MIRIS observation of near-infrared diffuse Galactic light

TL;DR

This study presents precise near-infrared observations of diffuse Galactic light at high Galactic latitudes, correlating it with far-IR dust emission, and analyzes dust properties in the MBM32 cloud, suggesting limited dust growth.

Contribution

It provides the most accurate DGL measurements to date and compares observed spectra with dust models to infer dust grain size distribution.

Findings

Linear correlation between optical and near-IR DGL in MBM32

Observed near-IR DGL color matches models without very large grains

Dust growth in MBM32 is likely limited due to low density

Abstract

We report near-infrared (IR) observations of high Galactic latitude clouds to investigate diffuse Galactic light (DGL), which is starlight scattered by interstellar dust grains. The observations were performed at $1.1$ and $1.6\,\rm{\mu m}$ with a wide-field camera instrument, the Multi-purpose Infra-Red Imaging System (MIRIS) onboard the Korean satellite STSAT-3. The DGL brightness is measured by correlating the near-IR images with a far-IR $100\,\rm{\mu m}$ map of interstellar dust thermal emission. The wide-field observation of DGL provides the most accurate DGL measurement achieved to date. We also find a linear correlation between optical and near-IR DGL in the MBM32 field. To study interstellar dust properties in MBM32, we adopt recent dust models with or without $\rm{\mu m}$-sized very large grains and predict the DGL spectra, taking into account reddening effect of interstellar radiation field. The result shows that observed color of the near-IR DGL is closer to the model spectra without very large grains. This may imply that dust growth in the observed MBM32 field is not active owing to its low density of interstellar medium.