Astronomy and Astrophysics – Astronomy
Scientific paper
Dec 1999
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1999aas...195.7403d&link_type=abstract
American Astronomical Society, 195th AAS Meeting, #74.03; Bulletin of the American Astronomical Society, Vol. 31, p.1478
Astronomy and Astrophysics
Astronomy
Scientific paper
Studies to map the cosmic microwave background radiation have discovered "galactic foreground" microwave emission correlated with interstellar matter. Draine & Lazarian (1998a,b; hereafter DL98a,b) have proposed that this emission is electric dipole radiation from rapidly-rotating ultrasmall a ≲ 15 Angstroms interstellar grains, and have shown that the population of ultrasmall grains previously indicated by infrared observations should in fact radiate in the microwave with approximately the observed intensity. The rotational excitation and damping of these ultrasmall grains is due to a variety of processes, including damping by electric dipole radiation, excitation and damping by collisions with ions and neutrals, excitation and damping due to long-range interactions with passing ions (``plasma drag''), and excitation and damping resulting from absorption of optical-UV photons and emission of IR photons. DL98b estimated the rotational emission by assuming that the grains of a given radius would have a Maxwellian distribution of rotational velocities, but this is only a rough approximation since the excitation and damping of rotation is nonthermal. We obtain the rotational distribution function using a semiclassical calculation, including all of the important physical processes. We show how, for each grain size, the different physical processes contribute to the "rotational transition matrix", and we then solve numerically for the steady-state rotational populations. The microwave emission spectrum is computed from the rotational distribution functions. The overall emission spectra are similar to the estimates of DL98b, but there are some differences. The microwave emission spectrum is predicted for realistic grain size distributions, and found to be in good agreement with recent observations. This research was supported in part by NSF grant AST-9619429 and NASA grant NAG5-7030. References: Draine, B.T., & Lazarian, A. 1998a, ApJ, 494, L19 (DL98a); Draine, B.T., & Lazarian, A. 1998b, ApJ, 508, 157 (DL98b)
Draine Bruce T.
Li Aigen
No associations
LandOfFree
Microwave Emission from Interstellar Grains: The Rotational Distribution Function does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Microwave Emission from Interstellar Grains: The Rotational Distribution Function, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Microwave Emission from Interstellar Grains: The Rotational Distribution Function will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1743364