Chemical signatures of shocks in hot cores

¹ Department of Physics and Astronomy, University College London, London WC1E 6BT, UK
² Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy
³ Department of Physics and Astronomy, University of Leeds, Leeds, LS2 9JT, UK

Corresponding author: S. Viti, sv@star.ucl.ac.uk

Received: 4 August 1999
Accepted: 26 February 2001

Abstract

The characteristic chemistry of hot cores arises from the abrupt evaporation of icy mantles when a massive star begins to irradiate the interstellar gas in its vicinity. Such stars are also likely to generate powerful winds which may initiate shocks in the same interstellar gas. In this paper, we consider whether chemical signatures of the passage of a shock through a hot core can be identified. We find that if hydrogenation occurs on surfaces and freeze-out of heavy gas-phase atoms and molecules is complete before the hot core is established then no such chemical signature exists. However, if some residual material is present in the gas when the hot core is established then the following molecular abundance ratios are significantly affected by the presence of a shock: NS/CS, SO/CS, and HCO/H₂CO. This result is more evident if injection of ices into the gas occurs over a finite period, rather than instantaneously. We conclude that these molecular abundance ratios may be useful tracers of the dynamical history of hot cores, and that follow-up observational studies are required.