APEX Millimeter Observations of Methanol Emission Toward High-mass Star-forming Cores
Artikel i vetenskaplig tidskrift, 2019

We present 247 GHz molecular line observations of methanol (CH3OH) toward 16 massive star-forming regions using the APEX telescope with an angular resolution of 25 ''. The sample covers a range of evolutionary states, including warm molecular cores (WMCs), hot molecular cores, and ultracompact H II regions. The hot cores, all of which include UC H II regions, show rich molecular line spectra, although the strength of different species and transitions varies from source to source. In contrast, the warm cores do not show significant molecular line emission. Multiple methanol transitions are detected toward nine of the hot cores; eight of these had enough transitions to use the rotation diagram method to estimate rotational temperatures and column densities. The temperatures lie in the range of 104-190 K and column densities from 3 x 10(16) to 7 x 10(18) cm(-2). Using the average methanol line parameters, we estimate virial masses, which fall in the range from 145 to 720 M-circle dot and proved to be significantly higher than the measured gas masses. We discuss possible scenarios to explain the chemical differences between hot cores and WMCs. One of the observed methanol lines, 4(2)-5(1)A(+) at 247.228 GHz, is predicted to show Class II maser emission, similar in intensity to previously reported J(0)-J(-1)E masers at 157 GHz. We did not find any clear evidence for maser emission among the observed sources, however, a weak maser in this line may exist in G345.01+1.79.

stars: protostars

stars: formation

ISM: molecules

masers

stars: massive

Författare

Vicente Hernandez-Hernandez

Universidad Nacional Autonoma de Mexico

Consejo Quintanarroense Ciencia & Tecnol

Stan Kurtz

Universidad Nacional Autonoma de Mexico

Sergei Kalenskii

Russian Academy of Sciences

Polina Golysheva

Russian Academy of Sciences

Moscow State University

Guido Garay

Universidad de Chile (UCH)

Luis Zapata

Universidad Nacional Autonoma de Mexico

Per Bergman

Chalmers, Rymd-, geo- och miljövetenskap, Onsala rymdobservatorium

Astronomical Journal

0004-6256 (ISSN) 1538-3881 (eISSN)

Vol. 158 1 18

Ämneskategorier

Astronomi, astrofysik och kosmologi

DOI

10.3847/1538-3881/ab2047

Mer information

Senast uppdaterat

2019-08-26