the time evolution of unstable polar rings.In an oblate galaxy potential, even if the ring is not sufficientlymassive to be stabilized, self-gravity can still cause thecharacteristic warp up toward the pole. In the triaxial potential, whenthe inclination of the polar ring is not such that its precession ratematches the galaxy tumbling speed, the ring can wobble gently in aquasiperiodic manner if it is massive enough, but is disrupted if itsmass is too low.
| A neutral hydrogen survey of polar-ring galaxies, 1: Green Bank observations of the northern sample
We present the results of a neutral hydrogen survey conducted with theGreen Bank 140 foot radio telescope of 47 northern objects in thepolar-ring galaxy atlas of Whitmore et al. (1990). We detected 39 ofthese above our detection limit of 1.7 Jy km/s; the average measuredflux of 21 Jy km/s corresponds to an average neutral hydrogen mass of5.3 x 109 solar mass for a Hubble constant ofHzero = 75 km/s/Mpc. For the polar-ring galaxies in oursample that have also been observed with radio arrays, we find that the21 full width at half maximum (FWHM) Green Bank beam often includes muchmore flux than found by the synthesis instruments for the polar ringsalone; some of these galaxies are known to have gas-rich companions. Wecompare the neutral hydrogen content of the sample to the blueluminosity and Infrared Astronomical Satellite (IRAS) fluxes. The HI-mass-to-blue-light ratios of the confirmed and probable polar ringsare around unity in solar units, indicating that polar-ring galaxies (ortheir environments) are as gas-rich as typical irregular galaxies. Fortheir blue luminosity, the confirmed polar rings are underluminous inthe far infrared, as compared with the rest of the sample. They are alsofar infrared (FIR) underluminous for their H I masses, which suggeststhat most of the gas in the ring may be in stable orbits, rather thanflowing inward to trigger star formation in the central galaxy. The moredisordered class of 'related objects,' which includes a number ofobvious mergers, is highly luminous in the far infrared. Detailed notesfor each galaxy, including information about companions within the GB140 min beam that may contribute to the total H I line integral and itswidth, are contained in the Appendix.
| 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 spectroscopic survey of some Zwicky compact galaxies
Spectroscopic observations of 58 compact galaxies identified by Zwickyin two southern fields are described. Half of these show red continuaand are either circular, lenticular, or elliptical in shape. They areapparently giant elliptical and S0 galaxies. The remaining blue and veryblue galaxies, almost without exception, show emission features. Two ofthe objects are previously unreported Seyfert galaxies, and a furthertwo appear to be very similar to the isolated extragalactic H II regionsdescribed by Searle and Sargent. A comparison of data for all thecompact galaxies described here with Holmberg's photometry anddimensions of bright field galaxies suggests that the compacts do nothave unusually high average surface brightnesses.
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