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

Abstract

Listen

Translate article

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.