Dust in a compact, cold, high-velocity cloud: A new approach to removing foreground emission

Abstract

Because isolated high-velocity clouds (HVCs) are found at great distances from the Galactic radiation field and because they have subsolar metallicities, there have been no detections of dust in these structures. A key problem in this search is the removal of foreground dust emission. Using the Effelsberg-Bonn HI Survey and the Planck far-infrared data, we investigate a bright, cold, and clumpy HVC. This cloud apparently undergoes an interaction with the ambient medium and thus has great potential to form dust. To remove the local foreground dust emission we used a regularised, generalised linear model and we show the advantages of this approach with respect to other methods. To estimate the dust emissivity of the HVC, we set up a simple Bayesian model with mildly informative priors to perform the line fit instead of an ordinary linear least-squares approach. We find that the foreground can be modelled accurately and robustly with our approach and is limited mostly by the cosmic infrared background. Despite this improvement, we did not detect any significant dust emission from this promising HVC. The 3-sigma upper limit to the dust emissivity is an order of magnitude below the typical values for the Galactic interstellar medium.

Accepted by A&A, 9 pages, 11 figures

References in corpus (4)

• The Effelsberg-Bonn HI Survey: Milky Way gas. First data release
• The Structure of Dark Molecular Gas in the Galaxy - I: A Pilot Survey for 18-cm OH Emission Towards $l\approx 105^{°},b\approx +1^{°}$
• The Overlooked Potential of Generalized Linear Models in Astronomy - I: Binomial Regression
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• All-sky census of Galactic high-latitude molecular intermediate-velocity clouds
• Is the cluster environment quenching the Seyfert activity in elliptical and spiral galaxies?
• Detection of Dust in High-Velocity Cloud Complex C -- Enriched Gas Accreting onto the Milky Way