Oral Presentation

Imaging the event-horizon-scale structure of Sgr A* with sparse modeling

Author(s): Kazuki Kuramochi (The University of Tokyo/NAOJ), Kazunori Akiyama (MIT), Hung-Yi Pu, Keiichi Asada (ASSIA), Shiro Ikeda (The Institute of Statistical Mathematics), Fumie Tazaki, Mareki Honnma (NAOJ)

Presenter: Mareki Honma (Mizusawa VLBI Observatory, NAOJ)

The super-massive black hole Sgr A* residing the center of our Milkey way galaxy exhibits the largest apparent angular size in the Universe. Sgr A* provides an excellent opportunity to image the immediate vicinity of the event horizon with the Event Horizon Telescope (EHT). Two important issues have remained for imaging the silhouette of Sgr A*. First, its size is comparable to the diffraction limit of EHT, requiring a super-resolution imaging. This issue can be resolved with LASSO, a technique of the sparse modeling, providing a good fidelity image even in a super-resolution regime (Honma et al. 2014). Another issue is the interstellar scattering effect caused by the tenuous interstellar plasma in our line of sight that scatters radio waves from Sgr A*. It blurs an interferometric image and reduces its effective resolution. We present realistic simulated observations of Sgr A* with EHT including the interstellar effect. We found that LASSO can overcome also the effect of interstellar scattering, making it promising to image Sgr A*.