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Mareki Honma

Bio: Mareki Honma is an academic researcher from Graduate University for Advanced Studies. The author has contributed to research in topics: Very-long-baseline interferometry & Maser. The author has an hindex of 33, co-authored 140 publications receiving 4092 citations. Previous affiliations of Mareki Honma include National Institutes of Natural Sciences, Japan & Japan Society for the Promotion of Science.


Papers
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Journal ArticleDOI
TL;DR: In this article, a unified rotation curve of the Galaxy was reconstructed from the existing data by re-calculating the distances and velocities for a set of galactic constants R0 =8 kpc and V0 =200 km s −1.
Abstract: We present a unified rotation curve of the Galaxy re-constructed from the existing data by re-calculating the distances and velocities for a set of galactic constants R0 =8 kpc and V0 =200 km s −1 . We decompose it into a bulge with de Vaucouleurs-law profile of half-mass scale radius 0.5 kpc and mass 1.8 ×10 10 M⊙, an exponential disk of scale radius 3.5 kpc of 6.5 ×10 10 M⊙, and an isothermal dark halo of terminal velocity 200 km s −1 . The r 1/4 -law fit was obtained for the first time for the Milky Way’s rotation curve. After fitting by these fundamental structures, two local minima, or the dips, of rotation velocity are prominent at radii 3 and 9 kpc. The 3-kpc dip is consistent with the observed bar. It is alternatively explained by a massive ring with the density maximum at radius 4 kpc. The 9-kpc dip is clearly exhibited as the most peculiar feature in the galactic rotation curve. We explain it by a massive ring of amplitude as large as 0.3 to 0.4 times the disk density with the density peak at radius 11 kpc. This great ring may be related to the Perseus arm, while no peculiar feature of HI-gas is associated.

337 citations

Journal ArticleDOI
TL;DR: In this paper, the authors measured the trigonometric parallaxes and proper motions of five massive star-forming regions toward the Cygnus X complex and reported the following distances within a 10% accuracy: 1.30+0.12 −0.11 -0.
Abstract: Context. Whether the Cygnus X complex consists of one physically connected region of star formation or of multiple independent regions projected close together on the sky has been debated for decades. The main reason for this puzzling scenario is the lack of trustworthy distance measurements.Aims. We aim to understand the structure and dynamics of the star-forming regions toward Cygnus X by accurate distance and proper motion measurements.Methods. To measure trigonometric parallaxes, we observed 6.7 GHz methanol and 22 GHz water masers with the European VLBI Network and the Very Long Baseline Array.Results. We measured the trigonometric parallaxes and proper motions of five massive star-forming regions toward the Cygnus X complex and report the following distances within a 10% accuracy: 1.30+0.07 -0.07 kpc for W 75N, 1.46+0.09 -0.08 kpc for DR 20, 1.50+0.08 -0.07 kpc for DR 21, 1.36+0.12 -0.11 kpc for IRAS 20290+4052, and 3.33+0.11 -0.11 kpc for AFGL 2591. While the distances of W 75N, DR 20, DR 21, and IRAS 20290+4052 are consistent with a single distance of 1.40 ± 0.08 kpc for the Cygnus X complex, AFGL 2591 is located at a much greater distance than previously assumed. The space velocities of the four star-forming regions in the Cygnus X complex do not suggest an expanding Stromgren sphere.

303 citations

Journal ArticleDOI
TL;DR: In this article, the authors present a list of authors who have contributed to the work of the authors of this paper: Akiyama, Kazunori; Algaba, Juan Carlos; Alberdi, Antxon; Alef, Walter; Anantua, Richard; Asada, Keiichi; Azulay, Rebecca; Baczko, Anne-Kathrin; Ball, David; Balokovic, Mislav; Barrett, John; Benson, Bradford A.; Bintley, Dan; Blackburn, Lindy; Blundell
Abstract: Full list of authors: Akiyama, Kazunori; Algaba, Juan Carlos; Alberdi, Antxon; Alef, Walter; Anantua, Richard; Asada, Keiichi; Azulay, Rebecca; Baczko, Anne-Kathrin; Ball, David; Balokovic, Mislav; Barrett, John; Benson, Bradford A.; Bintley, Dan; Blackburn, Lindy; Blundell, Raymond; Boland, Wilfred; Bouman, Katherine L.; Bower, Geoffrey C.; Boyce, Hope Bremer, Michael; Brinkerink, Christiaan D.; Brissenden, Roger; Britzen, Silke; Broderick, Avery E.; Broguiere, Dominique; Bronzwaer, Thomas; Byun, Do-Young; Carlstrom, John E.; Chael, Andrew; Chan, Chi-kwan; Chatterjee, Shami; Chatterjee, Koushik; Chen, Ming-Tang; Chen, Yongjun; Chesler, Paul M.; Cho, Ilje; Christian, Pierre; Conway, John E.; Cordes, James M.; Crawford, Thomas M.; Crew, Geoffrey B.; Cruz-Osorio, Alejandro; Cui, Yuzhu; Davelaar, Jordy; De Laurentis, Mariafelicia; Deane, Roger; Dempsey, Jessica; Desvignes, Gregory; Dexter, Jason; Doeleman, Sheperd S.; Eatough, Ralph P.; Falcke, Heino; Farah, Joseph; Fish, Vincent L.; Fomalont, Ed; Ford, H. Alyson; Fraga-Encinas, Raquel; Friberg, Per; Fromm, Christian M.; Fuentes, Antonio; Galison, Peter; Gammie, Charles F.; Garcia, Roberto; Gelles, Zachary; Gentaz, Olivier; Georgiev, Boris; Goddi, Ciriaco; Gold, Roman; Gomez, Jose L.; Gomez-Ruiz, Arturo I.; Gu, Minfeng; Gurwell, Mark; Hada, Kazuhiro; Haggard, Daryl; Hecht, Michael H.; Hesper, Ronald; Himwich, Elizabeth; Ho, Luis C.; Ho, Paul; Honma, Mareki; Huang, Chih-Wei L.; Huang, Lei; Hughes, David H.; Ikeda, Shiro; Inoue, Makoto; Issaoun, Sara; James, David J.; Jannuzi, Buell T.; Janssen, Michael; Jeter, Britton; Jiang, Wu; Jimenez-Rosales, Alejandra; Johnson, Michael D.; Jorstad, Svetlana; Jung, Taehyun; Karami, Mansour; Karuppusamy, Ramesh; Kawashima, Tomohisa; Keating, Garrett K.; Kettenis, Mark; Kim, Dong-Jin; Kim, Jae-Young; Kim, Jongsoo; Kim, Junhan; Kino, Motoki; Koay, Jun Yi; Kofuji, Yutaro; Koch, Patrick M.; Koyama, Shoko; Kramer, Michael; Kramer, Carsten; Krichbaum, Thomas P.; Kuo, Cheng-Yu; Lauer, Tod R.; Lee, Sang-Sung; Levis, Aviad; Li, Yan-Rong; Li, Zhiyuan; Lindqvist, Michael; Lico, Rocco; Lindahl, Greg; Liu, Jun; Liu, Kuo; Liuzzo, Elisabetta; Lo, Wen-Ping; Lobanov, Andrei P.; Loinard, Laurent; Lonsdale, Colin; Lu, Ru-Sen; MacDonald, Nicholas R.; Mao, Jirong; Marchili, Nicola; Markoff, Sera; Marrone, Daniel P.; Marscher, Alan P.; Marti-Vidal, Ivan; Matsushita, Satoki; Matthews, Lynn D.; Medeiros, Lia; Menten, Karl M.; Mizuno, Izumi; Mizuno, Yosuke; Moran, James M.; Moriyama, Kotaro; Moscibrodzka, Monika; Muller, Cornelia; Musoke, Gibwa; Mus Mejias, Alejandro; Michalik, Daniel; Nadolski, Andrew; Nagai, Hiroshi; Nagar, Neil M.; Nakamura, Masanori; Narayan, Ramesh; Narayanan, Gopal; Natarajan, Iniyan; Nathanail, Antonios; Neilsen, Joey; Neri, Roberto; Ni, Chunchong; Noutsos, Aristeidis; Nowak, Michael A.; Okino, Hiroki; Olivares, Hector; Ortiz-Leon, Gisela N.; Oyama, Tomoaki; Ozel, Feryal; Palumbo, Daniel C. M.; Park, Jongho; Patel, Nimesh; Pen, Ue-Li; Pesce, Dominic W.; Pietu, Vincent; Plambeck, Richard; PopStefanija, Aleksandar; Porth, Oliver; Potzl, Felix M.; Prather, Ben; Preciado-Lopez, Jorge A.; Psaltis, Dimitrios; Pu, Hung-Yi; Ramakrishnan, Venkatessh; Rao, Ramprasad; Rawlings, Mark G.; Raymond, Alexander W.; Rezzolla, Luciano; Ricarte, Angelo; Ripperda, Bart; Roelofs, Freek; Rogers, Alan; Ros, Eduardo; Rose, Mel; Roshanineshat, Arash; Rottmann, Helge; Roy, Alan L.; Ruszczyk, Chet; Rygl, Kazi L. J.; Sanchez, Salvador; Sanchez-Arguelles, David; Sasada, Mahito; Savolainen, Tuomas; Schloerb, F. Peter; Schuster, Karl-Friedrich; Shao, Lijing; Shen, Zhiqiang; Small, Des; Sohn, Bong Won; SooHoo, Jason; Sun, He; Tazaki, Fumie; Tetarenko, Alexandra J.; Tiede, Paul; Tilanus, Remo P. J.; Titus, Michael; Toma, Kenji; Torne, Pablo; Trent, Tyler; Traianou, Efthalia; Trippe, Sascha; van Bemmel, Ilse; van Langevelde, Huib Jan; van Rossum, Daniel R.; Wagner, Jan; Ward-Thompson, Derek; Wardle, John; Weintroub, Jonathan; Wex, Norbert; Wharton, Robert; Wielgus, Maciek; Wong, George N.; Wu, Qingwen; Yoon, Doosoo; Young, Andre; Young, Ken; Younsi, Ziri; Yuan, Feng; Yuan, Ye-Fei; Zensus, J. Anton; Zhao, Guang-Yao; Zhao, Shan-Shan; Event Horizon Telescope Collaboration.-- This is an open access article, original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.

294 citations

Journal ArticleDOI
TL;DR: In this article, high-resolution central-to-outer rotation curves for Sb, SB, SBb, Sc, and SBc galaxies were presented, showing a steep nuclear rise and high-velocity central rotation followed by a broad maximum in the disk and then a flat rotation due to the massive halo.
Abstract: We present high-resolution central-to-outer rotation curves for Sb, SBb, Sc, and SBc galaxies. We discuss their general characteristics, particularly their central behavior, as well as dependencies on morphological types, activity, and peculiarity. The rotation curves generally show a steep nuclear rise and high-velocity central rotation, followed by a broad maximum in the disk and then a flat rotation due to the massive halo. Since the central high velocity and steep rise are common to all massive galaxies, they cannot be due to noncircular motions. Disk rotation curves of barred galaxies show larger dispersion than those of normal galaxies, probably because of noncircular motions. Interacting galaxies often show perturbed outer rotation curves, while their central rotation shows no particular peculiarity. In addition, central activities, such as starbursts and active galactic nuclei, appear to show no particular correlation with the property of rotation curves. This would suggest that the central activities are triggered by a more local effect than the global dynamical property.

266 citations

Journal ArticleDOI
TL;DR: In this article, the authors presented the initial results of multiepoch VLBI observations of 22 GHz H2O masers in the Orion KL region with VERA (VLBI Exploration of Radio Astrometry).
Abstract: We present the initial results of multiepoch VLBI observations of 22 GHz H2O masers in the Orion KL region with VERA (VLBI Exploration of Radio Astrometry). With the VERA dual-beam receiving system, we carried out phase-referencing VLBI astrometry, and successfully detected the annual parallax of Orion KL to be 2.29 ˙ 0.10 mas, corresponding to a distance of 437 ˙ 19 pc from the Sun. The distance to Orion KL was determined for the first time with the trigonometric parallax method in these observations. Although this value is consistent with that previously reported, 480 ˙ 80 pc, which was estimated from a statistical parallax method using the proper motions and radial velocities of the H2O maser features, our new results provide a much more accurate value with an uncertainty of only 4%. In addition to the annual parallax, we detected an absolute proper motion of the maser feature, suggesting an outflow motion powered by the radio source I along with the systematic motion of source I itself.

235 citations


Cited by
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[...]

08 Dec 2001-BMJ
TL;DR: There is, I think, something ethereal about i —the square root of minus one, which seems an odd beast at that time—an intruder hovering on the edge of reality.
Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

33,785 citations

Journal ArticleDOI
Kazunori Akiyama, Antxon Alberdi1, Walter Alef2, Keiichi Asada3  +403 moreInstitutions (82)
TL;DR: In this article, the Event Horizon Telescope was used to reconstruct event-horizon-scale images of the supermassive black hole candidate in the center of the giant elliptical galaxy M87.
Abstract: When surrounded by a transparent emission region, black holes are expected to reveal a dark shadow caused by gravitational light bending and photon capture at the event horizon. To image and study this phenomenon, we have assembled the Event Horizon Telescope, a global very long baseline interferometry array observing at a wavelength of 1.3 mm. This allows us to reconstruct event-horizon-scale images of the supermassive black hole candidate in the center of the giant elliptical galaxy M87. We have resolved the central compact radio source as an asymmetric bright emission ring with a diameter of 42 +/- 3 mu as, which is circular and encompasses a central depression in brightness with a flux ratio greater than or similar to 10: 1. The emission ring is recovered using different calibration and imaging schemes, with its diameter and width remaining stable over four different observations carried out in different days. Overall, the observed image is consistent with expectations for the shadow of a Kerr black hole as predicted by general relativity. The asymmetry in brightness in the ring can be explained in terms of relativistic beaming of the emission from a plasma rotating close to the speed of light around a black hole. We compare our images to an extensive library of ray-traced general-relativistic magnetohydrodynamic simulations of black holes and derive a central mass of M = (6.5 +/- 0.7) x 10(9) M-circle dot. Our radio-wave observations thus provide powerful evidence for the presence of supermassive black holes in centers of galaxies and as the central engines of active galactic nuclei. They also present a new tool to explore gravity in its most extreme limit and on a mass scale that was so far not accessible.

2,589 citations

Journal ArticleDOI
TL;DR: In this paper, the authors review progress over the past decade in observations of large-scale star formation, with a focus on the interface between extragalactic and Galactic studies.
Abstract: We review progress over the past decade in observations of large-scale star formation, with a focus on the interface between extragalactic and Galactic studies. Methods of measuring gas contents and star-formation rates are discussed, and updated prescriptions for calculating star-formation rates are provided. We review relations between star formation and gas on scales ranging from entire galaxies to individual molecular clouds.

2,525 citations

15 Mar 1979
TL;DR: In this article, the experimental estimation of parameters for models can be solved through use of the likelihood ratio test, with particular attention to photon counting experiments, and procedures presented solve a greater range of problems than those currently in use, yet are no more difficult to apply.
Abstract: Many problems in the experimental estimation of parameters for models can be solved through use of the likelihood ratio test. Applications of the likelihood ratio, with particular attention to photon counting experiments, are discussed. The procedures presented solve a greater range of problems than those currently in use, yet are no more difficult to apply. The procedures are proved analytically, and examples from current problems in astronomy are discussed.

1,748 citations