Study on astrophysical masers in the era of SKA/SKA-VLBI

Astrophysical masers are a unique probe of rapid transition phases of stellar evolution such as birth of stars, evolution of hyper and ultra-compact HII regions, long-period stellar pulsation with copious mass loss in their final evolution, and death of stars exhibiting preplanetary and planetary nebulae. They are also a important probe of the structures and the dynamics of the nearby galaxies such as the Milky Way, Magellanic Clouds, and external galaxies hosting starbursts and Keplerian disks around super massive blackholes. The probe uniqueness of the astrophysical maser is attributed to their compactness that enables
us to conduct high precision astrometry and trigonometry and a wide variety of their patio-kinematics tracing the individual phases of the events for short periods. The present radio interferometers and VLBI networks are challenging to yield trigonometry over a distance of 10 kpc and tracing the evolutionary events lasting for only decades or episodic events as short as a few days. Some of the projects focus their science targets to cosmology and general relativity.

In my colloquium talk, out of the introduction topics mentioned above, I will focus my talk on trigonometry of maser sources yielded with the Square Kilometre Array (SKA) Phase 1. This is one of the science cases that have been planned as Japanese scientific contributions to SKA1. Its key issue is the scientific and technical feasibility in the low frequency band, corresponding to SKA1-MID Band 2 around 1.6 GHz, in which atmospheric effects on the astrometry should be carefully considered. Our VLBI demonstration of the trigonometry for 1.6 GHz circumstellar maser sources has been reported in Orosz et al. (2017).
I hope to discuss a plan of systematic trigonometry with SKA-VLBI for the circumstellar maser sources in the Galactic bulge, which is accessible only in radio and infrared astrometry and a unique field for the dynamics of the Milky Way.

19/03/2020 - 12:30
Dr. Prof Hiroshi Imai
Universidad de Kagoshima, Japon