Letter to the Editor

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

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 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 regions is not photoionized and is essentially , this is lightly ionized by fluxes of low energy cosmic rays (CR) produced by processes originating in the hot stars which illuminate the regions.