Exploring the interstellar medium of NGC 891 at millimeter wavelengths using the NIKA2 camera

TL;DR

This study used the NIKA2 camera to observe NGC 891 at millimeter wavelengths, revealing dust properties, warm dust regions, and a variation in small grain mass fraction across the galaxy.

Contribution

First millimeter-wave observations of NGC 891 with detailed SED fitting to analyze dust properties and distribution in an edge-on galaxy.

Findings

Detected diffuse dust emission at all wavelengths from mid-IR to mm.

Found mm excess emission in the outer disk regions.

Small dust grains constitute 9.5% of total dust mass in the plane, increasing to 20% at high |z|.

Abstract

In the framework of the IMEGIN Large Program, we used the NIKA2 camera on the IRAM 30-m telescope to observe the edge-on galaxy NGC 891 at 1.15 mm and 2 mm and at a FWHM of 11.1" and 17.6", respectively. Multiwavelength data enriched with the new NIKA2 observations fitted by the HerBIE SED code (coupled with the THEMIS dust model) were used to constrain the physical properties of the ISM. Emission originating from the diffuse dust disk is detected at all wavelengths from mid-IR to mm, while mid-IR observations reveal warm dust emission from compact HII regions. Indications of mm excess emission have also been found in the outer parts of the galactic disk. Furthermore, our SED fitting analysis constrained the mass fraction of the small (< 15 Angstrom) dust grains. We found that small grains constitute 9.5% of the total dust mass in the galactic plane, but this fraction increases up to ~ 20% at large distances (|z| > 3 kpc) from the galactic plane.