The far-infrared signature of dust in high-latitude regions

Details The far-infrared signature of dust in high-latitude regions The far-infrared signature of dust in high-latitude regions

Dec 2003

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2003mnras.346..403d&link_type=abstract

Monthly Notices of the Royal Astronomical Society, Volume 346, Issue 2, pp. 403-414.

Astronomy and Astrophysics

Astronomy

32

Ism: Clouds, Dust, Extinction, Infrared: Ism

Scientific paper

We present ISOPHOT observations of eight interstellar regions in the 60-200 μm wavelength range. The regions belong to mostly quiescent high-latitude clouds and have optical extinction peaks from AV~1-6 mag. From the 150- and 200-μm emission, we derived colour temperatures for the classical big grain component which show a clear trend of decreasing temperature with increasing 200-μm emission. The 200-μm emission per unit AV, however, does not drop at lower temperatures. This fact can be interpreted in terms of an increased far-infrared (FIR) emissivity of the big grains. We developed a two-component model including warm dust with the temperature of the diffuse interstellar medium (ISM) of T= 17.5 K, and cold dust with T= 13.5 K and FIR emissivity increased by a factor of >4. A mixture of the two components can reproduce the observed colour variations and the ratios I200/AV and τ200/AV. The relative abundance of small grains with respect to the big grains shows significant variations from region to region at low column densities. However, in lines of sight of higher column density, our data indicate the disappearance of small grains, perhaps a signature of adsorption/coagulation of dust. The larger size and porous structure could also explain the increased FIR emissivity. Our results from eight independent regions suggest that these grains might be ubiquitous in the galactic ISM.

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