The JCMT Nearby Galaxies Legacy Survey III: Comparisons of cold dust, polycyclic aromatic hydrocarbons, molecular gas, and atomic gas in NGC 2403

TL;DR

This study investigates the spatial relationships among PAHs, cold dust, molecular gas, and atomic gas in NGC 2403 using multi-wavelength data, revealing how gas-to-dust ratios and metallicity influence galaxy composition.

Contribution

It provides a detailed analysis of the correlations and radial profiles of dust and gas components in NGC 2403, highlighting the impact of metallicity on the gas-to-dust ratio.

Findings

Gas-to-dust ratio increases with radius, from ~100 to ~400.

Metallicity strongly influences the gas-to-dust ratio.

CO and PAH emissions have similar radial scale lengths but are uncorrelated locally.

Abstract

We used 3.6, 8.0, 70, 160 micron Spitzer Space Telescope data, James Clerk Maxwell Telescope HARP-B CO J=(3-2) data, National Radio Astronomy Observatory 12 meter telescope CO J=(1-0) data, and Very Large Array HI data to investigate the relations among PAHs, cold (~20 K) dust, molecular gas, and atomic gas within NGC 2403, an SABcd galaxy at a distance of 3.13 Mpc. The dust surface density is mainly a function of the total (atomic and molecular) gas surface density and galactocentric radius. The gas-to-dust ratio monotonically increases with radius, varying from ~100 in the nucleus to ~400 at 5.5 kpc. The slope of the gas-to-dust ratio is close to that of the oxygen abundance, suggesting that metallicity strongly affects the gas-to-dust ratio within this galaxy. The exponential scale length of the radial profile for the CO J=(3-2) emission is statistically identical to the scale length for the stellar continuum-subtracted 8 micron (PAH 8 micron) emission. However, CO J=(3-2) and PAH 8 micron surface brightnesses appear uncorrelated when examining sub-kpc sized regions.