The nature of the methanol maser ring G23.657-00.127
I. The distance through trigonometric parallax measurements
Toruń Centre for Astronomy, Nicolaus Copernicus University, Gagarina 11, 87-100 Toruń, Poland e-mail: [annan;msz]@astro.uni.torun.pl
2 Max-Planck-Insitut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany e-mail: firstname.lastname@example.org
3 Joint Institute for VLBI in Europe, Postbus 2, 7990 AA Dwingeloo, The Netherlands e-mail: email@example.com
4 Sterrewacht Leiden, Leiden University, Postbus 9513, 2300 RA Leiden, The Netherlands
5 Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA e-mail: firstname.lastname@example.org
Accepted: 10 September 2008
Context. Methanol masers are associated with young high-mass stars and are an important tool for investigating the process of massive star formation.
Aims. The recently discovered methanol maser ring in G23.657-00.127 provides an excellent “laboratory” for a detailed study of the nature and physical origin of methanol maser emission, as well as parallax and proper motion measurements.
Methods. Multi-epoch observations of the 12.2 GHz methanol maser line from the ring were conducted using the Very Long Baseline Array. Interferometric observations with milliarcsecond resolution enabled us to track single maser spots in great detail over a period of 2 years.
Results. We have determined the trigonometric parallax of G23.657-00.127 to be 0.313 ± 0.039 mas, giving a distance of kpc. The proper motion of the source indicates that it is moving with the same circular velocity as the LSR, but it shows a large peculiar motion of ≈35 km s-1 toward the Galactic center.
Key words: stars: formation / ISM: molecules / instrumentation: high angular resolution / astrometry / masers
© ESO, 2008