Water Maser Kinematics in RCW142

The Mizusawa VLBI Observatory in Japan, one of the stations in KaVA. Image credit: National Astronomical Observatory of Japan

High-mass star formation is thought to be different to low-mass star formation, mainly in the way high-mass young stellar objects accrete mass in the presence of strong radiation pressure and gravitational instability due to conservation of angular momentum. Episodic outflows may give a clue to the accretion process, but observations of such events in protostars are difficult due to the dense environments they reside in, their rarity, and the short timescales.

Masers, with their compact spatial nature and high brightness temperatures allow for accurate measurements of the spatio-kinematics of outflows in massive young stellar objects (MYSOs). Using VLBI, masers have been able to reveal various substructures such as bowshocks, accretion disks, helical jets, and hypercompact HII regions.

Methanol masers in RCW142. Image credit: (Fujisawa et al., 2014)

In this project, we are using the KaVA (KVN and VERA Array) to observe the water masers in the high-mass star-forming region RCW142. RCW142 is an MYSO with a unique two-phase nature; a young accretion disk signature plus a late stage weak HII region. Both methanol and hydroxyl masers have been observed in the source, and a constant increase in the methanol maser flux has been observed over the past 10 years under the iMet program (Yonekura et al., 2016). Kinematics of the water masers in RCW142 will be used to study the outflows in RCW142, and consequently the accretion process in high-mass star formation.

Monitoring of 6.7 GHz methanol maser flux in RCW142. Image credit: iMet

References

2016

  1. PASJ
    The Hitachi and Takahagi 32 m radio telescopes: Upgrade of the antennas from satellite communication to radio astronomy
    Yoshinori Yonekura, Yu Saito, Koichiro Sugiyama, Kang Lou Soon, Munetake Momose, and 30 more authors
    Publications of the Astronomical Society of Japan, May 2016
    HTML

2014

  1. PASJ
    Observations of 6.7 GHz methanol masers with East-Asian VLBI Network. I. VLBI images of the first epoch of observations
    Kenta Fujisawa, Koichiro Sugiyama, Kazuhito Motogi, Kazuya Hachisuka, Yoshinori Yonekura, and 24 more authors
    Publications of the Astronomical Society of Japan, Apr 2014
    HTML