Paper

• Science with the Cherenkov Telescope Array
  Cherenkov Telescope Array Consortium; Acharya, B. S.; Agudo, I.; Al Samarai, I.; Alfaro, R.; Alfaro, J.; Alispach, C.; Alves Batista, R.; Amans, J. -P.; Amato, E.; Ambrosi, G.; Antolini, E.; Antonelli, L. A.; Aramo, C.; Araya, M.; Armstrong, T.; Arqueros, F.; Arrabito, L.; Asano, K.; Ashley, M.; Backes, M.; Balazs, C.; Balbo, M.; Ballester, O.; Ballet, J.; Bamba, A.; Barkov, M.; Barres de Almeida, U.; Barrio, J. A.; Bastieri, D.; Becherini, Y.; Belfiore, A.; Benbow, W.; Berge, D.; Bernardini, E.; Bernardini, M. G.; Bernardos, M.; Bernlöhr, K.; Bertucci, B.; Biasuzzi, B.; Bigongiari, C.; Biland, A.; Bissaldi, E.; Biteau, J.; Blanch, O.; Blazek, J.; Boisson, C.; Bolmont, J.; Bonanno, G.; Bonardi, A.; Bonavolontà, C.; Bonnoli, G.; Bosnjak, Z.; Böttcher, M.; Braiding, C.; Bregeon, J.; Brill, A.; Brown, A. M.; Brun, P.; Brunetti, G.; Buanes, T.; Buckley, J.; Bugaev, V.; Bühler, R.; Bulgarelli, A.; Bulik, T.; Burton, M.; Burtovoi, A.; Busetto, G.; Canestrari, R.; Capalbi, M.; Capitanio, F.; Caproni, A.; Caraveo, P.; Cárdenas, V.; Carlile, C.; Carosi, R.; Carquín, E.; Carr, J.; Casanova, S.; Cascone, E.; Catalani, F.; Catalano, O.; Cauz, D.; Cerruti, M.; Chadwick, P.; Chaty, S.; Chaves, R. C. G.; Chen, A.; Chen, X.; Chernyakova, M.; Chikawa, M.; Christov, A.; Chudoba, J.; Cieślar, M.; Coco, V.; Colafrancesco, S.; Colin, P.; Conforti, V.; Connaughton, V.; Conrad, J.; Contreras, J. L.; Cortina, J.; Costa, A.; Costantini, H.; Cotter, G.; Covino, S.; Crocker, R.; Cuadra, J.; Cuevas, O.; Cumani, P.; D'Aì, A.; D'Ammando, F.; D'Avanzo, P.; D'Urso, D.; Daniel, M.; Davids, I.; Dawson, B.; Dazzi, F.; De Angelis, A.; de Cássia dos Anjos, R.; De Cesare, G.; De Franco, A.; de Gouveia Dal Pino, E. M.; de la Calle, I.; de los Reyes Lopez, R.; De Lotto, B.; De Luca, A.; De Lucia, M.; de Naurois, M.; de Oña Wilhelmi, E.; De Palma, F.; De Persio, F.; de Souza, V.; Deil, C.; Del Santo, M.; Delgado, C.; della Volpe, D.; Di Girolamo, T.; Di Pierro, F.; Di Venere, L.; Díaz, C.; Dib, C.; Diebold, S.; Djannati-Ataï, A.; Domínguez, A.; Dominis Prester, D.; Dorner, D.; Doro, M.; Drass, H.; Dravins, D.; Dubus, G.; Dwarkadas, V. V.; Ebr, J.; Eckner, C.; Egberts, K.; Einecke, S.; Ekoume, T. R. N.; Elsässer, D.; Ernenwein, J. -P.; Espinoza, C.; Evoli, C.; Fairbairn, M.; Falceta-Goncalves, D.; Falcone, A.; Farnier, C.; Fasola, G.; Fedorova, E.; Fegan, S.; Fernandez-Alonso, M.; Fernández-Barral, A.; Ferrand, G.; Fesquet, M.; Filipovic, M.; Fioretti, V.; Fontaine, G.; Fornasa, M.; Fortson, L.; Freixas Coromina, L.; Fruck, C.; Fujita, Y.; Fukazawa, Y.; Funk, S.; Füßling, M.; Gabici, S.; Gadola, A.; Gallant, Y.; Garcia, B.; Garcia López, R.; Garczarczyk, M.; Gaskins, J.; Gasparetto, T.; Gaug, M.; Gerard, L.; Giavitto, G.; Giglietto, N.; Giommi, P.; Giordano, F.; Giro, E.; Giroletti, M.; Giuliani, A.; Glicenstein, J. -F.; Gnatyk, R.; Godinovic, N.; Goldoni, P.; Gómez-Vargas, G.; González, M. M.; González, J. M.; Götz, D.; Graham, J.; Grandi, P.; Granot, J.; Green, A. J.; Greenshaw, T.; Griffiths, S.; Gunji, S.; Hadasch, D.; Hara, S.; Hardcastle, M. J.; Hassan, T.; Hayashi, K.; Hayashida, M.; Heller, M.; Helo, J. C.; Hermann, G.; Hinton, J.; Hnatyk, B.; Hofmann, W.; Holder, J.; Horan, D.; Hörandel, J.; Horns, D.; Horvath, P.; Hovatta, T.; Hrabovsky, M.; Hrupec, D.; Humensky, T. B.; Hütten, M.; Iarlori, M.; Inada, T.; Inome, Y.; Inoue, S.; Inoue, T.; Inoue, Y.; Iocco, F.; Ioka, K.; Iori, M.; Ishio, K.; Iwamura, Y.; Jamrozy, M.; Janecek, P.; Jankowsky, D.; Jean, P.; Jung-Richardt, I.; Jurysek, J.; Kaaret, P.; Karkar, S.; Katagiri, H.; Katz, U.; Kawanaka, N.; Kazanas, D.; Khélifi, B.; Kieda, D. B.; Kimeswenger, S.; Kimura, S.; Kisaka, S.; Knapp, J.; Knödlseder, J.; Koch, B.; Kohri, K.; Komin, N.; Kosack, K.; Kraus, M.; Krause, M.; Krauß, F.; Kubo, H.; Kukec Mezek, G.; Kuroda, H.; Kushida, J.; La Palombara, N.; Lamanna, G.; Lang, R. G.; Lapington, J.; Le Blanc, O.; Leach, S.; Lees, J. -P.; Lefaucheur, J.; Leigui de Oliveira, M. A.; Lenain, J. -P.; Lico, R.; Limon, M.; Lindfors, E.; Lohse, T.; Lombardi, S.; Longo, F.; López, M.; López-Coto, R.; Lu, C. -C.; Lucarelli, F.; Luque-Escamilla, P. L.; Lyard, E.; Maccarone, M. C.; Maier, G.; Majumdar, P.; Malaguti, G.; Mandat, D.; Maneva, G.; Manganaro, M.; Mangano, S.; Marcowith, A.; Marín, J.; Markoff, S.; Martí, J.; Martin, P.; Martínez, M.; Martínez, G.; Masetti, N.; Masuda, S.; Maurin, G.; Maxted, N.; Mazin, D.; Medina, C.; Melandri, A.; Mereghetti, S.; Meyer, M.; Minaya, I. A.; Mirabal, N.; Mirzoyan, R.; Mitchell, A.; Mizuno, T.; Moderski, R.; Mohammed, M.; Mohrmann, L.; Montaruli, T.; Moralejo, A.; Morcuende-Parrilla, D.; Mori, K.; Morlino, G.; Morris, P.; Morselli, A.; Moulin, E.; Mukherjee, R.; Mundell, C.; Murach, T.; Muraishi, H.; Murase, K.; Nagai, A.; Nagataki, S.; Nagayoshi, T.; Naito, T.; Nakamori, T.; Nakamura, Y.; Niemiec, J.; Nieto, D.; Nikołajuk, M.; Nishijima, K.; Noda, K.; Nosek, D.; Novosyadlyj, B.; Nozaki, S.; O'Brien, P.; Oakes, L.; Ohira, Y.; Ohishi, M.; Ohm, S.; Okazaki, N.; Okumura, A.; Ong, R. A.; Orienti, M.; Orito, R.; Osborne, J. P.; Ostrowski, M.; Otte, N.; Oya, I.; Padovani, M.; Paizis, A.; Palatiello, M.; Palatka, M.; Paoletti, R.; Paredes, J. M.; Pareschi, G.; Parsons, R. D.; Pe'er, A.; Pech, M.; Pedaletti, G.; Perri, M.; Persic, M.; Petrashyk, A.; Petrucci, P.; Petruk, O.; Peyaud, B.; Pfeifer, M.; Piano, G.; Pisarski, A.; Pita, S.; Pohl, M.; Polo, M.; Pozo, D.; Prandini, E.; Prast, J.; Principe, G.; Prokhorov, D.; Prokoph, H.; Prouza, M.; Pühlhofer, G.; Punch, M.; Pürckhauer, S.; Queiroz, F.; Quirrenbach, A.; Rainò, S.; Razzaque, S.; Reimer, O.; Reimer, A.; Reisenegger, A.; Renaud, M.; Rezaeian, A. H.; Rhode, W.; Ribeiro, D.; Ribó, M.; Richtler, T.; Rico, J.; Rieger, F.; Riquelme, M.; Rivoire, S.; Rizi, V.; Rodriguez, J.; Rodriguez Fernandez, G.; Rodríguez Vázquez, J. J.; Rojas, G.; Romano, P.; Romeo, G.; Rosado, J.; Rovero, A. C.; Rowell, G.; Rudak, B.; Rugliancich, A.; Rulten, C.; Sadeh, I.; Safi-Harb, S.; Saito, T.; Sakaki, N.; Sakurai, S.; Salina, G.; Sánchez-Conde, M.; Sandaker, H.; Sandoval, A.; Sangiorgi, P.; Sanguillon, M.; Sano, H.; Santander, M.; Sarkar, S.; Satalecka, K.; Saturni, F. G.; Schioppa, E. J.; Schlenstedt, S.; Schneider, M.; Schoorlemmer, H.; Schovanek, P.; Schulz, A.; Schussler, F.; Schwanke, U.; Sciacca, E.; Scuderi, S.; Seitenzahl, I.; Semikoz, D.; Sergijenko, O.; Servillat, M.; Shalchi, A.; Shellard, R. C.; Sidoli, L.; Siejkowski, H.; Sillanpää, A.; Sironi, G.; Sitarek, J.; Sliusar, V.; Slowikowska, A.; Sol, H.; Stamerra, A.; Stanič, S.; Starling, R.; Stawarz, Ł.; Stefanik, S.; Stephan, M.; Stolarczyk, T.; Stratta, G.; Straumann, U.; Suomijarvi, T.; Supanitsky, A. D.; Tagliaferri, G.; Tajima, H.; Tavani, M.; Tavecchio, F.; Tavernet, J. -P.; Tayabaly, K.; Tejedor, L. A.; Temnikov, P.; Terada, Y.; Terrier, R.; Terzic, T.; Teshima, M.; Testa, V.; Thoudam, S.; Tian, W.; Tibaldo, L.; Tluczykont, M.; Todero Peixoto, C. J.; Tokanai, F.; Tomastik, J.; Tonev, D.; Tornikoski, M.; Torres, D. F.; Torresi, E.; Tosti, G.; Tothill, N.; Tovmassian, G.; Travnicek, P.; Trichard, C.; Trifoglio, M.; Troyano Pujadas, I.; Tsujimoto, S.; Umana, G.; Vagelli, V.; Vagnetti, F.; Valentino, M.; Vallania, P.; Valore, L.; van Eldik, C.; Vandenbroucke, J.; Varner, G. S.; Vasileiadis, G.; Vassiliev, V.; Vázquez Acosta, M.; Vecchi, M.; Vega, A.; Vercellone, S.; Veres, P.; Vergani, S.; Verzi, V.; Vettolani, G. P.; Viana, A.; Vigorito, C.; Villanueva, J.; Voelk, H.; Vollhardt, A.; Vorobiov, S.; Vrastil, M.; Vuillaume, T.; Wagner, S. J.; Wagner, R.; Walter, R.; Ward, J. E.; Warren, D.; Watson, J. J.; Werner, F.; White, M.; White, R.; Wierzcholska, A.; Wilcox, P.; Will, M.; Williams, D. A.; Wischnewski, R.; Wood, M.; Yamamoto, T.; Yamazaki, R.; Yanagita, S.; Yang, L.; Yoshida, T.; Yoshiike, S.; Yoshikoshi, T.; Zacharias, M.; Zaharijas, G.; Zampieri, L.; Zandanel, F.; Zanin, R.; Zavrtanik, M.; Zavrtanik, D.; Zdziarski, A. A.; Zech, A.; Zechlin, H.; Zhdanov, V. I.; Ziegler, A.; Zorn, J., The Cherenkov Telescope Array, CTA, will be the major global observatory for very high energy gamma-ray astronomy over the next decade and beyond. The scientific potential of CTA is extremely broad: from understanding the role of relativistic cosmic particles to the search for dark matter. CTA is an explorer of the extreme universe, probing environments from the immediate neighbourhood of black holes to cosmic voids on the largest scales. Covering a huge range in photon energy from 20 GeV to 300 TeV, CTA will improve on all aspects of performance with respect to current instruments. The observatory will operate arrays on sites in both hemispheres to provide full sky coverage and will hence maximize the potential for the rarest phenomena such as very nearby supernovae, gamma-ray bursts or gravitational wave transients. With 99 telescopes on the southern site and 19 telescopes on the northern site, flexible operation will be possible, with sub-arrays available for specific tasks. CTA will have important synergies with many of the new generation of major astronomical and astroparticle observatories. Multi-wavelength and multi-messenger approaches combining CTA data with those from other instruments will lead to a deeper understanding of the broad-band non-thermal properties of target sources. The CTA Observatory will be operated as an open, proposal-driven observatory, with all data available on a public archive after a pre-defined proprietary period. Scientists from institutions worldwide have combined together to form the CTA Consortium. This Consortium has prepared a proposal for a Core Programme of highly motivated observations. The programme, encompassing approximately 40% of the available observing time over the first ten years of CTA operation, is made up of individual Key Science Projects (KSPs), which are presented in this document...., Science with the Cherenkov Telescope Array
  2019
• A technique for estimating the absolute gain of a photomultiplier tube
  A Takahashi; M.; Inome; Y.; Yoshii; S.; Bamba; A.; Gunji; S.; Hadasch; D.; Hayashida; M.; Katagiri; H.; Konno; Y.; Kubo; H.; Kushida; J.;; Nakajima; D.; Nakamori; T.; Nagayoshi; T.; Nishijima; K.; Nozaki; S.;; Mazin; D.; Mashuda; S.; Mirzoyan; R.; Ohoka; H.; Orito; R.; Saito; T.;; Sakurai; S.; Takeda; J.; Teshima; M.; Terada; Y.; Tokanai; F.; Yamamoto; T.; Yoshida; T., Detection of low-intensity light relies on the conversion of photons to photoelectrons, which are then multiplied and detected as an electrical signal. To measure the actual intensity of the light, one must know the factor by which the photoelectrons have been multiplied. To obtain this amplification factor, we have developed a procedure for estimating precisely the signal caused by a single photoelectron. The method utilizes the fact that the photoelectrons conform to a Poisson distribution. The average signal produced by a single photoelectron can then be estimated from the number of noise events, without requiring analysis of the distribution of the signal produced by a single photoelectron. The signal produced by one or more photoelectrons can be estimated experimentally without any assumptions. This technique, and an example of the analysis of a signal from a photomultiplier tube, are described in this study., ELSEVIER SCIENCE BV
  Nuclear Instruments and Methods in Physics Research A, 21 Jun. 2018, [Reviewed]
• Prototyping Hexagonal Light Concentrators Using High-Reflectance Specular Films for the Large-Sized Telescopes of the Cherenkov Telescope Array
  A.Okumura; T.V.Dang; S.Ono; S.Tanaka; M.Hayashida; J.Hinton; H.Katagiri; K.Noda; M.Teshima; T.Yamamoto; T.Yoshida, We have developed a prototype hexagonal light concentrator for the Large-Sized Telescopes of the Cherenkov Telescope Array. To maximize the photodetection efficiency of the focal-plane camera pixels for atmospheric Cherenkov photons and to lower the energy threshold, a specular film with a very high reflectance of 92-99% has been developed to cover the inner surfaces of the light concentrators. The prototype has a relative anode sensitivity (which can be roughly regarded as collection efficiency) of about 95 to 105% at the most important angles of incidence. The design, simulation, production procedure, and performance measurements of the light-concentrator prototype are reported., IOP PUBLISHING LTD
  Journal of Instrumentation, 06 Dec. 2017, [Reviewed]
• Constraints on Physical Conditions for the Acceleration on Ultra-high-energy Cosmic Rays in Nearby Active Galactic Nuclei Observed with the Fermi Large Area Telescope
  M.Kagaya; H.Katagiri; T.Yoshida; A.Fukuda, We investigated the possibility of acceleration of ultra-high-energy cosmic rays (UHECRs) in nearby active galactic nuclei (AGNs) using archival multi-wavelength observational data, and then we constrained their physical conditions, i.e., the luminosity of the synchrotron radiation and the size of the acceleration site. First, we investigated the spatial correlation between the arrival directions of UHECRs and the positions of nearby AGNs in the Fermi third gamma-ray source catalog. We selected 27 AGNs as candidates of accelerators of UHECRs. Then, we evaluated the physical conditions in the acceleration regions of these AGNs via the Pe'er and Loeb method, which uses the peak luminosity of synchrotron radiation and the peak flux ratio of inverse Compton scattering to synchrotron radiation. From the evaluation, we found that six AGNs have the ability to accelerate ultra-high-energy (UHE) protons in the AGN cores. Furthermore, we found that the minimum acceleration size must be more than a few kpc for acceleration of UHE protons in the AGN lobes., IOP PUBLISHING LTD
  The Astrophysical Journal, 14 Nov. 2017
• Prospects for Cherenkov Telescope Array Observations of the Young Supernova Remnant RX J1713.7-3946
  F.Acero; R.Aloisio; J.Amans; T.Yoshida; et al., We perform simulations for future Cherenkov Telescope Array (CTA) observations of RX J1713.7-3946, a young supernova remnant (SNR) and one of the brightest sources ever discovered in very high energy (VHE) gamma rays. Special attention is paid to exploring possible spatial (anti) correlations of gamma rays with emission at other wavelengths, in particular X-rays and CO/H I emission. We present a series of simulated images of RX J1713.7-3946 for CTA based on a set of observationally motivated models for the gamma-ray emission. In these models, VHE gamma rays produced by high-energy electrons are assumed to trace the nonthermal X-ray emission observed by XMM-Newton, whereas those originating from relativistic protons delineate the local gas distributions. The local atomic and molecular gas distributions are deduced by the NANTEN team from CO and H I observations. Our primary goal is to show how one can distinguish the emission mechanism(s) of the gamma rays (i.e., hadronic versus leptonic, or a mixture of the two) through information provided by their spatial distribution, spectra, and time variation. This work is the first attempt to quantitatively evaluate the capabilities of CTA to achieve various proposed scientific goals by observing this important cosmic particle accelerator., IOP PUBLISHING LTD
  The Astrophysical Journal, 09 May 2017, [Reviewed]
• Development of a low-cost-high-sensitivity Compton camera using CsI (Tl) scintillators (gamma I)
  M. Kagaya; H. Katagiri; R. Enomoto; R. Hanafusa; M. Hosokawa; Y. Itoh; H. Muraishi; K. Nakayama; K. Satoh; T. Takeda; M. M. Tanaka; T. Uchida; T. Watanabe; S. Yanagita; T. Yoshida; K. Umehara, We have developed a novel low-cost gamma-ray imaging Compton camera gamma I that has a high detection efficiency. Our motivation for the development of this detector was to measure the arrival directions of gamma rays produced by radioactive nuclides that were released by the Fukushima Daiichi nuclear power plant accident in 2011. The detector comprises two arrays of inorganic scintillation detectors, which act as a scatterer and an absorber. Each array has eight scintillation detectors, each comprising a large CsI (TI) scintillator cube of side 3.5 cm, which is inexpensive and has a good energy resolution. Energies deposited by the Compton scattered electrons and subsequent photoelectric absorption, measured by each scintillation counter, are used for image reconstruction. The angular resolution was found to be 3.5 after using an image-sharpening technique. With this angular resolution, we can resolve a 1 m(2) radiation hot spot that is located at a distance of 10 m from the detector with a wide field of view of 1 sr. Moreover, the detection efficiency 0.68 cps/MBq at 1 m for 662 keV (7.6 cps/mu Sv/h) is sufficient for measuring low-level contamination (i.e., less than 1 mu Sv/h) corresponding to typical values in large areas of eastern Japan. In addition to the laboratory tests, the imaging capability of our detector was verified in various regions with dose rates less than 1 mu Sv/h (e.g., Fukushima city). (C) 2015 Elsevier B.V. All rights reserved., ELSEVIER SCIENCE BV
  NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT, Dec. 2015, [Reviewed]
• Electron acceleration with improved Stochastic Differential Equation method: Cutoff shape of electron distribution in test-particle limit
  Ryo Yamazaki; Tatsuo Yoshida; Yuka Tsuchihashi; Ryosuke Nakajima; Yutaka Ohira; Shohei Yanagita, We develop a method of stochastic differential equation to simulate electron acceleration at astrophysical shocks. Our method is based on Ito's stochastic differential equations coupled with a particle splitting, employing a skew Brownian motion where an asymmetric shock crossing probability is considered. Using this code, we perform simulations of electron acceleration at stationary plane parallel shock with various parameter sets, and studied how the cutoff shape, which is characterized by cutoff shape parametera, changes with the momentum dependence of the diffusion coefficient beta. In the age-limited cases, we reproduce previous results of other authors, a approximate to 2 beta. In the cooling-limited cases, the analytical expectation a approximate to beta + 1 is roughly reproduced although we recognize deviations to some extent. In the case of escape-limited acceleration, numerical result fits analytical stationary solution well, but deviates from the previous asymptotic analytical formula a approximate to beta. (C) 2015 Elsevier B.V. All rights reserved., ELSEVIER SCIENCE BV
  JOURNAL OF HIGH ENERGY ASTROPHYSICS, Mar. 2015, [Reviewed]
• Constraints on acceleration of ultra-high-energy cosmic rays in fermi gamma-ray sources　　　　　　　　　　　　　　　
  Mika Kagaya; Hideaki Katagiri; Tatsuo Yoshida, We investigate the candidates of accelerator of ultra-high-energy cosmic rays (UHECRs) using the multi-wavelength spectral energy distributions, and discuss about the ability to accelerate UHECRs and constrain their physical conditions (acceleration site and size). The current experimental statistics of UHECRs is not sufficient for identification of the sources, although a spatial correlation between the arrival directions of UHECRs and nearby active galactic nuclei (AGNs) has been discussed using the data of the Pierre Auger Observatory and the Telescope Array. Some authors have discussed about the acceleration of UHECRs using various methods. Among them, Pe'er and Loeb (2012) derived constraints on the ability of AGNs to produce UHECRs by using observational quantities which are synchrotron peak luminosity and the peak flux ratio of inverse Compton scattering to synchrotron emission. For adopting this method, we need data of gammaray observation to determine the peak flux for high-energy region due to inverse Compton scattering. Thus, we focused on the Fermi Large Area Telescope gamma-ray sources. We investigated a spatial correlation between AGNs and the arrival directions of UHECRs, and we selected six AGNs as candidates of accelerator of UHECRs. We analyzed their spectral energy distributions by using multi-wavelength archival observational data. By introducing the constraints of Pe'er and Loeb (2012), we evaluate the physical conditions in the acceleration regions of these six AGNs and discuss whether they can accelerate to UHECRs. From the analysis, we found that three AGNs have ability to accelerate UHE protons to UHECRs in the AGN cores. Furthermore, we constrained the minimum size of the acceleration region for each source when UHE particles are accelerated in the AGN lobes. If UHE protons are accelerated, a few kpc-100 kpc are required as the minimum acceleration size. In the case of acceleration of heavy nucleus, the heavy particles can be accelerated in the AGN lobes if the size is larger than a few kpc. In this paper, we show that we achieved to establish a test method for individual candidate sources of acceleration of UHECRs., Proceedings of Science (PoS)
  Proceedings of Science, 2015
• Simulating Cherenkov Telescope Array observation of RX J1713.7-3946　　　　　　　　　　　　　　　
  T. Nakamori; H. Katagiri; H. Sano; T. Yoshida(31 番目); 他28 人
  Proceedings of the 34th International Cosmic Ray Conference, 2015
• The Optical System for the Large Size Telescope of the Cherenkov Telescope Array
  M. Hayashida; K. Noda; M. Teshima; T. Yoshida(23 番目); 他19 人, The Cherenkov Telescope Array (CTA) project aims to implement the world's largest next generation of Very High Energy gamma-ray Imaging Atmospheric Cherenkov Telescopes devoted to the observation from a few tens of GeV to more than 100 TeV. To view the whole sky, two CTA sites are foreseen, one for each hemisphere. The sensitivity at the lowest energy range will be dominated by four Large Size Telescopes, LSTs, located at the center of each array and designed to achieve observations of high red-shift objects with the threshold energy of 20 GeV. The LST is optimized also for transient low energy sources, such as Gamma Ray Bursts (GRB), which require fast repositioning of the telescope. The overall design and the development status of the first LST telescope will be discussed., SPIE
  Proceedings of the 34th International Cosmic Ray Conference,, 2015
• Prototyping of Hexagonal Light Concentrators for the Large-Sized Telescopes of the Cherenkov Telescope Array　　　　　　　　　　　　　　　
  A. Okumura; S. Ono; S. Tanaka; M. Hayashida; H. Katagiri; T. Yoshida(6 番目)
  Proceedings of the 34th International Cosmic Ray Conference, 2015
• Development of a high detection efficiency and low-cost imaging gamma-ray camera γI　　　　　　　　　　　　　　　
  M. Kagaya; R. Enomoto; R. Hanafusa; Y. Itoh; H. Katagiri; H. Muraishi; K. Nakayama; K. Satoh; T. Takeda; M. M. Tanaka; T. Uchida; T. Watanabe; S. Yanagita; T. Yoshida, We developed a novel Compton camera γI using CsI (Tl) scintillators which has high detection efficiency and is low-cost. Our motivation for the development of this detector is measuring gamma rays produced by radioactive nuclides from Fukushima Daiichi Nuclear Power Plant accident. Our detector consists of two arrays of detectors which act as a Compton scatterer and absorber. Energies deposited by Compton scattered electrons and subsequent photoelectric absorption measured by photomultipliers are used for image reconstruction. Each array consists of 8 large CsI (Tl) scintillator cubes, 3.5 cm on a side, which are inexpensive and have good energy resolution. The angular resolution is around 3.5° by using an image sharpening technique, and the detection efficiency is typically more than 10 times better than other detectors for the same purpose. We did measurement tests for contaminated area around 1 μSv/h. The imaging capability was verified by test measurements in Fukushima Prefecture together with the laboratory tests. In this paper, we reported the development of γI and the results of the measurement tests., Proceedings of Science (PoS)
  Proceedings of Science, 2014
• The large size telescope of the Cherenkov Telescope Array
  G. Ambrosi; Y. Awane; H. Baba; T. Yoshida(126 番目); 他123 人, The Cherenkov Telescope Array (CTA) project aims to implement the world's largest next generation of Very High Energy gamma-ray Imaging Atmospheric Cherenkov Telescopes devoted to the observation from a few tens of GeV to more than 100 TeV. To view the whole sky, two CTA sites are foreseen, one for each hemisphere. The sensitivity at the lowest energy range will be dominated by four Large Size Telescopes, LSTs, located at the center of each array and designed to achieve observations of high red-shift objects with the threshold energy of 20 GeV. The LST is optimized also for transient low energy sources, such as Gamma Ray Bursts (GRB), which require fast repositioning of the telescope. The overall design and the development status of the first LST telescope will be discussed., SPIE-INT SOC OPTICAL ENGINEERING
  Proceedings of the SPIE, 2014
• Introducing the CTA concept
  B.S. Acharya; M. Actis; T. Aghajani; T. Yoshida(961 番目) et al., The Cherenkov Telescope Array (CTA) is a new observatory for very high-energy (VHE) gamma rays. CTA has ambitions science goals, for which it is necessary to achieve full-sky coverage, to improve the sensitivity by about an order of magnitude, to span about four decades of energy, from a few tens of GeV to above 100 TeV with enhanced angular and energy resolutions over existing VHE gamma-ray observatories. An international collaboration has formed with more than 1000 members from 27 countries in Europe, Asia, Africa and North and South America. In 2010 the CTA Consortium completed a Design Study and started a three-year Preparatory Phase which leads to production readiness of CTA in 2014. In this paper we introduce the science goals and the concept of CTA, and provide an overview of the project. © 2013 Elsevier B.V. All rights reserved.
  Astroparticle Physics, 2013, [Reviewed]
• Searches for very high energy gamma rays from blazars with,CANGAROO-III telescope in 2005-2009
  Y. Mizumura; J. Kushida; K. Nishijima; T. Yoshida(30 番目) et al., We have searched for very high energy (VHE) gamma rays from four blazars using the CANGAROO-III imaging atmospheric Cherenkov telescope. We report the results of the observations of H 2356-309, PKS 2155-304, PKS 0537-441, and 3C 279, performed from 2005 to 2009, applying a new analysis to suppress the effects of the position dependence of Cherenkov images in the field of view. No significant VHF gamma ray emission was detected from any of the four blazars. The GeV gamma-ray spectra of these objects were obtained by analyzing Fermi/LAT archival data. Wide range (radio to VHE gamma-ray bands) spectral energy distributions (SEDs) including CANGAROO-III upper limits. GeV gamma-ray spectra, and archival data, even though they are non-simultaneous, are discussed using a one-zone synchrotron self-Compton (SSC) model in combination with a external Compton (EC) radiation. The HBLs (H 2356-309 and PKS 2155-304) can be explained by a simple SSC model, and PKS 0537-441 and 3C 279 are well modeled by a combination of SSC and EC model. We find a consistency with the blazar sequence in terms of strength of magnetic field and component size. (C) 2012 Elsevier B.V. All rights reserved., ELSEVIER SCIENCE BV
  Astroparticle Physics, 2012, [Reviewed]
• CANGAROO-III Observation of TeV Gamma Rays from the Unidentified Gamma-Ray Source HESS J1614-518
  T. Mizukami; H. Kubo; T. Yoshida et al., We report the detection, with the CANGAROO-III imaging atmospheric Cherenkov telescope array, of a very high energy gamma-ray signal from the unidentified gamma-ray source HESS J1614-518, which was discovered in the H. E. S. S. Galactic plane survey. Diffuse gamma-ray emission was detected above 760 GeV at the 8.9 sigma level during an effective exposure of 54 hr from 2008 May to August. The spectrum can be represented by a power law: (8.2 +/- 2.2(stat) +/- 2.5(sys)) x 10(-12) x (E/1 TeV)(-gamma) cm(-2) s(-1) TeV-1 with a photon index gamma of 2.4 +/- 0.3(stat) +/- 0.2(sys), which is compatible with that of the H.E.S.S. observations. By combining our result with multiwavelength data, we discuss the possible counterparts for HESS J1614-518 and consider radiation mechanisms based on hadronic and leptonic processes for a supernova remnant (SNR), stellar winds from massive stars, and a pulsar wind nebula (PWN). Although a leptonic origin from a PWN driven by an unknown pulsar remains possible, hadronic-origin emission from an unknown SNR is preferred., IOP PUBLISHING LTD
  Ap.J., 2011
• Design concepts for the Cherenkov Telescope Array CTA: an advanced facility for ground-based high-energy gamma-ray astronomy
  M. Actis; G. Agnetta; F. Aharonian; T. Yoshida(662 番目) et al., Ground-based gamma-ray astronomy has had a major breakthrough with the impressive results obtained using systems of imaging atmospheric Cherenkov telescopes. Ground-based gamma-ray astronomy has a huge potential in astrophysics, particle physics and cosmology. CTA is an international initiative to build the next generation instrument, with a factor of 5-10 improvement in sensitivity in the 100 GeV-10 TeV range and the extension to energies well below 100 GeV and above 100 TeV. CTA will consist of two arrays (one in the north, one in the south) for full sky coverage and will be operated as open observatory. The design of CTA is based on currently available technology. This document reports on the status and presents the major design concepts of CTA., SPRINGER
  Experimental Astronomy, 2011
• Simulations of diffusive shock acceleration with Adaptive Mesh Refinement scheme and Stochastic Differential Equation method　　　　　　　　　　　　　　　
  K. Yamashita; M. Den; T. Ogawa; T. Yoshida
  38th COSPAR Scientific Assembly, 2010
• Observations of the unidentified VHE gamma-ray source HESS J1614-518 with CANGAROO-III
  T. Mizukami; H. Kubo; T. Tanimori; M. Akimoto; G. V. Bicknell; R. W. Clay; P. G. Edwards; R. Enomoto; S. Gunji; S. Hara; T. Hara; S. Hayashi; H. Ishioka; S. Kabuki; F. Kajino; H. Katagiri; A. Kawachi; T. Kifune; R. Kiuchi; T. Kunisawa; J. Kushida; T. Matoba; Y. Matsubara; I. Matsuzawa; Y. Mizumura; Y. Mizumoto; M. Mori; H. Muraishi; T. Naito; T. Nakamori; K. Nakayama; K. Nishijima; M. Ohishi; Y. Otake; S. Ryoki; K. Saito; Y. Sakamoto; V. Stamatescu; T. Suzuki; D. L. Swaby; G. Thornton; F. Tokanai; Y. Toyota; K. Tsuchiya; S. Yanagita; Y. Yokoe; T. Yoshida; T. Yoshikoshi; Y. Yukawa, HESS J1614-518 is one of the unidentified VHE gamma-ray sources discovered with the H.E.S.S. observatory in their Galactic plane survey. We observed HESS J1614-518 with the CANGAROO-III imaging atmospheric Cerenkov telescope array located in South Australia, from May to August in 2008. We detected a diffuse gamma-ray emission above 760 GeV at more than 5 sigma level during an effective exposure of 54 hours. The differential flux is consistent with H.E.S.S.. We discuss the possible counterpart using results of the followup observations by the X-ray satellites Suzaku and Swift.
  31st International Cosmic Ray Conference, ICRC 2009, 01 Jan. 2009
• Reanalysis of Data Taken by the Cangaroo 3.8 Meter Imaging Atmospheric Cherenkov　　　　　　　　　　　　　　　
  T. Yoshikoshi; M. Mori; T. Yoshida(13 番目) et al.
  Ap.J., 2009
• CANGAROO-III Search for TeV Gamma Rays from Two Clusters of Galaxies
  R. Kiuchi; M. Mori; T. Yoshida(48 番目) et al., Because accretion and merger shocks in clusters of galaxies may accelerate particles to high energies, clusters are candidate sites for the origin of ultra-high-energy (UHE) cosmic rays. A prediction was presented for gamma-ray emission from a cluster of galaxies at a detectable level with the current generation of imaging atmospheric Cherenkov telescopes. The gamma-ray emission was produced via inverse Compton upscattering of cosmic microwave background photons by electron-positron pairs generated by collisions of UHE cosmic rays in the cluster. We observed two clusters of galaxies, Abell 3667 and Abell 4038, searching for very high energy gamma-ray emission with the CANGAROO-III atmospheric Cherenkov telescope system in 2006. The analysis showed no significant excess around these clusters, yielding upper limits on the gamma-ray emission. From a comparison of the upper limit for the northwest radio relic region of Abell 3667 with a model prediction, we derive a lower limit for the magnetic field of the region of similar to 0.1 mu G. This shows the potential of gamma-ray observations in studies of the cluster environment. We also discuss the flux upper limit from cluster center regions using a model of gamma-ray emission from neutral pions produced in hadronic collisions of cosmic-ray protons with the intracluster medium. The derived upper limit of the cosmic-ray energy density within this framework is an order of magnitude higher than that of our Galaxy., IOP PUBLISHING LTD
  Ap.J., 2009, [Reviewed]
• CANGAROO-III Observation of TeV Gamma Rays from the Vicinity of PSR B1706-44
  R. Enomoto; J. Kushida; T. Nakamori; T. Kifune; T. Yoshida(51番目) et al., Observation by the CANGAROO-III stereoscopic system of the Imaging Cherenkov Telescope has detected extended emission of TeV gamma rays in the vicinity of the pulsar PSR B1706-44. The strength of the signal observed as gamma-ray-like events varies when we apply different ways of emulating background events. The reason for such uncertainties is argued in relevance to gamma rays embedded in the "OFF-source data," that is, unknown sources and diffuse emission in the Galactic plane, namely, the existence of a complex structure of TeV gamma-ray emission around PSR B1706-44., IOP PUBLISHING LTD
  Ap.J, 2009, [Reviewed]
• Search for VHE gamma rays from SS433/W50 with the CANGAROO-II telescope
  Sei. Hayashi; F. Kajino; T. Naito; T. Yoshida(50番目) et al., SS433, located at the center of the supernova remnant W50, is a close proximity binary system consisting of a compact star and a normal star. jets of material are directed outwards from the vicinity of the compact star symmetrically to the east and west. Non-thermal hard X-ray emission is detected from lobes lying on both sides. Shock accelerated electrons are expected to generate VHE gamma rays through the inverse-Compton process in the lobes. Observations of the western X-ray lobe region of SS433/W50 system have been performed to detect VHE gamma rays using the 10 m CANGAROO-II telescope in August and September, 2001, and July and September, 2002. The total observation times are 85.2 h for ON Source, and 80.8 h for OFF source data. No significant excess of VHE gamma rays has been found at three regions of the western X-ray lobe of SS433/W50 system. We have derived 99% confidence level upper limits to the fluxes of gamma rays and have set constraints on the strengths of the magnetic fields assuming the synchrotron/inverse-Compton model for the wide energy range of photon spectrum from radio to TeV. The derived lower limits are 4.3 mu G for the center of the brightest X-ray emission region and 6.3 mu G for the far end from SS433 in the western X-ray lobe. In addition, we suggest that the spot-like X-ray emission may provide a major contribution to the hardest X-ray spectrum in the lobe. (C) 2009 Elsevier B.V. All rights reserved., ELSEVIER SCIENCE BV
  Astroparticle Physics, 2009
• CANGAROO-III Observations of the 2006 Outburst of PKS 2155-304
  Y. Sakamoto; K. Nishijima; T. Mizukami; E. Yamazaki; J. Kushida; R.Enomoto; M. Ohishi; T.Yoshida(44番目); et al., We have used the CANGAROO-III imaging atmospheric Cerenkov telescopes to observe the high-frequency-peaked BL Lacertae (HBL) object PKS 2155 - 304 between 2006 July 28 (MJD 53,944) and August 2, triggered by the H. E. S. S. report that the source was in a high state of TeV gamma-ray emission. A signal was detected at the 4.8 - level in an effective live time of 25.1 hr during the outburst period. The flux of very high energy gamma rays from the CANGAROO-III observations shows variability on the timescale of less than a few hours. The averaged integral flux above 660 GeV is ( 1.6 +/- 0.3(stat) +/- 0.5(syst)) x 10(-11) cm(-2) s(-1), which corresponds to similar to 45% of the flux observed from the Crab Nebula. Follow-up observations between August 17 (MJD 53,964) and 25 indicate that the source activity had decreased., UNIV CHICAGO PRESS
  Ap.J., 2008, [Reviewed]
• Observation of an Extended Very High Energy Gamma-Ray Emission from MSH 15-52 with CANGAROO-III
  T. Nakamori; H. Kubo; T. Yoshida et al., We have observed the supernova remnant MSH 15-52 (G320.4-1.2), which contains the gamma-ray pulsar PSR B1509-58, using the CANGAROO-III imaging atmospheric Cerenkov telescope array from 2006 April to June. We detected gamma rays above 810 GeVat the 7 sigma level during a total effective exposure of 48.4 hr. We obtained a differential gamma-ray flux at 2.35 TeV of (7.9 +/- 1.5(stat) +/- 1.7(sys)) x 10(-13) cm(-2) s(-1) TeV-1, with a photon index of 2.21 +/- 0: 39(stat) +/- 0.40(sys), which is compatible with that of the H. E. S. S. observation in 2004. The morphology shows extended emission compared to our point spread function. We consider the plausible origin of the high-energy emission based on a multiwavelength spectral analysis and energetics arguments., IOP PUBLISHING LTD
  Ap.J., 2008, [Reviewed]
• CANGAROO-III Search for Gamma Rays from Kepler’s Supernova,Remnant
  R. Enomoto; Y. Higashi; T. Yoshida et al., Kepler's supernova, discovered in 1604 October, produced a remnant that has been well studied observationally in the radio, infrared, optical, and X-ray bands, and theoretically. Some models have predicted a TeV gamma-ray flux that is detectable with current Imaging Cerenkov Atmospheric Telescopes. We report on observations carried out in 2005 April with the CANGAROO-III Telescope. No statistically significant excess was observed, and limitations on the allowed parameter range in the model are discussed., UNIV CHICAGO PRESS
  Ap.J., 2008, [Reviewed]
• Observation of Very High Energy Gamma Rays from HESS J1804-216,with CANGAROO-III Telescopes
  Y. Higashi; H. Kubo; T. Yoshida et al., We observed the unidentified TeV gamma-ray source HESS J1804-216 with the CANGAROO-III atmospheric Cerenkov telescopes from 2006 May to July. We detected very high energy gamma rays above 600 GeVat the 10 sigma level in an effective exposure of 76 hr. We obtained a differential flux of (5: 0 +/- 1.5(stat) +/- 1.6(sys))x 10(-12)(E/1 TeV)(-alpha) cm(-2) s(-1) TeV-1 with a photon index alpha of 2.69 +/- 0.30stat +/- 0.34(sys), which is consistent with that of the H. E. S. S. observation in 2004. We also confirm the extended morphology of the source. By combining our result with multiwavelength observations, we discuss the possible counterparts of HESS J1804-216 and the radiation mechanism based on leptonic and hadronic processes for a supernova remnant and a pulsar wind nebula., UNIV CHICAGO PRESS
  Ap.J., 2008, [Reviewed]
• Very high energy gamma-ray observations of the Galactic Plane with the CANGAROO-III telescopes
  M. Ohishi; M. Mori; Y. Adachi; T. Yoshida(58 番目) et al., We have searched for very high energy gamma-ray emission from two points (l = -19 degrees.5 and l = +13 degrees) on the galactic plane (b = 0 degrees) using the CANGAROO-III stereoscopic observation system in 2004. Stereo analysis using 2-fold coincidence data was performed, which aims for the measurement of the diffuse component flux and also allows a search for unknown point sources in the field of view. No significant excess associated with the galactic plane was found for either region. Assuming that the gamma-ray spectrum is a single power law between a few GeV and 600 GeV, upper limits to the spectral index were obtained: -2.17 and -2.12 for the l = -19 degrees.5 and l = +13 degrees regions, respectively. A search was made for point sources in the l = -19 degrees.5 region, with no source with a statistical significance exceeding 4 a being found in the field of view. Typical flux upper limits of about 20% of the Crab nebula flux were obtained in that region., TATA INST FUNDAMENTAL RESEARCH
  Astroparticle Physics, 2008, [Reviewed]
• Observation of VHE gamma rays from HESS J1804-216 with CANGAROO-III Telescopes
  Y. Higashi; G. V. Bicknell; R. W. Clay; P. G. Edwards; R. Enomoto; S. Gunji; S. Hara; T. Hara; T. Hattori; S. Hayashi; Y. Hirai; K. Inoue; C. Itoh; S. Kabuki; F. Kajino; H. Katagiri; A. Kawachi; T. Kifune; R. Kiuchi; H. Kubo; J. Kushida; Y. Matsubara; T. Mizukami; Y. Mizumoto; R. Mizuniwa; M. Mori; H. Muraishi; Y. Muraki; T. Naito; T. Nakamori; S. Nakano; D. Nishida; K. Nishijima; M. Ohishi; Y. Sakamoto; A. Seki; V. Stamatescu; T. Suzuki; D. L. Swaby; T. Tanimori; G. Thornton; F. Tokanai; K. Tsuchiya; S. Watanabe; Y. Yamada; E. Yamazaki; S. Yanagita; T. Yoshida; T. Yoshikoshi; Y. Yukawa, The H.E.S.S. collaboration has reported the detection of the gamma-ray emission from eight new sources located in the Galactic Plane. HESS J1804-216 is one of the brightest, and its size and photon index suggest it as one of the largest and softest sources. We observed HESS J1804-216 with CANGAROO-III telescopes from May to July in 2006. We detected gamma-ray signals with ∼ 10ω level during an effective exposure of 74.8 hours. The differential flux and emission size are consistent with that of H.E.S.S..
  Proceedings of the 30th International Cosmic Ray Conference, ICRC 2007, 01 Jan. 2007
• Time variation of the flux of TeV gamma-rays from PKS 2155-304
  K. Nishijima; Y. Sakamoto; E. Yamazaki; T. Mizukami; J. Kushida; G. Bicknell; R. Clay; P. Edwards; R. Enomoto; S. Gunji; S. Hara; T. Hara; T. Hattori; S. Hayashi; Y. Higashi; Y. Hirai; K. Inoue; C. Itoh; S. Kabuki; F. Kajino; H. Katagiri; A. Kawachi; T. Kifune; R. Kiuchi; H. Kubo; Y. Matsubara; Y. Mizumoto; R. Mizuniwa; M. Mori; H. Muraishi; Y. Muraki; T. Naito; T. Nakamori; S. Nakano; D. Nishida; M. Ohishi; A. Seki; V. Stamatescu; T. Suzuki; D. Swaby; T. Tanimori; G. Thornton; F. Tokanai; K. Tsuchiya; S. Watanabe; Y. Yamada; S. Yanagita; T. Yoshida; T. Yoshikoshi; Y. Yukawa, We have observed the blazar PKS 2155-304 between 2006 July 28 to August 2 and between August 17 to 25 with the CANGAROO-III imaging atmospheric Cherenkov telescope in South Australia, which was triggered by the alert from the H.E.S.S. that the strong outburst of TeV gamma-ray emission was detected. The flux variation of very high energy gamma-rays was studied. The highest activity during our observations was seen early night in July 28 up to 180 % Crab flux level. The source activity had decreased in August.
  Proceedings of the 30th International Cosmic Ray Conference, ICRC 2007, 01 Jan. 2007
• Detection of 2006 TeV-outburst of PKS 2155-304 with the CANGAROO-III telescope
  Y. Sakamoto; K. Nishijima; E. Yamazaki; T. Mizukami; J. Kushida; G. Bicknell; R. Clay; P. Edwards; R. Enomoto; S. Gunji; S. Hara; T. Hara; T. Hattori; S. Hayashi; Y. Higashi; Y. Hirai; K. Inoue; C. Itoh; S. Kabuki; F. Kajino; H. Katagiri; A. Kawachi; T. Kifune; R. Kiuchi; H. Kubo; Y. Matsubara; Y. Mizumoto; R. Mizuniwa; M. Mori; H. Muraishi; Y. Muraki; T. Naito; T. Nakamori; S. Nakano; D. Nishida; M. Ohishi; A. Seki; V. Stamatescu; T. Suzuki; D. Swaby; T. Tanimori; G. Thornton; F. Tokanai; K. Tsuchiya; S. Watanabe; Y. Yamada; S. Yanagita; T. Yoshida; T. Yoshikoshi; Y. Yukawa, We present the detection of nearby BL Lacertae object PKS 2155-304 with the CANGAROOIII imaging atmospheric Cherenkov telescope system. This observation was triggered by the H.E.S.S. report in July 2006 that the outburst at TeV gamma-ray energy range occured on this object. Observations have been performed between 2006 July 28 and August 2. A signal from PKS 2155-304 was detected at 5.7 σ level using the dataset of zenith angle < 30°. The time averaged integral flux above 620GeV and the differential energy spectrum are obtained.
  Proceedings of the 30th International Cosmic Ray Conference, ICRC 2007, 01 Jan. 2007
• Observations of extended VHE gamma-ray emission from MSH 15-52 with CANGAROO-III
  T. Nakamori; G. V. Bicknell; R. W. Clay; P. G. Edwards; R. Enomoto; S. Gunji; S. Hara; T. Hara; T. Hattori; S. Hayashi; Y. Higashi; Y. Hirai; K. Inoue; C. Itoh; S. Kabuki; F. Kajino; H. Katagiri; A. Kawachi; T. Kifune; R. Kiuchi; H. Kubo; J. Kushida; Y. Matsubara; T. Mizukami; Y. Mizumoto; R. Mizuniwa; M. Mori; H. Muraishi; Y. Muraki; T. Naito; S. Nakano; D. Nishida; K. Nishijima; M. Ohishi; Y. Sakamoto; A. Seki; V. Stamatescu; T. Suzuki; D. L. Swaby; T. Tanimori; G. Thornton; F. Tokanai; K. Tsuchiya; S. Watanabe; Y. Yamada; E. Yamazaki; S. Yanagita; T. Yoshida; T. Yoshikoshi; Y. Yukawa, The gamma-ray pulsar PSR B1509-58, surrounded by the supernova remnant MSH15-52, was expected to be a Very High Energy gamma-ray source. The CANGAROO-I 3.8 m telescope reported a marginal detection of VHE gamma-rays above 1.9 TeV and recently H.E.S.S. detected an extended signal along with the pulsar jets, from sub-TeV to tens of TeV. We observed MSH15-52 using CANGAROO-III imaging atmospheric Cherenkov telescope array located in South Australia, from April to June in 2006. We observed gamma-rays above 810 GeV with 7 ω level during a total exposure of 48.4 hours, which is consistent with that of H.E.S.S.. Its morphology shows an extended emission compared to our Point Spread Function. We discuss the possible origin of the high energy emission by multi wavelength spectral analysis and energetics.
  Proceedings of the 30th International Cosmic Ray Conference, ICRC 2007, 01 Jan. 2007
• A possible explanation of photon emission from supernova remnants by jitter radiation
  T. Ogasawara; Tatsuo Yoshida; S. Yanagita; and T. Kifune, Corresponding, We investigate a possibility that non-thermal X-ray emission in a supernova remnant(SNR) is produced by jitter radiation, which is the analogue of synchrotron radiation in small-scale random magnetic fields. We can fit the multi-wavelength data of SNRs RX J1713.7-3946 (G347.3-0.5) and RX J0852.0-4622 (G266.6-1.2) by constructing pure jitter and inverse Compton (IC) emission models. We find that the physical fit parameters of random magnetic fields take values of several tens of mu G strength and of the order of similar to 10(7) cm correlation length. These properties of random magnetic fields in collisionless shock of SNRs are discussed., SPRINGER
  Ap. and S.S., 2007, [Reviewed]
• Erratum: Evidence of TeV gamma-ray emission from the nearby starburst galaxy NGC 253
  C. Itoh; R. Enomoto; S. Yanagita; T. Yoshida; 他41人
  Astronomy and Astrophysics, 2007, [Reviewed]
• CANGAROO-III Search for Gamma Rays from SN 1987A and the Surrounding Field
  R. Enomoto; G. V. Bicknell; R. W. Clay; Tatsuo Yoshida(42番目); 他41人, Optical images of SN 1987A show a triple-ring structure. The inner (dust) ring has recently increased in brightness and in the number of hot spots, suggesting that the supernova shock wave has collided with the dense preexisting circumstellar medium, a scenario supported by radio and X-ray observations. Such a shocked environment is widely expected to result in the acceleration of charged particles and the accompanying emission of very high energy gamma-rays. Here we report the results of observations made in 2004 and 2006, yielding upper limits on the TeV gamma-ray flux, which are compared with a theoretical prediction. In addition, we set upper limits on the TeV flux for four high-energy objects which are located within the same field of view of the observation: the superbubble 30 DorC, the Crab-like pulsar PSR B0540-69, the X-ray binary LMC X-1, and the supernova remnant N157B., UNIV CHICAGO PRESS
  Ap.J., 2007, [Reviewed]
• CANGAROO-III Search for Gamma Rays from Centaurus A ,and the Omega Centauri Region
  S. Kabuki; R. Enomoto; G. V. Bicknell; Tatsuo Yoshida(45番目); 他44人, We have observed the giant radio galaxy Centaurus A and the globular cluster omega Centauri in the TeV energy region using the CANGAROO III stereoscopic system. The system has been in operation since 2004 with an array of four Imaging Atmospheric Cerenkov Telescopes ( IACT) with similar to 100m spacings. The observations were carried out in 2004 March and April. In total, approximately 10 hr of data were obtained for each target. No statistically significant gamma-ray signal has been found above 420 GeV over a wide angular region (a 1 degrees radius from the pointing center), and we derive flux upper limits using the wholefield of view. Implications for the total energy of cosmic rays and the density of the cold dark matter are considered., UNIV CHICAGO PRESS
  Ap.J, 2007, [Reviewed]
• Numerical studies on the structure of the cosmic ray electron halo in starburst galaxies　　　　　　　　　　　　　　　
  S.Miyake; S.Yanagita; and Tatsuo Yoshida
  Ap. and S.S., 2007, [Reviewed]
• CANGAROO III Observations of the Supernova Remnant RX J0852.0-4622
  R. Enomoto; S. Watanabe; T. Tanimori; Tatsuo Yoshida(48番目); 他47人, Sub-TeV gamma-ray emission from the northwest rim of the supernova remnant RX J0852.0-4622 was detected with the CANGAROO II telescope and recently confirmed by the HESS group. In addition, the HESS data revealed a very wide (up to 2 degrees in diameter), shell-like profile of the gamma-ray emission. We carried out CANGAROO III observations in 2005 January and February with three telescopes and show here the results of threefold coincidence data. We confirm the HESS results about the morphology and the energy spectrum and find that the energy spectrum in the NW rim is consistent with that of the whole remnant., UNIV CHICAGO PRESS
  The Astrophysical Journal, 2006, [Reviewed]
• TeV γ-rays from old supernova remnants
  R. Yamazaki; K.Kohri; A. Bamba; Tatsuo Yoshida; T. Tsuribe; and F. Takahara, We study the emission from an old supernova remnant (SNR) with an age of around 10(5) yr and that from a giant molecular cloud (GMC) encountered by the SNR. When the SNR age is around 10(5) yr, proton acceleration is efficient enough to emit TeV gamma-rays both at the shock of the SNR and that in the GMC. The maximum energy of primarily accelerated electrons is so small that TeV gamma-rays and X-rays are dominated by hadronic processes, pi(o)-decay and synchrotron radiation from secondary electrons, respectively. However, if the SNR is older than several 10(5) yr, there are few high-energy particles emitting TeV gamma-rays because of the energy-loss effect and/or the wave-damping effect occurring at low-velocity isothermal shocks. For old SNRs or SNR-GMC interacting systems capable of generating TeV gamma-ray emitting particles, we calculated the ratio of TeV gamma-ray (1-10 TeV) to X-ray (2-10 keV) energy flux and found that it can be more than similar to 10(2). Such a source showing large flux ratio may be a possible origin of recently discovered unidentified TeV sources., BLACKWELL PUBLISHING
  Monthly Notices of the Royal Astronomical Society, 2006, [Reviewed]
• A Search for Sub-TeV Gamma Rays from the Vela Pulsar Region with CANGAROO-III
  R. Enomoto; K. Tsuchiya; Y. Adachi; S. Kabuki; P. G. Edwards; Tatsuo Yoshida(52番目); 他49人, We made stereoscopic observations of the Vela pulsar region with two of the 10 m diameter CANGAROO-III imaging atmospheric Cerenkov telescopes in 2004 January and February in a search for sub-TeV gamma rays from the pulsar and surrounding regions. We describe the observations, provide a detailed account of the calibration methods, and introduce the improved and bias-free analysis techniques employed for CANGAROO-III data. No evidence of gamma-ray emission is found from either the pulsar position or the previously reported position offset by 0.degrees 13, and the resulting upper limits are a factor of 5 less than the previously reported flux from observations with the CANGAROO-I 3.8 m telescope. Following the recent report by the H. E. S. S. group of TeV gamma-ray emission from the pulsar wind nebula, which is similar to 0.degrees 5 south of the pulsar position, we examined this region and found supporting evidence for emission extended over similar to 0.degrees 6., UNIV CHICAGO PRESS
  The Astrophysical Journal, 2006
• Galactic Modulation of Extragalactic Cosmic Rays: Possible Origin of the Knee in the Cosmic Ray Spectrum
  H. Muraishi; S. Yanagita; and Tatsuo Yoshida, The existence of the spectral break near 3 x 10(15) eV in the cosmic ray spectrum (referred to as the 'knee') is one of the biggest questions in cosmic ray astrophysics. In addition, the origin of cosmic rays above the knee energies (between 10(15) and 10(18) eV) is also yet unknown. In this paper, we investigate how the hypothetical extragalactic CRs, after modulation by the galactic wind, contribute to the knee in the CR spectrum. We numerically calculate the modulated energy spectrum of the hypothetical cosmic rays coming into the galaxy from just outside of the "galactic sphere", where the galactic wind terminates. We show that the observed knee structure is reproduced precisely by a superposition of the modulated component and the galactic cosmic rays originating from supernova remnants., PROGRESS THEORETICAL PHYSICS PUBLICATION OFFICE
  Progress of Theoretical Physics, 2005, [Reviewed]
• A Spatial and Spectral Study of Nonthermal Filaments in Historical Supernova Remnants: Observational Results with Chandra
  A. Bamba; R. Yamazaki; Tatsuo Yoshida; . Terasawa; and K. Koyama, The outer shells of young supernova remnants (SNRs) are the most plausible acceleration sites of high-energy electrons with the diffusive shock acceleration (DSA) mechanism. We studied spatial and spectral properties close to the shock fronts in four historical SNRs (Cas A, Kepler's remnant, Tycho's remnant, and RCW86) with excellent spatial resolution of Chandra. In all of the SNRs, hard X-ray emissions were found on the rims of the SNRs, which concentrate in very narrow regions ( so-called filaments); apparent scale widths on the upstreamside are below or on the order of the point-spread function of Chandra, while they are 0.'' 5 - 40 '' (0.01 - 0.4 pc) on the downstream side with most reliable distances. The spectra of these filaments can be fitted with both thermal and nonthermal ( power law and SRCUT) models. The former requires unrealistic high temperature (greater than or similar to 2 keV) and low abundances (less than or similar to 1 solar) for emission from young SNRs and may be thus unlikely. The latter reproduces the spectra with best-fit photon indices of 2.1 - 3.8, or roll-off frequencies of (0.1 28) x 10(17) Hz, which reminds us of the synchrotron emission from electrons accelerated via DSA. We consider various physical parameters as functions of the SNR age, including the previous results on SN 1006; the filament width on the downstream side increases with the SNR age, and the spectrum becomes softer, keeping a nonthermal feature. It was also found that a function, that is, the roll-off frequency divided by the square of the scale width on the downstream side, shows negative correlation with the age, which might provide us some information on the DSA theory., UNIV CHICAGO PRESS
  Ap.J., 2005, [Reviewed]
• Detection of Gamma-rays around 1 TeV from RX J0852.0-4622 by CANGAROO-II
  H. Katagiri; R. Enomoto; L. T. Ksenofontov; M. Mori; Tatsuo Yoshida(50番目); 他46人, We have detected gamma-ray emission at the 6 sigma level at energies greater than 500 GeV from the supernova remnant RX J0852.0 - 4622 (G266.2 - 1.2) using the CANGAROO-II imaging atmospheric Cerenkov telescope. The flux was 0.12 times that of Crab at 1 TeV. The signal centroid is consistent with the peak of the X-ray emission in the northwest rim of the remnant., UNIV CHICAGO PRESS
  Ap.J., 2005, [Reviewed]
• Status of the CANGAROO-III project
  Kubo, H.; Asahara, A.; Bicknell, G. V.; Clay, R. W.; Doi, Y.; Edwards, P. G.; Enomoto, R.; Gunji, S.; Hara, S.; Hara, T.; Hattori, T.; Hayashi, Sei.; Itoh, C.; Kabuki, S.; Kajino, F.; Katagiri, H.; Kawachi, A.; Kifune, T.; Ksenofontov, L. T.; Kurihara, T.; Kurosaka, R.; Kushida, J.; Matsubara, Y.; Miyashita, Y.; Mizumoto, Y.; Mori, M.; Moro, H.; Muraishi, H.; Muraki, Y.; Naito, T.; Nakase, T.; Nishida, D.; Nishijima, K.; Ohishi, M.; Okumura, K.; Patterson, J. R.; Protheroe, R. J.; Sakamoto, N.; Sakurazawa, K.; Swaby, D. L.; Tanimori, T.; Tanimura, H.; Thornton, G.; Tokanai, F.; Tsuchiya, K.; Uchida, T.; Watanabe, S.; Yamaoka, T.; Yanagita, S.; Yoshida, T.; Yoshikoshi, T., The CANGAROO-III project, which consists of an array of four 10-m atmospheric Cherenkov telescopes for gamma-ray astrophysics, started in 1999 in Woomera, South Australia. The first 10-m telescope has been in operation since 2000, and stereoscopic observations with the first and second telescopes started in 2002. The full array will be operational in 2003. Here we report on the status of the CANGAROO-III project including the results of observations with the first telescope....
  New Astronomy Reviews, Apr. 2004
• A Search for TeV Gamma-Ray Emission from the PSR B1259-63/SS 2883 Binary System with the CANGAROO-II 10 Meter Telescope
  A. Kawachi; T. Naito; J.R. Patterson; P.G. Edwards; Tatsuo Yoshida(45番目); 他41人, Observations of the PSR B1259-63/SS 2883 binary system using the CANGAROO-II Cerenkov telescope are reported. This nearby binary consists of a 48 ms radio pulsar in a highly eccentric orbit around a Be star and offers a unique laboratory to investigate the interactions between the outflows of the pulsar and Be star at various distances. It has been pointed out that the relativistic pulsar wind and the dense mass outflow of the Be star may result in the emission of gamma rays up to TeV energies. We have observed the binary in 2000 and 2001, similar to47 and similar to157 days after the 2000 October periastron. Upper limits at the 0.13-0.54 crab level are obtained. A new model calculation for high-energy gamma-ray emission from the Be star outflow is introduced, and the estimated gamma-ray flux, considering bremsstrahlung, inverse Compton scattering, and the decay of neutral pions produced in proton-proton interactions, is found to be comparable to the upper limits of these observations. Comparing our results with these model calculations, we constrain the mass-outflow parameters of the Be star., UNIV CHICAGO PRESS
  Ap.J., 2004, [Reviewed]
• Detection of Sub-TeV Gamma Rays from the Galactic Center Direction by CANGAROO-II
  K. Tsuchiya; R. Enomoto; L. T. Ksenofontov; M. Mori; T. Naito; Tatsuo Yoshida(50番目); 他45人, We have detected sub-TeV gamma-ray emission from the direction of the Galactic center ( GC) using the CANGAROO-II Imaging Atmospheric Cerenkov Telescope. We detected a statistically significant excess at energies greater than 250 GeV. The flux was 1 order of magnitude lower than that of the Crab Nebula at 1 TeV with a soft spectrum proportional to E(-4.6 +/- 0.5). The signal centroid is consistent with the GC direction, and the observed profile is consistent with a pointlike source. Our data suggest that the GeV source 3EG J1746 - 2851 is identical to this TeV source, and we study the combined spectra to determine the possible origin of the gamma-ray emission. We also obtain an upper limit on the cold dark matter density in the Galactic halo., IOP PUBLISHING LTD
  Ap.J., 2004, [Reviewed]
• Constraints on the diffusive shock acceleration from the nonthermal X-ray thin shells in SN 1006 NE rim
  R. Yamazaki; Tatsuo Yoshida; T. Terasawa; A. Bamba; and K. Koyama, Characteristic scale lengths of nonthermal X-rays from the SN 1006 NE rim, which are observed by Chandra, are interpreted in the context of diffusive shock acceleration with the assumption that the observed spatial profile of nonthermal X-rays corresponds to that of accelerated electrons with energies of a few tens of TeV To explain the observed scale lengths, we construct two simple models with a test particle approximation, where the maximum energy of accelerated electrons is determined by the age of SN 1006 (age-limited model) or the energy loss (energy loss-limited model), and constrain the magnetic field configuration and the diffusion coefficients of accelerated electrons. When the magnetic field is nearly parallel to the shock normal, the magnetic field should be in the range of 20-85 muG and highly turbulent both upstream and downstream, which means that the mean free path of accelerated electrons is of the order of their gyro-radius (Bohm limit). This situation can be realized both in the age-limited and energy loss-limited model. On the other hand, when the magnetic field is nearly perpendicular to the shock normal, which can exist only in the age-limited case, the magnetic field is several muG upstream and 14-20 muG downstream, and the upstream magnetic field is less turbulent than the downstream., E D P SCIENCES
  Astron.Astrophys., 2004, [Reviewed]
• Self-similar collapse with cooling and heating in an expanding universe
  S Uchida; T Yoshida, Last, We derive self-similar solutions including cooling and heating in an Einstein-de Sitter universe, and investigate the effects of cooling and heating on the gas density and temperature distributions. We assume that the cooling rate has a power-law dependence on the gas density and temperature, Lambda proportional to rho(A)T(B), and that the heating rate is Gamma proportional to rhoT. The values of A and B are chosen by requiring that the cooling time is proportional to the Hubble time in order to obtain similarity solutions. In the region where the cooling rate is greater than the heating rate, a cooling inflow is established, and the gas is compressed and heats up. Because the compression is greater in the inner region than in the outer region, the temperature becomes an increasing profile toward the centre. In particular, when a large infall velocity is produced due to an enormous energy loss, the slope of the density approaches a value that depends on A, B, and the velocity slope, and the slope of the temperature approaches -1. On the other hand, in the region where the heating rate is greater than the cooling rate, the infall velocity is suppressed, compression of the gas is weakened, and the gas cools down. The slope of the density becomes shallow due to suppression of the contraction, and the temperature is lower than that without heating. The self-similar collapse presented here gives insights to the effects of cooling and heating on the gas distributions in galaxies and clusters of galaxies., BLACKWELL PUBLISHING LTD
  Mon. Not. of R. Astr. Soc., 2004, [Reviewed]
• A search for TeV gamma rays from SN 1987A in 2001
  R Enomoto; LT Ksenofontov; H Katagiri; K Tsuchiya; A Asahara; GV Bicknell; RW Clay; PG Edwards; S Gunji; S Hara; T Hara; H Hattori; S Hayashi; S Hayashi; C Itoh; S Kabuki; F Kajino; A Kawachi; T Kifune; H Kubo; J Kushida; Y Matsubara; Y Mizumoto; M Mori; H Moro; H Muraishi; Y Muraki; T Naito; T Nakase; D Nishida; K Nishijima; M Ohishi; K Okumura; Patterson, JR; RJ Protheroe; K Sakurazawa; DL Swaby; T Tanimori; F Tokanai; H Tsunoo; T Uchida; A Watanabe; S Watanabe; S Yanagita; T Yoshida; T Yoshikoshi, We searched for TeV gamma rays from the remnant of SN 1987A around 5400 days after the supernova. The observations were carried out in 2001, from November 16 to December 11, using the CANGAROO-II imaging atmospheric Cerenkov telescope. In total, 708 minutes of ON- and 1019 minutes of OFF-source data were obtained under good conditions. The detection threshold was estimated to be 1 TeV, owing to the mean zenith angle of 39degrees. The upper limits for the gamma-ray flux were obtained and compared with the previous observations and theoretical models. The observations indicate that the gamma-ray luminosity is lower than 1 x 10(37) ergs s(-1) at similar to10 TeV., UNIV CHICAGO PRESS
  ASTROPHYSICAL JOURNAL, Jul. 2003, [Reviewed]
• Development of an atmospheric Cherenkov imaging camera for the CANGAROO-III experiment
  S Kabuki; K Tsuchiya; K Okumura; R Enomoto; T Uchida; H Tsunoo; S Hayashi; S Hayashi; F Kajino; A Maeshiro; Tada, I; C Itoh; A Asahara; GV Bicknell; RW Clay; PG Edwards; S Gunji; S Hara; T Hara; T Hattori; H Katagiri; A Kawachi; T Kifune; H Kubo; J Kushida; Y Matsubara; Y Mizumoto; M Mori; H Moro; H Muraishi; Y Muraki; T Naito; T Nakase; D Nishida; K Nishijima; M Ohishi; Patterson, JR; RJ Protheroe; K Sakurazawa; DL Swaby; T Tanimori; F Tokanai; A Watanabe; S Watanabe; S Yanagita; T Yoshida; T Yoshikoshi, A Cherenkov imaging camera for the CANGAROO-III experiment has been developed for observations of gamma-ray-induced air showers at energies from 10(11) to 10(14) eV. The camera consists of 427 pixels, arranged in a hexagonal shape at 0.17degrees intervals, each of which is a 3/4in. diameter photomultiplier module with a Winston-cone-shaped light guide. The camera was designed to have a large dynamic range of signal linearity, a wider field of view, and an improvement in photon-collection efficiency compared with the CANGAROO-II camera. The camera, and a number of the calibration experiments made to test its performance, are described in detail in this paper. (C) 2003 Elsevier Science B.V. All rights reserved., ELSEVIER SCIENCE BV
  NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT, Mar. 2003, [Reviewed]
• Back-transformation of high-pressure,phases in a shock melt vein of an H-chondrite during Back-transformation of high-pressure phases in a shock melt vein of an H-chondrite during atmospheric passage: Implications for the survival of high-pressure phases after decompression, Erratum, ibid. 219, 171-171(2003)　　　　　　　　　　　　　　　
  M. Kimura; M. Chen; Tatsuo Yoshida; A. El Goresy; and E. Ohtani
  Earth and Planetary Science Letters, 2003
• Back-transformation of high-pressure phases in a shock melt vein of an H-chondrite during Back-transformation of high-pressure phases in a shock melt vein of an H-chondrite during atmospheric passage: Implications for the survival of high-pressure phases　　　　　　　　　　　　　　　
  M. Kimura; M. Chen; Tatsuo Yoshida; A. El Goresy; E. Ohtani
  Earth and Planetary Science Letters, 2003
• Constraints on Cold Dark Matter in the Gamma-Ray Halo of NGC 253
  R. Enomto; Tatsuo Yoshida; S. Yanagita; and C. Itoh, A gamma-ray halo in the nearby starburst galaxy NGC 253 was found by the CANGAROO-II Imaging Atmospheric Cerenkov Telescope. By fitting the energy spectrum with expected curves from cold dark matter (CDM) annihilations, we constrain the CDM annihilation rate in the halo of NGC 253. Upper limits for the CDM density were obtained in the wide mass range between 0.5 and 50 TeV. Although these limits are higher than the expected values, they are complementary to the other experimental techniques, especially considering the extended energy coverage. We also investigate the next astronomical targets to improve these limits., UNIV CHICAGO PRESS
  Ap.J, 2003, [Reviewed]
• Evidence of TeV gamma-ray emission from the nearby starburst galaxy NGC 253
  C. Itoh; R. Enomto; S. Yanagita; Tatsuo Yoshida(4番目); 他41人, TeV gamma-rays were recently detected from the nearby normal spiral galaxy NGC 253 (Itoh et al. 2002). Observations to detect the Cherenkov light images initiated by gamma-rays from the direction of NGC 253 were carried out in 2000 and 2001 over a total period of similar to150 hours. The orientation of images in gamma-ray-like events is not consistent with emission from a point source, and the emission region corresponds to a size greater than 10 kpc in radius. Here, detailed descriptions of the analysis procedures and techniques are given., E D P SCIENCES
  Astron.Astrophys., 2003
• Galactic Gamma-Ray Halo of the Nearby Starburst Galaxy NGC 253
  C. Itoh; R. Enomto; S. Yanagita; Tatsuo Yoshida; and T. G. Turu, Corresponding, Recently, the CANGAROO-II telescope detected diffuse TeV gamma-ray emission from a nearby edge-on starburst galaxy, NGC 253. The emission mechanism is discussed in this report. We review the emissions of radio-to-TeV gamma rays from NGC 253 and present a model of the nonthermal emissions due to synchrotron radiations and inverse Compton scatterings. A halo model successfully explains the multiband spectrum of NGC 253., UNIV CHICAGO PRESS
  Ap.J., 2003, [Reviewed]
• Modeling of “Gradual” Solar Energetic Particle Events Using a Stochastic Differential Equation Method
  M. Den; Tatsuo Yoshida; and K. Yamashita, We have modeled "gradual" solar energetic particle events through numerical simulations using a Stochastic Differential Equation (SDE) method. We consider that energetic particle events axe roughly divided into two groups: (1) where the shock was driven by coronal mass ejections (CMEs) associated with large solar flares, and (2) where they have no related solar events apart from the CMEs. (The detailed classification of energetic particle events was discussed in our previous paper.) What we call "gradual" solar energetic particle events belong to the former group. Particles with energies greater than 10 MeV are observed within several hours after the occurrence of flares and CMEs in many gradual events. By applying the SDE method coupled with particle splitting, to diffusive acceleration, we found that an injection of high energy particles is necessary for early enhancement of such a high-energy proton flux and that it should not be presumed that the solar wind particles act as the seed population. (C) 2003 COSPAR. Published by Elsevier Ltd. All rights reserved., PERGAMON-ELSEVIER SCIENCE LTD
  Advances in Space Research, 2003, [Reviewed]
• Enhancement in Low-Energy Region of a Proton Flux Associated with Interplanetary Shock Waves
  M. Den; Tatsuo Yoshida; and K. Yamashita, We study time evolution of an energy spectrum of a proton flux in the range of 47-4750 keV for the energetic particle event occurred on 255 DOY in 1999, which we consider as one of typical diffusive acceleration events associated with interplanetary shocks and irrespective of large X-ray solar flares. Fast enhancement during evolution is found in the range of less than about 0.5 MeV. Our previous numerical simulations using Stochastic Differential Equation method could not show this behavior, although we obtained results showing a power law energy spectrum, which suggesting that energetic particles are accelerated diffusively by shock waves, the first-order Fermi acceleration. We consider that less than 0.5 MeV protons need to exist to explain behavior of the observational energy spectrum and perform numerical simulations in order to investigate proper injection models for this event. (C) 2003 COSPAR. Published by Elsevier Ltd. All rights reserved., PERGAMON-ELSEVIER SCIENCE LTD
  Advances in Space Research, 2003, [Reviewed]
• Observation of gamma rays greater than 10 TeV from Markarian 421
  K Okumura; A Asahara; GV Bicknell; PG Edwards; R Enomoto; S Gunji; S Hara; T Hara; S Hayashi; C Itoh; S Kabuki; F Kajino; H Katagiri; J Kataoka; A Kawachi; T Kifune; H Kubo; J Kushida; S Maeda; A Maeshiro; Y Matsubara; Y Mizumoto; M Mori; M Moriya; H Muraishi; Y Muraki; T Naito; T Nakase; K Nishijima; M Ohishi; Patterson, JR; K Sakurazawa; R Suzuki; DL Swaby; K Takano; T Takano; T Tanimori; F Tokanai; K Tsuchiya; H Tsunoo; K Uruma; A Watanabe; S Yanagita; T Yoshida; T Yoshikoshi, We have observed Markarian 421 in 2001 January and March with the CANGAROO-II imaging Cerenkov telescope during an extraordinarily high state at TeV energies. From 14 hr of observations at very large zenith angles, similar to70degrees, a signal of 298 +/- 52 gamma-ray-like events (5.7 sigma) was detected at E > 10 TeV, where a higher sensitivity is achieved than those of usual observations near the zenith, owing to a greatly increased collecting area. Under the assumption of an intrinsic power-law spectrum, we derived a differential energy spectrum dN/dE p (3.3 +/- 0.9(stat) +/- 0.3(syst)) x 10(-13) (E/10 TeV)(-(4.0+/-0.60.9, stat +/-0.3syst)) photons cm(-2) s(-1) TeV-1, which is steeper than those previously measured around 1 TeV and supports the evidence for a cutoff in the spectrum of Mrk 421. However, the 4 sigma excess at energies greater than 20 TeV in our data favors a cutoff energy of similar to8 TeV, at the upper end of the range previously reported from measurements at TeV energies., UNIV CHICAGO PRESS
  ASTROPHYSICAL JOURNAL, Nov. 2002, [Reviewed]
• Design study of CANGAROO-III, stereoscopic imaging atmospheric Cherenkov telescopes for sub-TeV gamma-ray detection
  R Enomoto; S Hara; A Asahara; GV Bicknell; PG Edwards; S Gunji; T Hara; J Jimbo; F Kajino; H Katagiri; J Kataoka; A Kawachi; T Kifune; H Kubo; J Kushida; Y Matsubara; Y Mizumoto; M Mori; M Moriya; H Muraishi; Y Muraki; T Naito; T Nakase; K Nishijima; K Okumura; Patterson, JR; K Sakurazawa; DL Swaby; K Takano; T Tanimori; T Tamura; K Tsuchiya; K Uruma; S Yanagita; T Yoshida; T Yoshikoshi; A Yuki, CANGAROO-III is an imaging atmospheric Cherenkov telescope array of four 10-m telescopes for very high energy (sub-TeV) gamma-ray astronomy. A design study of the CANGAROO-III telescope system was carried out using the Monte Carlo technique in order to optimize the pixel size and the telescope spacing. Studies were also made of observations at low elevation angles. (C) 2002 Elsevier Science B.V. All rights reserved., ELSEVIER SCIENCE BV
  ASTROPARTICLE PHYSICS, Jan. 2002, [Reviewed]
• The acceleration of cosmic-ray protons in the supernova remnant RX J1713, 7-3946(共著)
  R Enomoto; T Tanimori; T Naito; T Yoshida; S Yanagita; M Mori; PG Edwards; A Asahara; GV Bicknell; S Gunji; S Hara; T Hara; S Hayashi; C Itoh; S Kabuki; F Kajino; H Katagiri; J Kataoka; A Kawachi; T Kifune; H Kubo; J Kushida; S Maeda; A Maeshiro; Y Matsubara; Y Mizumoto; M Moriya; H Muraishi; Y Muraki; T Nakase; K Nishijima; M Ohishi; K Okumura; Patterson, JR; K Sakurazawa; R Suzuki; DL Swaby; K Takano; T Takano; F Tokanai; K Tsuchiya; H Tsunoo; K Uruma; A Watanabe; T Yoshikoshi, Protons with energies up to similar to10(15) eV are the main component(1) of cosmic rays, but evidence for the specific locations where they could have been accelerated to these energies has been lacking(2). Electrons are known to be accelerated to cosmic-ray energies in supernova remnants(3,4), and the shock waves associated with such remnants, when they hit the surrounding interstellar medium, could also provide the energy to accelerate protons. The signature of such a process would be the decay of pions (pi(0)), which are generated when the protons collide with atoms and molecules in an interstellar cloud: pion decay results in gamma-rays with a particular spectral-energy distribution(5,6). Here we report the observation of cascade showers of optical photons resulting from g-rays at energies of similar to10(12) eV hitting Earth's upper atmosphere, in the direction of the supernova remnant RX J1713.7-3946. The spectrum is a good match to that predicted by pion decay, and cannot be explained by other mechanisms., NATURE PUBLISHING GROUP
  Nature, 2002
• Detection of diffuse TeV gamma-ray emission from the neaby starburst galaxy NGC253(共著)
  C Itoh; R Enomoto; S Yanagita; T Yoshida; A Asahara; GV Bicknell; RW Clay; PG Edwards; S Gunji; S Hara; T Hara; T Hattori; S Hayashi; S Hayashi; S Kabuki; F Kajino; H Katagiri; A Kawachi; T Kifune; H Kubo; J Kushida; Y Matsubara; Y Mizumoto; M Mori; H Moro; H Muraishi; Y Muraki; T Naito; T Nakase; D Nishida; K Nishijima; K Okumura; M Ohishi; Patterson, JR; RJ Protheroe; K Sakurazawa; DL Swaby; T Tanimori; F Tokanai; K Tsuchiya; H Tsunoo; T Uchida; A Watanabe; S Watanabe; T Yoshikoshi, We report the TeV gamma-ray observations of the nearby normal spiral galaxy NGC 253. At a distance of similar to2.5 Mpc, NGC 253 is one of the nearest starburst galaxies. This relative closeness, coupled with the high star formation rate in the galaxy, make it a good candidate TeV gamma-ray source. Observations were carried out in 2000 and 2001 with the CANGAROO-II 10 m imaging atmospheric Cerenkov telescope. TeV gamma-ray emission is detected at the similar to11sigma level with a flux of (7.8 +/- 2.5) x 10(-12) cm(-2) s(-1) at energies > 0.5 TeV. The data indicate that the emission region is broader than the point spread function of our telescope., E D P SCIENCES
  Astronomy and Astrophysics, 2002
• Self-gravitational instability of an isothermal gaseous slab under high external pressure
  M Umekawa; R Matsumoto; S Miyaji; T Yoshida, ASTRONOMICAL SOC PACIFIC
  GALAXIES AND THEIR CONSTITUENTS AT THE HIGHEST ANGULAR RESOLUTIONS, 2001, [Reviewed]
• Particle acceleration in interplanetary shocks: Classification of energetic particle events and modeling
  M Den; T Yoshida; K Yamashita, Gradual solar energetic particle events using data observed by EPAM (Electron, Proton, and Alpha Monitor), SWEPAM (Solar Wind Electron, Proton and Alpha Monitor) and Magnetic Field Experiment (MAG) on the ACE are studied. The energetic particle events are classified in four types according to the variance in the flux, the characteristic duration time of the events and the maximum energy of the accelerated particles. We perform the modeling of typical events by using numerical simulations for two types. We apply the stochastic differential equation method coupled with the particle splitting to diffusive acceleration, and obtain the energy spectrum and the spatial distribution of the accelerated particles. The relation between the different classes of the events and injection model is discussed., AMER INST PHYSICS
  SOLAR AND GALACTIC COMPOSITION, 2001, [Reviewed]
• Fragmentation of Cosmology Collapsed Layers(共著)
  T Hosokawa; T Oishi; T Yoshida; M Yokosawa, The fragmentation and dynamics of pancake-like collapsed layers are discussed. The fragmentation theory for an isothermal gas layer is extended to the case of the transverse expansion or contraction of a layer with two components. The expansion of a layer suppresses the growth of a perturbation and the contraction enhances the perturbation. It is shown that the growth rate increases exponentially with the deceleration of expansion. The critical wave number for the instability is almost constant for various rates of the expansion. The linear interaction of a perturbation between the cooled layer and a hot layer composed of dark matter changes the growth rate. The growth rate of the cooled layer is superior to the maximum value of the growth rate in isolated cases when the scale heights of both layers are not so different. This fragmentation theory is applied to cosmologically collapsed layers that were calculated by numerical simulations. The cooled layers produced by the collapse with transverse expansion have nearly the same density and temperature over a wide scale range of primordial density fluctuations, lambda = 1-20 Mpc. The mass of fragmentation is determined by evaluating the growth time of the perturbation and the accretion time of the cooled layer. The typical masses of the fragmentation are distributed over a narrow mass scale of 10(7-8) M.. A large dynamic range of the calculation, 10(6-8), is required to simulate the central region of the collapsed layer for the fluctuation wavelength, lambda = 10 Mpc. A calculation method with extremely large dynamic range is also presented., OXFORD UNIV PRESS
  Publications of the Astronomical Society of Japan, 2000
• Evidence for TeV gamma-vay emission from the shell type SNR RXJ1713.7-3946(共著)
  H Muraishi; T Tanimori; S Yanagita; T Yoshida; M Moriya; T Kifune; SA Dazeley; PG Edwards; S Gunji; S Hara; T Hara; A Kawachi; H Kubo; Y Matsubara; Y Mizumoto; M Mori; Y Muraki; T Naito; K Nishijima; Patterson, JR; GP Rowell; T Sako; K Sakurazawa; R Susukita; T Tamura; T Yoshikoshi, We report the results of TeV gamma-ray observations of the shell type SNR RXJ1713.7-3946 (G347.3-0.5). The discovery of strong non-thermal X-ray emission from the northwest part of the remnant strongly suggests the existence of electrons with energies up to similar to 100 TeV in the remnant, making the SNR a good candidate TeV gamma-ray source. We observed RX J1713.7-3946 from May to August 1998 with the CANGAROO 3.8m atmospheric imaging Cerenkov telescope and obtained evidence for TeV gamma-ray emission from the NW rim of the remnant with the significance of similar to 5.6 sigma. The observed TeV gamma-ray flux from the NW rim region was estimated to be (5.3 +/- 0.9[statistical] +/- 1.6[systematic]) x 10(-12) photons cm(-2) s(-1) at energies greater than or equal to 1.8 +/- 0.9 TeV. The data indicate that the emitting region is much broader than the point spread function of our telescope. The extent of the emission is consistent with that of hard X-rays observed by ASCA. This TeV gamma-ray emission can be attributed to the Inverse Compton scattering of the Cosmic Microwave Background Radiation by shock accelerated ultra-relativistic electrons. Under this assumption, a rather low magnetic field of similar to 11 mu G is deduced for the remnant from our observation., EDP SCIENCES S A
  Astronomy and Astrophysics, 2000
• Radio to TeV gamma-ray emission from SN 1006 and shock acceleration around its rim
  T. Naito; T. Yoshida; M. Mori; T. Tanimori
  Astronomische Nachrichten, 1999, [Reviewed]
• Self-Gravitational Instability of Isothermal Gaseous Slab under High Pressure (共著)
  M Umekawa; R Matsumoto; S Miyaji; T Yoshida, Last, We carried out two-dimensional hydrodynamic simulations to study the nonlinear growth of the gravitational instability of a self-gravitating isothermal gaseous slab confined by external pressure. When the external pressure is low, the Jeans instability creates dense collapsing clumps for long-wavelength perturbations. When the external pressure is high (P-ext/P-00 > 0.64 where P-00 is the initial mid-plane pressure and P-ext is the external pressure), an incompressible mode of gravitational instability creates clumps, the mass of which is smaller than the Jeans mass. The clumps merge due to mutual gravitational attraction. Although each clump cannot collapse gravitationally when its mass exceeds the Jeans mass by merging, the merged clump collapses gravitationally. These results indicate that when the external pressure is high, star formation can be triggered by the merging of low-mass Jeans stable clumps. In high external pressure regions, we expect that the mass function of collapsing clumps in the clouds has a peak around the Jeans mass., OXFORD UNIV PRESS
  Publications of the Astronomical Society of Japan, 1999
• Discovery of Tev Gamma Rays from SN1006 : Further Evidence for the Supernova Remnant Origin of Cosmic Rays (共著)
  T Tanimori; Y Hayami; S Kamei; SA Dazeley; PG Edwards; S Gunji; S Hara; T Hara; J Holder; A Kawachi; T Kifune; R Kita; T Konishi; A Masaike; M Matsubara; T Matsuoka; Y Mizumoto; M Mori; M Moriya; H Muraishi; Y Muraki; T Naito; K Nishijima; S Oda; S Ogio; Patterson, JR; MD Roberts; GP Rowell; K Sakurazawa; T Sako; Y Sato; R Susukita; A Suzuki; R Suzuki; T Tamura; GJ Thornton; S Yanagita; T Yoshida; T Yoshkoshi, In this Letter we report the discovery of TeV gamma-ray emission from a supernova remnant made with the CANGAROO 3.8 m telescope. TeV gamma rays were detected at the sky position and extension coincident with the northeast rim of shell-type supernova remnant (SNR) SN 1006 (Type: Ia). SN 1006 has been a most likely candidate for an extended TeV gamma-ray source, since the clear synchrotron X-ray emission from the rims was recently observed by ASCA (Koyama et al.), which is strong evidence for the existence of very high energy (up to hundreds of TeV) electrons in the SNR. The observed TeV gamma-ray flux was (2.4 +/- 0.5 [statistical] +/- 0.7 [systematic]) x 10(-12) cm(-2) s(-1) (greater than or equal to 3.0 +/- 0.9 TeV) and (4.6 +/- 0.6 +/- 1.4) x 10(-12) cm(-2) s(-1) (greater than or equal to 1.7 +/- 0.5 TeV) from the 1996 and 1997 observations, respectively. Also, we set an upper limit on the TeV gamma-ray emission from the southwest rim, which is estimated to be 1.1 x 10(-12) s(-1) (greater than or equal to 1.7 +/- 0.5 TeV, 95% confidence level) in the 1997 data. The TeV gamma rays can be attributed to the 2.7 K cosmic background photons upscattered by electrons of energies up to about 10(14) eV by the inverse Compton process. The observed flux of the TeV gamma rays, together with that of the nonthermal X-rays, gives firm constraints on the acceleration process in the SNR shell; a magnetic field of 6.5 +/- 2 mu G is inferred from both the synchrotron X-rays and the inverse Compton TeV gamma rays, which provides entirely consistent evidence that electrons of energies up to 10(14) eV are produced via shock acceleration in SN 1006., UNIV CHICAGO PRESS
  The Astrophysical Journal, 1998
• Non-linear study of magetothermal instability in coolinf flows (共著)
  M HATTORI; T YOSHIDA; A HABE, We have performed two-dimensional numerical magnetohydrodynamical calculations in order to investigate the effects of magnetic field on the evolution of non-linear perturbations in cooling flows. We have shown that the vertical magnetic field can suppress vortex motion in a non-linear perturbation, and can help the growth of thermal instability. We have found that the vertical wavelength of perturbations cannot be larger than some critical value for the perturbations to be supported by the magnetic tension. This upper limit depends on the ratio of the gas pressure plasma to the magnetic pressure, plasma beta, in cooling flows, with the upper limit becoming smaller as the ratio becomes larger, and it is very small in the expected cooling flow environment of 0.017(beta/600)(-1) kpc. This small upper limit may be related to the suppression of massive-star formation in cooling flows., BLACKWELL SCIENCE LTD
  Monthly Notices of the Royal Astronomical Society, 1995
• A Stochastic Simulation Method for Partide Acceleration and Non-Thermal Photon Emission in Astrophysical Processes (共著)
  T YOSHIDA; S YANAGITA, Lead, A versatile numerical method is developed to simulate the time dependent particle acceleration in shocks and the non-thermal photon emission thereof. Our method is based on Ita's stochastic differential equations couples with a particle splitting. This method is applied to photon emission, KYOTO UNIV
  Progress of Theoretical Physios, 1994
• Effect of Deceleration on the Gravitational Instability of Shocked Gas Layers (共著)
  T YOSHIDA; A HABE, Lead, We have performed two-dimensional hydrodynamic calculations to investigate effect of deceleration on the gravitational instability of isothermal shocked gas layers. We give the time evolution of the decelerating shocked layer with the corrugation-type perturbation. Our numerical results show that the density perturbation is produced by the tangential flows caused by the corrugated shock front and by the effective gravity due to the deceleration and the gas pressure. The growth rate of the density perturbation and the evolution of the perturbation depend on the initial wavelength of the corrugation-type perturbation. We find that there is the most unstable wave number. In this case, the density perturbation grows well due to the decelerating shock instability in t(cr), where it is the time that the self -gravity of the layer becomes equal to the deceleration of the layer. After t(cr), the density perturbation continues to grow fast due to the gravitational instability. In this way, the deceleration accelerates the gravitational instability. The gravitational collapse occurs in a half of the free fall time t(ff) of the preshock gas. On the other hand, if the density perturbation does not grow enough in t(cr), the gravitational collapse occurs in t(ff) or the gravitational collapse does not occur. We discuss the condition of the fast gravitational collapse. Our numerical results suggest that the deceleration of the dense layer in the molecular clouds formed by the H(II) regions accelerates the formation of the cores, which are observed in molecular clouds beside H(II) regions., KYOTO UNIV
  Progress of Theoretical Physics, 1992
• Numerical study of the non-linear stage of thermal instability in cooling flows-II. The non-linear perturbation in the case of a spherically symmetric background flow (共著)
  T YOSHIDA; M HATTORI; A HABE, Lead, We have performed two-dimensional numerical hydrodynamical calculations of thermal instability in cooling flows in a spherical coordinate system, in order to investigate the evolution of the non-linear axisymmetric perturbation. If the relative density contrast is smaller than the critical value the perturbation decays, due to the formation of the vortex ring before the perturbation cools. We carry out one-dimensional spherically symmetric calculations, and show that even if the density contrast is smaller than the critical value, in the case of the spherically symmetric perturbation it can cool. Our numerical results show that the non-radial motion is very important for the evolution of the non-linear perturbation. We give the criterion for the amplitude and size of perturbations which are thermally unstable. We show that only if the density contrast of the perturbation is very large, can the thermal instability develop in the spherically symmetric background cooling flow. These results indicate that the apparently pervasive and extensive mass deposition occurring in real cooling flows remains unexplained and what makes thermal instability occur - for example a magnetic field may be needed., BLACKWELL SCIENCE LTD
  Monthly Notices of the Royal Astronomical Society, 1991
• Two-Dimensional Simulations of Hydrodynamic Instability in Supernova Explosion. II (共著)　　　　　　　　　　　　　　　
  Progress of Theoretical Physics, 1991
• Two-Dimensional Simulation of Hydrodynamic Instability in Supernova Explosions (共著)　　　　　　　　　　　　　　　
  Lead
  Progress of Theoretical Physics, 1990
• Non-Equilibrium Thermal X-Ray Emission in Early Phase of Supernova Remnant (共著)
  T YOSHIDA; H HANAMI, Lead, KYOTO UNIV
  Progress of Theoretical Physics, 1988