Contatto di riferimento: Marcello Giroletti
Abstract:
We present our new observational studies on the relativistic jet and accretion flow of M 87 with VLBA, EVN, and SMA. M87 is one of the nearest objects, possesses huge black hole mass of 6.6 times 10^9 M_sun. Therefore, it is the one of the primary targets for the imaging the shadow of the black hole with future submm VLBI. As we observe black hole as the shadow in the emitting region, understanding of the relativistic jet and accretion flow is one of the crucial information to extract physics from the shadow image. On the relativistic jet, we revealed that the jet is gradually accelerated from sub- to ultra relativistic speed (Asada et al. 2014, ApJL, 781, 2). Together with our studies on collimation property of the jet based on structural observation using VLBA, EVN and MERLIN (Nakamura & Asada, 2013, ApJ, 775, 118, Asada, K. & Nakamura, M. 2012, ApJL, 745, 28), we conclude that the M 87 jet can be well-explained in the framework of magneto-hydrodynamic (MHD) jets theory. On the accretion flow, we conducted SMA polarimetric observations towards M 87 in order to probe the property of the accretion flow of M87 (Kuo, KA et al. 2014, ApJL, 783, 33). We succeeded to derive an RM, which is an indicator of the column density, and estimated mass accretion rate onto the SMBH. Our estimated mass accretion rate is already two orders of magnitude smaller than that at the outer part of the accretion flow (~10^5 r_s). This significant suppression of the mass accretion rate at the inner region is expected with the radiatively inefficient accretion flow (RIAF) model.