IUE--IRAS Studies of the Infrared Cirrus

Abstract

The authors have studied correlations of IRAS infrared cirrus fluxes with interstellar parameters toward 256 OB stars observed with IUE. The 60 and 100 μm fluxes correlate with N(H I), n, E(B - V), spectral type, vertical distance from the Galactic plane, and general UV illumination. No correlation was found with abundances of Si, Mn, Fe, S, or Zn. The physical grain temperatures derived from the 60 - 100 μm flux ratio range from 14 to 48K, with hotter grains in the halo. Cirrus emission is enhanced toward several high-latitude OB associations. The grain abundance ratio, ≡10^-7 by number relative to H, is derived from 60 and 100 μm flux ratios and the H column along the line of sight. The authors estimate a minimum grain size between 2 and 15 Å.