Journal Article

Chemistry of dense clumps near moving Herbig–Haro objects

H. Christie, S. Viti, D. A. Williams, J. M. Girart and O. Morata

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 416, issue 1, pages 288-293
Published in print September 2011 | ISSN: 0035-8711
Published online August 2011 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2011.19032.x
Chemistry of dense clumps near moving Herbig–Haro objects

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Localized regions of enhanced emission from HCO+, NH3 and other species near Herbig–Haro objects (HHOs) have been interpreted as arising in a photochemistry stimulated by the HHO radiation on high-density quiescent clumps in molecular clouds. Static models of this process have been successful in accounting for the variety of molecular species arising ahead of the jet; however, recent observations show that the enhanced molecular emission is widespread along the jet as well as ahead. Hence, a realistic model must take into account the movement of the radiation field past the clump. It was previously unclear as to whether the short interaction time between the clump and the HHO in a moving source model would allow molecules such as HCO+ to reach high enough levels, and to survive for long enough to be observed. In this work we model a moving radiation source that approaches and passes a clump. The chemical picture is qualitatively unchanged by the addition of the moving source, strengthening the idea that enhancements are due to evaporation of molecules from dust grains. In addition, in the case of several molecules, the enhanced emission regions are longer lived. Some photochemically induced species, including methanol, are expected to maintain high abundances for ∼104 yr.

Keywords: Herbig–Haro objects

Journal Article.  3958 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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