Visual extinction towards the Omega Nebula (M17) and the ionization of nitrogen in the nebulaстатья
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Дата последнего поиска статьи во внешних источниках: 18 июля 2013 г.
Аннотация:We estimate the absolute intensity of the Halpha emission line in M17 based on spectroscopic observations with the 70 cm telescope of the Fesenkov Astrophysical Institute and the 1.25 m telescope of the Sternberg Astronomical Institute's Crimean Laboratory. The visual extinction, A(v) is derived for about 250 regions in the nebula via a comparison of the optical (Halpha) and radio (21 cm continuum) emissions. The A, values for the eastern, optically bright, part of the nebula are 2-6(m). For the western part, which is covered by a dark cloud, the extinction is A(v) = 7-14.5(m). We derived I(Halpha)/I([NII] lambda6584) ratios and estimated the degree of ionization of nitrogen in the nebula; we find that most nitrogen is in the [NIII] state. (C) 2005 Pleiades Publishing Inc.