The Guilty Secrets of Dust in Nearby Galaxies

Two-part seminar given to the East Asian Observatory, 2017.

Transcript

1. ϰ
   d
   Chris Clark
   Simon Schofield
   Haley Gomez
   Jonathan Davies
   

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2. •
   The Elusive ϰ
   d
   Chris Clark
   

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3. M
   d
   = M
   g
   ε
   d
   f
   Z
   M
   d = Dust mass
   M
   g = Gas mass
   ε
   d = ISM dust-to-metals ratio = 0.5 +/- 0.1
   f
   Z = ISM metal mass fraction (ie, ISM metallicty)
   Chris Clark
   

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4. Improvements Over James et al (2002)
   Using data from the HRS
   • We now have Herschel photometry; James et al only had IRAS &
   SCUBA, and so could not constrain dust temperature.
   • We have integrated (and normalised) ISM metallicites from drift-
   scan spectroscopy
   • We have integrated CO maps; they only had central pointings.
   • James et al did not consider the effect of oxygen depletion on
   their metallicites – we do.
   • James et al did not account for Helium or gas-phase metals in
   their ISM masses – we do.
   Chris Clark
   

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5. •
   Chris Clark
   

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6. •
   Chris Clark
   

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7. An Empirical Value For κ
   d
   • Κ
   500
   = 0.051 m2 kg-1 (+/- ~0.24 dex)
   Chris Clark
   

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8. Chris Clark
   

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9. Chris Clark
   DustPedia Overview
   • THEMIS – A physically-motivated dust model based upon
   laboratory observations of astrophysical minerals (see papers by
   A Jones, N Ysard).
   • SKIRT – Radiative transfer modelling suite that can fit a dust
   model to galaxy observations in 3D (see papers by M Baes, P De
   Camps, S Verstoken).
   • A hierarchical Bayesian SED fitting toolkit that can be used to
   model both galaxies both globally and pixel-by-pixel (see papers
   by F Galliano).
   • A database of multiwavelength imagery and photometry database
   for all 876 nearby galaxies observed by Herschel for which
   V<3000 km/s and D25<1’ (see upcoming paper by me).
   

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10. Chris Clark
    

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