令和7年度第11回STPPセミナー
令和7年度第11回STPPセミナー
2025/06/30
発表者:大家 寛 (スタッフ)
発表タイトル:
日) 中心性極端２重星型超巨大ブラックホールのJet 形成機構―M87銀河の場合
英) Mechanism of the Jet Formation due to Extreme Central Binary of Super Massive Black Hole -The case M87 galaxy
要旨:
日) 中心性極端２重星型超巨大ブラックホールのJet 形成機構―M87銀河の場合
宇宙における活動銀河核（AGN）に関するJet形成の研究史に於いて、基本的概念は単独の超巨大BHの自転とそのエネルギーが発生源とされてきた。本研究は天の川銀河中心BHが中心性極端２重星型超巨大BH（ECB-SMBH）であるとの観測結果（2019, http://hdl.handle.net/10097/00126480）を出発点として、M87*においても、観測電波像、（Miyoshi et al, (2022), ApJ, 933,36 及び Lu et al. (2023),Nature, 616, 686)からECB-SMBHの存在を結論して来た（Oya,2024, doi. 10.33140/ATCP.07.02.11）。それは、42億倍（M87*-A）と22億倍（M87*-B）太陽質量を持つSMBHより成り、周期133.8日で周回し合っていて、M87*-Bは半径9.67ｘ10E15 cmの軌道を速度0.16cで運航し、伴う降着円盤の外縁となる進行フロント領域には0.8cで運航しているバイナリーの共 通降着円盤を追いかける形で衝撃波を形成する。M87*-Bの降着円盤は中心BHの強い重力に平衡すべく亜光速で回転するプラズマが強力なトロイダル磁場と共存しているが、形成される衝撃波フロントでは磁力線凝縮により局所的に強められていて、衝撃波に接するバイナリー共通降着円盤領域に衝撃波通過時間に対応する鋭い誘導電場を励起する。その結果、接する共通降着円盤側の一帯からイオンが主導する形でプラズマが噴射される。
噴射されたプラズマはJetを形成するが以下の3段階の変遷を経た後Jet状態を終え。最終的に宇宙空間に拡散して行く。第一段階では、噴射プラズマは発射点の軌道運行速度成分を保持したまま同時に垂直速度成分を得て、斜め方向に直線放射運動を初めるが、観測されるJetは発射源座標の円軌道を反映し、半径が時間経過に比例して拡大するスパイラルとして観測される。以降第2段階に入るが、Jet の形態は静的平衡ではなく、Jetを構成するイオン流に主導されて起こるプラズマ中電流を主体に、発生する局所磁場と、ローレンツ力を擁する電磁力を主体とする動的平衡状態によってJet形態が結果している。具体的には円筒形Jetの半径方向の運動が抑圧され振動状態を経て、停止方向に向かう一方、円筒周辺方向への運動開始と、Jet軸方向への加速が顕著になる。M87―Jetが円筒型で周縁からの電磁波放射が卓越している現象が説明されると共に、最も特徴は円筒形Jet軸に鋭角方向に形どられる縞模様がこのバイナリーJet論では自然に説明される。即ちの縞模様の間隔がECB-SMBHの公転周期134日を直接反映している事が確認され、これは従来のJet形成論で見られるプラズマ不安定論を否定するものとなる。 第３段階ではらせん状に運動するイオン主導プラズマはらせん状磁場を形成しForce Free 状態に入り、Jet の長期にわたる動的平衡状態を得ている。
Jet 観測の主要手段である電波放射について、大方はシンクロトロン放射機構を信じ結論しているがJetの磁場観測は非常に遅れていて、プラズマ密度と共に放射電波強度とスペクトルの定量的評価は先送りになっている。こうした中で本研究は特殊相対論下で起こる高速電子と非常に広くMHz帯からX線に至るまでの周波数帯でのプラズマ波動との特殊共鳴現象に着目し、実際にJetからの電磁波放射の有力候補の可能性を考慮しつつ、究明を開始している。
英) The current of this study started from the observations of decameter radio wave pulses at 21.86 MHz to detect spins of the supermassive black hole from Sgr A* at the center of Milky way galaxy , using Tohoku University long baseline interferometer system. The results of data analyses indicated （2019, http://hdl.handle.net/10097/00126480）that there exists the extreme central binary of super massive black hole (ECB-SMBH) orbiting with a period of 2200±50 sec ; the member of binary consists of Gaa with mass of 2.2 million solar mass and Gab with 1.9 million solar mass moving with velocities of 0.18 c and 0.21 c, respectively. The existence of ECB-SMBH necessarily requires the negation of the generation of the gravitational waves (NGW) from the SMBH; the negation is theoretically proposed (https://doi.org/10.33140/EESRR.06.01.01) also in the current of this study. The confirmation of the negation of gravitational waves from ECB-SMBH is, however, mandatory subject to continue the present study.
One of unexpected chance to confirm NGW-SMBH arrived by presentations of two radio wave source images of the center of the elliptic galaxy M87 presented by Miyoshi et al. (2022, ApJ, 933,36) and Lu. et al. (2023,Nature, 616, 686) from which the existence of ECB-SMBH for M87* is concluded by this current study(Oya,2024, doi. 10.33140/ATCP.07.02.11). That is, the subject of confirmation of NGW frrom the SMBH becomes equivalent to the confirmation of the existence of ECB-SMBH at M87*, because imagined merging moment would occur within 9 years, if we apply the regular concept of the generation of the gravitational waves from the binary of BH to the proposed M87*, ECB-SMBH. Because no remarkable activity to proceed the confirmation of the existence of ECB-SMBH at M87* yet, then, we started to investigate the possible effects of ECB-SMBH on the M87 jet focusing on the differences between traditional case of single SMBH assumption.
In this binary origin theory of M87 jet formation, the starting point of jet is located at the shock front region of minor member of M87 ECB-SMBH, M87*-B which has 2.2 billion solar mass orbiting with period of 133.8 d with velocity of 0.16c associated with wide accretion disc that is associated with intense toroidal magnetic fields. Because of the movement of M87*-B with velocity higher than 0.8c of moving velocity of M87*-A , and its accreting disc, the shock wave is formed at the front edge region of the disc. Consequently, strong pulsative electric fields are induced, in the common accreting disc contacting to the moving shock front region due to pulsating passage of compressed intense magnetic fields; by this shock wave associated pulse electric fields then, the ions which become main material of the jet are launched upwards keeping the intrinsic orbital velocity in horizontal direction, together with electrons. In details, electrons which are started towards opposite direction in the initial moment are eventually forced to run with ions being leaded in the launched direction.
After being launched, motions of ions keep leading to control the dynamics and structure of the jet while electrons are slaved, even moving, with high velocities, around the steadily proceeding ions; therefore, we can assume the occurrence of electric current, even low rate, corresponding to the ion motions considering to slight delay of averaged transport positions of electrons because of the thermal dispersion of electron motions and trapping with locally generated electrostatic fields. By analyzing the dynamics of the jet neglecting thermal pressure as approximation , we verify three stages of dynamical balance phases of the jet. The first stage is the phase of radial expansion where ions associated with slight delaying electrons (ISDE) keep straight expansion following the direction of almost same with initial launching moment; the shapes of the jet can be observed as a rapidly expanding spiral. The second stage is the phase of transient where radial motion of ISDE gradually depressed with start of the oscillation while ISDEs start to take rotational movement in perpendicular direction to the jet axis together with acceleration of movement toward the jet axis; the most remarkable shape of jet feature in this phase is characterized by zebra like stripes whose repetition cycle of pattern from thin to thick feature clearly coincides with the orbital period ,134 d, of the binary whose accretion disc has role of the launcher of the jet. In addition to the zebra like stripe, we realize another oscillation that is harmonized with the period of zebra like stripe resulting the period of 5 to 8 times of the orbital period of the ECB-SMBH. The third stage is the phase of accomplishment of the long persisting jet before entering the ending phase where thermalization of jet motions become dominant ; the dynamics in the third stage is characterized by the force free situation controlled by helical motions of ions coupled with helical structure of the magnetic fields along the jet axis. The predicted plasma density distribution across the cylinder shaped jet corresponding to the force free situation reveals feature that are describable by Bessel functions which well coincide with the observed radio emission intensity across the cylinder of the jet.
Finally we investigated the possibility of the radiation mechanism of the well believed synchrotron radiation processes concerning electrons in the jet. It is clarified that magnetic fields intensity still on the way of research and we meet a situation that there is possibility of weaker magnetic field than 0.1~ 1 G . We propose then as alternative to synchrotron radiation mechanism; that is, we try to find coherent Cerenkov radiation mechanism that can only be possible to have resonance condition ,in the regime of the special relativity, finding specific coordinate transformation between wave propagating frame and frame of electron beams with extremely high velocity.