Research Note

Vindicating single-T modified blackbody fits to Herschel SEDs^⋆

INAF – Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Florence, Italy
e-mail: sbianchi@arcetri.astro.it

Received: 7 December 2012
Accepted: 22 February 2013

Abstract

I show here that the bulk of the dust mass in a galaxy can be equivalently estimated from i) the full spectral energy distribution of dust emission, using the approach of Draine & Li (2007, ApJ, 657, 810) that includes a distribution of dust grains and a range of interstellar radiation field intensities; ii) the emission in the wavelength range 100  μm ≤ λ ≤ 500  μm (covered by the Herschel Space Observatory), by fitting a simpler single-temperature modified blackbody to the data. Recent claims to the contrary should be interpreted as a caveat in the simpler fits to use an absorption cross section which is consistent both in the normalization and in the spectral index β with that of the full dust model. I also show that the dust mass does not depend significantly on the choice of β, if both the dust mass and the absorption cross section are derived with the same assumption on β.