# A multi-transition molecular line study of candidate massive young stellar objects associated with methanol masers

## TL;DR

This study investigates the molecular environments of candidate massive young stellar objects associated with methanol masers using multi-transition line observations, revealing outflows and diverse kinematic regimes.

## Contribution

It provides new insights into the physical conditions and kinematic environments of MYSOs signposted by methanol masers through multi-line molecular observations.

## Key findings

- 64% of sources show molecular outflows
- Methanol masers trace diverse kinematic regimes
- Physical conditions refined for maser models

## Abstract

We characterize the molecular environment of candidate massive young stellar objects (MYSOs) signposted by methanol masers. Single pixel observations of 10 transitions of HCO^+, CO and CS isotopomers were carried out, using the IRAM 30m telescope. We studied a sample of 28 targets for which the 6.7GHz maser emission positions are known with a sub-arcsecond accuracy. The systemic velocity inferred from the optically thin lines agrees within 3km/s with the central velocity of the maser emission for most of the sources. About 64% of the sources show line wings in one or more transitions of CO, HCO^+ and CS species, indicating the presence of molecular outflows. Comparison of the widths of line wings and methanol maser emission suggests that the 6.7GHz maser line traces the environment of MYSO of various kinematic regimes. Therefore conditions conducive for the methanol maser can exist in the inner parts of molecular clouds or circumstellar discs as well as in the outer parts associated with molecular outflows. Calculations of the physical conditions based on the CO and HCO^+ lines and the CS line intensity ratios refine the input parameters for maser models.