%0 Journal Article
%T Anomalous Microwave Emission from Star Forming Regions
%A Anna M. M. Scaife
%J Advances in Astronomy
%D 2013
%I Hindawi Publishing Corporation
%R 10.1155/2013/390287
%X The evidence for microwave emission from spinning dust grains has been strengthened considerably by its detection in a number of discrete astrophysical objects associated with star formation. These detections, in combination with statistical constraints on its presence on large angular scales in the diffuse ISM, have provided strong observational confirmation of an emission mechanism still referred to as anomalous. This emission has a peaked spectrum with a maximum in the microwave band; the present review discusses the continuum radio emission mechanisms which can contribute to this region of the electromagnetic spectrum, collects published results on the prevalence of anomalous microwave emission in a variety of star formation regions, presents the overall conclusions that may be drawn from the detections so far, and discusses the prospects for future research on the anomalous microwave emission attributed to spinning dust within star forming regions. 1. Introduction The interstellar medium (ISM) of our galaxy and others is volume dominated by a small number of components. These components are differentiated by their temperature, ionization state, and density: the cold neutral medium (CNM) with hydrogen density £¿cm£¿3 and temperature 100£¿K, containing very little ionized material and no molecular gas; the warm neutral medium (WNM) with hydrogen density £¿cm£¿3 and temperatures of 5000¨C104£¿K, a low ionization fraction and no molecular component; the warm ionized medium (WIM), which has much in common with the WNM except that it is almost entirely ionized; as well as the low density hot ionized medium (HIM), with £¿cm£¿3 and temperatures of £¿K, which was first proposed by McKee and Ostriker ([1]; see also [2]) as the result of supernova shocks acting on the ambient ISM, and lead to the phrase ¡°the violent ISM¡± being coined [3]. Between them these components make up three phases, where they exist with densities regulated by pressure equilibrium: the hot phase of the HIM, the cooler combined warm phase of the WIM and WNM, and the cold CNM phase [4]. In addition to these three phases there also exist quasistatic, long-lived components with pressures far in excess of the ambient ISM, which have a much smaller volume filling factor but represent the bulk of mass in the galaxy. These giant cloud components are virialized and gravitationally bound, and their increased pressure is a result of an ongoing internal struggle to produce pressure gradients which will balance their own self-gravity. Unlike the ambient ISM phases, these clouds are largely molecular with
%U http://www.hindawi.com/journals/aa/2013/390287/