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T. Jackson (Princeton), M.W. Werner, T.N. Gautier (JPL/Caltech)
Polarimetry of far infrared emission from the interstellar medium has found polarization exceeding 5% in many sources, approaching 10% in some cases. The polarization mechanism appears to be emission from elongated, magnetically-aligned, grains, and the high fractional polarization suggests efficient alignment. If filamentary structures in the interstellar medium trace the magnetic field, then polarimetry of the emission from such filaments could allow the grain alignment to be studied without complications due to varying field orientation along the line of sight. At high galactic latitudes where polarimetry of the cosmic microwave background will be carried out, observations of such filaments might provide useful local polarization standards and permit an assessment of the potential polarization of the galactic foreground. To meet these and similar needs, we have compiled a catalog of filamentary structures in the interstellar medium by developing a suitable pattern recognition algorithm and applying it to the 100um images from the IRAS Sky Survey Atlas. The catalog contains 83 filaments at high galactic latitude, 47 at low galactic latitude, and 10 in the Large Magellanic Cloud. Length [typically 30 arcmin or greater], straightness, and brightness criteria are applied to make the low latitude objects suitable for study with a far infrared polarimeter on SOFIA, and to make these and the high latitude objects suitable for study with a balloon-borne radiometer operating in the sub-millimeter. The brightness is tabulated at 100um, based on the ISSA catalog, and at both 100um and 340GHz based on the Davis et al estimates of the absolute sky brightness.
This work was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. T. Jackson held a Summer Undergraduate Research Fellowship at JPL/Caltech.