The Serpens Molecular Cloud in ¹²CO and ¹³CO: High Resolution and Large Field of View

Abstract

We used ¹²CO and ¹³CO J = 2-1 emission, to map 1.04 deg² of the Serpens molecular cloud with 38" spatial and 0.3 km s⁻¹ spectral resolution. Our molecular tracer study is important because our maps resolve kinematic properties for the entire Serpens cloud. We compare integrated intensity, velocity centroid, and velocity dispersion maps to positions of Young Stellar Objects (YSOs) and 1.1 mm emission from previous work. Our final result is a total H-nuclei (HI + 2 H₂) column density map, referred to as the N(H) map, which we find using an escape probability statistical equilibrium model that estimates ¹²CO column density (to infer the H₂ column) and the radiation field (to infer the HI column) from our ¹²CO and ¹³CO data. The average column densities in the Serpens core, Serpens South, and VV Ser regions are 8.6 x 10²¹, 10.0 x 10²¹, and 6.7 x 10²¹ cm⁻², respectively. Our final measurement for the mass of Serpens is 1860 M(sun). We conclude that this is a lower bound because ¹²CO and ¹³CO are self-absorbed in the Serpens core and Serpens South regions. Our N(H) map provides an observational test for numerical models of low-mass star forming clouds.