2015ApJ...814...31K

We present observations of HDCO and H₂ CO emission toward a sample of 15 Class 0 protostars in the Orion A and B clouds. Of these, 11 protostars are Herschel-identified PACS Bright Red Sources (PBRSs) and 4 are previously identified protostars. Our observations revealed the chemical properties of the PBRS envelope for the first time. The column densities of HDCO and H₂CO are derived from single-dish observations at an angular resolution of ∼20" (∼8400 AU). The degree of deuteration in H₂CO ([HDCO]/[H₂CO]) was estimated to range from 0.03 to 0.31. The deuterium fractionation of most PBRSs (70%) is similar to that of the non-PBRS sources. Three PBRSs (30%) exhibit high deuterium fractionation, larger than 0.15. The large variation of the deuterium fractionation of H₂CO in the whole PBRS sample may reflect the diversity in the initial conditions of star-forming cores. There is no clear correlation between the [HDCO]/[H₂CO] ratio and the evolutionary sequence of protostars. ApJ98444\subject_ section 029 Current Universe