# Trigonometric Parallaxes of 6.7 GHz Methanol Masers

## TL;DR

This study uses VLBI observations of 6.7 GHz methanol masers to measure precise parallaxes and distances to five star-forming regions, improving our understanding of Galactic structure and motions.

## Contribution

It provides high-precision trigonometric parallaxes for five star-forming regions using methanol masers, with accuracies as good as 22 microarcseconds, advancing Galactic distance measurements.

## Key findings

- Distances to five regions are precisely measured.
- Regions lag Galactic rotation by ~17 km/s.
- Method achieves parallax accuracy of ~22 microarcseconds.

## Abstract

Emission from the 6.7 GHz methanol maser transition is very strong, is relatively stable, has small internal motions, and is observed toward numerous massive star-forming regions in the Galaxy. Our goal is to perform high-precision astrometry using this maser transition to obtain accurate distances to their host regions. Eight strong masers were observed during five epochs of VLBI observations with the European VLBI Network between 2006 June, and 2008 March. We report trigonometric parallaxes for five star-forming regions, with accuracies as good as $\sim22 \mathrm{\mu}$as. Distances to these sources are $2.57^{+0.34}_{-0.27}$ kpc for ON 1, $0.776^{+0.104}_{-0.083}$ kpc for L 1206, $0.929^{+0.034}_{-0.033}$ kpc for L 1287, $2.38^{+0.13}_{-0.12}$ kpc for NGC 281-W, and $1.59^{+0.07}_{-0.06}$ kpc for S 255. The distances and proper motions yield the full space motions of the star-forming regions hosting the masers, and we find that these regions lag circular rotation on average by $\sim$17 km s$^{-1}$, a value comparable to those found recently by similar studies.