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|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.
|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. 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.
|Arcsecond Positions of UGC Galaxies|
We present accurate B1950 and J2000 positions for all confirmed galaxiesin the Uppsala General Catalog (UGC). The positions were measuredvisually from Digitized Sky Survey images with rms uncertaintiesσ<=[(1.2")2+(θ/100)2]1/2,where θ is the major-axis diameter. We compared each galaxymeasured with the original UGC description to ensure high reliability.The full position list is available in the electronic version only.
|Kinematics of the Hercules supercluster|
The Hercules supercluster consists of the Abell clusters A2147, A2151,and A2152. Previous studies of the kinematics have been confounded bythe difficulty of correctly assigning galaxies to the individualclusters, which are not well separated. Our study has a total of 468available velocities for galaxies in the region, 175 of them new. Thereare 414 galaxies in the supercluster, about three times the number usedin the previous supercluster study. We verify the existence of the threeindividual clusters and compute their individual dynamical parameters.We investigate several techniques for assigning galaxy membership toclusters in this crowded field. We use the KMM mixture-modelingalgorithm to separate the galaxies into clusters; we find that A2152 hasa higher mean velocity than previous studies have reported. A2147 andA2152 also have lower velocity dispersions: 821 and 715 km/s,respectively. The assignment of galaxies to either A2152 or A2147requires velocity and position information. We study the kinematics ofthe supercluster using the two-body formalism of Beers et al. (1982) andconclude that A2147 and A2151 are probably bound to each other and thatthe supercluster as a whole may also be bound. The mass of thesupercluster, if bound, is (7.6 +/- 2.0) 10 exp 15/h M(solar); with thesupercluster luminosity, (1.4 +/- 0.2) 10 exp 13/sq h L(solar), thisyields 0.34 +/- 0.1.
|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.
|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.
|An image database. II. Catalogue between δ=-30deg and δ=70deg.|
A preliminary list of 68.040 galaxies was built from extraction of35.841 digitized images of the Palomar Sky Survey (Paper I). For eachgalaxy, the basic parameters are obtained: coordinates, diameter, axisratio, total magnitude, position angle. On this preliminary list, weapply severe selection rules to get a catalog of 28.000 galaxies, wellidentified and well documented. For each parameter, a comparison is madewith standard measurements. The accuracy of the raw photometricparameters is quite good despite of the simplicity of the method.Without any local correction, the standard error on the total magnitudeis about 0.5 magnitude up to a total magnitude of B_T_=17. Significantsecondary effects are detected concerning the magnitudes: distance toplate center effect and air-mass effect.
|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.
|A CCD survey of galaxies. IV. Observations with the 2.1 M telescope at San Pedro Martir.|
Continuing a CCD survey of galaxies belonging or projected onto the Comaand Hercules Superclusters, to the A262 and Cancer clusters, we presentisophote maps and photometric profiles in the Johnson system of 111galaxies (67 in the V and B bands, 42 only in V, 2 only in B) obtainedwith the 2.1 m telescope at San Pedro Martir (Baja California, Mexico).
|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.
|The CO emission of ring galaxies.|
Using the 15m SEST and 30m IRAM telescope we have observed 16 ringgalaxies in the 2CO10 transition and detected 14. Six ring galaxies havebeen detected in the ^12^CO(2-1) line. The Cartwheel, often consideredas the prototype of ring galaxies, has not been detected. We suggestthat the weak CO emission of this galaxy is due to its low metallicity.The observations do not exclude the possibility that the Cartwheel maybe H_2_rich and actively forming stars. We also present new HIdetections of six rings. We have compared the CO emission of the ringgalaxies with that of the distance-limited sample of Sage (1993a,b) andfound that ring galaxies are bright in CO compared to normal galaxies.If the standard conversion factor from CO emissivities into H_2_columndensities holds for ring galaxies, this suggests that a large amount ofmolecular gas is available for star formation and that ring galaxies areactively forming stars. This result is in agreement with the highfar-infrared luminosities of ring galaxies. We have also observed twoHoag-type objects in CO but have detected neither of them.
|Galaxy structures in the Hercules region|
216 redshifts have been obtained in a region of 981 sq deg south of theHercules supercluster. 172 of these redshifts are of galaxies withmpg less than or equal to 15.1, 110 of which had no previousvelocity measurement. 44 new redshifts are of galaxies fainter thanmpg = 15.1. With these new data we have been able to define asample in a vast region (approximately 1700 sq deg) around Herculeslimited to mpg less than or equal to 15.1 with a velocitycompleteness of 81.5%. 189 galaxies have been morphologically classifiedso that all galaxies in the sample with known velocity now also haveknown morphology. The magnitude limited sample, including 556 galaxies,is then used to identify and describe galaxy structures in the region.We find that the overdense volume is small, that its overall appearanceis that of a coral branch floating in a sea of nothing and that earlyand late type galaxies defined different structures.
|Can the Hoag object be a galaxy with a polar ring?|
A model of the Hoag object as an oblate triaxial S0 galaxy surrounded byan elliptical polar ring is proposed. Parameters of the core and thering are determined along with the view angle at which the modeloptimally simulates the properties of the object. It is noted that thecharacteristics of all known Hoag-type galaxies can be explained in thesame way, and that this significantly increases the number of galaxieswith polar rings.
|On the nature of Hoag-type galaxy NGC 6028 and related objects|
Surface photometry has been done on the nearest and brightest Hoag-typegalaxy, NGC 6028, which is known to be a peculiar galaxy consisting of aluminous core surrounded by a faint, apparently detached ring. Most ofthe Hoag-type galaxies are found to have oval-shaped cores, and it issuggested that the outer rings of both NGC 6028 and Hoag-type galaxiesmay be formed through mechanisms related to the oval structures of thecentral cores. A countereffect of the ring formation relating to apossible dissolution of barred structures is discussed briefly. Theaccretion hypothesis for the origin of outer rings is considered, andpossible interactions between the accreting gas and the hot, X-rayemitting gas around elliptical galaxies are discussed.
|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.
|Multicolor photoelectric photometry of ringlike galaxies.|
|The structure and evolution of Hoag's object|
New imaging, photometric, and spectroscopic observations of Hoag'sobject, a 16th magnitude galaxy consisting of an almost perfectly roundcore surrounded by a faint, apparently detached ring is presented. Theobservations and reduction procedures are addressed, and the physicalproperties of the galaxy and of its components are described, includingthe velocities, brightness profile, kinematics, and gas content. Oldhypotheses about Hoag's object are reviewed, and a new one is proposedin which the object owes its structure to an accretion event some timeago.
|The Distance to the Hercules Supercluster. II. Application of Tertiary Indicators and an Estimate of the Hubble Constant|
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1986ApJS...62..283B&db_key=AST
|The distance to the Hercules supercluster. I - Basic data for 220 galaxies in CGCG field 108.|
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1986ApJS...62..255B&db_key=AST
|Shells and rings around galaxies|
It is pointed out that the outer parts of galaxies often exhibitdistinct surface brightness enhancements. The development of rings andshells around galaxies has been ascribed to mechanisms in which theinteraction of a galaxy with its neighbors plays a key role. Accordingto some concepts, the big events, such as those leading to the formationof ring galaxies, are interspersed with an entire set of smaller ones.In particular, small galaxies in a group are inclined to fall into theirbigger neighbors without affecting the latter very much. After theevent, the big galaxy is provided with certain features, taking intoaccount ellipticals with shells, and S0s with polar rings. A review isconducted of the properties of these types of galaxies, insofar as theiroutskirts have identifiable shells or rings. Attention is given to ringgalaxies, outer rings around spirals and S0s, polar ring galaxies, andshells around elliptical galaxies.
|On the cigar-shaped ring galaxies|
In light of the ongoing debate as to whether cigar-shaped or 'spindle'ring galaxies have an oblate or prolate central body, photographic andspectroscopic data are presented and discussed. Ring galaxy parametersand redshifts are shown, and the flattening distribution for the mainparts of the ring galaxies is compared with that found by de Vaucouleurs(1959) for E galaxies. Specific attention is given to the ring galaxyNGC 2685. It is concluded that central structures of both oblate andprolate types evidently exist.
|A comparison of distance scales for early-type galaxies|
The distance scales of elliptical and lenticular galaxies areintercompared, based on the velocity dispersion indicator derived from arevised Faber-Jackson relation. The scales are found to be in nearperfect agreement with scales derived from the luminosity index and fromthe 21 cm line width indicator. The scales are also in excellentagreement with the distance scale derived by Michard (1979). Additionsare offered for the general catalog of 424 early-type galaxies, and aseries of reduction equations is presented which reduces the externalerrors in the distance moduli.
|Coupling of prolate E galaxies with equatorial rings.|
|Velocity dispersion profiles of clusters of galaxies|
Line-of-sight velocity dispersion profiles (sigma profiles) arepresented for 13 clusters of galaxies having at least 30 radialvelocities. The clusters considered include A2151, A1367, Virgo, A426,A1656, A2199, Cancer, A194, Fornax, A262, Centaurus, A2319, and PegasusI. All the sigma profiles are fitted to simple power laws over theradial interval from 0.1 to 2.0 times the virial radius and are found tofall into four classifications. In view of the amount of masssegregation implied, the amount of central concentration observed, andthe predominant galaxy morphology, it is suggested that theseclassifications represent a dynamical age sequence. Statistical testsare applied to two features appearing in some sigma profiles: thepresence of a local minimum that coincides with the local minimum notedin surface density or surface brightness profiles and a decrease inline-of-sight velocity dispersion in the cores of certain clusters.Possible dynamical implications of these features are discussed in termsof Wielen's (1974) N-body simulations.
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