A COMPLETE Look at the Use of IRAS Emission Maps to Estimate Extinction and Dust Temperature

Abstract

We have created new dust temperature and column density maps of Perseus, Ophiuchus, and Serpens using 60 and 100 mu m data from the Improved Reprocessing of the IRAS Survey ( IRIS) recalibration of Infrared Astronomical Satellite ( IRAS) data. We describe an optimized method for finding the dust temperature, emissivity spectral index, and optical depth using optical and near-infrared extinction maps. The creation of these temperature and extinction maps ( covering tens of square degrees of molecular clouds) is one of the first results from the ongoing Coordinated Molecular Probe Line Extinction Thermal Emission ( COMPLETE) Survey of Star-Forming Regions. However, while the extinctions derived from the IRIS emission maps are globally accurate, we warn that far-infrared emission is not a good proxy for extinction on the scale of 1 pixel (similar to 5'). In addition to describing the global dust properties of these clouds, we have found two particularly interesting features in the column density and temperature maps. In the Ophiuchus dark cloud complex, the new dust temperature map shows a little-known warm ( 25 K) dust ring with a 2 pc diameter. This shell is approximately centered on the B star rho Ophiuchus, 1 degrees north of the well-studied rho Oph star-forming cluster. In Perseus, the column density map shows a 10 pc diameter ring, a feature not apparent in the filamentary chain of clouds seen in molecular gas. These rings are further discussed in detail in our companion papers.