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Date and Time of the Query: 2019-05-23 T15:48:49 PDT
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For refcode 1992A&A...255...49K:
Retrieve 128 NED objects in this reference.
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Copyright by European Southern Observatory (ESO). Reproduced by permission
1992A&A...255...49K A sensitive radio continuum survey of low surface brightness dwarf galaxies U. Klein, C. Giovanardi, D.R. Altschuler, and E. Wunderlich Max-PIanck-Institut fur Radioastronomie, Auf dem Hugel 69, W-5300 Bonn 1, Federal Republic of Germany Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5,1-50125 Firenze, Italy Centro Astronomia Infrarossa, C.N.R., Largo E. Fermi 5,1-50125 Firenze, Italy Physics Department, University of Puerto Rico, Faculty of Natural Sciences, Rio Piedras, Puerto Rico 00931 Arecibo Observatory, P.O. Box 995, Arecibo, Puerto Rico 00613 Received February 28, accepted November 5, 1991 Abstract. A sample of 128 low-surface brightness dwarf galaxies (LSBDGs) mainly from the UGC catalogue has been observed at 4.75 GHz with the Effelsberg loom telescope. Only ~16% of the galaxies have been detected, the 2-{sigma} detection limit being between 2 and 3 mJy/beam area. This detection rate is much lower than that of "active" dwarf galaxies such as blue compact dwarf glaxies (BCDGs). The radio luminosity of LSBDGs appears to be correlated with, and roughly proportional to their blue luminosity; such a correlation is indistinguishable from the one observed in giant spirals. This confirms the suggestion made in previous papers that, as far as the general radio continuum properties are concerned, LSBDGs behave as scaled-down versions of spirals. Spectral indices can be derived or estimated for 11 LSDGs on the basis of the present and previous radio continuum surveys. Although the scatter is large, these spectral indices are suggestive of a nonthermal origin of the radio continuum emission. They also fall in the range of values typical for normal spirals. We have used the measured flux densities to roughly estimate total magnetic field strengths in LSBDGs, assuming energy equipartition between magnetic fields and cosmic rays. The resulting field strengths are in the range of 2-4 micro G, substantially lower than what is derived for massive spiral galaxies. The ratios of radio-to-far-infrared flux of LSBDGs appear to be high as compared to normal spiral galaxies. These two facts together are suggestive of the possibility that the injection of relativistic particles occurred, or promptly followed, an active phase with a star-formation rate exceeding the one presently observable. Key words: dwarf galaxies - radio continuum - magnetic fields
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