Stephen Eales, Matthew W. L. Smith, Robbie Auld, Maarten Baes, George J. Bendo, Simone Bianchi, Alessandro Boselli, Laure Ciesla, David Clements, Asantha Cooray, Luca Cortese, Jon Davies, Ilse De Looze, Maud Galametz, Walter Gear, Gianfranco Gentile, Haley Gomez, Jacopo Fritz, Tom Hughes, Suzanne Madden, Laura Magrini, Michael Pohlen, Luigi Spinoglio, Joris Verstappen, Catherine Vlahakis, Christine D. Wilson
It has often been suggested that an alternative to the standard CO/21-cm
method for estimating the mass of the interstellar medium (ISM) in a galaxy
might be to estimate the mass of the ISM from the continuum dust emission. In
this paper, we investigate the potential of this technique using Herschel
observations of ten galaxies in the Herschel Reference Survey and in the
Herschel Virgo Cluster Survey. We show that the emission detected by Herschel
is mostly from dust that has a temperature and emissivity index similar to that
of dust in the local ISM in our galaxy, with the temperature generally
increasing towards the centre of each galaxy. We calibrate the dust method
using the CO and 21-cm observations to provide an independent estimate of the
mass of hydrogen in each galaxy, solving the problem of the uncertain `X
factor' for the molecular gas by minimizing the dispersion in the ratio of the
masses estimated using the two methods. With the calibration for the dust
method and the estimate of the X-factor produced in this way, the dispersion in
the ratio of the two gas masses is 30%, which gives an upper limit on the
fundamental accuracy of the dust method. The calibration we obtain for the dust
method is very similar to an independent Herschel measurement for M31 and to
the calibration for the Milky Way from Planck measurements.
View original:
http://arxiv.org/abs/1202.0547
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