Modeling the Optical Colors of Galactic Cirrus Clouds in the Stripe 82 Region

TL;DR

This study models the optical colors of Galactic cirrus clouds using radiative transfer simulations to understand their properties and distinguish them from extragalactic features, aligning models with Stripe 82 observations.

Contribution

It introduces a detailed radiative transfer model of turbulent dust clouds that reproduces observed cirrus cloud colors and explores modifications to the interstellar radiation field.

Findings

Models match observed colors by adjusting ISRF intensities.

Color--color diagrams effectively differentiate Galactic cirrus from extragalactic features.

Results inform about dust properties and ISRF variations.

Abstract

Observations have shown that the optical colors of Galactic cirrus clouds differ significantly from those of extragalactic sources; thus, they can be used to distinguish Galactic cirrus from extragalactic low surface brightness (LSB) features. To understand these properties, we calculate radiative transfer models in dust clouds, where photons are incident from the ambient interstellar medium (ISM). Dust clouds are modeled to mimic a turbulent medium using a fractional Brownian motion algorithm, resulting in a lognormal density distribution and a power-law power spectral density that are appropriate for the ISM. The results are compared with optical observations of cirrus clouds in the Stripe 82 region. The observed color--color ($g-r$, $r-i$, and $i-z$) diagrams of the cirrus clouds can be reproduced by scattered light if the interstellar radiation field (ISRF) of Mathis et al. (as updated by Draine) is modified, either by reducing the intensities in the $i$ and $z$ bands or by enhancing those in the $g$ and $r$ bands. Similar results can also be obtained by adjusting the scattering albedos at the corresponding wavelengths. This demonstrates that the color--color diagrams are effective not only for identifying extragalactic LSB features but also for studying the ISRF and the properties of interstellar dust.