Modelling the diffuse dust emission around Orion

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, α = 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.

AstroSat/UVIT Study of the Diffuse Ultraviolet Radiation in the Dwarf Galaxy Holmberg II

“…In order to predict the dust scattered intensities in the FUV for Ho II, we have used a single scattering radiative transfer model successfully used for the Orion region by Shalima et al (2006). This model constrains the albedo α and the asymmetry factor g of the dust grains (Shalima et al 2006;Saikia et al 2018) in the galaxy. Since Galactic diffuse UV emission has been known to originate mainly from the forward scattering by optically thin clouds in front of hot UV emitting stars (Sujatha et al 2007), a single scattering model with dust distributed in a sheet in front of the clusters is considered here.…”