The origin of the molecular emission around the southern hemisphere Re 4 IRS – HH 188 region
Institut de Ciències de l'Espai (CSIC- IEEC), Campus UAB – Facultat de Ciències, Torre C5 – parell 2, 08193 Bellaterra, Catalunya, Spain e-mail: email@example.com
2 Department of Physics and Astronomy, University College London, London WC1E 6BT, UK
Accepted: 10 May 2007
Aims.We present SEST observations of the molecular environment ahead of the southern Herbig-Haro object 188 (HH 188), associated with the low-mass protostar Re 4 IRS. We have also used the SuperCosmos Hα survey to search for Hα emission associated with the Re 4 IRS – HH 188 region. The aim of the present work is to study the properties of the molecular gas and to better characterize this southern star forming region.
Methods.We mapped the HCO+ 3–2 and H13CO+ 1–0 emission around the YSO and took spectra of the CH3OH 20–10 A+ and 2-1–1-1 E and SO 65–54 towards the central source. Column densities are derived and different scenarios are considered to explain the origin of the molecular emission.
Results.HCO+ arises from a relatively compact region around the YSO; however, its peak emission is displaced to the south following the outflow direction. Our chemical analysis indicates that a plausible scenario is that most of the emission arises from the cold, illuminated dense gas ahead of the HH 188 object. We have also found that HH 188, a high excitation object, seems to be part of a parsec scale and highly collimated HH system. Re 4 IRS is probably a binary protostellar system, in the late Class 0 or Class I phase. One of the protostars, invisible in the near-IR, seems to power the HH 188 system.
Key words: ISM: individual objects: HH 188 / ISM: abundances / ISM: clouds / ISM: molecules / radio lines: ISM / stars: formation
© ESO, 2007