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Kino, M.,Takahara, F.,Hada, K.,Akiyama, K.,Nagai, H.,Sohn, B. W. IOP Publishing 2015 The Astrophysical journal Vol.803 No.1
<P>We explore the degree of magnetization at the jet base of M87 by using the observational data of the event horizon telescope (EHT) at 230 GHz obtained by Doeleman et al. By utilizing the method in Kino et al., we derive the energy densities of the magnetic fields (U-B) and electrons and positrons (U-+/-) in the compact region detected by EHT (the EHT region) with its FWHM size. 40 mu as. First, we assume that an optically thick region for synchrotron self-absorption (SSA) exists in the EHT. region. Then, we find that the SSA-thick region should not be too large, in order to. not. overproduce the Poynting power at the EHT. region. The allowed ranges of the angular size and the magnetic-field strength of the SSA-thick region are 21 mu as <= theta(thick) <= 26.3 mu as and 50 G <= B-tot <= 124 G, respectively. Correspondingly, U-B >> U-+/- is realized in this case. We further examine the composition of plasma and energy density of protons by utilizing the Faraday rotation measurement at 230 GHz obtained by Kuo et al. Then, we find that U-B >> U-+/- + U-p still holds in the SSA-thick region. Second, we examine the case when the EHT. region is fully SSA-thin. Then, we find that U-B >> U-+/- still holds unless protons are relativistic. Thus, we conclude that the magnetically driven jet scenario in M87 is viable in terms of energetics close to the Innermost Stable Circular Orbit scale unless the EHT. region is fully SSA-thin and relativistic protons dominated.</P>
Fossil Shell in 3C 84 as TeV<i>γ</i>-Ray Emitter and Cosmic-Ray Accelerator
Kino, M.,Ito, H.,Wajima, K.,Kawakatu, N.,Nagai, H.,Itoh, R. American Astronomical Society 2017 The Astrophysical journal Vol.843 No.2
<P>We explore physical properties of the shocked external medium (i. e., a shell) in 3C 84 associated with the recurrent radio lobe born around 1960. In the previous work of Ito et al., we investigated a dynamical and radiative evolution of such a shell after the central engine stops the jet launching, and we found that a fossil- shell emission overwhelms that of the rapidly fading radio lobe. We apply this model to 3C 84 and find the following.. (1) The fossil shell made of shocked diffuse ambient matter with the number density of 0.3 cm(-3) radiates bright inverseCompton (IC) emission with the seed photons of the radio emission from the central compact region and the IC emission is above the sensitivity threshold of the Cherenkov Telescope Array (CTA). (2) When the fossil shell is produced in a geometrically. thick ionized plasma with the number density of 10(3)cm(-3),. the field strength in the shell may reach about 17. mG in the presence of magnetic fields amplification and the radio emission becomes comparable to the sensitivity of deep imaging VLBI observations. The. possible production of ultra high-energy cosmic-rays (UHECRs) in the dense shocked plasma is also argued.</P>
KEY SCIENCE OBSERVATIONS OF AGNs WITH THE KaVA ARRAY
KINO, MOTOKI,NIINUMA, KOTARO,ZHAO, GUANG-YAO,SOHN, BONG WON The Korean Astronomical Society 2015 天文學論叢 Vol.30 No.2
KaVA (KVN and VERA Array) is a new combined VLBI array composed of KVN (Korean VLBI Network) and VERA (VLBI Exploration of Radio Astrometry). Here, we report the following two issues. (1) We review the initial results of imaging observations of M87 at 23 GHz following Niinuma et al. (2014). The KaVA images reveal extended outflows including complex substructures such as knots and limb-brightening, in agreement with previous VLBI observations. KaVA achieves a high dynamic range of ~1000, more than three times better than that achieved by VERA alone. (2) Based on subsequent observations and discussions led by the KaVA AGN SubWorking Group, we set monitoring observations of Sgr $A^{\ast}$ and M87 as our Key Science Project (hereafter KSP) because of the closeness and largeness of their central super-massive black holes. The main science goals of the KSP are (i) testing the magnetically-driven-jet paradigm by mapping velocity fields of the M87 jet, and (ii) obtaining tight constraints on physical properties of the radio emitting region in Sgr $A^{\ast}$. Towards KSP, we show the first preliminary images of M87 at 23 GHz and Sgr $A^{\ast}$ at 43 GHz with the bandwidth of 256 MHz.
Fossil shell emission in dying radio loud AGNs
Kino, M.,Ito, H.,Kawakatu, N.,Orienti, M.,Nagai, H.,Wajima, K.,Itoh, R. WILEY‐VCH Verlag 2016 Astronomische Nachrichten Vol.337 No.1
<P>We investigate shell emission associated with dying radio loud AGNs. First, based on our recent work by Ito et al. (2015), we describe the dynamical and spectral evolution of shells after stopping the jet energy injection. We find that the shell emission overwhelms that of the radio lobes soon after stopping the jet energy injection because fresh electrons are continuously supplied into the shell via the forward shock, while the radio lobes rapidly fade out without jet energy injection. We find that such fossil shells can be a new class of target sources for SKA telescope. Next, we apply the model to the nearby radio source 3C84. Then, we find that the fossil shell emission in 3C84 is less luminous in the radio band while it is bright in the TeV gamma-ray band and can be detectable by CTA. (C) 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim</P>