Letter to the Editor

Astrochemical confirmation of the rapid evolution of massive YSOs and explanation for the inferred ages of hot cores

¹ Department of Physics and Astronomy, Denison University, Granville, OH, 43023, USA e-mail: doty@denison.edu
² Sterrewacht Leiden, PO Box 9513, 2300 RA Leiden, The Netherlands
³ Department of Astronomy, University of Florida, PO Box 112055, Gainesville, FL, 32611, USA

Received: 30 March 2006
Accepted: 8 May 2006

Abstract

Aims. To understand the roles of infall and protostellar evolution on the envelopes of massive young stellar objects (YSOs).

Methods. The chemical evolution of gas and dust is traced, including infall and realistic source evolution. The temperatures are determined self-consistently. Both ad/desorption of ices using recent laboratory temperature-programmed-desorption measurements are included.

Results. The observed water abundance jump near 100 K is reproduced by an evaporation front which moves outward as the luminosity increases. Ion-molecule reactions produce water below 100 K. The age of the source is constrained to yrs since YSO formation. It is shown that the chemical age-dating of hot cores at ~–10⁴ yr and the disappearance of hot cores on a timescale of ~10⁵ yr is a natural consequence of infall in a dynamic envelope and protostellar evolution. Dynamical structures of ~ such as disks should contain most of the complex second generation species. The assumed order of desorption kinetics does not affect these results.