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|The WSRT wide-field H I survey. I. The background galaxy sample|
We have used the Westerbork array to carry out an unbiased wide-fieldsurvey for H I emission features, achieving an RMS sensitivity of about18 mJy/Beam at a velocity resolution of 17 km s-1 over 1800deg2 and between -1000 < VHel <+6500 kms-1. The primary data consists of auto-correlation spectrawith an effective angular resolution of 49' FWHM, althoughcross-correlation data were also acquired. The survey region is centeredapproximately on the position of Messier 31 and is Nyquist-sampled over60x 30o in RA x Dec. More than 100 distinct features aredetected at high significance in each of the two velocity regimes(negative and positive LGSR velocities). In this paper we present theresults for our H I detections of external galaxies at positive LGSRvelocity. We detect 155 external galaxies in excess of 8sigma inintegrated H I flux density. Plausible optical associations are foundwithin a 30' search radius for all but one of our H I detections in DSSimages, although several are not previously cataloged or do not havepublished red-shift determinations. Our detection without a DSSassociation is at low galactic latitude. Twenty-three of our objects aredetected in H I for the first time. We classify almost half of ourdetections as ``confused'', since one or more companions is catalogedwithin a radius of 30' and a velocity interval of 400 km s-1.We identify a handful of instances of significant positional offsetsexceeding 10 kpc of unconfused optical galaxies with the associated H Icentroid, possibly indicative of severe tidal distortions or uncatalogedgas-rich companions. A possible trend is found for an excess of detectedH I flux in unconfused galaxies within our large survey beam relative tothat detected previously in smaller telescope beams, both as function ofincreasing distance and increasing gas mass. This may be an indicationfor a diffuse gaseous component on 100 kpc scales in the environment ofmassive galaxies or a population of uncataloged low mass companions. Weuse our galaxy sample to estimate the H I mass function from our surveyvolume. Good agreement is found with the HIPASS BGC results, but onlyafter explicit correction for galaxy density variations with distance.Table 1 is only available in electronic form at the CDS via anonymousftp to cdsarc.u-strasbg.fr (184.108.40.206) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/406/829 and Fig. 3 is onlyavailable in electronic form at http://www.edpsciences.org
|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.
|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.
|A survey of the Pisces-Perseus supercluster. V - The declination strip +33.5 deg to +39.5 deg and the main supercluster ridge|
Measurements of 544 radial velocities, 229 optical and 315 in the 21 cmH I line, are presented for galaxies, mostly in the declination stripbetween +33.5 and +39.5 deg in the region of the Pisces-Perseussupercluster. These are combined with other available data toinvestigate the linear structure identified as the main superclusterridge. The main ridge of the supercluster extends at least 50/h Mpcbefore it disappears into the zone of avoidance east of Perseus.Confinement both on the plane of the sky and in the velocity dimensionimply an axial ratio of greater than 10:1 and an inclination withrespect to the plane of the sky of less than about 12 degrees. Therelative proximity, low inclination to the plane of the sky, and highcontrast relative to the foreground and background, help to make thePisces-Perseus filament one of the most prominent features in theextragalactic sky on large scales.
|Galaxies possibly resembling M82-type galaxies|
A list of 298 galaxies with possible features of M82 galaxies ispresented. This list contains those Irr II candidates whose images onPalomar photographs shown no trace of dust although the objects are redand suspected to be peculiar.
|Recognition and classification of galaxies with optical jets|
Deep images and spectra are presented for galaxies reported in variouscatalogs to have jets, as well as in a search of the SRC J survey platesin a region near the south galactic pole. Most of these are shown to besuperpositions, polar rings, tidal features, or artifacts of theoriginal plate material. Examples are shown of ten ways that false jetscan be produced, with more detailed case studies for several systems.Based on this experience, several criteria for the brightness, location,and symmetry of genuine optical jets are suggested, which should yieldsurvey samples much less contaminated by 'false alarms' than existingones. Among the objects that remain as optical-jet candidates, ESO0610-23 shows a linear, radial chain of H II regions on the outskirts ofan amorphous system with complex internal structure, UGC 3995 is a closepair of spirals, one of which has a type 2 Seyfert nucleus and apparentknotty jet, and NGC 1598 has the radial features previously reported,but considerable chaotic outer structure as well. Several systems (suchas AM 0207-49 and ESO 2330-38) illustrate the intrinsic difficulty ofseparating jets and tidal tails on morphological grounds alone incertain cases.
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