Astronomy and Astrophysics – Astronomy
Scientific paper
Jan 1994
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994phdt........13j&link_type=abstract
PhD Dissertation, California Univ. Los Angeles, CA United States
Astronomy and Astrophysics
Astronomy
Black Body Radiation, Dust, Grains, Absorption Cross Sections, Thermodynamic Equilibrium, Emission Spectra, Galactic Evolution, Cosmic Background Explorer Satellite, Astronomical Models, Needles, Spheres, Disks (Shapes), Carbon, Graphite, Interstellar Matter, Galaxies, Red Shift, Quadratic Programming
Scientific paper
We constructed cl, dla, old_cl, and old_dla type fractals grains and needle, sphere, and disk different material types (graphite and carbon) were calculated for 13 size steps from 1 monomer (60 atoms) up to 4096 monomers (245760 atoms) in factor of two steps. Due to efficient emission and absorption, the fractal dust grains are in non-thermal-equilibrium situation in the interstellar medium. With the absorption cross sections, and the numerical method for non-thermal-equilibrium radiation (Guhathakurta and Drain 1989), we were able to calculate the emission spectra, after four different size distributions (l/N1.5, 1/N2.0, l/N2.5, 1/N3.0) were assigned to determine the number of the grains in each size step of every type of the grains. The 56 different dust models of the spectrum from which the CMBR contribution were subtracted off are, then, used to fit the FIRAS spectrum of the Galaxy by COBE. After Quadratic programming, four types of dust were turned out to fit the FIRAS spectrum; l/N1.5 of graphite CL(3.8%), DLA (6.0%), OLD_DLA(2.2%) and 1/N3.0 of carbon DLA(88.0%). The fit favors the small size, low conductivity, fractal type dust grains. The emissions from the four types of dust were integrated from z = 0 to 103 with a constant number density of galaxy with redshift, and were compared to the FIRAS distortion limit of the CMBR from a perfect black body. The integrated emission added to the CMBR, or the integrated spectrum of deviation from a perfect black body is well below the FIRAS distortion limit. Allowing a galaxy number density vary with redshift, we could also test whether the evolutionary models of galaxies with some index's (nz = n0(1 + z)index) can be accommodated under the constraint of the FIRAS observation. The spectrum of deviation from the evolutionary models were fitted to the FIRAS residual from a perfect black body. Since we do not know the true CMBR temperature and the Galactic correction, the fit has linear free parameters of the temperature of the CMBR and the Galactic correction. The fit shows the evolutionary index up to 1.4 is acceptable. Blain and Longair (1994)'s simple model of galaxy formation with as high index as 1.5 seems to be inconsistent with the FIRAS limits.
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