Large-scale [C II] 158 μm emission from the Orion-Eridanus superbubble

Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands
e-mail: ainilsabdullah@gmail.com

Received: 22 February 2020
Accepted: 29 April 2020

Abstract

In this study, we analyzed the [C II] 158 μm emission from the Orion-Eridanus region measured by the Cosmic Background Explorer. Morphologically, the [C II] emission traces prominent star-forming regions this area. The analysis takes into account five different components of the interstellar medium (ISM) that can contribute to the [C II] emission: compact H II regions, dense Photon-Dominated Region, surfaces of molecular clouds, the Warm Ionized Medium, and the Cold Neutral Medium. We estimate the contribution from each object of interest to the observed [C II] emission based upon the physical properties of the object and validate our results by making a comparison with existing “small” scale maps. Inside the ~400 parsec aperture radius that we investigate, surfaces of molecular clouds exposed to radiation from nearby stellar clusters are the dominant contributor to the observed global [C II] flux. These molecular cloud surfaces are exposed to moderate radiation fields (G₀ ~ 100 times the average interstellar radiation field) and are moderately dense (n_H ~ 10³ cm⁻³). In addition, extended low-density ionized gas, along with large-scale ionized gas structures (Barnard’s Loop; λ Ori) also make a substantial contribution. The implications of this study for the analysis of extragalactic [C II] observations are assessed.