Kim, Dawoon E.; Di Gesu, Laura; Liodakis, Ioannis and 133
Affiliation:
Abstract:
We conducted a polarimetry campaign from radio to X-ray wavelengths of the high-synchrotron-peak (HSP) blazar Mrk 421, including Imaging X-ray Polarimetry Explorer (IXPE) measurements on 2022 December 6-8. We detected X-ray polarization of Mrk 421 with a degree of ΠX=14±1% and an electric-vector position angle ψX=107±3∘ in the 2-8 keV band. From the time variability analysis, we find a significant episodic variation in ψX. During 7 months from the first IXPE pointing of Mrk 421 in 2022 May, ψX varied across the range of 0∘ to 180∘, while ΠX maintained similar values within ∼10-15%. Furthermore, a swing in ψX in 2022 June was accompanied by simultaneous spectral variations. The results of the multiwavelength polarimetry show that the X-ray polarization degree was generally ∼2-3 times greater than that at longer wavelengths, while the polarization angle fluctuated. Additionally, based on radio, infrared, and optical polarimetry, we find that rotation of ψ occurred in the opposite direction with respect to the rotation of ψX over longer timescales at similar epochs. The polarization behavior observed across multiple wavelengths is consistent with previous IXPE findings for HSP blazars. This result favors the energy-stratified shock model developed to explain variable emission in relativistic jets. The accompanying spectral variation during the ψX rotation can be explained by a fluctuation in the physical conditions, e.g., in the energy distribution of relativistic electrons. The opposite rotation direction of ψ between the X-ray and longer-wavelength polarization accentuates the conclusion that the X-ray emitting region is spatially separated from that at longer wavelengths.
W.-J. Kim1, 5, J. S. Urquhart2, V. S. Veena1, 3, G. A. Fuller1, 4, P. Schilke1, and K-T Kim5, 6
Affiliation:
1 I. Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, 50937 Köln, Germany e-mail: wonjukim@ph1.uni-koeln.de
2 Centre for Astrophysics and Planetary Science, University of Kent, Ingram Building, Canterbury, Kent CT2 7NH, UK
3 Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
4 Jodrell Bank Centre for Astrophysics, Department of Physics and Astronomy, the University of Manchester, Oxford Road, Manch-
ester M13 9PL, UK
5 Korea Astronomy and Space Science Institute, 776 Daedeokdae-ro, Yuseong-gu, Daejeon 34055, Republic of Korea
6 University of Science and Technology, Korea (UST), 217 Gajeong-ro, Yuseong-gu, Daejeon 34113, Republic of Korea
Abstract:
Aims. The application of silicon monoxide (SiO) as a shock tracer arises from its propensity to occur in the gas phase as a result of shock-induced phenomena, including outflow activity and interactions between molecular clouds and expanding Hii regions or supernova remnants. For this work, we searched for indications of shocks toward 366 massive star-forming regions by observing the ground rotational transition of SiO (v = 0, J = 1 − 0) at 43 GHz with the Korean VLBI Network (KVN) 21 m telescopes to extend our understanding on the origins of SiO in star-forming regions.
Methods. We analyzed the thermal SiO 1 – 0 emission and compared the properties of SiO emission with the physical parameters of associated massive dense clumps as well as 22 GHz H2 O and Class I 44 GHz CH3 OH maser emission.
Results. We detected SiO emission toward 104 regions that consist of 57 IRDCs, 21 HMPOs, and 26 UCHiis. Out of 104 sources, 71 and 80 sources have 22 GHz H2 O and 44 GHz Class I CH3 OH maser counterparts, respectively. The determined median SiO column density, N(SiO), and abundance, X(SiO), relative to N(H2) are 8.12×1012 cm−2 and 1.28×10−10, respectively. These values are similar to those obtained toward other star-forming regions and also consistent with predicted values from shock models with low-velocity shocks (≲10 – 15 km s−1). For sources with dust temperatures of (Tdust) ≲ 20 K, we find that N(SiO) and X(SiO) derived with the J = 1 − 0 transition are a factor ∼ 3 larger than those from the previous studies obtained with SiO 2 – 1. While the X(SiO) does not exhibit any strong correlation with the evolutionary stages of their host clumps, LSiO is highly correlated with dust clump mass, and LSiO/Lbol also has a strong negative correlation with Tdust. This shows that colder and younger clumps have high LSiO/Lbol suggestive of an evolutionary trend. This trend is not due to excess emission at higher velocities, such as SiO wing features, as the colder sources with high LSiO/Lbol ratios lack wing features. Comparing SiO emission with H2O and Class I CH3OH masers, we find a significant correlation between LSiO/Lbol and LCH3OH/Lbol ratios, whereas no similar correlation is seen for the H2O maser emission. This suggests a similar origin for the SiO and Class I CH3OH emission in these sources.
Conclusions. We demonstrate that in cold regions SiO J = 1 − 0 may be a better tracer of shocks than a higher J transition of SiO. Lower Tdust (and so probably less globally evolved) sources appear to have higher LSiO relative to their Lbol. The SiO 1 – 0 emission toward infrared dark sources (Tdust ≲ 20 K), which do not contain identified outflow sources, may be related to other mechanisms producing low-velocity shocks (5 – 15 km s−1 ) for example, arising from cloud-cloud collisions, shocks triggered by expanding Hii regions, global infall, or converging flows.
1Astro Space Center, Lebedev Physical Institute, Russian Academy of Sciences, Profsoyuznaya str. 84/32, Moscow, 117997, Russia 2Korea Astronomy and Space Science Institute, Yuseong-gu, Daejeon 34055, Republic of Korea
3INAF Istituto di Radioastronomia, via Gobetti 101, 40129 Bologna, Italy
Abstract:
In this paper, we describe the first multi-frequency synthesis observations of blazar 0059+581 made with the Radioastron space- ground interferometer in conjunction with the Korean VLBI Network (KVN), Medicina and Torun ground telescopes. We conducted these observations to assess the spaceground interferometer multi-frequency mode capability for the first time.
Antonio Fuentes 1  , José L. Gómez 1  , José M. Martí2,3, Manel Perucho2,3, Guang-Yao Zhao1, Rocco Lico 1,4, Andrei P. Lobanov 5, Gabriele Bruni 6, Yuri Y. Kovalev 5,7, Andrew Chael 8, Kazunori Akiyama 9,10,11,
Katherine L. Bouman 12, He Sun12, Ilje Cho 1, Efthalia Traianou1,
Teresa Toscano 1, Rohan Dahale 1,13, Marianna Foschi 1,
Leonid I. Gurvits 14,15, Svetlana Jorstad 16,17, Jae-Young Kim 5,18,19, Alan P. Marscher16, Yosuke Mizuno 20,21,22, Eduardo Ros 5 & Tuomas Savolainen5,23,24
Affiliation:
1Instituto de Astrofísica de Andalucía (CSIC), Granada, Spain. 2Departament d’Astronomia i Astrofísica, Universitat de València, Burjassot, Spain. 3Observatori Astronòmic, Universitat de València, Paterna, Spain. 4Istituto di Radioastronomia, INAF, Bologna, Italy. 5Max-Planck-Institut für Radioastronomie, Bonn, Germany. 6Istituto di Astrofisica e Planetologia Spaziali, INAF, Rome, Italy. 7Lebedev Physical Institute of the Russian Academy
of Sciences, Moscow, Russia. 8Princeton Gravity Initiative, Princeton University, Princeton, NJ, USA. 9Haystack Observatory, Massachusetts Institute of Technology, Westford, MA, USA. 10National Astronomical Observatory of Japan, Mitaka, Japan. 11Black Hole Initiative at Harvard University, Cambridge, MA, USA. 12California Institute of Technology, Pasadena, CA, USA. 13Indian Institute of Science Education and Research Kolkata, Mohanpur, India. 14Joint Institute for VLBI ERIC (JIVE), Dwingeloo, The Netherlands. 15Aerospace Faculty, Delft University of Technology, Delft, The Netherlands. 16Institute for Astrophysical Research, Boston University, Boston, MA, USA. 17Astronomical Institute, St. Petersburg State University, St. Petersburg, Russia. 18Department of Astronomy and Atmospheric Sciences, Kyungpook National University, Daegu, Republic of Korea. 19Korea Astronomy and Space Science Institute, Daejeon, Republic of Korea. 20Tsung-Dao Lee Institute, Shanghai Jiao Tong University, Shanghai, People’s Republic of China. 21School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai, People’s Republic of China. 22Institut für Theoretische Physik, Goethe-Universit ät Frankfurt, Frankfurt am Main, Germany. 23Department of Electronics and Nanoengineering, Aalto University, Aalto, Finland. 24Metsähovi Radio Observatory,
Aalto University, Kylmälä, Finland
Abstract:
Supermassive black holes at the centre of active galactic nuclei power some of the most luminous objects in the Universe. Typically, very-long-baseline interferometric observations of blazars have revealed only funnel-like morphologies with little information on the internal structure of the ejected plasma or have lacked the dynamic range to reconstruct the extended jet emission. Here we present microarcsecond-scale angular resolution images of the blazar 3C 279 obtained at 22 GHz with the space very-long-baseline interferometry mission RadioAstron, which allowed us to resolve the jet transversely and reveal several filaments produced by plasma instabilities
in a kinetically dominated flow. The polarimetric properties derived
from our high-angular-resolution and broad-dynamic-range images are consistent with the presence of a helical magnetic field threaded to the jet. We infer a clockwise rotation as seen in the direction of flow motion with an intrinsic helix pitch angle of ~45° and a Lorentz factor of ~13 at the time of observation. We also propose a model to explain blazar jet radio variability in which emission features travelling down the jet may manifest as a result of differential Doppler boosting within the filaments, as opposed to the standard shock-in-jet model. Characterizing such variability is particularly important given the relevance of blazar physics from cosmic particle acceleration to standard candles in cosmology.
1Research Center for Intelligent Computing Platforms, Zhejiang Laboratory, Hangzhou, China. 2Tsung-Dao Lee Institute, Shanghai Jiao Tong University, Shanghai, China. 3Astronomical Science Program, The Graduate University for Advanced Studies, Mitaka, Japan. 4Mizusawa VLBI Observatory, National Astronomical Observatory of Japan, Oshu, Japan. 5Institute for Cosmic Ray Research, The University of Tokyo, Kashiwa, Japan. 6Kogakuin University of Technology & Engineering, Academic Support Center, Hachioji, Japan. 7South-Western Institute For Astronomy Research, Yunnan University, Kunming, China. 8School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai, China. 9Institut für Theoretische Physik, Goethe-Universität Frankfurt, Frankfurt, Germany. 10Korea Astronomy and Space Science Institute, Daejeon, Republic of Korea. 11Department of Astronomy, Yonsei University, Seodaemun-gu, Republic of Korea. 12Department of Astronomy, Graduate School of Science, The University of Tokyo, Bunkyo, Japan. 13Department of Physics and Astronomy, Seoul National University, Gwanak-gu, Republic of Korea. 14Department of Intelligence, Air Force Early Warning Academy, Wuhan, China. 15Institute of Astronomy and Astrophysics, Academia Sinica, Hilo, HI, USA. 16Shanghai Astronomical Observatory, Chinese Academy of Sciences, Shanghai, China. 17Key Laboratory of Radio Astronomy and Technology, Chinese Academy of Sciences, Beijing, China. 18Department of Physics, Faculty of Science, Universiti Malaya, Kuala Lumpur, Malaysia. 19Instituto de Astrofísica de Andalucía - CSIC, Glorieta de la Astronomía s/n, Granada, Spain. 20DIFA Bologna University, Bologna, Italy. 21INAF-Istituto di Radioastronomia, Bologna, Italy. 22University of Science and Technology, Yuseong-gu, Republic of Korea. 23Max-Planck-Institut für Radioastronomie, Bonn, Germany. 24Graduate School of Sciences and Technology for Innovation, Yamaguchi University, Yamaguchi, Japan. 25The Research Institute for Time Studies, Yamaguchi University, Yamaguchi, Japan. 26Joint Institute for VLBI ERIC, Dwingeloo, the Netherlands. 27Center for Computational Sciences, University of Tsukuba, Tsukuba, Japan. 28Graduate School of Science, Osaka Metropolitan University, Sakai, Japan. 29Department of Natural Sciences, Faculty of Arts and Sciences, Komazawa University, Setagaya, Japan. 30Tokyo Electron Technology Solutions Limited, Oshu City, Japan. 31SNU Astronomy Research Center, Seoul National University, Gwanak-gu, Republic of Korea. 32National Radio Astronomy Observatory, Charlottesville, VA, USA. 33Massachusetts Institute of Technology Haystack Observatory, Westford, MA, USA. 34Black Hole Initiative at Harvard University, Cambridge, MA, USA. 35Xinjiang Astronomical Observatory, Chinese Academy of Sciences, Urumqi, China. 36Toyo University, Bunkyo-ku, Japan. 37Department of Physics and Astronomy, Sejong University, Gwangjin-gu, Republic of Korea. 38Department of Astronomy and Atmospheric Sciences, Kyungpook National University, Daegu, Republic of Korea. 39INAF - Osservatorio Astronomico di Cagliari, Selargius, CA, Italy. 40Institute of Applied Astronomy, Russian Academy of Sciences, St. Petersburg, Russia. 41National Astronomical Research Institute of Thailand (Public Organization), Chiangmai, Thailand. 42National Astronomical Observatories, Chinese Academy of Sciences, Beijing, China. 43Center for Astronomy, Ibaraki University, Mito, Japan. 44Unaffiliated: Evgeniya Kravchenko. ✉e-mail: yuzhu_cui77@163.com
Abstract:
The nearby radio galaxy M87 offers a unique opportunity to explore the connections between the central supermassive black hole and relativistic jets. Previous studies
of the inner region of M87 revealed a wide opening angle for the jet originating near the black hole1–4. The Event Horizon Telescope resolved the central radio source and found an asymmetric ring structure consistent with expectations from general relativity5. With a baseline of 17 years of observations, there was a shift in the jet’s transverse position, possibly arising from an 8- to 10-year quasi-periodicity3. However, the origin of this sideways shift remains unclear. Here we report an analysis of radio observations over 22 years that suggests a period of about 11 years for the variation
in the position angle of the jet. We infer that we are seeing a spinning black hole that induces the Lense–Thirring precession of a misaligned accretion disk. Similar jet precession may commonly occur in other active galactic nuclei but has been challenging to detect owing to the small magnitude and long period of the variation.
Istituto Nazionale di Astrofisica Istituto di Radioastronomia, Via P. Gobetti, 101, 40129 Bologna, Italy Dipartimento di Fisica e Astronomia, Bologna University, 40129 Bologna, Italy
Research Center for Intelligent Computing Platforms, Zhejiang Laboratory, Hangzhou 311100, China Mizusawa VLBI Observatory, National Astronomical Observatory of Japan, 2-12 Hoshigaoka,
Oshu 023-0861, Japan
Department of Astronomical Science, The Graduate University for Advanced Studies, SOKENDAI,
2-21-1 Osawa, Mitaka 181-8588, Japan
Department of Physics and Astronomy, Seoul National University, Gwanak-ro 1, Gwanak-gu,
Seoul 08826, Republic of Korea
Department of Astronomy, Yonsei University, Yonsei-ro 50, Seodaemun-gu, Seoul 03722, Republic of Korea Korea Astronomy and Space Science Institute, Daedeok-daero 776, Yuseong-gu,
Daejeon 34055, Republic of Korea
Department of Astronomy and Space Science, University of Science and Technology, Gajeong-ro 217, Yuseong-gu, Daejeon 34113, Republic of Korea
Abstract:
WepresentheretheEastAsiatoItalyNearlyGlobalVLBI(EATINGVLBI)project.How this project started and the evolution of the international collaboration between Korean, Japanese, and Italian researchers to study compact sources with VLBI observations is reported. Problems related to the synchronization of the very different arrays and technical details of the telescopes involved are presented and discussed. The relatively high observation frequency (22 and 43 GHz) and the long baselines between Italy and East Asia produced high-resolution images. We present example images to demonstrate the typical performance of the EATING VLBI array. The results attracted international researchers and the collaboration is growing, now including Chinese and Russian stations. New in progress projects are discussed and future possibilities with a larger number of telescopes and a better frequency coverage are briefly discussed herein.
T. Savolainen1,2,3 , G. Giovannini4,13 , Y. Y. Kovalev3,5,6 , M. Perucho7,8, J. M. Anderson9 , G. Bruni10 ,
P. G. Edwards11 , A. Fuentes12 , M. Giroletti13 , J. L. Gómez12, K. Hada14, S.-S. Lee15,16 , M. M. Lisakov3,5 , A. P. Lobanov3,6 , J. López-Miralles7, M. Orienti13 , L. Petrov17 , A. V. Plavin5,6 , B. W. Sohn15,16 ,
K. V. Sokolovsky18,19 , P. A. Voitsik5 , and J. A. Zensus3
Affiliation:
1 Aalto University Department of Electronics and Nanoengineering, PL 15500, 00076 Aalto, Finland e-mail: tuomas.k.savolainen@aalto.fi
2 Aalto University Metsähovi Radio Observatory, Metsähovintie 114, 02540 Kylmälä, Finland
3 Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
4 Dipartimento di Fisica e Astronomia, Universitá di Bologna, via Gobetti 93/2, 40129 Bologna, Italy
5 Lebedev Physical Institute of the Russian Academy of Sciences, Leninsky prospekt 53, 119991 Moscow, Russia
6 Moscow Institute of Physics and Technology, Institutsky per. 9, Dolgoprudny, Moscow region 141700, Russia
7 Departament d’Astronomia i Astrofísica, Universitat de València, C/ Dr. Moliner, 50, 46100 Burjassot, València, Spain
8 Observatori Astronòmic, Universitat de València, C/ Catedràtic José Beltrán 2, 46980 Paterna, València, Spain
9 Helmholtz Centre Potsdam, GFZ German Research Centre for Geosciences, Telegrafenberg 14473 Potsdam, Germany
10 INAF – Istituto di Astrofisica e Planetologia Spaziali, via del Fosso del Cavaliere 100, 00133 Roma, Italy
11 CSIRO Space and Astronomy, Epping, NSW 1710, Australia
12 Instituto de Astrofísica de Andalucía-CSIC, Glorieta de la Astronomía s/n, 18008 Granada, Spain
13 INAF – Istituto di Radio Astronomia, via P. Gobetti 101, 40129 Bologna, Italy
14 Mizusawa VLBI Observatory, National Astronomical Observatory of Japan, 2-12 Hoshigaoka, Mizusawa, Oshu, Iwate 023-0861, Japan
15 Korea Astronomy and Space Science Institute, Yuseong-gu, Daejeon 34055, Korea
16 Korea University of Science and Technology, Yuseong-gu, Daejeon 34113, Korea
17 NASA Goddard Space Flight Center, Greenbelt, ND 20771, USA
18 Center for Data Intensive and Time Domain Astronomy, Department of Physics and Astronomy, Michigan State University,
567 Wilson Rd, East Lansing, MI 48824, USA
19 Sternberg Astronomical Institute, Moscow State University, Universitetskii pr. 13, 119992 Moscow, Russia
Abstract:
We present RadioAstron space-based very long baseline interferometry (VLBI) observations of the nearby radio galaxy 3C84 (NGC 1275) at the centre of the Perseus cluster. The observations were carried out during a perigee passage of the Spektr-R spacecraft on September 21–22, 2013 and involved a global array of 24 ground radio telescopes observing at 5 GHz and 22 GHz, together with the Space Radio Telescope (SRT). Furthermore, the Very Long Baseline Array (VLBA) and the phased Very Large Array (VLA) observed the source quasi-simultaneously at 15 GHz and 43 GHz. Fringes between the ground array and the SRT were detected on baseline lengths up to 8.1 times the Earth’s diameter, providing unprecedented resolution for 3C 84 at these wavelengths. We note that the corresponding fringe spacing is 125 μas at 5 GHz and 27 μas at 22 GHz. Our space-VLBI images reveal a previously unseen sub-structure inside the compact ∼1 pc long jet that was ejected about ten years earlier. In the 5 GHz image, we detected, for the first time, low-intensity emission from a cocoon-like structure around the restarted jet. Our results suggest that the increased power of the young jet is inflating a bubble of hot plasma as it carves its way through the ambient medium of the central region of the galaxy. Here, we estimate the minimum energy stored in the mini-cocoon, along with its pressure, volume, expansion speed, and the ratio of heavy particles to relativistic electrons, as well as the density of the ambient medium. About half of the energy delivered by the jet is dumped into the mini-cocoon and the quasi-spherical shape of the bubble suggests that this energy may be transferred to a significantly larger volume of the interstellar medium than what would be accomplished by the well-collimated jet on its own. The pressure of the hot mini-cocoon also provides a natural explanation for the almost cylindrical jet profile seen in the 22 GHz RadioAstron image.
Hyunwook Ro 1,2,* , Kunwoo Yi 3, Yuzhu Cui 4,5 , Motoki Kino 6,7, Kazuhiro Hada 8,9 , Tomohisa Kawashima 10, Yosuke Mizuno 4,11,12, Bong Won Sohn 1,2,13 and Fumie Tazaki 14
Affiliation:
1 2
3
4 5 6
7 8
9
10
11 12
13 14
*
Department of Astronomy, Yonsei University, Yonsei-ro 50, Seodaemun-gu, Seoul 03722, Republic of Korea Korea Astronomy & Space Science Institute, Daedeokdae-ro 776, Yuseong-gu,
Daejeon 34055, Republic of Korea
Department of Physics and Astronomy, Seoul National University, Gwanak-gu,
Seoul 08826, Republic of Korea
Tsung-Dao Lee Institute, Shanghai Jiao Tong University, Shanghai 201210, China
Research Center for Intelligent Computing Platforms, Zhejiang Laboratory, Hangzhou 311100, China Academic Support Center, Kogakuin University of Technology and Engineering, 2665-1 Nakano, Hachioji, Tokyo 192-0015, Japan
National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan
Mizusawa VLBI Observatory, National Astronomical Observatory of Japan, 2-12 Hoshigaoka, Mizusawa, Oshu, Iwate 023-0861, Japan
Department of Astronomical Science, The Graduate University for Advanced Studies (SOKENDAI), 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan
Institute for Cosmic Ray Research, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa,
Chiba 277-8582, Japan
School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China
Institut für Theoretische Physik, Goethe Universität, Max-von-Laue Str. 1,
D-60438 Frankfurt am Main, Germany
Department of Astronomy and Space Science, University of Science and Technology, Yuseong-gu, Daejeon 34113, Republic of Korea
Tokyo Electron Technology Solutions Limited, Iwate 023-1101, Japan
Correspondence: hwro@yonsei.ac.kr
Abstract:
RecentVLBImonitoringhasfoundtransversemotionsoftheM87jet.However,dueto the limited cadence of previous observations, details of the transverse motion have not been fully revealed yet. We have regularly monitored the M87 jet at KVN and VERA Array (KaVA) 22 GHz from December 2013 to June 2016. The average time interval of the observation is ∼0.1 year, which is suitable for tracking short-term structural changes. From these observations, the M87 jet is well represented by double ridge lines in the region 2–12 mas from the core. We found that the ridge lines exhibit transverse oscillations in all observed regions with an average period of 0.94 ± 0.12 years. When the sinusoidal fit is performed, we found that the amplitude of this oscillation is an order of ∼0.1 mas, and the oscillations in the northern and southern limbs are almost in phase. Considering the amplitude, it does not originate from Earth’s parallax. We propose possible scenarios of the transverse oscillation, such as the propagation of jet instabilities or magneto-hydrodynamic (MHD) waves or perturbed mass injection around magnetically dominated accretion flows.
Journal of the Korean Astronom ical Society (한국천문 학회지) 2023, 56, 159
Authors:
Jeong Ae Lee1,★, Taehyun Jung1,2, Bong Won Sohn 1,2, and Do-Young Byun 1,2
Affiliation:
1Korean Astronomy and Space Science Institute, 776, Daedeokdae-ro, Yuseong-gu, Daejeon, Republic of Korea 2University of Science ans Technology, Yuseong-gu, Daejeon, Republic of Korea
Abstract:
The main goal of the Korean VLBI Network Calibrator Survey (KVNCS) is to expand the VLBI calibrators catalog for KVN, KaVA (KVN and VERA Array), EAVN (East-Asian VLBI Network), and other extended regions. The second KVNCS (KVNCS2) aimed to detect VLBI fringes of new candidates for calibrators in the K band. Out of the 1533 sources whose single-dish flux density in the K band was measured with KVN telescopes (Lee et al. 2017), 556 sources were observed with KVN in the K band. KVNCS2 confirmed the detection of VLBI fringes of 424 calibrator candidates over a single baseline. All detected sources had a high Signal-to-Noise Ratio (SNR) of >25. Finally, KVNCS2 confirmed 347 new candidates as VLBI calibrators in the K band, resulting in a 5% increase in the sky coverage compared to previous studies. The spatial distribution was quasi-uniform across the observable region (Dec. > −32.5◦). In addition, the possibility as calibrator candidates for the detected sources was checked, using an analysis of the flux-flux relationship. Ultimately, the KVNCS catalog will not only become the VLBI calibrator list but is also useful as a database of compact radio sources for astronomical studies.
1Korea Astronomy & Space Science Institute, 776, Daedeokdae-ro, Yuseong-gu, Daejeon 34055, Korea
2National Astronomical Research Institute of Thailand (Public Organization), 260 Moo 4, T. Donkaew, A. Maerim, Chiang Mai, 50180, Thailand
3Shanghai Astronomical Observatory, Chinese Academy of Sciences, 80 Nandan Road, Shanghai, 200030, China
4Mizusawa VLBI Observatory, National Astronomical Observatory of Japan, 2-12 Hoshigaoka, Mizusawa, Oshu, Iwate 023-0861, Japan
5The Iwate Nippo Co., Ltd., 3-7 Uchimaru, Morioka, Iwate 020-8622, Japan
6Ulsan National Institute of Science and Technology UNIST-gil 50, Eonyang-eup, Ulju-gun,
Ulsan 44919, Repblic of Korea
7Mizusawa VLBI Observatory, National Astronomical Observatory of Japan, 2-21-1 Osawa,
Mitaka, Tokyo 181-8588, Japan
8Amanogawa Galaxy Astronomy Research Center, Graduate School of Science and
Engineering, Kagoshima University, 1-21-35 Korimoto Kagoshima
9Xinjiang Astronomical Observatory, Chinese Academy of Sciences, Urumqi 830011, China 10Faculty of Education and Human Sciences, Department of School Education, Teikyo
University of Science, 2-2-1 Senju-Sakuragi, Adachi, Tokyo 120-0045, Japan
11Key Laboratory of Radio Astronomy, Chinese Academy of Sciences, Nanjing 210008, China
Abstract:
We aim to reveal the structure and kinematics of the Outer-Scutum-Centaurus (OSC) arm located on the far side of the Milky Way through very long baseline interferometry (VLBI) as- trometry using KaVA, which is composed of KVN (Korean VLBI Network) and VERA (VLBI Exploration of Radio Astrometry). We report the proper motion of a 22 GHz H2O maser source, which is associated with the star-forming region G034.84−00.95, to be (μαcosδ, μδ) = (−1.61±0.18, −4.29±0.16) mas yr−1 in equatorial coordinates (J2000). We estimate the 2D kinematic distance to the source to be 18.6±1.0 kpc, which is derived from the variance- weighted average of kinematic distances with LSR velocity and the Galactic-longitude com- ponent of the measured proper motion. Our result places the source in the OSC arm and implies that G034.84−00.95 is moving away from the Galactic plane with a vertical velocity of
−38±16 km s−1. Since the H I supershell GS033+06−49 is located at a kinematic distance
roughly equal to that of G034.84−00.95, it is expected that gas circulation occurs between the
outer Galactic disk around G034.84−00.95 with a Galactocentric distance of 12.8+1.0 kpc and −0.9
halo. We evaluate possible origins of the fast vertical motion of G034.84−00.95, which are (1) supernova explosions and (2) cloud collisions with the Galactic disk. However, neither of the possibilities are matched with the results of VLBI astrometry as well as spatial distributions of H II regions and H I gas.
The Astrophysical Journal Letters, 953:L28 (10pp), 2023 August 20
Authors:
Riccardo Middei1,2 , Matteo Perri1,2 , Simonetta Puccetti1, Ioannis Liodakis3 , Laura Di Gesu4, Alan P. Marscher5 , Nicole Rodriguez Cavero6 , Fabrizio Tavecchio7 , Immacolata Donnarumma4 , Marco Laurenti8,9 , Svetlana G. Jorstad5,10
Iván Agudo11 , Herman L. Marshall12 , Luigi Pacciani13 , Dawoon E. Kim13,14,15 , Francisco José Aceituno11, Giacomo Bonnoli7,11 , Víctor Casanova11, Beatriz Agís-González11 , Alfredo Sota11, Carolina Casadio16,17 ,
Juan Escudero11 , Ioannis Myserlis18,19 , Albrecht Sievers18, Pouya M. Kouch3,20 , Elina Lindfors3, Mark Gurwell21 Garrett K. Keating21 , Ramprasad Rao21, Sincheol Kang22 , Sang-Sung Lee22,23 , Sang-Hyun Kim22,23 ,Whee Yeon Cheong22,23 Matteo Bachetti26, Hyeon-Woo Jeong22,23 , Emmanouil Angelakis24, Alexander Kraus19 , Lucio A. Antonelli1,25 , Luca Baldini27,28 , Wayne H. Baumgartner29 , Ronaldo Bellazzini27 , Stefano Bianchi30 ,, Raffaella Bonino31,32 , Alessandro Brez27 , Niccolò Bucciantini33,34,35 , Fiamma Capitanio13 Stephen D. Bongiorno29 Simone Castellano27 , Elisabetta Cavazzuti36 , Chien-Ting Chen37 , Stefano Ciprini1,38 , Enrico Costa13 ,Alessandra De Rosa13 , Ettore Del Monte13 , Niccolò Di Lalla39 , Alessandro Di Marco13 , Victor Doroshenko40 , Michal Dovčiak41 , Steven R. Ehlert29 , Teruaki Enoto42 , Yuri Evangelista13 , Sergio Fabiani13 , Riccardo Ferrazzoli13 Javier A. García43 , Shuichi Gunji44 , Kiyoshi Hayashida45,66, Jeremy Heyl46 , Wataru Iwakiri47 , Philip Kaaret29 Vladimir Karas41 , Fabian Kislat48 , Takao Kitaguchi42, Jeffery J. Kolodziejczak29 , Henric Krawczynski49 ,Fabio La Monaca13 , Luca Latronico31 , Simone Maldera31 , Alberto Manfreda50 , Frédéric Marin51 ,Andrea Marinucci36 Fabio Muleri13
Chiara Oppedisano31 Pierre-Olivier Petrucci59 Jacco Vink64 , Martin C. Weisskopf29 , Kinwah Wu63 , Fei Xie13,65 , and Silvia Zane63
Affiliation:
Space Science Data Center, Agenzia Spaziale Italiana, Via del Politecnico snc, I-00133 Roma, Italy;2 INAF Osservatorio Astronomico di Roma, Via Frascati 33, I-00078 Monte Porzio Catone (RM), Italy
3 Finnish Centre for Astronomy with ESO, University of Turku, FI-20014 Turky, Finland
4 ASI—Agenzia Spaziale Italiana, Via del Politecnico snc, I-00133 Roma, Italy
5 Institute for Astrophysical Research, Boston University, 725 Commonwealth Avenue, Boston, MA 02215, USA
6 Physics Department, McDonnell Center for the Space Sciences, and Center for Quantum Leaps, Washington University in St. Louis, St. Louis, MO 63130, USA 7 INAF Osservatorio Astronomico di Brera, Via E. Bianchi 46, I-23807 Merate (LC), Italy
8 INFN—Sezione di Roma “Tor Vergata,” Via della Ricerca Scientifica 1, I-00133 Roma, Italy
9 Space Science Data Center, SSDC, ASI, Via del Politecnico snc, I-00133 Roma, Italy
10 Saint Petersburg State University, 7/9 Universitetskaya nab., St. Petersburg 199034 Russia
11 Instituto de Astrofísica de Andalucía, IAA-CSIC, Glorieta de la Astronomía s/n, E-18008 Granada, Spain
12 MIT Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA 13 INAF Istituto di Astrofisica e Planetologia Spaziali, Via del Fosso del Cavaliere 100, I-00133 Roma, Italy
14 Dipartimento di Fisica, Università degli Studi di Roma “La Sapienza,” Piazzale Aldo Moro 5, I-00185 Roma, Italy
15 Dipartimento di Fisica, Università degli Studi di Roma “Tor Vergata,” Via della Ricerca Scientifica 1, I-00133 Roma, Italy
16 Institute of Astrophysics, Foundation for Research and Technology—Hellas, Voutes, 7110 Heraklion, Greece
17 Department of Physics, University of Crete, 70013 Heraklion, Greece
18 Institut de Radioastronomie Millimétrique, Avenida Divina Pastora, 7, Local 20, E-18012 Granada, Spain
19 Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn, Germany
20 Department of Physics and Astronomy, University of Turku, FI-20014 Turku, Finland
21 Center for Astrophysics | Harvard & Smithsonian, 60 Garden Street, Cambridge, MA 02138 USA
22 Korea Astronomy and Space Science Institute, 776 Daedeok-daero, Yuseong-gu, Daejeon 34055, Republic of Korea
23 University of Science and Technology, Korea, 217 Gajeong-ro, Yuseong-gu, Daejeon 34113, Republic of Korea
24 Section of Astrophysics, Astronomy & Mechanics, Department of Physics, National and Kapodistrian University of Athens, Panepistimiopolis Zografos 15784, Greece
25 INAF Osservatorio Astronomico di Roma, Via Frascati 33, I-00040 Monte Porzio Catone (RM), Italy
26 INAF Osservatorio Astronomico di Cagliari, Via della Scienza 5, I-09047 Selargius (CA), Italy
27 Istituto Nazionale di Fisica Nucleare, Sezione di Pisa, Largo B. Pontecorvo 3, I-56127 Pisa, Italy
28 Dipartimento di Fisica, Università di Pisa, Largo B. Pontecorvo 3, I-56127 Pisa, Italy
29 NASA Marshall Space Flight Center, Huntsville, AL 35812, USA
30 Dipartimento di Matematica e Fisica, Università degli Studi Roma Tre, Via della Vasca Navale 84, I-00146 Roma, Italy
31 Istituto Nazionale di Fisica Nucleare, Sezione di Torino, Via Pietro Giuria 1, I-10125 Torino, Italy
32 Dipartimento di Fisica, Università degli Studi di Torino, Via Pietro Giuria 1, I-10125 Torino, Italy
33 INAF Osservatorio Astrofisico di Arcetri, Largo Enrico Fermi 5, I-50125 Firenze, Italy
34 Dipartimento di Fisica e Astronomia, Università degli Studi di Firenze, Via Sansone 1, I-50019 Sesto Fiorentino (FI), Italy
35 Istituto Nazionale di Fisica Nucleare, Sezione di Firenze, Via Sansone 1, I-50019 Sesto Fiorentino (FI), Italy
36 Agenzia Spaziale Italiana, Via del Politecnico snc, I-00133 Roma, Italy
37 Science and Technology Institute, Universities Space Research Association, Huntsville, AL 35805, USA
38 Istituto Nazionale di Fisica Nucleare, Sezione di Roma “Tor Vergata”, Via della Ricerca Scientifica 1, I-00133 Roma, Italy
Abstract:
The lower-energy peak of the spectral energy distribution of blazars has commonly been ascribed to synchrotron radiation from relativistic particles in the jets. Despite the consensus regarding jet emission processes, the particle acceleration mechanism is still debated. Here, we present the first X-ray polarization observations of PG 1553 +113, a high-synchrotron-peak blazar observed by the Imaging X-ray Polarimetry Explorer (IXPE). We detect an X-ray polarization degree of (10 ± 2)% along an electric-vector position angle of ψX = 86° ± 8°. At the same time, the radio and optical polarization degrees are lower by a factor of ∼3. During our IXPE pointing, we observed the first orphan optical polarization swing of the IXPE era, as the optical angle of PG 1553+113 underwent a smooth monotonic rotation by about 125°, with a rate of ∼17° day–1. We do not find evidence of a similar rotation in either radio or X-rays, which suggests that the X-ray and optically emitting regions are separate or, at most, partially cospatial. Our spectropolarimetric results provide further evidence that the steady-state X-ray emission in blazars originates in a shock-accelerated and energy-stratified electron population.
The Astrophysical Journal, 952:34 (17pp), 2023 July 20
Authors:
Jae-Young Kim1,2 , Tuomas Savolainen2,3,4 , Petr Voitsik5 , Evgeniya V. Kravchenko5,6 , Mikhail M. Lisakov2,5 ,
Yuri Y. Kovalev2,5,6 Philip G. Edwards11 Kazuhiro Hada15,16 , Hendrik Müller2, Andrei P. Lobanov2,6, Kirill V. Sokolovsky7,8,9 , Gabriele Bruni10 , Cormac Reynolds12 , Uwe Bach2 , Leonid I. Gurvits13,14 , Thomas P. Krichbaum2 , Marcello Giroletti17 , Monica Orienti17, James M. Anderson18 , Sang-Sung Lee19 Bong Won Sohn19 , and J. Anton Zensus2
Affiliation:
1 Department of Astronomy and Atmospheric Sciences, Kyungpook National University, Daegu 702-701, Republic of Korea; jykim@knu.ac.kr
2 Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn, Germany
3 Aalto University Department of Electronics and Nanoengineering, PL 15500, FI-00076 Aalto, Finland
4 Aalto University Metsähovi Radio Observatory, Metsähovintie 114, FI-02540 Kylmälä, Finland
5 Lebedev Physical Institute of the Russian Academy of Sciences, Leninsky prospekt 53, 119991 Moscow, Russia
6 Moscow Institute of Physics and Technology, Dolgoprudny, Institutsky per., 9, Moscow 141700, Russia
7 Department of Astronomy, University of Illinois at Urbana-Champaign, 1002 W. Green Street, Urbana, IL 61801, USA
8 Center for Data Intensive and Time Domain Astronomy, Department of Physics and Astronomy, Michigan State University, 567 Wilson Road, East Lansing, MI 48824, USA
9 Sternberg Astronomical Institute, Moscow State University, Universitetskij pr. 13, 119992 Moscow, Russia
10 INAF-Istituto di Astrofisica e Planetologia Spaziali, via Fosso del Cavaliere 100, I-00133 Roma, Italy
11 CSIRO Astronomy and Space Science, P.O. Box 76, Epping, NSW, 1710, Australia
12 CSIRO Astronomy and Space Science, P.O. Box 1130, Bentley, WA 6102, Australia
13 Joint Institute for VLBI ERIC (JIVE), Oude Hoogeveensedijk 4, NL-7991 PD Dwingeloo, The Netherlands
14 Faculty of Aerospace Engineering, Delft University of Technology, Kluyverweg 1, NL-2629 HS Delft, The Netherlands
15 Mizusawa VLBI Observatory, National Astronomical Observatory of Japan, 2-12 Hoshigaoka, Mizusawa, Oshu, Iwate 023-0861, Japan
16 Department of Astronomical Science, The Graduate University for Advanced Studies (SOKENDAI), 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan
17 Istituto Nazionale di Astrofisica, Istituto di Radioastronomia (IRA), via Gobetti 101, I-40129, Bologna, Italy
18 Leibniz Institute for Agricultural Engineering and Bioeconomy, Max-Eyth-Allee 100, D-14469 Potsdam-Bornim, Germany
19 Korea Astronomy and Space Science Institute, 776 Daedeok-daero, Yuseong-gu, Daejeon 34055, Republic of Korea
Abstract:
We present results from the first 22 GHz space very long baseline interferometric (VLBI) imaging observations of M87 by RadioAstron. As a part of the Nearby AGN Key Science Program, the source was observed in 2014 February at 22 GHz with 21 ground stations, reaching projected (u, v) spacings up to ∼11 Gλ. The imaging experiment was complemented by snapshot RadioAstron data of M87 obtained during 2013–2016 from the AGN Survey Key Science Program. Their longest baselines extend up to ∼25 Gλ. For all of these measurements, fringes are detected only up to ∼2.8 Earth diameter or ∼3 Gλ baseline lengths, resulting in a new image with angular resolution of ∼150 μas or ∼20 Schwarzschild radii spatial resolution. The new image not only shows edge- brightened jet and counterjet structures down to submilliarcsecond scales but also clearly resolves the VLBI core region. While the overall size of the core is comparable to those reported in the literature, the ground-space fringe detection and slightly superresolved RadioAstron image suggest the presence of substructures in the nucleus, whose minimum brightness temperature exceeds TB,min ~ 1012 K. It is challenging to explain the origin of this record-high TB,min value for M87 by pure Doppler boosting effect with a simple conical jet geometry and known jet speed. Therefore, this can be evidence for more extreme Doppler boosting due to a blazar-like small jet viewing angle or highly efficient particle acceleration processes occurring already at the base of the outflow.
Journal of the Korean Astrono mical Society (한국천문 학회지) 2023, 56, 1, 1-9
Authors:
Minchul Kam 1, Sascha Trippe 1,2,⋆, Do-Young Byun 3, Jongho Park 3,4, Sincheol Kang 3, Naeun Shin 1,3, Sang-Sung Lee 3, and Taehyun Jung 3
Affiliation:
1Department of Physics and Astronomy, Seoul National University, Gwanak-gu, Seoul 08826, Republic of Korea 2SNU Astronomy Research Center, Seoul National University, Gwanak-gu, Seoul 08826, Republic of Korea
3Korea Astronomy and Space Science Institute, Daedeok-daero 776, Yuseong-gu, Daejeon 34055, Republic of Korea 4Institute of Astronomy and Astrophysics, Academia Sinica, P.O. Box 23-141, Taipei 10617, Taiwan
⋆Corresponding Author: S. Trippe, trippe@snu.ac.kr
Abstract:
The Crab nebula is widely used as a polarization angle calibrator for single-dish radio observations because of its brightness, high degree of linear polarization, and well-known polarization angle over a wide frequency range. However, the Crab nebula cannot be directly used as a polarization angle calibrator for single-dish observations with the Korean VLBI Network (KVN), because the beam size of the telescopes is smaller than the size of the nebula. To determine the polarization angle of the Crab nebula as seen by KVN, we use 3C 286, a compact polarized extragalactic radio source whose polarization angle is well-known, as a reference target. We observed both the Crab nebula and 3C 286 with the KVN from 2017 to 2021 and find that the polarization angles at the total intensity peak of the Crab nebula (equatorial coordinates (J2000) R.A. = 05h34m32.3804s and Dec = 22◦00′44.0982′′) are 154.2◦ ± 0.3◦ , 151.0◦ ± 0.2◦ , 150.0◦ ± 1.0◦ , and 151.3◦ ± 1.1◦ at 22, 43, 86, and 94 GHz, respectively. We also find that the polarization angles at the pulsar position (RA = 05h34m31.971s and Dec = 22◦00′52.06′′) are 154.4◦ ± 0.4◦, 150.7◦ ± 0.4◦, and 149.0◦ ± 1.0◦ for the KVN at 22, 43, and 86 GHz. At 129 GHz, we suggest to use the values 149.0◦ ± 1.6◦ at the total intensity peak and 150.2◦ ± 2.0◦ at the pulsar position obtained with the Institute for Radio Astronomy in the Millimeter Range (IRAM) 30-meter Telescope. Based on our study, both positions within the Crab nebula can be used as polarization angle calibrators for the KVN single-dish observations.
G. Surcis1 , W. H. T. Vlemmings2 , C. Goddi1,3,4,5 , J. M. Torrelles6,7, J. F. Gómez8 , A. Rodríguez-Kamenetzky9 , C. Carrasco-González10 , S. Curiel11, S.-W. Kim12, J.-S. Kim12 , and H. J. van Langevelde13,14
Affiliation:
1 INAF – Osservatorio Astronomico di Cagliari, Via della Scienza 5, 09047 Selargius, Italy e-mail: gabriele.surcis@inaf.it
2 Department of Space, Earth and Environment, Chalmers University of Technology, Onsala Space Observatory, 439 92 Onsala, Sweden
3 Dipartimento di Fisica, Università degli Studi di Cagliari, SP Monserrato-Sestu km 0.7, 09042 Monserrato, Italy
4 INFN, Sezione di Cagliari, Cittadella Univ., 09042 Monserrato (CA), Italy
5 Universidade de São Paulo, Instituto de Astronomia, Geofísica e Ciências Atmosféricas, Departamento de Astronomia, São Paulo
SP 05508-090, Brazil
6 Institut de Ciències de l’Espai (ICE, CSIC), Can Magrans s/n, 08193 Cerdanyola del Vallès, Barcelona, Spain
7 Institut d’Estudis Espacials de Catalunya (IEEC), Carrer del Gran Capità, 2, 08034 Barcelona, Spain
8 Instituto de Astrofísica de Andalucía, CSIC, Glorieta de la Astronomía s/n, 18008 Granada, Spain
9 Instituto de Astronomía Teórica y Experimental (IATE, CONICET-UNC), Laprida 854, Córdoba X5000BGR, Argentina
10 Instituto de Radioastronomía y Astrofísica (IRyA-UNAM), 58341 Morelia, Mexico
11 Instituto de Astronomía, Universidad Nacional Autónoma de México (UNAM), Apdo Postal 70-264 México, D.F., Mexico
12 Korea Astronomy and Space Science Institute, 776 Daedeokdaero, Yuseong, Daejeon 305-348, Republic of Korea
13 Joint Institute for VLBI ERIC, Oude Hoogeveensedijk 4, 7991 PD Dwingeloo, The Netherlands
14 Sterrewacht Leiden, Leiden University, Postbus 9513, 2300 RA Leiden, The Netherlands
Abstract:
Context. Several radio sources have been detected in the high-mass star-forming region W75N(B), with the massive young stellar objects VLA 1 and VLA 2 shown to be of particular interest among them. These objects are thought to be at different evolutionary stages: VLA 1 is in the early stage of photoionization and driving a thermal radio jet, while VLA 2 is a thermal, collimated ionized wind surrounded by a dusty disk or envelope. In both sources, 22GHz H2O masers have been detected in the past. Those around VLA 1 show a persistent linear distribution along the thermal radio jet, while those around VLA 2 have traced the evolution from a non-collimated to a collimated outflow over a period of ∼20 yr. The magnetic field inferred from the H2O masers has shown an orientation rotation following the direction of the major-axis of the shell around VLA 2, whereas it is immutable around VLA 1. Aims. By monitoring the polarized emission of the 22GHz H2O masers around both VLA1 and VLA2 over a period of six years, we aim to determine whether the H2O maser distributions show any variation over time and whether the magnetic field behaves accordingly.
Methods. The European VLBI Network was used in full polarization and phase-reference mode in order to determine the absolute
positions of the 22GHz H2O masers with a beam size of ∼1mas and to determine the orientation and the strength of the magnetic
field. We observed four epochs separated by two years from 2014 to 2020.
Results. We detected polarized emission from the H2O masers around both VLA1 and VLA2 in all the epochs. By comparing the
H2 O masers detected in the four epochs, we find that the masers around VLA 1 are tracing a nondissociative shock originating from
the expansion of the thermal radio jet, while the masers around VLA 2 are tracing an asymmetric expansion of the gas that is halted in
the northeast where the gas likely encounters a very dense medium. We also found that the magnetic field inferred from the H2 O masers
in each epoch can be considered as a portion of a quasi-static magnetic field estimated in that location rather than in that time. This
allowed us to study the morphology of the magnetic field around both VLA 1 and VLA 2 locally across a larger area by considering the
vectors estimated in all the epochs as a whole. We find that the magnetic field in VLA 1 is located along the jet axis, bending toward
the north and south at the northeasterly and southwesterly ends of the jet, respectively, reconnecting with the large-scale magnetic
field. The magnetic field in VLA 2 is perpendicular to the expansion directions until it encounters the denser matter in the northeast,
where the magnetic field is parallel to the expansion direction and agrees with the large-scale magnetic field. We also measured the
magnetic field strength along the line of sight in three of the four epochs, with resulting values of −764 mG < BVLA 1 < −676 mG and ||
−355mG<BVLA2 <−2426mG.
MONTHL Y NOTICES OF THE ROYAL ASTRON OMICAL SOCIETY 2023, 523, 5703-5818
Authors:
Hyeon-Woo Jeong ,1,2 Sang-Sung Lee ,1,2‹ Whee Yeon Cheong ,1,2 Jae-Young Kim ,3,4 Jee Won Lee ,2 Sincheol Kang ,2 Sang-Hyun Kim ,1,2 B. Rani ,2,5,6 Jongho Park 2 and Mark
A. Gurwell 7
Affiliation:
1Astronomy and Space Science, University of Science and Technology, 217 Gajeong-ro, Yuseong-gu, Daejeon 34113, Republic of Korea
2Korea Astronomy and Space Science Institute, 776 Daedeok-daero, Yuseong-gu, Daejeon 34055, Republic of Korea 3Department of Astronomy and Atmospheric Sciences, Kyungpook National University, Daegu 702-701, Republic of Korea 4Max-Planck-Institut fu ̈r Radioastronomie, Auf dem Hu ̈gel 69, D-53121 Bonn, Germany
5NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA
6Department of Physics, American University, Washington, DC 20016, USA
7Center for Astrophysics | Harvard & Smithsonian, 60 Garden Street, Cambridge, MA 02138, USA
Abstract:
We present the results of a radio multifrequency (3−340 GHz) study of the blazar 3C 454.3. After subtracting the quiescent spectrum corresponding to optically thin emission, we found two individual synchrotron self-absorption (SSA) features in the wide-band spectrum. The one SSA had a relatively low turnover frequency (νm) in the range of 3−37 GHz (lower νm SSA spectrum, LSS), and the other one had a relatively high νm of 55−124 GHz (higher νm SSA spectrum, HSS). Using the SSA parameters,weestimatedB-fieldstrengthsatthesurfacewhereopticaldepthτ =1.TheestimatedB-fieldstrengthswere>7 and > 0.2 mG for the LSS and HSS, respectively. The LSS-emitting region was magnetically dominated before the 2014 June γ -ray flare. The quasi-stationary component (C), ∼0.6 mas apart from the 43 -GHz radio core, became brighter than the core with decreasing observing frequency, and we found that component C was related to the LSS. A decrease in jet width was found near component C. As a moving component, K14 approached component C, and the flux density of the component was enhanced while the angular size decreased. The high intrinsic brightness temperature in the fluid frame was obtained as TB, int ≈ (7.0 ± 1.0) × 1011 K from the jet component after the 2015 August γ -ray flare, suggesting that component C is a high-energy emitting region. The observed local minimum of jet width and re-brightening behaviour suggest a possible recollimation shock in component C.
1 Department of Astronomy, Yonsei University, Yonsei-ro 50, Seodaemun-gu, Seoul 03722, Republic of Korea
e-mail: hwro@yonsei.ac.kr
2 Korea Astronomy & Space Science Institute, Daedeokdae-ro 776, Yuseong-gu, Daejeon 34055, Republic of Korea
3 National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan
4 Kogakuin University of Technology & Engineering, Academic Sup- port Center, 2665-1 Nakano, Hachioji, Tokyo 192-0015, Japan
5 University of Science and Technology, Gajeong-ro 217, Yuseong-gu, Daejeon 34113, Republic of Korea
6 Mizusawa VLBI Observatory, National Astronomical Observatory of Japan, 2-12 Hoshigaoka, Mizusawa, Oshu, Iwate 023-0861, Japan
7 Department of Astronomical Science, The Graduate University for Advanced Studies (SOKENDAI), 2-21-1 Osawa, Mitaka, Tokyo
181-8588, Japan
8 Institute of Astronomy and Astrophysics, Academia Sinica, 11F
of Astronomy-Mathematics Building, AS/NTU No. 1, Sec. 4,
Roosevelt Rd, Taipei 10617, Taiwan, ROC
9 Department of Physics and Astronomy, Seoul National University,
1 Gwanak-ro Gwanak-gu, Seoul 08826, Republic of Korea
10 Department of General Science & Education, National Institute of Technology, Hachinohe College, 16-1 Tamonoki, Uwanotai,
Hachinohe City, Aomori 039-1192, Japan
11 Research Center for Intelligent Computing Platforms, Zhejiang
Laboratory, Hangzhou 311100, PR China
12 Tsung-Dao Lee Institute, Shanghai Jiao Tong University, Shanghai
201210, PR China
13 Department of Physics and Astronomy, Sejong University, 209
Neungdong-ro, Gwangjin-gu, Seoul 05006, Republic of Korea
14 Institute for Cosmic Ray Research, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8582, Japan
15 Shanghai Astronomical Observatory, Chinese Academy of Sciences, 80 Nandan Road, Shanghai 200030, PR China
16 SNU Astronomy Research Center (SNUARC), Seoul National University, 1 Gwanak-ro Gwanak-gu, Seoul 08826, Republic of Korea
17 Department of Physics, Faculty of Science, University of Malaya, 50603 Kuala Lumpur, Malaysia
18 Department of Astronomy and Atmospheric Sciences, Kyungpook National University, Daegu 702-701, Republic of Korea
19 Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
20 Graduate School of Science, Osaka Metropolitan University, Osaka 599-8531, Japan
21 The Research Institute of Time Studies, Yamaguchi University, Yoshida 1677-1, Yamaguchi-city, Yamaguchi 753-8511, Japan
22 Key Laboratory of Radio Astronomy, Chinese Academy of Sciences, Nanjing 210008, PR China
23 Instituto de Astrofísica de Andalucía – CSIC, Glorieta de la Astronomía s/n, 18008 Granada, Spain
24 Graduate School of Sciences and Technology for Innovation, Yamaguchi University, 1677-1 Yoshida, Yamaguchi, Yamaguchi 753-8511, Japan
25 Joint Institute for VLBI ERIC, 7991 PD Dwingeloo, The Netherlands
26 Tokyo Electron Technology Solutions Limited, Iwate 023-1101, Japan
27 Massachusetts Institute of Technology Haystack Observatory, 99 Millstone Road, Westford, MA 01886, USA
28 Black Hole Initiative at Harvard University, 20 Garden Street, Cambridge, MA 02138, USA
29 Xinjiang Astronomical Observatory, Chinese Academy of Sciences, Urumqi 830011, PR China
30 Toyo University, 5-28-20 Hakusan, Bunkyo-ku, Tokyo 112-8606, Japan
31 Niigata University, 8050 Ikarashi 2-no-cho, Nishi-ku, Niigata 950- 2181, Japan
32 National Astronomical Research Institute of Thailand (Public Orga- nization), 260 Moo 4, T. Donkaew, A. Maerim, Chiangmai 50180, Thailand
33 Department of Astronomy, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033, Japan
34 Department of Physics, UNIST, Ulsan 44919, Republic of Korea
35 Basic Science Research Institute, Chungbuk National University, Chungdae-ro 1, Seowon-Gu, Cheongju, Chungbuk 28644, Republic
of Korea
Abstract:
Context. Because of its proximity and the large size of its black hole, M 87 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 M 87 jet are limited to the innermost part of the jet (?100 rs) or to HST-1 (∼105 rs). No attempt has yet been made to measure the magnetic field strength in between.
Aims. We aim to infer the magnetic field strength of the M 87 jet out to a distance of several thousand rs by tracking the distance-dependent changes in the synchrotron spectrum of the jet from high-resolution very long baseline interferometry observations.
Methods. 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 Very Long Baseline Array (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.
Results. The overall spectral morphology is broadly consistent over the course of these observations. The observed synchrotron spectrum rapidly steepens from α22−43 GHz ∼ −0.7 at ∼2 mas to α22−43 GHz ∼ −2.5 at ∼6 mas. In the KaVA observations, the spectral index remains unchanged until ∼10 mas, but this trend is unclear in the VLBA observations. 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 rs− ∼4500 rs in the deprojected distance) has a range of B = (0.3−1.0 G) (z/2mas)−0.73. Extrapolating to the Event Horizon Telescope scale yields consistent results, suggesting that the majority of the magnetic flux of the jet near the black hole is preserved out to ∼4500 rs without significant dissipation.
Abel L. Peirson1 , Michela Negro2,3,4 , Ioannis Liodakis5 , Riccardo Middei6,7 , Dawoon E. Kim8,9,10 Alan P. Marscher11 , Herman L. Marshall12 , Luigi Pacciani8 , Roger W. Romani1 , Kinwah Wu13 Alessandro Di Marco8 , Niccoló Di Lalla1 , Nicola Omodei1 , Svetlana G. Jorstad11,14 , Iván Agudo15 Pouya M. Kouch5,16, Elina Lindfors5, Francisco José Aceituno15, Maria I. Bernardos15, Giacomo Bonnoli15,17 Víctor Casanova15, Maya García-Comas15, Beatriz Agís-González15 , César Husillos15 , Alessandro Marchini18
, ,
, ,
, Alfredo Sota15 , Carolina Casadio19,20 , Juan Escudero15 , Ioannis Myserlis21,22 , Albrecht Sievers21, Mark Gurwell23 ,
Ramprasad Rao23, Ryo Imazawa24 , Mahito Sasada25, Yasushi Fukazawa24,26,27 , Koji S. Kawabata24,26,27 ,
Makoto Uemura24,26,27, Tsunefumi Mizuno28 , Tatsuya Nakaoka26, Hiroshi Akitaya29 , Yeon Cheong30,31, Hyeon-Woo Jeong30,31, Sincheol Kang30, Sang-Hyun Kim30,31, Sang-Sung Lee30,31, Emmanouil Angelakis32, Alexander Kraus22,
Nicoló Cibrario33 , Immacolata Donnarumma34 , Juri Poutanen17 Matteo Bachetti35 , Luca Baldini36,37 , Wayne H. Baumgartner38
, Fabrizio Tavecchio17 , Lucio A. Antonelli6,7 , , Ronaldo Bellazzini36 , Stefano Bianchi39 ,
, Niccoló Bucciantini42,43,44 , Fiamma Capitanio8
Stephen D. Bongiorno38 , Raffaella Bonino40,41 , Alessandro Brez36
Simone Castellano36 , Elisabetta Cavazzuti34 , Chien-Ting Chen45 , Stefano Ciprini6,46 , Enrico Costa8 ,
, ,
,
Alessandra De Rosa8 , Ettore Del Monte8 , Laura Di Gesu34, Victor Doroshenko47 , Michal Dovčiak48 , Steven R. Ehlert38 , Teruaki Enoto49 , Yuri Evangelista8 , Sergio Fabiani8 , Riccardo Ferrazzoli8 , Javier A. Garcia50
Shuichi Gunji51 , Kiyoshi Hayashida52, Jeremy Heyl53 , Wataru Iwakiri54 , Philip Kaaret38 , Vladimir Karas48 Takao Kitaguchi49, Jeffery J. Kolodziejczak38 , Henric Krawczynski55 , Fabio La Monaca8 , Luca Latronico40
Grzegorz Madejski1, Simone Maldera40 , Alberto Manfreda36 , Frédéric Marin56 , Andrea Marinucci34 , Francesco Massaro40,41 , Giorgio Matt39 , Ikuyuki Mitsuishi57, Fabio Muleri8 , C.-Y. Ng58 , Stephen L. O’Dell38
, ,
,
Chiara Oppedisano40 , Alessandro Papitto7 , George G. Pavlov59 , Matteo Perri6,7, Melissa Pesce-Rollins36 , Pierre-Olivier Petrucci60 , Maura Pilia35 , Andrea Possenti35 , Simonetta Puccetti6 , Brian D. Ramsey38 , John Rankin8
Ajay Ratheesh8 , Oliver J. Roberts45 , Carmelo Sgró36 , Patrick Slane61 , Paolo Soffitta8, Gloria Spandre36 , Douglas A. Swartz45 , Toru Tamagawa49 , Roberto Taverna62 , Yuzuru Tawara57, Allyn F. Tennant38 , Nicholas E. Thomas38 , Francesco Tombesi46,63,64 , Alessio Trois35 , Sergey Tsygankov17 , Roberto Turolla13,62 ,
Jacco Vink65 , Martin C. Weisskopf38 , Fei Xie8,66 , and Silvia Zane13
Affiliation:
1 Department of Physics and Kavli Institute for Particle Astrophysics and Cosmology, Stanford University, Stanford, CA 94305, USA; alpv95@stanford.edu
2 University of Maryland, Baltimore County, Baltimore, MD 21250, USA
3 NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA
4 Center for Research and Exploration in Space Science and Technology, NASA/GSFC, Greenbelt, MD 20771, USA
5 Finnish Centre for Astronomy with ESO, University of Turku, FI-20014 Turku, Finland
6 Space Science Data Center, Agenzia Spaziale Italiana, Via del Politecnico snc, I-00133 Roma, Italy
7 INAF Osservatorio Astronomico di Roma, Via Frascati 33, I-00078 Monte Porzio Catone (RM), Italy
8 INAF Istituto di Astrofisica e Planetologia Spaziali, Via del Fosso del Cavaliere 100, I-00133 Roma, Italy
9 Dipartimento di Fisica, Universitá degli Studi di Roma “La Sapienza”, Piazzale Aldo Moro 5, I-00185 Roma, Italy
10 Dipartimento di Fisica, Universitá degli Studi di Roma “Tor Vergata”, Via della Ricerca Scientifica 1, I-00133 Roma, Italy
11 Institute for Astrophysical Research, Boston University, 725 Commonwealth Avenue, Boston, MA 02215, USA
12 MIT Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA 14 Mullard Space Science Laboratory, University College London, Holmbury St. Mary, Dorking, Surrey RH5 6NT, UK
15 Astronomical Institute, St. Petersburg State University, 28 Universitetsky prospekt, Peterhof, St. Petersburg 198504, Russia
16 Instituto de Astrofísica de Andalucía, IAA-CSIC, Glorieta de la Astronomía s/n, E-18008 Granada, Spain
17 Department of Physics and Astronomy, University of Turku, FI-20014 Turku, Finland
18 INAF Osservatorio Astronomico di Brera, Via E. Bianchi 46, I-23807 Merate (LC), Italy
19 University of Siena, Astronomical Observatory, Via Roma 56, I-53100 Siena, Italy
20 Institute of Astrophysics, Foundation for Research and Technology - Hellas, Voutes, 7110 Heraklion, Greece
21 Department of Physics, University of Crete, 70013 Heraklion, Greece
22 Institut de Radioastronomie Millimétrique, Avenida Divina Pastora, 7, Local 20, E-18012 Granada, Spain
23 Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn, Germany
24 Center for Astrophysics—Harvard & Smithsonian, 60 Garden Street, Cambridge, MA 02138 USA
25 Department of Physics, Graduate School of Advanced Science and Engineering, Hiroshima University Kagamiyama, 1-3-1 Higashi–Hiroshima, Hiroshima 739- 8526, Japan
26 Department of Physics, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8551, Japan
27 Hiroshima Astrophysical Science Center, Hiroshima University 1-3-1 Kagamiyama, Higashi–Hiroshima, Hiroshima 739-8526, Japan
28 Core Research for Energetic Universe (Core-U), Hiroshima University, 1-3-1 Kagamiyama, Higashi–Hiroshima, Hiroshima 739-8526, Japan
29 Hiroshima Astrophysical Science Center, Hiroshima University, 1-3-1 Kagamiyama, Higashi–Hiroshima, Hiroshima 739-8526, Japan
30 Planetary Exploration Research Center, Chiba Institute of Technology 2-17-1 Tsudanuma, Narashino, Chiba 275-0016, Japan
31 Korea Astronomy & Space Science Institute, Daedeokdae-ro 776, Yuseong-gu, Daejeon 34055, Republic Of Korea
32 University of Science and Technology, Gajeong-ro 217, Yuseong- gu, Daejeon 34113, Republic Of Korea
33 Section of Astrophysics, Astronomy & Mechanics, Department of Physics, National and Kapodistrian University of Athens, Panepistimiopolis Zografos 15784, Greece
34 Dipartimento di Fisica, Universitá degli Studi di Torino, Via Pietro Giuria 1, I-10125 Torino, Italy
35 ASI - Agenzia Spaziale Italiana, Via del Politecnico snc, I-00133 Roma, Italy
37 INAF Osservatorio Astronomico di Cagliari, Via della Scienza 5, I-09047 Selargius (CA), Italy
38 Istituto Nazionale di Fisica Nucleare, Sezione di Pisa, Largo B. Pontecorvo 3, I-56127 Pisa, Italy
Abstract:
We report the first >99% confidence detection of X-ray polarization in BL Lacertae. During a recent X-ray/γ-ray
outburst, a 287 ks observation (2022 November 27–30) was taken using the Imaging X-ray Polarimetry Explorer
(IXPE), together with contemporaneous multiwavelength observations from the Neil Gehrels Swift observatory
and XMM-Newton in soft X-rays (0.3–10 keV), NuSTAR in hard X-rays (3–70 keV), and optical polarization from
the Calar Alto and Perkins Telescope observatories. Our contemporaneous X-ray data suggest that the IXPE energy
band is at the crossover between the low- and high-frequency blazar emission humps. The source displays
significant variability during the observation, and we measure polarization in three separate time bins.
Contemporaneous X-ray spectra allow us to determine the relative contribution from each emission hump. We find
>99% confidence X-ray polarization P = 21.7+5.6 % and electric vector polarization angle 2 – 4keV -7.9
ψ2–4keV=−28.°7±8.°7 in the time bin with highest estimated synchrotron flux contribution. We discuss possible implications of our observations, including previous IXPE BL Lacertae pointings, tentatively concluding that synchrotron self-Compton emission dominates over hadronic emission processes during the observed epochs.
Ru-Sen Lu1,2,3 ✉, Keiichi Asada4 ✉, Thomas P. Krichbaum3 ✉, Jongho Park4,5, Fumie Tazaki6,7, Hung-Yi Pu4,8,9, Masanori Nakamura4,10, Andrei Lobanov3, Kazuhiro Hada7,11 ✉,
Kazunori Akiyama12,13,14, Jae-Young Kim3,5,15, Ivan Marti-Vidal16,17, José L. Gómez18, Tomohisa Kawashima19, Feng Yuan1,20,21, Eduardo Ros3, Walter Alef3, Silke Britzen3, Michael Bremer22, Avery E. Broderick23,24,25, Akihiro Doi26,27, Gabriele Giovannini28,29, Marcello Giroletti29, Paul T. P. Ho4, Mareki Honma7,11,30, David H. Hughes31, Makoto Inoue4, Wu Jiang1, Motoki Kino14,32, Shoko Koyama4,33, Michael Lindqvist34, Jun Liu3,
Alan P. Marscher35, Satoki Matsushita4, Hiroshi Nagai11,14, Helge Rottmann3,
Tuomas Savolainen3,36,37, Karl-Friedrich Schuster22, Zhi-Qiang Shen1,2, Pablo de Vicente38, R. Craig Walker39, Hai Yang1,21, J. Anton Zensus3, Juan Carlos Algaba40, Alexander Allardi41, Uwe Bach3, Ryan Berthold42, Dan Bintley42, Do-Young Byun5,43, Carolina Casadio44,45, Shu-Hao Chang4, Chih-Cheng Chang46, Song-Chu Chang46, Chung-Chen Chen4, Ming-Tang Chen47, Ryan Chilson47, Tim C. Chuter42, John Conway34, Geoffrey B. Crew13, Jessica T. Dempsey42,48, Sven Dornbusch3, Aaron Faber49, Per Friberg42,
Javier González García38, Miguel Gómez Garrido38, Chih-Chiang Han4, Kuo-Chang Han46, Yutaka Hasegawa50, Ruben Herrero-Illana51, Yau-De Huang4, Chih-Wei L. Huang4,
Violette Impellizzeri52,53, Homin Jiang4, Hao Jinchi54, Taehyun Jung5, Juha Kallunki37,
Petri Kirves37, Kimihiro Kimura55, Jun Yi Koay4, Patrick M. Koch4, Carsten Kramer22,
Alex Kraus3, Derek Kubo47, Cheng-Yu Kuo56, Chao-Te Li4, Lupin Chun-Che Lin57,
Ching-Tang Liu4, Kuan-Yu Liu4, Wen-Ping Lo4,58, Li-Ming Lu46, Nicholas MacDonald3,
Pierre Martin-Cocher4, Hugo Messias51,59, Zheng Meyer-Zhao4,48, Anthony Minter60,
Dhanya G. Nair61, Hiroaki Nishioka4, Timothy J. Norton62, George Nystrom47, Hideo Ogawa50, Peter Oshiro47, Nimesh A. Patel62, Ue-Li Pen4, Yurii Pidopryhora3,63, Nicolas Pradel4, Philippe A. Raffin47, Ramprasad Rao62, Ignacio Ruiz64, Salvador Sanchez64, Paul Shaw4, William Snow47, T. K. Sridharan53,62, Ranjani Srinivasan4,62, Belén Tercero38, Pablo Torne64, Efthalia Traianou3,18, Jan Wagner3, Craig Walther42, Ta-Shun Wei4, Jun Yang34 & Chen-Yu Yu4
Affiliation:
1Shanghai Astronomical Observatory, Chinese Academy of Sciences, Shanghai, People’s Republic of China. 2Key Laboratory of Radio Astronomy, Chinese Academy of Sciences, Nanjing, People’s Republic of China. 3Max-Planck-Institut für Radioastronomie, Bonn, Germany. 4Institute of Astronomy and Astrophysics, Academia Sinica, Taipei, Taiwan, ROC. 5Korea Astronomy and Space Science Institute, Daejeon, Republic of Korea. 6Simulation Technology Development Department, Tokyo Electron Technology Solutions, Oshu, Japan. 7Mizusawa VLBI Observatory, National Astronomical Observatory of Japan, Oshu, Japan.
8Department of Physics, National Taiwan Normal University, Taipei, Taiwan, ROC. 9Center of Astronomy and Gravitation, National Taiwan Normal University, Taipei, Taiwan, ROC. 10Department of General Science and Education, National Institute of Technology, Hachinohe College, Hachinohe City, Japan. 11Department of Astronomical Science, The Graduate University for Advanced Studies, SOKENDAI, Mitaka, Japan. 12Black Hole Initiative, Harvard University, Cambridge, MA, USA. 13Massachusetts Institute of Technology Haystack Observatory, Westford, MA, USA. 14National Astronomical Observatory of Japan, Mitaka, Japan. 15Department of Astronomy and Atmospheric Sciences, Kyungpook National University, Daegu, Republic of Korea. 16Departament d’Astronomia i Astrofísica, Universitat de València, Valencia, Spain. 17Observatori Astronòmic, Universitat de València, Valencia, Spain. 18Instituto de Astrofísica de Andalucía–CSIC, Granada, Spain. 19Institute for Cosmic Ray Research, The University of Tokyo, Chiba, Japan. 20Key Laboratory for Research in Galaxies and Cosmology, Chinese Academy of Sciences, Shanghai, People’s Republic of China. 21School of Astronomy and Space Sciences, University of Chinese Academy of Sciences, Beijing, People’s Republic of China. 22Institut de Radioastronomie Millimétrique, Saint Martin d’Hères, France. 23Department of Physics and Astronomy, University of Waterloo, Waterloo, Ontario, Canada. 24Waterloo Centre for Astrophysics, University of Waterloo, Waterloo, Ontario, Canada. 25Perimeter Institute for Theoretical Physics, Waterloo, Ontario, Canada. 26Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Sagamihara, Japan. 27Department of Space and Astronautical Science, The Graduate University for Advanced Studies, SOKENDAI, Sagamihara, Japan. 28Dipartimento di Fisica e Astronomia, Università di Bologna, Bologna, Italy. 29Istituto di Radio Astronomia, INAF, Bologna, Italy. 30Department of Astronomy, Graduate School of Science, The University of Tokyo, Tokyo, Japan. 31Instituto Nacional de Astrofísica, Óptica y Electrónica, Puebla, Mexico. 32Academic Support Center, Kogakuin University of Technology and Engineering, Hachioji, Japan. 33Graduate School of Science and Technology, Niigata University, Niigata, Japan. 34Department of Space, Earth and Environment, Chalmers University of Technology, Onsala Space Observatory, Onsala, Sweden. 35Institute for Astrophysical Research, Boston University, Boston, MA, USA. 36Department of Electronics and Nanoengineering, Aalto University, Aalto, Finland. 37Metsähovi Radio Observatory, Aalto University, Kylmälä, Finland. 38Observatorio de Yebes, IGN, Yebes, Spain. 39National Radio Astronomy Observatory, Socorro, NM, USA. 40Department of Physics, Faculty of Science, Universiti Malaya, Kuala Lumpur, Malaysia. 41University of Vermont, Burlington, VT, USA. 42East Asian Observatory, Hilo, HI, USA. 43University of Science and Technology, Daejeon, Republic of Korea. 44Institute of Astrophysics, Foundation for Research and Technology, Heraklion, Greece. 45Department of Physics, University of Crete, Heraklion, Greece. 46System Development Center, National Chung-Shan Institute of Science and Technology, Taoyuan, Taiwan, ROC. 47Institute of Astronomy and Astrophysics, Academia Sinica, Hilo, HI, USA. 48ASTRON, Dwingeloo, The Netherlands. 49Western University, London, Ontario, Canada. 50Graduate School of Science, Osaka Metropolitan University, Osaka, Japan. 51European Southern Observatory, Santiago, Chile. 52Leiden Observatory, University of Leiden, Leiden, The Netherlands. 53National Radio Astronomy Observatory, Charlottesville, VA, USA. 54Electronic Systems Research Division, National Chung-Shan Institute of Science and Technology, Taoyuan, Taiwan, ROC. 55Japan Aerospace Exploration Agency, Tsukuba, Japan. 56Department of Physics, National Sun Yat-Sen University, Kaohsiung City, Taiwan, ROC. 57Department of Physics, National Cheng Kung University, Tainan, Taiwan, ROC.
58Department of Physics, National Taiwan University, Taipei, Taiwan, ROC. 59Joint ALMA Observatory, Santiago, Chile. 60Green Bank Observatory, Green Bank, WV, USA. 61Astronomy Department, Universidad de Concepción, Concepción, Chile. 62Center for Astrophysics | Harvard & Smithsonian, Cambridge, MA, USA. 63Argelander-Institut für Astronomie, Universität Bonn, Bonn, Germany. 64Institut de Radioastronomie Millimétrique, Granada, Spain. ✉e-mail: rslu@shao.ac.cn; asada@asiaa.sinica.edu.tw; tkrichbaum@mpifr-bonn.mpg.de; kazuhiro.hada@nao.ac.jp

Abstract:
The nearby radio galaxy M87 is a prime target for studying black hole accretion and jet
formation1,2. Event Horizon Telescope observations of M87 in 2017, at a wavelength of
1.3 mm, revealed a ring-like structure, which was interpreted as gravitationally lensed
emission around a central black hole3. Here we report images of M87 obtained in 2018,
at a wavelength of 3.5 mm, showing that the compact radio core is spatially resolved.
High-resolution imaging shows a ring-like structure of 8.4+0.5 Schwarzschild radii in −1.1
diameter, approximately 50% larger than that seen at 1.3 mm. The outer edge at 3.5 mm is also larger than that at 1.3 mm. This larger and thicker ring indicates a substantial contribution from the accretion flow with absorption effects, in addition to the gravitationally lensed ring-like emission. The images show that the edge-brightened jet connects to the accretion flow of the black hole. Close to the black hole, the emission profile of the jet-launching region is wider than the expected profile of a black-hole-driven jet, suggesting the possible presence of a wind associated with the accretion flow.
Xiaopeng Cheng , Ilje Cho 2, , Tomohisa Kawashima 3,, Motoki Kino 4,5,, Guang-Yao Zhao 2 , Juan-Carlos Algaba 6 , Yutaro Kofuji 7, Sang-Sung Lee 1,8 , Jee-Won Lee 1 , Whee Yeon Cheong 1,8 , Wu Jiang 9 and Junghwan Oh 10
Affiliation:
Korea Astronomy and Space Science Institute, Daedeok-daero 776, Yuseong-gu,
Daejeon 34055, Republic of Korea
Instituto de Astrofísica de Andalucía—CSIC, Glorieta de la Astronomía s/n, 18008 Granada, Spain
Institute for Cosmic Ray Research, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa,
Chiba 277-8582, Japan
National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan
Academic Support Center, Kogakuin University of Technology & Engineering, 2665-1 Nakano, Hachioji, Tokyo 192-0015, Japan
Department of Physics, Faculty of Science, University of Malaya, Kuala Lumpur 50603, Malaysia
Mizusawa VLBI Observatory, National Astronomical Observatory of Japan, 2-12 Hoshigaoka, Mizusawa, Oshu, Iwate 023-0861, Japan
University of Science and Technology, Gajeong-ro 217, Yuseong-gu, Daejeon 34113, Republic of Korea Shanghai Astronomical Observatory, Chinese Academy of Sciences, Nandan Road 80, Shanghai 200030, China Joint Institute for VLBI ERIC, Oude Hoogeveensedijk 4, 7991 PD Dwingeloo, The Netherlands
Abstract:
Inthiswork,westudiedtheGalacticCentersupermassiveblackhole(SMBH),Sagittarius A* (Sgr A∗ ), with the KVN and VERA Array (KaVA)/East Asian VLBI Network (EAVN) monitoring observations. Especially in 13 May 2019, Sgr A∗ experienced an unprecedented bright near infra-red (NIR) flare; so, we find a possible counterpart at 43 GHz (7 mm). As a result, a large temporal variation of the flux density at the level ∼15.4%, with the highest flux density of 2.04 Jy, is found on 11 May 2019. Interestingly, the intrinsic sizes are also variable, and the area and major-axis size showmarginalcorrelationwithfluxdensitywith2σ. Thus,weinterpretthattheemissionregion at 43 GHz follows the larger-when-brighter relation in 2019. The possible origins are discussed with an emergence of a weak jet/outflow component and the position angle change of the rotation axis of the accretion disk in time.
1 Korea Astronomy and Space Science Institute, 776 Daedeok-daero, Yuseong-gu, Daejeon, Republic of Korea; cho@kasi.re.kr
2 Seoul National University, 1, Gwanak-ro, Gwanak-gu, Seoul, Republic of Korea
Abstract:
We performed simultaneous monitoring observations of the 22.2 GHz H2O and 43.1/42.8/86.2/129.3 GHz SiO masers toward the red supergiant VX Sagittarii using the Korean VLBI Network single-dish telescopes. The observations were conducted about every 2 months from 2013 May to 2019 January (30 epochs in total). They included four optical maxima in the active phase of the optical pulsation cycles. The line profile of a H2O maser always comprised various velocity components with a wider velocity range and varied from highly redshifted to blueshifted velocities with respect to the stellar velocity, in contrast to those of the SiO masers. We examined the relation between peak intensities and velocities of 11 detailed components in the line profile of the H2O maser and the pulsation phases. The peak intensity of each component generally exhibited a better correlation with the pulsation phases than that of total intensity. The peak velocities of several components gradually decreased or increased with respect to the stellar velocity, implying an accelerating motion and the development of asymmetries in the H2O maser region. The characteristics of four transition SiO maser properties were compared according to the stellar pulsation phases. The intensity and velocity variation trend of the 43.1 GHz SiO maser was similar to that of the 42.8 GHz SiO maser. However, the variation trend of the 43.1 and 42.8 GHz SiO masers was different from that of the 86.2 and 129.3 GHz SiO masers. This difference stems from the different location of each maser reflecting a different excitation condition.
Fumie Tazaki 1,* , Yuzhu Cui 2,3 , Kazuhiro Hada 4 , Motoki Kino 4,5, Ilje Cho 6 , Guang-Yao Zhao 6 , Kazunori Akiyama 4,7,8 , Yosuke Mizuno 2,9,10 , Hyunwook Ro 11,12 , Mareki Honma 4,13,14, Ru-Sen Lu 15,16,17 , Zhi-Qiang Shen 15,16, Lang Cui 18 and Yoshinori Yonekura 19
Affiliation:
Tokyo Electron Technology Solutions Limited, Iwate 023-1101, Japan
Tsung-Dao Lee Institute, Shanghai Jiao Tong University, Shanghai 201210, China
Research Center for Intelligent Computing Platforms, Zhejiang Laboratory, Hangzhou 311100, China Mizusawa VLBI Observatory, National Astronomical Observatory of Japan, Iwate 023-0861, Japan Academic Support Center, Kogakuin University of Technology and Engineering, Tokyo 192-0015, Japan Instituto de Astrofísica de Andalucía-CSIC, Glorieta de la Astronomía s/n, E-18008 Granada, Spain Massachusetts Institute of Technology Haystack Observatory, Westford, MA 01886, USA
Black Hole Initiative, Harvard University, Cambridge, MA 02138, USA
School of Physics & Astronomy, Shanghai Jiao Tong University, 800 Dongchuan Road,
Shanghai 200240, China
10 Institut für Theoretische Physik, Goethe-Universität Frankfurt, Max-von-Laue-Straße 1, D-60438 Frankfurt am Main, Germany
11 Department of Astronomy, Yonsei University, Seodaemun-gu, Seoul 03722, Republic of Korea
12 Korea Astronomy and Space Science Institute, Yuseong-gu, Daejeon 34055, Republic of Korea
13 Department of Astronomical Science, The Graduate University for Advanced Studies, SOKENDAI,
Tokyo 181-8588, Japan
14 Institute of Astronomy, The University of Tokyo, Tokyo 181-0015, Japan
15 Shanghai Astronomical Observatory, Chinese Academy of Sciences, Shanghai 200030, China
16 Key Laboratory of Radio Astronomy, Chinese Academy of Sciences, Nanjing 210008, China
17 Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn, Germany
18 Xinjiang Astronomical Observatory, CAS, 150 Science 1-Street, Urumqi 830011, China
19 Center for Astronomy, Ibaraki University, Ibaraki 310-8512, Japan
Abstract:
Obtaininghigh-resolutionimagesatcentimeter-or-longerwavelengthsisvitalforunder- standing the physics of jets. We reconstructed images from the M87 22 GHz data observed with the East Asian VLBI Network (EAVN) by using the regularized maximum likelihood (RML) method, which is different from the conventional imaging method CLEAN. Consequently, a bright core and jet extending about 30 mas to the northwest were detected with a higher resolution than in the CLEAN image. The width of the jet was 0.5 mas at 0.3 mas from the core, consistent with the width measured in the 86 GHz image in the previous study. In addition, three ridges were able to be detected at around 8 mas from the core, even though the peak-to-peak separation was only 1.0 mas. This indicates that the RML image’s spatial resolution is at least 30% higher than that of the CLEAN image. This study is an important step for future multi-frequency and high-cadence observations of the EAVN to discuss the more detailed structure of the jet and its time variability.
Kitiyanee Asanok1 , Malcolm D. Gray1,2 , Tomoya Hirota3,4 , Koichiro Sugiyama1 , Montree Phetra5,
Busaba H. Kramer1,6 , Tie Liu7,8 , Kee-Tae Kim8 , and Bannawit Pimpanuwat2
Affiliation:
1 National Astronomical Research Institute of Thailand, 260 Moo 4, Tambol Donkaew, Amphur Maerim, Chiang Mai, 50180, Thailand; kitiyanee@narit.or.th
2 The University of Manchester, Jodrell Bank Centre for Astrophysics, School of Physics and Astronomy, Alan Turing Building, M139PL, UK
3 Mizusawa VLBI Observatory, National Astronomical Observatory of Japan, Osawa 2-21-1, Mitaka-shi, Tokyo, 181-8588, Japan
4 Department of Astronomical Sciences, SOKENDAI (The Graduate University for Advanced Studies), Osawa 2-21-1, Mitaka-shi, Tokyo, 181-8588, Japan 5 Graduate School, Department of Physics and Material Science, Faculty of Science, Chiang Mai University, Chiang Mai, 50200, Thailand
6 Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, Bonn, D-53121, Germany
7 Shanghai Astronomical Observatory, Chinese Academy of Sciences, 80 Nandan Road, Shanghai, 200030, Peopleʼs Republic of China
8 Korea Astronomy and Space Science Institute, 776 Daedeokdae-ro, Yuseong-gu, Daejeon, 34055, Republic of Korea
Abstract:
We report the proper motions of 22 GHz water masers toward W49 N that were observed by the KVN and VERA Array (KaVA) during 2017 February–May. We found 263, 268, and 310 features in three successive epochs; they were distributed in a region of size 4 × 4 arcsec2. The strongest flux density was in the third epoch, and its averaged value was 18,090 Jy at VLSR +0.47 km s−1. For 102 H2O maser features, proper motion was detected across all three epochs. The average proper motions in R.A. and decl. offset were −0.352 and +0.890 mas yr−1, respectively. The morphology of the distribution of the H2O maser features was found to be a bipolar outflow structure with an inclination angle of 37° ± 13° to the line of sight, and the features were expanding from a well- defined outflow center. A model of the source combining expansion and rotation yielded a distance to W49 of 11.12 ± 0.96 kpc that is consistent with the results from trigonometric parallax. A redshifted lobe was situated in the northeast direction and a blueshifted lobe in the southwest direction. We also discussed the location of the powerful flaring H2O maser feature at VLSR = + 6 km s−1 and its possible mechanisms on the basis of spatial structures for the maser feature in VLBI maps observed with the KaVA, timed just before and during the rebrightening phase.