Herschel/SPIRE Observations of the Dusty Disk of NGC 4244

TL;DR

This study uses Herschel/SPIRE images to analyze the dust distribution and properties of the edge-on spiral galaxy NGC 4244, revealing a clumpy, extended dust disk with implications for ISM structure.

Contribution

First detailed modeling of NGC 4244's dust disk combining Herschel data with radiative transfer models, highlighting a large dust scale-length and clumpy distribution.

Findings

Dust disk is clumpy and truncated at stellar disk break radius.

Clumpy model better reproduces observed morphology and SED.

Dust mass and scale-length are higher than previous estimates.

Abstract

We present Herschel/SPIRE images at 250, 350, and 500 {\mu}m of NGC 4244, a typical low-mass, disk-only and edge-on spiral galaxy. The dust disk is clumpy and shows signs of truncation at the break radius of the stellar disk. This disk coincides with the densest part of the Hi disk. We compare the Spectral Energy Distribution, including the new SPIRE fluxes, to 3D radiative transfer models; a smooth model disk and a clumpy model with embedded heating. Each model requires a very high value for the dust scale-length (h(dust) = 2 - 5 h(stars)), higher dust masses than previous models of NGC 4244 (Md = 0.47 - 1.39 \times 10e7 Msun) and a face-on optical depth of {\tau}(V) = 0.4 - 1.12, in agreement with previous disk opacity studies. The vertical scales of stars and dust are similar. The clumpy model much better mimics the general morphology in the submm images and the general SED. The inferred gas-to-dust mass ratio is compatible with those of similar low-mass disks. The relatively large radial scale-length of the dust disk points to radial mixing of the dusty ISM within the stellar disk. The large vertical dust scale and the clumpy dust distribution of our SED model are both consistent with a scenario in which the vertical structure of the ISM is dictated by the balance of turbulence and self-gravity.