Astronomy and Astrophysics – Astronomy
Scientific paper
Jan 2010
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010aas...21543118h&link_type=abstract
American Astronomical Society, AAS Meeting #215, #431.18; Bulletin of the American Astronomical Society, Vol. 42, p.365
Astronomy and Astrophysics
Astronomy
Scientific paper
The explanation of the anomalous microwave foreground emission based on the model of electric dipole emission from spinning dust grains proposed in Draine & Lazarian (1998ab) has been confirmed by numerous observations. In this paper we present a refinement of the original model by improving our description of a number of physical effects. First, we consider a grain rotating with angular velocity at an arbitrary angle with the grain symmetric axis (i.e., imperfect alignment) and derive the rotational damping and excitation coefficients from the infrared emission, plasma-grain interactions and electric dipole emission. The angular velocity distribution for this subtle case is calculated using the Langevin equation. Our results show that both the peak frequency of emission spectra and emissivity increase significantly for all chosen idealized environments. Second, we provide a detailed numerical study of effects of transient spin up of grains induced by collisions with ions. We show that in the presence of such impulses emission spectrum becomes broader, although the effect in terms of total emissivity is minor. In addition, we present an improved model of photoexcitation of spinning grains. We show that our model corresponds to observations, and in particular, for Warm Ionized Medium (WIM), our results can explain the new bump at 40 GHz reported by 5-year Wilkinson Microwave Anisotropy Probe (WMAP) data.
Draine Bruce
Hoang Thiem
Lazarian Alex
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