The apparent anti-correlation between the mass opacity of interstellar dust and the surface-density of interstellar gas

Abstract

Recent analyses of $Herschel$ observations suggest that in nearby disc galaxies the dust mass opacity at $500\mu \mathrm{m}$, ${\kappa }_{500}$, decreases with increasing gas surface density, ${\Sigma }_{\mathrm{ISM}}$ (Clark et al. 2019). This apparent anti-correlation between ${\kappa }_{500}$ and ${\Sigma }_{\mathrm{ISM}}$ is opposite to the behaviour expected from theoretical dust evolution models; in such models, dust in denser, cooler regions (i.e. regions of increased ${\Sigma }_{\mathrm{ISM}}$) tends to grow and therefore to have increased ${\kappa }_{500}$. We show, using a toy model, that the presence of a range of dust temperatures along the line of sight can lead to spuriously low estimated values of ${\kappa }_{500}$. If in regions of higher ${\Sigma }_{\mathrm{ISM}}$ the range of dust temperatures extends to lower values (as seems likely), the magnitude of this effect may be sufficient to explain the apparent anti-correlation between ${\kappa }_{500}$ and ${\Sigma }_{\mathrm{ISM}}$. Therefore there may not be any need for spatial variation in the intrinsic dust properties that run counter to theoretical expectations.

5 pages, 5 figures. MNRASL accepted 14/02/20

References in corpus (7)

• Infrared Emission from Interstellar Dust. IV. The Silicate-Graphite-PAH Model in the Post-Spitzer Era
• A Unified Representation of Gas-Phase Element Depletions in the Interstellar Medium
• DustPedia - A Definitive Study of Cosmic Dust in the Local Universe
• High-resolution, 3D radiative transfer modeling : I. The grand-design spiral galaxy M51
• The mass, location and heating of the dust in the Cassiopeia A supernova remnant
• High-Resolution Radiative Transfer Modelling of M33
• Dust emissivity and absorption cross section in DustPedia late-type galaxies

Cited by in corpus (6)

• Dust, CO and [CI]: Cross-calibration of molecular gas mass tracers in metal-rich galaxies across cosmic time
• The Quest for the Missing Dust: II -- Two Orders of Magnitude of Evolution in the Dust-to-Gas Ratio Resolved Within Local Group Galaxies
• Close-up view of a luminous star-forming galaxy at z=2.95
• Constraining early-time dust formation in core-collapse supernovae
• Dust emissivity in resolved spiral galaxies
• The Quest for the Missing Dust: I -- Restoring Large Scale Emission in Herschel Maps of Local Group Galaxies