Dust Emission in Galaxies at Millimeter Wavelengths: Cooling of star forming regions in NGC6946

TL;DR

This study maps the millimeter-wavelength dust emission in NGC6946, revealing the distribution, temperature, and emissivity of dust, and highlighting the interstellar radiation field's role in heating cold dust in galaxy regions.

Contribution

It provides the first detailed spatial mapping of pure dust emission at millimeter wavelengths in NGC6946, including dust properties derived from Bayesian modeling.

Findings

Interarm regions show dominant 2mm emission, indicating heating by the interstellar radiation field.

Dust temperature and emissivity vary across the galaxy, with detailed maps produced.

The study separates dust emission from other contributions like free-free, synchrotron, and CO line emissions.

Abstract

Interstellar dust plays an important role in the formation of molecular gas and the heating and cooling of the interstellar medium. The spatial distribution of the mm-wavelength dust emission from galaxies is largely unexplored. The NIKA2 Guaranteed Time Project IMEGIN (Interpreting the Millimeter Emission of Galaxies with IRAM and NIKA2) has recently mapped the mm emission in the grand design spiral galaxy NGC6946. By subtracting the contributions from the free-free, synchrotron, and CO line emission, we map the distribution of the pure dust emission at 1:15mm and 2mm. Separating the arm/interarm regions, we find a dominant 2mm emission from interarms indicating the significant role of the general interstellar radiation field in heating the cold dust. Finally, we present maps of the dust mass, temperature, and emissivity index using the Bayesian MCMC modeling of the spectral energy distribution in NGC6946.