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Interstellar Cloud (interstellar + cloud)
Selected AbstractsPhoton transport with a localized source in locally convex spacesMATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 9 2006Meri Lisi Abstract This paper deals with the study of a mathematical model of photon transport in an interstellar cloud where a localized source is present. The source is represented by a Dirac delta functional. The problem is studied in the setting of locally convex spaces. By means of the theory of semigroups on locally convex spaces and the adjoint approach, we prove existence and uniqueness of the solution. Copyright © 2006 John Wiley & Sons, Ltd. [source] Identification of the boundary surface of an interstellar cloud from a measurement of the photon far-fieldMATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 6 2004A. Belleni-Morante Abstract We study an inverse problem for photon transport in a host medium (e.g. an interstellar cloud), that occupies a bounded and strictly convex region ,,R3. Under the assumption that the cross-sections and the sources are known, we identify the boundary surface , = ,,(within a suitable family F of surfaces), provided that one value of the photon number density is measured at some given location far from ,. Copyright © 2004 John Wiley & Sons, Ltd. [source] Two stellar mass functions combined into one by the random sampling model of the initial mass functionMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 3 2000Bruce G. Elmegreen The turnover in the stellar initial mass function (IMF) at low mass suggests the presence of two independent mass functions that combine in different ways above and below a characteristic mass given by the thermal Jeans mass in the cloud. In the random sampling model introduced earlier, the Salpeter IMF at intermediate to high mass follows primarily from the hierarchical structure of interstellar clouds, which is sampled by various star formation processes and converted into stars at the local dynamical rate. This power-law part is independent of the details of star formation inside each clump and therefore has a universal character. The flat part of the IMF at low mass is proposed here to result from a second, unrelated, physical process that determines only the probability distribution function for final star mass inside a clump of a given mass, and is independent of both this clump mass and the overall cloud structure. Both processes operate for all potentially unstable clumps in a cloud, regardless of mass, but only the first shows up above the thermal Jeans mass, and only the second shows up below this mass. Analytical and stochastic models of the IMF that are based on the uniform application of these two functions for all masses reproduce the observations well. [source] The interstellar magnetic field near the Galactic centerASTRONOMISCHE NACHRICHTEN, Issue 1 2010K. Ferrière Abstract We review the current observational knowledge of the interstellar magnetic field within ,150 pc ofthe Galactic center. We also discuss the various theoretical scenarios that have been put forward to explain the existing observations. Our critical overview leads to two important conclusions: (1) The interstellar magnetic field near the GC is approximately poloidal on average in the diffuse intercloud medium and approximately horizontal in dense interstellar clouds. (2) In the general intercloud medium, the field is relatively weak and probably close to equipartition with cosmic rays (B , (6,20) , G), but there exist a number of localized filaments where the field is much stronger (some filaments could possibly have B , 1 mG). In dense interstellar clouds, the field is probably rather strong, with typical values ranging between a few 0.1 mG and a few mG (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | ||||||||||