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On the Observed Rapid Motions in Extragalactic Radio Sources
Using interferometric methods, radio astronomers have shown that veryrapid motions involving radio jets are detectable in a variety of activecenters: the nuclei of low-redshift radio galaxies, QSOs and BL Lacobjects, and active binary systems containing a black hole or a neutronstar in our own Galaxy. By comparing the positions of about 80extragalactic sources of this type with the position of the galaxies inthe de Vaucouleurs catalog and the updated QSO catalog ofVéron-Cetty and Véron, it is shown that about 50% of themlie within 1° of a low-redshift spiral galaxy, and about 15% lie soclose to galaxies (Δθ<=10') that theassociations are highly significant. Thus, the sources are probablyphysically associated with these galaxies. All the galaxies areclassified as spiral. In addition, many of the sources have other QSOslying very close to them. These results suggest that the motionsobserved in these radio sources, as well as in the nuclei of radiogalaxies and in Galactic microquasars, and perhaps in many more QSOs andother objects, are all similar and are mildly relativistic, and they donot require us to invoke large Lorentz factors. Some of the problemsassociated with this picture are discussed.
| 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.
| Northern dwarf and low surface brightness galaxies. II - The Green Bank neutral hydrogen survey
The paper reports neutral hydrogen observations of a large sample ofdwarf and other low surface brightness galaxies. A detailed discussionand error analysis of the observations are presented, and spectra aredisplayed for 329 galaxies detected for the first time, or detected withsubstantially better signal-to-noise ratios than achieved previously.The positions on the sky of 667 galaxies meeting the present selectioncriteria north of delta = 38 deg are shown. The distribution of theredshifts of galaxies detected at Green Bank is illustrated. The GreenBank detections tapered off strongly below the median H I flux of 3.7 Jykm/s detected at Arecibo: only 12 percent of the Green Bank sample wasdetected with smaller fluxes.
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