Grain Alignment in the Taurus Dark Cloud
نویسنده
چکیده
Variations in polarization e ciency (p=A) of interstellar grains as a function of environment place vital constraints on models for the mechanism of their alignment. We use polarimetry of background eld stars to investigate alignment in the Taurus dark cloud as a function of optical depth for extinctions of AK < 2:5 (AV < 25). Results show a strong systematic trend in polarization e ciency with extinction. We discuss the possibility of a relationship between p=A and icy grain mantle growth, since mantles are detected in Taurus only for extinctions where p=A is lowest. A simple density model of alignment by paramagnetic alignment (Davis & Greenstein 1951) predicts that the magnetic eld strength (B) scales with density to the power = 0:28. Subject headings: dust, extinction | polarization | ISM: magnetic elds | ISM: individual (Taurus Cloud)
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