Temperature Profiles and the Effect of AGN on Submillimeter Emission from BLAST Observations of Resolved Galaxies

TL;DR

This study uses BLAST submillimeter observations to analyze dust temperature profiles and the influence of active galactic nuclei on the emission from nearby galaxies, providing new insights into dust properties and AGN contributions.

Contribution

It presents the first resolved submillimeter maps of nearby galaxies, estimates dust mass and temperature, and introduces a method to constrain AGN influence using core flux fractions.

Findings

Resolved dust temperature and mass profiles for multiple galaxies.

Estimated dust mass absorption coefficient at 250 microns.

Upper limits on AGN contribution based on core flux fractions.

Abstract

Over the course of two flights, the Balloon-borne Large Aperture Submillimeter Telescope (BLAST) made resolved maps of seven nearby (<25 Mpc) galaxies at 250, 350, and 500 microns. During its June 2005 flight from Sweden, BLAST observed a single nearby galaxy, NGC 4565. During the December 2006 flight from Antarctica, BLAST observed the nearby galaxies NGC 1097, NGC 1291, NGC 1365, NGC 1512, NGC 1566, and NGC 1808. We fit physical dust models to a combination of BLAST observations and other available data for the galaxies observed by Spitzer. We fit a modified blackbody to the remaining galaxies to obtain total dust mass and mean dust temperature. For the four galaxies with Spitzer data, we also produce maps and radial profiles of dust column density and temperature. We measure the fraction of BLAST detected flux originating from the central cores of these galaxies and use this to calculate a "core fraction," an upper limit on the "AGN fraction" of these galaxies. We also find our resolved observations of these galaxies give a dust mass estimate 5-19 times larger than an unresolved observations would predict. Finally, we are able to use these data to derive a value for the dust mass absorption co-efficient of kappa = 0.29 +/-0.03 m^2 kg^-1 at 250 microns. This study is an introduction to future higher-resolution and higher-sensitivity studies to be conducted by Herschel and SCUBA-II.