Stringent upper limits to the solid NH₃ abundance towards W 33A from near-IR spectroscopy with the Very Large Telescope^*

¹ Raymond and Beverly Sackler Laboratory for Astrophysics, Leiden Observatory, PO Box 9513, 2300 RA Leiden, The Netherlands
² Leiden Observatory, PO Box 9513, 2300 RA Leiden, The Netherlands

Corresponding author: W. A. Schutte, schutte@strw.leidenuniv.nl

Received: 19 September 2002
Accepted: 14 November 2002

Abstract

We obtained near-infrared spectroscopy of the high mass young stellar object W 33A between 1.9–2.5 μm in search of absorption features of circumstellar ices. The 2.27 μm band of is positively identified in the spectrum, its intensity being fully consistent with the column density derived earlier from the methanol bands at 3.54 and 3.91 μm. The 2.21 μm band of solid , on the other hand, was not detected. This shows that the quantity of solid towards W 33A is at least 3 times lower than earlier estimates based on the umbrella mode at 9 μm.