Exploring water chemistry in protostellar envelopes

Water is a key molecule in both the physics and chemistry of star-forming regions. The goal of the Herschel guaranteed time key program 'Water in star-forming regions with Herschel (WISH)' is to study water and chemically related species during protostellar evolution. One of the species that is most closely linked to water in the chemical network is hydroxyl (OH). A better understanding of the origin of the OH emission and the OH abundance therefore helps to constrain the different paths in the water chemistry network. In this talk I will present our results on protostellar OH emission from observations with the HIFI and PACS instruments on board the Herschel Space Observatory. Our findings indicate that the OH emission predominantly emerges from the outflow rather than the protostellar envelope and the derived OH/H2O abundance ratios are in agreement with the current picture of the water chemistry.