Water and methanol ice in L 1544^★

¹ Universitäts-Sternwarte München, Ludwig-Maximilians-Universität, Scheinerstr. 1, 81679 München, Germany
² Ural Federal University, 620002, 19 Mira street, Yekaterinburg, Russia
e-mail: anton@urfu.ru
³ Visiting Leading Researcher, Ventspils International Radio Astronomy Center, Inženieru 101, 3601 Ventspils, Latvia
⁴ Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrasse 1, 85748 Garching, Germany
⁵ Centro de Astrobiología, Instituto Nacional de Técnica Aeroespacial Ctra de Torrejón a Ajalvir, km 4 28850 Torrejón de Ardoz, Madrid, Spain
⁶ Universidad Nacional, Autonóma de México Km 107 Carretera Tijuana-Ensenada 22870 Ensenada, BC, Mexico
⁷ Universität Wien, Department of Astrophysics Türkenschanzstraße 17 (Sternwarte), 1180 Wien, Austria

Received: 26 July 2019
Accepted: 8 December 2020

Abstract

Context. Methanol and complex organic molecules have been found in cold starless cores, where a standard warm-up scenario would not work because of the absence of heat sources. A recent chemical model attributed the presence of methanol and large organics to the efficient chemical desorption and a class of neutral-neutral reactions that proceed fast at low temperatures in the gas phase.

Aims. The model calls for a high abundance of methanol ice at the edge of the CO freeze-out zone in cold cloud cores.

Methods. We performed medium-resolution spectroscopy toward three field stars behind the starless core L 1544 at 3 μm to constrain the methanol ice abundance and compare it with the model predictions.

Results. One of the field stars shows a methanol ice abundance of 11% with respect to water ice. This is higher than the typical methanol abundance previously found in cold cloud cores (4%), but is 4.5 times lower than predicted. The reason for the disagreement between the observations and the model calculations is not yet understood.