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Issue A&A
Volume 437, Number 1, July I 2005
Page(s) L11 - L14
Section Letters
DOI http://dx.doi.org/10.1051/0004-6361:200500129



A&A 437, L11-L14 (2005)
DOI: 10.1051/0004-6361:200500129

Letter

Temperature fluctuations in H II regions: Ionization by cosmic rays as a key mechanism

C. Giammanco1 and J. E. Beckman1, 2

1  Instituto de Astrofísica de Canarias, C. vía Láctea s/n, 38200, La Laguna, Tenerife, Spain
    e-mail: corrado@ll.iac.es
2  Consejo Superior de Investigaciones Científicas, Spain

(Received 1 April 2005 / Accepted 18 May 2005 )

Abstract
We present a detailed model capable of explaining quantitatively the temperature fluctuations observed in luminous, large $\ion{H}{ii}$ regions. The model is based on two assumptions which we justify on the basis of observations: that the major fraction of the hydrogen in the clouds that form the $\ion{H}{ii}$ regions is not photoionized and is essentially $\ion{H}{i}$, this $\ion{H}{i}$ is lightly ionized by fluxes of low energy cosmic rays (CR) produced by processes originating in the hot stars which illuminate the regions.


Key words: ISM: general -- ISM: HII regions -- ISM: clouds -- ISM: photon escape -- elementary particles -- methods: analytical  -- methods: data analysis

SIMBAD Objects in preparation



© ESO 2005


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