Molecules in Bipolar Outflows

Abstract

Bipolar outflows constitute some of the best laboratories to study shock chemistry in the interstellar medium. A number of molecular species have their abundance enhanced by several orders of magnitude in the outflow gas, likely as a combined result of dust mantle disruption and high temperature gas chemistry, and therefore become sensitive indicators of the physical changes taking place in the shock. Identifying these species and understanding their chemical behavior is therefore of high interest both to chemical studies and to our understanding of the star-formation process. Here we review some of the recent progress in the study of the molecular composition of bipolar outflows, with emphasis in the tracers most relevant for shock chemistry. As we discuss, there has been rapid progress both in characterizing the molecular composition of certain outflows as well as in modeling the chemical processes likely involved. However, a number of limitations still affect our understanding of outflow chemistry. These include a very limited statistical approach in the observations and a dependence of the models on plane-parallel shocks, which cannot reproduce the observed wing morphology of the lines. We finish our contribution by discussing the chemistry of the so-called extremely high velocity component, which seems different from the rest of the outflow and may originate in the wind from the very vicinity of the protostar.

15 pages, 7 figures. Contribution to the IAU Conference "The Molecular Universe" held in Toledo in June 2011

References in corpus (11)

• Testing grain-surface chemistry in massive hot-core regions
• Water in Star-Forming Regions with the Herschel Space Observatory (WISH): Overview of key program and first results
• A molecular survey of outflow gas: velocity-dependent shock chemistry and the peculiar composition of the EHV gas
• Quasi-classical rate coefficient calculations for the rotational (de)excitation of H2O by H2
• Spitzer observations of HH54 and HH7-11: mapping the H2 ortho-to-para ratio in shocked molecular gas
• The CHESS chemical Herschel surveys of star forming regions: Peering into the protostellar shock L1157-B1. I. Shock chemical complexity
• Warm SiO gas in molecular bullets associated with protostellar outflows
• The clumpy structure of the chemically active L1157 outflow
• Spitzer spectral line mapping of protostellar outflows: II H2 emission in L1157
• Water in low-mass star-forming regions with Herschel (WISH-LM): High-velocity H2O bullets in L1448-MM observed with HIFI
• SWAS Observations of Water in Molecular Outflows

Cited by in corpus (5)

• High-pressure, low-abundance water in bipolar outflows. Results from a Herschel-WISH survey
• H2O line mapping at high spatial and spectral resolution - Herschel observations of the VLA1623 outflow
• HD101584: Circumstellar characteristics and evolutionary status
• HH 114 MMS: a new chemically active outflow
• Interstellar Complex Organic Molecules in SiO-traced massive outflows