Dust in the SINGS Galaxy Sample

Abstract

Dust models have been applied to interpret the IR emission from65 galaxies in the SINGS galaxy survey, allowing dust masses, PAH fractions,and starlight intensities to be determined. The dust models reproduce theglobal SEDs without requiring “cold” (T $\lesssim$ 12 K) dust. The bulk of theIR emission appears to be radiated by dust in the diffuse ISM,with starlight intensities similar to the intensity in the solar neighborhood.A fraction f_PDR of the IR emission is radiated by dust in regions ofhigh starlight intensities (e.g., PDRs), with median f_PDR = 0.08.The dust composition is characterized by q_PAH, the fraction ofthe dust mass contributed by PAHs with <10³ C atoms.Galaxies with metallicities Z/Z_๏ < 0.2 tend to have q_PAH $\lesssim$ 0.01, but galaxies with Z/Z_๏ > 0.4 have q_PAH = 0.02 - 0.05.Over the entire sample, with Z/Z_๏ ranging from 0.1 to 1, theobservations are consistent with a constant fraction of interstellarmetals being in dust, with M_dust/M_H ≈ 0.01(Z/Z_๏).