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Powerful relativistic jets in active galactic nuclei (AGN) are believed to be originated from the accretion of material onto the supermassive black hole (SMBH)1. The nearby radio galaxy M87 is one of the best examples of this phenomenon, and the recent detection of a black-hole shadow with the Event Horizon Telescope provided compelling evidence for this paradigm2. However, whether the central SMBH in M87 has a spin or not, a fundamental parameter of a BH along with the mass, remains unconstrained by observations since the appearance of the photon ring is rather insensitive to the spin2-4. A clue to this challenge is to trace the long-term evolution of the innermost jet base where the central BH and accretion disk tightly regulate its flow dynamics. Here we report an extensive analysis of the morphological evolution of the M87 jet nozzle based on 170 high-resolution radio images spanning more than two decades. The ensemble of the data reveals a periodic (a period of 11 years) variation of the jet direction with a peak-to-peak amplitude of ~10 deg on the sky. A successful fit of a precession model to the data as well as general-relativistic magnetohydrodynamic simulations strongly supports the presence of a spinning BH in M87, inducing a Lense-Thirring precession of a misaligned accretion disk by the frame-dragging effect5. Our results suggest that jet precession with a spinning BH can commonly exist in other more distant AGN but had evaded detection due to the small magnitude and long period of position angle variation.

Because of its proximity and the large size of its black hole, M87 is one of the best targets for studying the launching mechanism of active galactic nucleus jets. Currently, magnetic fields are considered to be an essential factor in the launching and accelerating of the jet. However, current observational estimates of the magnetic field strength of the M87 jet are limited to the innermost part of the jet or to HST-1. No attempt has yet been made to measure the magnetic field strength in between. We aim to infer the magnetic field strength of the M87 jet out to a distance of several thousand $r_s$ by tracking the distance-dependent changes in the synchrotron spectrum of the jet from high-resolution very long baseline interferometry observations. In order to obtain high-quality spectral index maps, quasi-simultaneous observations at 22 and 43 GHz were conducted using the KVN and VERA Array (KaVA) and the VLBA. We compared the spectral index distributions obtained from the observations with a model and placed limits on the magnetic field strengths as a function of distance. The overall spectral morphology is broadly consistent over the course of these observations. The observed synchrotron spectrum rapidly steepens from $\alpha_{22-43 GHz}$ ~ -0.7 at ~ 2 mas to $\alpha_{22-43 GHz}$ ~ -2.5 at ~ 6 mas. A spectral index model in which nonthermal electron injections inside the jet decrease with distance can adequately reproduce the observed trend. This suggests the magnetic field strength of the jet at a distance of 2 - 10 mas (~ 900 $r_s$ - ~ 4500 $r_s$ in the deprojected distance) has a range of $B=(0.3 - 1.0 G)(z/2 mas)^{-0.73}$. Extrapolating to the EHT scale yields consistent results, suggesting that the majority of the magnetic flux of the jet near the black hole is preserved out to ~ 4500 $r_s$ without significant dissipation., Comment: 16 pages, 9 figures. Accepted for publication in Astronomy & Astrophysics

Full list of authors: Cho, Ilje; Zhao, Guang-Yao; Kawashima, Tomohisa; Kino, Motoki; Akiyama, Kazunori; Johnson, Michael D.; Issaoun, Sara; Moriyama, Kotaro; Cheng, Xiaopeng; Algaba, Juan-Carlos; Jung, Taehyun; Sohn, Bong Won; Krichbaum, Thomas P.; Wielgus, Maciek; Hada, Kazuhiro; Lu, Ru-Sen; Cui, Yuzhu; Sawada-Satoh, Satoko; Shen, Zhiqiang; Park, Jongho; Jiang, Wu; Ro, Hyunwook; Yi, Kunwoo; Wajima, Kiyoaki; Lee, Jee Won; Hodgson, Jeffrey; Tazaki, Fumie; Honma, Mareki; Niinuma, Kotaro; Trippe, Sascha; An, Tao; Zhang, Yingkang; Lee, Jeong Ae; Oh, Se-Jin; Byun, Do-Young; Lee, Sang-Sung; Kim, Jae-Young; Oh, Junghwan; Koyama, Shoko; Asada, Keiichi; Wang, Xuezheng; Cui, Lang; Hagiwara, Yoshiaki; Nakamura, Masanori; Takamura, Mieko; Hirota, Tomoya; Sugiyama, Koichiro; Kawaguchi, Noriyuki; Kobayashi, Hideyuki; Oyama, Tomoaki; Yonekura, Yoshinori; Kim, Jongsoo; Hwang, Ju-Yeon; Jung, Dong-Kyu; Kim, Hyo-Ryoung; Kim, Jeong-Sook; Oh, Chung-Sik; Roh, Duk-Gyoo; Yeom, Jae-Hwan; Xia, Bo; Zhong, Weiye; Li, Bin; Zhao, Rongbing; Wang, Jinqing; Liu, Qinghui; Chen, Zhong.--This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited., Sagittarius A* (Sgr A*), the Galactic Center supermassive black hole (SMBH), is one of the best targets in which to resolve the innermost region of an SMBH with very long baseline interferometry (VLBI). In this study, we have carried out observations toward Sgr A* at 1.349 cm (22.223 GHz) and 6.950 mm (43.135 GHz) with the East Asian VLBI Network, as a part of the multiwavelength campaign of the Event Horizon Telescope (EHT) in 2017 April. To mitigate scattering effects, the physically motivated scattering kernel model from Psaltis et al. (2018) and the scattering parameters from Johnson et al. (2018) have been applied. As a result, a single, symmetric Gaussian model well describes the intrinsic structure of Sgr A* at both wavelengths. From closure amplitudes, the major-axis sizes are ∼704 ± 102 μas (axial ratio ∼${1.19}_{-0.19}^{+0.24}$) and ∼300 ± 25 μas (axial ratio ∼1.28 ± 0.2) at 1.349 cm and 6.95 mm, respectively. Together with a quasi-simultaneous observation at 3.5 mm (86 GHz) by Issaoun et al. (2019), we show that the intrinsic size scales with observing wavelength as a power law, with an index ∼1.2 ± 0.2. Our results also provide estimates of the size and compact flux density at 1.3 mm, which can be incorporated into the analysis of the EHT observations. In terms of the origin of radio emission, we have compared the intrinsic structures with the accretion flow scenario, especially the radiatively inefficient accretion flow based on the Keplerian shell model. With this, we show that a nonthermal electron population is necessary to reproduce the source sizes. © 2022. The Author(s). Published by the American Astronomical Society., I.C. and J.P. are supported by the National Research Foundation of Korea (NRF) via a Global PhD Fellowship grant (NRF-2015H1A2A1033752 and NRF-2014H1A2A1018695, respectively). I.C. acknowledges financial support by the Spanish Ministerio de Economía y Competitividad (grants PID2019-108995GB-C21) and the Junta de Andalucía (grant P18-FR-1769). G.-Y.Z. and T.J. are supported by the Korea Research Fellowship Program through the NRF (NRF-2015H1D3A1066561). I.C. and G.-Y.Z. acknowledge financial support from the State Agency for Research of the Spanish MCIU through the "Center of Excellence Severo Ochoa" award to the Instituto de Astrofísica de Andalucía (SEV-2017-0709). K.A. is supported by the National Science Foundation (NSF) through grants AST-1440254, AST-1614868, and AST-2034306. This work is partially supported by JSPS KAKENHI grant Nos. JP18K03656 (M.K.), JP18H03721 (K.N., M.K., K.H.), JP18K13594 (T.K.), JP18KK0090 (K.H.), JP19H01943 (K.H.), JP21H01137 (K.H., M.K.), and the Mitsubishi Foundation grant No. 201911019 (K.H.). J.-C.A. acknowledges support from the Malaysian Fundamental Research grant Scheme (FRGS) FRGS/1/2019/STG02 /UM/02/6. M.D.J. acknowledges support from the National Science Foundation (AST-1716536, AST-1935980) and the Gordon and Betty Moore Foundation (GBMF-5278). X.-P.C. and B.-W.S. are supported by Brain Pool Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science and ICT (2019H1D3A1A01102564). R.-S.L. is supported by the Max Planck Partner Group of the MPG and the CAS and acknowledges the support by the Key Program of the National Natural Science Foundation of China (grant No. 11933007) and Research Program of Fundamental and Frontier Sciences, CAS (grant No. ZDBS-LY-SLH011). J.P. acknowledges financial support through the EACOA Fellowship awarded by the East Asia Core Observatories Association, which consists of the Academia Sinica Institute of Astronomy and Astrophysics, the National Astronomical Observatory of Japan, Center for Astronomical Mega-Science, Chinese Academy of Sciences, and the Korea Astronomy and Space Science Institute. S.T. acknowledges financial support from the NRF via Basic Research grant 2019R1F1A1059721. This work was also supported in part by MEXT SPIRE, MEXT as "Priority Issue on post-K computer" (Elucidation of the Fundamental Laws and Evolution of the Universe) and as "Program for Promoting Researches on the Supercomputer Fugaku" (High-energy astrophysical phenomena in black holes and supernovae). J.S.K. (grant Nos. 2016R1A5A1013277 and 2020R1A2C1007219) and J.O. (grant No. 2021R1A6A3A01086420) has been supported by the Basic Science Research Program through the NRF funded by the Ministry of Education.

Taki, K., Takamura, M., Sotani, H. and Wakusawa, R. Management of the Acid-Base Balance by the Red Blood Cell Carbonic Anhydrase (RCA). I. Correlation of the RCA Activity and Acid-Base Balance in the in Vitro and in Vivo Experiments. Tohoku J. exp. Med., 1983, 139 (4) 339-348 - Changes in RCA activity are known to affect the acid-base balance, but a clear relationship between RCA activity and acid-base balance has not yet been established. The relationship between RCA activity and acid-base balance was studied in tonometry with 4 mixed gases for 6-9hr, in healthy adults at rest, in halothane anesthesia and in hypothermia. RCA activity increases when pH and HCO3-/PCO2 ratio increase and PCO2 decreases in vitro. It also increases when pH and HCO3-/PCO2 ratio decrease and the range of PCO2 broadens in vivo. The relationship between RCA activity and the HCO3-/PCO2 ratio is a fan shape, because a change of the HCO3-/ PCO2 ratio precedes the change of RCA activity. Some factor which increases the RCA activity may be produced secondarily in the body under the influence of high PCO2. Probably the acid-base balance is corrected by reduction of the RCA activity in the case of alkalosis, and the acid-base balance may be corrected by an increase in RCA activity in the case of acidosis