(Proposal ID) S13A-014

(PI) Nishiyama, Shogo

(Proposal Title)
A Celestial Show of the Century: Gas Cloud Accretion onto the SMBH Sgr A*

(Abstract)
A dense gas cloud, which is rapidly approaching the Galactic supermassive 
black hole (SMBH) Sgr A*, was discovered recently. In mid-2013, the cloud will 
be ~ 3,100 Schwarzschild radii from the SMBH at the pericenter of its 
eccentric orbit, and is predicted to interact with the accretion flow around 
the SMBH. Although it is very uncertain what will happen at the time of the 
cloud's pericentric passage, this event may presents a unique opportunity, 
that may never come again, to study the dynamics and properties of hot gas in 
the vicinity of the SMBH, and gas accretion onto it. From simulations, sudden 
increase of accretion rate onto the SMBH, and subsequent strong surge of 
emission from Sgr A* are expected. So we will carry out daily monitoring 
observations of Sgr A* in near-infrared and radio wavelengths, and we propose 
quick follow-up observations with Subaru, just after the beginning of the 
accretion event. Spectroscopic and imaging observations from 1.6 - 11 mu m 
will be conducted to understand processes responsible for near to mid-infrared 
emission during the accretion event. Using HiCIAO, polarimetric observations 
will be carried out to investigate the existence of jets/outflow which may be 
produced by the sudden mass accretion onto the SMBH.