Spitzer IRAC Colors of Nebulae Associated with Star-Forming Regions

TL;DR

This study uses Spitzer IRAC images to analyze infrared nebulae in star-forming regions, revealing details about dust composition, ultraviolet irradiation, and the physical conditions of the nebulae.

Contribution

It provides new insights into the infrared colors of nebulae, linking them to dust properties and UV irradiation in star-forming environments.

Findings

Nebula L1527 traces protostellar outflows.

Nebula colors indicate dust with PAH and high extinction.

Edges of nebulae are strongly irradiated by UV radiation.

Abstract

Star-forming regions are often associated with nebulosity. In this study, we investigated infrared diffuse emission in Spitzer IRAC images. The infrared nebula L1527 traces outflows emanating from a low-mass protostar. The nebular color is consistent with the color of a stellar photosphere with large extinction. Nebulae around the HII region W5-East are bright in the infrared. These colors are consistent with the model color of dust containing polycyclic aromatic hydrocarbon (PAH). The strength of ultraviolet irradiation of the nebulae and the small dust fraction were deduced from the infrared colors of the nebulae. We found that the edges of the nebulae are irradiated by strong ultraviolet radiation and have abundant small dust. Dust at the surface of the molecular cloud is thought to be destroyed by ultraviolet radiation from an early-type star.