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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
| Properties of tidally-triggered vertical disk perturbations
We present a detailed analysis of the properties of warps andtidally-triggered perturbations perpendicular to the plane of 47interacting/merging edge-on spiral galaxies. The derived parameters arecompared with those obtained for a sample of 61 non-interacting edge-onspirals. The entire optical (R-band) sample used for this study waspresented in two previous papers. We find that the scale height of disksin the interacting/merging sample is characterized by perturbations onboth large ( =~ disk cut-off radius) and short ( =~ z0)scales, with amplitudes of the order of 280 pc and 130 pc on average,respectively. The size of these large (short) -scale instabilitiescorresponds to 14% (6%) of the mean disk scale height. This is a factorof 2 (1.5) larger than the value found for non-interacting galaxies. Ahallmark of nearly all tidally distorted disks is a scale height thatincreases systematically with radial distance. The frequent occurrenceand the significantly larger size of these gradients indicate that diskasymmetries on large scales are a common and persistent phenomenon,while local disturbances and bending instabilities decline on shortertimescales. Nearly all (93%) of the interacting/merging and 45% of thenon-interacting galaxies studied are noticeably warped. Warps ofinteracting/merging galaxies are ~ 2.5 times larger on average thanthose observed in the non-interacting sample, with sizes of the order of340 pc and 140 pc, respectively. This indicates that tidal distortionsdo considerably contribute to the formation and size of warps. However,they cannot entirely explain the frequent occurrence of warped disks.Based on observations obtained at the European Southern Observatory(ESO, La Silla, Chile), Calar Alto Observatory operated by the MPIA(DSAZ, Spain), Lowell Observatory (Flagstaff,AZ, USA), and Hoher ListObservatory (Germany).
| The influence of interactions and minor mergers on the structure of galactic disks I. Observations and disk models
This paper is the first part in our series on the influence of tidalinteractions and minor mergers on the radial and vertical disk structureof spiral galaxies. We report on the sample selection, our observations,and data reduction. Surface photometry of the optical and near infrareddata of a sample of 110 highly-inclined/edge-on disk galaxies arepresented. This sample consists of two subsamples of 61 non-interactinggalaxies (control sample) and of 49 interacting galaxies/minor mergingcandidates. Additionally, 41 of these galaxies were observed in the nearinfrared. We show that the distribution of morphological types of bothsubsamples is almost indistinguishable, covering the range between 0<= T <= 9. An improved, 3-dimensional disk modelling- and fittingprocedure is described in order to analyze and to compare the diskstructure of our sample galaxies by using characteristic parameters. Wefind that the vertical brightness profiles of galactic disks respondvery sensitive even to small deviations from the perfect edge-onorientation. Hence, projection effects of slightly inclined disks maycause substantial changes in the value of the disk scale height and musttherefore be considered in the subsequent study. Based on observationsobtained at the European Southern Observatory (ESO, La Silla, Chile),Calar Alto Observatory operated by the MPIA (DSAZ, Spain), LowellObservatory (Flagstaff/AZ, USA), and Hoher List Observatory (Germany).
| The influence of interactions and minor mergers on the structure of galactic disks. II. Results and interpretations
We present the second part of a detailed statistical study focussed onthe effects of tidal interactions and minor mergers on the radial andvertical disk structure of spiral galaxies. In the first part wereported on the sample selection, observations, and applied disk models.In this paper the results are presented, based on disk parametersderived from a sample of 110 highly-inclined/edge-on galaxies. Thissample consists of two subsamples of 49 interacting/merging and 61non-interacting galaxies. Additionally, 41 of these galaxies wereobserved in the NIR. We find significant changes of the disk structurein vertical direction, resulting in ~ 1.5 times larger scale heights andthus vertical velocity dispersions. The radial disk structure,characterized by the cut-off radius and the scale length, shows nostatistically significant changes. Thus, the ratio of radial to verticalscale parameters, h/z0, is ~ 1.7 times smaller for the sampleof interacting/merging galaxies. The total lack of typical flat diskratios h/z0 > 7 in the latter sample implies that verticaldisk heating is most efficient for (extremely) thin disks. Statisticallynearly all galactic disks in the sample (93%) possess non-isothermalvertical luminosity profiles like the sech (60%) and exp (33%)distribution, independent of the sample and passband investigated. Thisindicates that, in spite of tidal perturbations and disk thickening, theinitial vertical distribution of disk stars is not destroyed byinteractions or minor mergers. Based on observations obtained at theEuropean Southern Observatory (ESO, La Silla, Chile), Calar AltoObservatory operated by the MPIA (DSAZ, Spain), Lowell Observatory(Flagstaff/AZ, USA), and Hoher List Observatory (Germany).
| 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.
| Southern Galaxy Catalogue.
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