The Quest for the Missing Dust: I -- Restoring Large Scale Emission in Herschel Maps of Local Group Galaxies

Abstract

Because the galaxies of the Local Group have such large angular sizes, much of their diffuse, large-angular-scale emission is filtered out by the Herschel data reduction process. In this work, we restore this previously missed dust in Herschel observations of the Large Magellanic Cloud, Small Magellanic Cloud, M31, and M33. We do this by combining Herschel data (including new reductions for the Magellanic Clouds), in Fourier space, with lower-resolution data from all-sky surveys (Planck, IRAS, and COBE) that did not miss the extended emission. With these new maps, we find that a significant amount of emission was missing from uncorrected Herschel data of these galaxies; over 20% in some bands. Our new photometry also resolves the disagreement between fluxes reported from older HERITAGE Magellanic Cloud Herschel reductions, and fluxes reported from other telescopes. More emission is restored in shorter wavelength bands, especially in the galaxies' peripheries, making these regions 20-40% bluer than before. We also find that the Herschel-PACS instrument response conflicts with the all-sky data, over the 20-90' angular scales to which they are both sensitive, by up to 31%. By binning our new data based on hydrogen column density, we are able to detect emission from dust at low ISM densities (at ${\Sigma }_{\mathrm{H}}<1{\mathrm{M}}_{\odot }\mathrm{p}{\mathrm{c}}^{-2}$ in some cases), and are able to detect emission at much lower densities (a factor of 2.2 lower on average, and more than a factor of 7 lower in several cases) than was possible with uncorrected data.

Accepted for publication in ApJ

References in corpus (27)

• Array Programming with NumPy
• The NumPy array: a structure for efficient numerical computation
• HI4PI: A full-sky HI survey based on EBHIS and GASS
• A Unified Representation of Gas-Phase Element Depletions in the Interstellar Medium
• HyperLEDA. III. The catalogue of extragalactic distances
• COLD GASS, an IRAM legacy survey of molecular gas in massive galaxies: I. Relations between H2, HI, stellar content and structural properties
• CMasher: Scientific colormaps for making accessible, informative and 'cmashing' plots
• SCUBA-2: iterative map-making with the Sub-Millimetre User Reduction Facility
• An excess of massive stars in the local 30 Doradus starburst
• The Spitzer Survey of the Small Magellanic Cloud: FIR Emission and Cold Gas in the SMC
• The Herschel-ATLAS Data Release 1 Paper I: Maps, Catalogues and Number Counts
• Dust and Gas in the Magellanic Clouds from the HERITAGE Herschel Key Project. I. Dust Properties and Insights into the Origin of the Submm Excess Emission
• A Wide-field High Resolution HI Mosaic of Messier 31: I. Opaque Atomic Gas and Star Formation Rate Density
• Modelling Dust Evolution in Galaxies with a Multiphase, Inhomogeneous ISM
• Destruction of Interstellar Dust in Evolving Supernova Remnant Shock Waves
• Particularly Efficient Star Formation in M33
• Cool dust heating and temperature mixing in nearby star-forming galaxies
• Low-temperature MIR to submillimeter mass absorption coefficient of interstellar dust analogues II: Mg and Fe-rich amorphous silicates
• METAL: The Metal Evolution, Transport, and Abundance in the Large Magellanic Cloud Hubble program. II. Variations of interstellar depletions and dust-to-gas ratio within the LMC
• Untangling the Nature of Spatial Variations of Cold Dust Properties in Star Forming Galaxies
• HI filaments are cold and associated with dark molecular gas. HI4PI based estimates of the local diffuse CO-dark H2 distribution
• The Large Magellanic Cloud stellar content with SMASH: I. Assessing the stability of the Magellanic spiral arms
• TurbuStat: Turbulence Statistics in Python
• Spatially Resolved Spitzer Spectroscopy of the Starburst Nucleus in NGC 5253
• The Herschel Virgo Cluster Survey. XX. Dust and gas in the foreground Galactic cirrus
• Deep Herschel PACS point spread functions
• The apparent anti-correlation between the mass opacity of interstellar dust and the surface-density of interstellar gas

Cited by in corpus (1)

• The HASHTAG project: The First Submillimeter Images of the Andromeda Galaxy from the Ground