Print Recently, a joint research team from National Time Service Center (NTSC) of the Chinese Academy of Sciences, Shanghai Astronomical Observatory (SHAO) of the Chinese Academy of Sciences and SKA Observatory searched 155 northern star forming regions for 4.7 GHz OH masers and discovered 8 new sources.
The research result was published in the Astrophysical Journal on April 1.
OH Masers are usually detected towards high-mass star formation regions (8 times the mass of the Sun). “Observing OH masers at different transitions in the same maser site could place strong constraints on the in-situ physical conditions, such as H2 density, temperature and velocity gradients”, said associated Professor Qiao Haihua.
In this work, the research team used the Shanghai Tianma Radio Telescope to search for 4.7 GHz OH masers in 155 star formation regions. They investigated the associations between the 18 detected 4.7 GHz OH masers with ground-state OH masers near 1.7 GHz, 6.7 GHz methanol masers and 22 GHz water masers.
They found that the presence of 1665 MHz OH masers is a better indicator of the presence of 4.7 GHz OH masers than 1720 MHz OH masers. They also found that the majority of the 4.7 GHz OH masers are associated with 6.7 GHz methanol and / or 22 GHz water masers.
The formation process of high-mass stars is a fundamental and hot topic in astrophysics. Observations of high-mass star formation processes are hindered by their large distances, high extinction and the short timescales of critical evolutionary phases. However, OH maser emission arises at radio frequency and is not affected by the dense optical-obscuring gas and dust, which exists at the early stages of high-mass star formation. Thus, we could use OH masers to probe high-mass stars at the earliest stages.
CONTACT:
XIONG Tiantian
National Time Service Center, CAS