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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 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
| Pair production in steady synchrotron self Compton models of active galactic nuclei.
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| The behavior of compact non-thermal sources with pair production
The behavior of a compact source of hard nonthermal radiation may bestrongly influenced by electron-positron pairs created by photon-photoncollisions. The effects on the spectrum and variability of a source areexamined when the primary spectrum is due to the Compton scattering ofblackbody soft photons by relativistic electrons injected with a fixedhigh Lorentz factor. Although the model spectra are successful inreproducing the power-law X-ray spectrum common to many Seyfert 1galaxies, they produce an annihilation feature which is too strong to beacceptable. Source variability is studied using power-spectral andcross-correlation analyses of the response of a model system to whitenoise. The characteristic lags which occur between different energybands in the emergent spectrum are identified.
| Alignments of galaxies in the Perseus supercluster
The relative orientations of the galaxies belonging to the Perseussupercluster are investigated. The result is a lack of alignment in anypreferred direction of the supercluster galaxies (ellipticals, spiralsand both), except in a selected region of the supercluster, whosesignificance is low. Moreover no evidence of anisotropy in the relativeorientations of neighboring galaxies has been found.
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