Very Large Array Ammonia Observations of the HH 111/HH 121 Protostellar System: A Detection of a New Source with a Peculiar Chemistry

Abstract

We present the results of Very Large Array NH₃ (J,K)=(1,1) and (2,2) observations of the HH 111/HH 121 protostellar system. HH 111, with a spectacular collimated optical jet, is one of the most well-known Herbig-Haro objects. We report the detection of a new source, NH₃-S, in the vicinity of HH 111/HH 121 (∼0.03 pc from the HH 111 jet source) in two epochs of the ammonia observations. This constitutes the first detection of this source, in a region that has been thoroughly covered previously by both continuum and spectral line interferometric observations. We study the kinematic and physical properties of HH 111 and the newly discovered NH₃-S. We also use HCO⁺ and HCN (J=4-3) data obtained with the James Clerk Maxwell Telescope and archival Atacama Large Millimeter/submillimeter Array ¹³CO, ¹²CO, and C¹⁸O (J=2-1), N₂D⁺ (J=3-2), and ¹³CS (J=5-4) data to gain insight into the nature of NH₃-S. The chemical structure of NH₃-S shows evidence for “selective freeze-out,” an inherent characteristic of dense cold cores. The inner part of NH₃-S shows subsonic nonthermal velocity dispersions indicating a “coherent core,” while they increase in the direction of the jets. Archival near- to far-infrared data show no indication of any embedded source in NH₃-S. The properties of NH₃-S and its location in the infrared dark cloud suggest that it is a starless core located in a turbulent medium, with the turbulence induced by Herbig-Haro jets and associated outflows. More data are needed to fully understand the physical and chemical properties of NH₃-S and if/how its evolution is affected by nearby jets.