Spectroscopic study of ‘CO’ and its isotopic mm/submillimeter lines from dark cloud Lynds 183

Abstract

We have made spectral line analysis of CO and its isotopic lines from dark cloud Lynds 183 (L183). Our dataset incorporates 12CO(1-0), 13CO(1-0) and 13CO(2-1) lines using NRAO-12 m and 12CO(3-2), 13CO(3-2) lines using CSO-10 m telescopes, respectively. Observations suggest steep north-south (direction with respect to the offset position (0, 0)) temperature gradient in the cloud. These are likely to be caused by non-uniform, Inter Stellar Radiation Field (ISRF) illumination due to the shadow of nearby L134 cloud complex. As the emission of radiation depends on local properties like density and kinetic temperature, the present study attempts to deduce the irradiation contrast (and the resulting temperature difference) using 1D Monte Carlo radiative transfer code RATRAN. The model results accord with the observed data and shows a temperature difference of ∼7 K mainly within the cloud envelope. This results in a non-uniform intensity distribution of both CO and its species.