Polarized Light from Star-forming Regions

o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o Studies f p larized radiati n fr m m lecular cl uds and the envir nments f pr t stars are pr viding inf rmati n ab ut the rientati ns and strengths f magnetic fields and the sizes and c mp siti ns f dust grains in these envir nments. This relati nship between dust grains, magnetic fields, and p larized light exists because dust grains aligned by magnetic fields will p larize backgr und starlight, which therwise w uld be unp larized, and will emit intrinsically p larized thermal radiati n; als , even unaligned dust grains will scatter ph t ns, s the dusty envir nments f y ung stars ften pr duce reflecti n nebulae. Imp rtantly, s me f the bservati nal results are pr viding the first ever measurements f magnetic field alignments and strengths n scales fr m 1000 AU t tens f parsecs in dense c res and m lecular cl uds. Such measurements are particularly valuable f r understanding the mechanisms f star f rmati n and the imp rtance f magnetic fields and utfl ws. In additi n, p larizati n studies are driving ideas that the size distributi ns and c mp siti ns f p pulati ns f dust grains ar und y ung stellar bjects may be quite different fr m th se assumed f r astr physical dust in the interstellar medium. This astr physically imp rtant inf rmati n is unavailable, at present, fr m any ther type f measurements.