350 μm Observations of Local Luminous Infrared Galaxies and the Temperature Dependence of the Emissivity Index

Abstract

We report 350 μm observations of 18 nearby luminous infrared galaxies (LIRGs) using the Submillimeter High Angular Resolution Camera II (SHARC-II) mounted on the Caltech Submillimeter Observatory (CSO) 10.4 m telescope. Combining our 350 μm flux measurements with the existing far-infrared (FIR) and submillimeter data, we fit a single-temperature model to the spectral energy distributions (SEDs) and find the dust temperatures, emissivity indices, and FIR luminosities having sample medians of Td=39.4+/-7.9 K, β=1.6+/-0.3, and LFIR=1011.2+/-0.6 Lsolar. An empirical inverse Td-β correlation, best described by Td=(9.86×109)1/(4.63+β), is established for the local LIRG sample, which we argue can be explained by the intrinsic interdependence between the dust temperature and grain emissivity index as physical parameters, as well as variations in grain properties in the interstellar medium (ISM).