Modelling the diffuse dust emission around Orion

TL;DR

This study analyzes the diffuse ultraviolet and infrared emission around Orion, determining dust properties and scattering behavior using observational data and modeling, revealing uniform optical parameters with regional variations.

Contribution

It extends existing FUV dust scattering models to regions beyond Orion's center, providing new measurements of dust albedo and phase function asymmetry.

Findings

Median dust albedo α = 0.7

Scattering phase function g = 0.6

Uniform optical parameters across regions

Abstract

We have studied the diffuse radiation in the surroundings of M42 using photometric data from the Galaxy Evolution Explorer (GALEX) in the far-ultraviolet (FUV) and infrared observations of the AKARI space telescope. The main source of the FUV diffuse emission is the starlight from the Trapezium stars scattered by dust in front of the nebula. We initially compare the diffuse FUV with the far-infrared (FIR) observations at the same locations. The FUV-IR correlations enable us to determine the type of dust contributing to this emission. We then use an existing model for studying the FUV dust scattering in Orion to check if it can be extended to regions away from the centre in a 10 deg radius. We obtain an albedo, {\alpha} = 0.7 and scattering phase function asymmetry factor, g = 0.6 as the median values for our dust locations on different sides of the central Orion region. We find a uniform value of optical parameters across our sample of locations with the dust properties varying significantly from those at the centre of the nebula.