18 OTTOBRE 2022 ore 15:00

Sub-millimeter H2O masers and dense molecular gas in nearby active nuclei

Prof. Dr. Yoshiaki Hagiwara (Toyo University, Giappone)
Sub-millimeter H2O masers and dense molecular gas in nearby active nuclei

Extragalactic 22 GHz H2O masers have been found in active galactic nuclei (AGN) and they are known to be a powerful tool for tracing a sub-parsec-scale disc, outflow, or some other kinematics around the active nucleus. In contrast, the properties of extragalactic (sub-)millimeter H2O masers have not yet been well studied to date, and so it is important to address them using (sub-)millimeter telescopes such as ALMA or APEX.

I will present the recent results of ALMA observations of sub-millimeter H2O masers toward the two nearby active galactic nuclei, NGC 4945 and Circinus galaxy, along with single-dish monitoring results of 22 GHz H2O maser at Tidbinbilla.

If time permits, the nature of well-known off-nuclear maser in the type 2 Seyfert galaxy NGC1068 will be discussed in comparison with the existing data from radio interferometry. Molecular lines of HCN and HCO+ were found at the location of the off-nuclear maser emission, providing information such as velocity fields and physical conditions of the dense molecular gases, which could help understand a total picture of the puzzling nuclear region of the galaxy.


Breve CV del Prof. Dr. Yoshiaki Hagiwara:

Prof. Yoshiaki Hagiwara (“Hagi”) is originally from Tokyo. He completed his PhD on the study of molecular gas in active galactic nuclei (AGN) using Nobeyama Millimeter Array (NMA) and the 45 m radio telescope at the Graduate University for Advanced Studies (SOKENDAI). He then spent about 5.5 years at Max-Planck Institute for radio astronomy (MPIfR) in Bonn, Germany and the Netherlands Institute for Radio Astronomy (ASTRON) in Dwingeloo, Netherlands as a postdoctoral fellow. And then he spent 2 years as a postdoctoral fellow and 8 years as an assistant professor at the National Astronomical Observatory of Japan (NAOJ) at Mitaka, Japan, where he supported the Space-VLBI project that was unfortunately canceled and later the commissioning of east-Asian VLBI. Since 2015, he moved to Toyo University, Tokyo in Japan. He is currently leading some efforts of the instrumentation of the front-end system and the commissioning and early science results for the VLBI Exploration of Radio Astrometry (VERA) of NAOJ, which aims to map out the magnetic fields in jets in AGN, star-forming regions, and late type stars using “ultra-wide" band recording to detect the weaker magnetic fields. He truly loves VLBI, which connects the hearts and minds of people around the world. He thinks that the global cooperative spirit cultivated by VLB scientists can solve the difficulties the world is currently experiencing. People may say he is a dreamer but he believes that he is not the only one.