Institution
Japan Aerospace Exploration Agency
Facility•Tokyo, Japan•
About: Japan Aerospace Exploration Agency is a facility organization based out in Tokyo, Japan. It is known for research contribution in the topics: Galaxy & Telescope. The organization has 4327 authors who have published 12054 publications receiving 208330 citations.
Papers published on a yearly basis
Papers
More filters
••
TL;DR: In this article, the expansion velocities of ejecta in Tycho's supernova remnant (SNR) are consistent with a spherically symmetric shell, based on Suzaku measurements of the Doppler broadened X-ray emission lines.
Abstract: We show that the expansion of ejecta in Tycho's supernova remnant (SNR) is consistent with a spherically symmetric shell, based on Suzaku measurements of the Doppler broadened X-ray emission lines. All of the strong Kα line emissions show broader widths at the center than at the rim, while the centroid energies are constant across the remnant (except for Ca). This is the pattern expected for Doppler broadening due to expansion of the SNR ejecta in a spherical shell. To determine the expansion velocities of the ejecta, we applied a model for each emission-line feature having two Gaussian components separately representing red- and blueshifted gas, and inferred the Doppler velocity difference between these two components directly from the fitted centroid energy difference. Taking into account the effect of projecting a three-dimensional shell to the plane of the detector, we derived average spherical expansion velocities independently for the Kα emission of Si, S, Ar, and Fe, and Kβ of Si. We found that the expansion velocities of Si, S, and Ar ejecta of 4700 ± 100 km s–1 are distinctly higher than that obtained from Fe Kα emission, 4000 ± 300 km s–1, which is consistent with segregation of the Fe in the inner ejecta. Combining the observed ejecta velocities with the ejecta proper-motion measurements by Chandra, we derived a distance to Tycho's SNR of 4 ± 1 kpc.
122 citations
••
TL;DR: In this paper, the authors reported the detection of kiloparsec (kpc)-scale radio structures in three radio-loud narrow-line Seyfert 1 (NLS1) galaxies from the Faint Images of the Radio Sky at Twenty-centimeters of the Very Large Array.
Abstract: We report the finding of kiloparsec (kpc)-scale radio structures in three radio-loud narrow-line Seyfert 1 (NLS1) galaxies from the Faint Images of the Radio Sky at Twenty-centimeters of the Very Large Array, which increases the number of known radio-loud NLS1s with kpc-scale structures to six, including two ?-ray-emitting NLS1s (PMN J0948+0022 and 1H 0323+342) detected by the Fermi Gamma-ray Space Telescope. The detection rate of extended radio emissions in NLS1s is lower than that in broad-line active galactic nuclei (AGNs) with a statistical significance. We found both core-dominated (blazar-like) and lobe-dominated (radio-galaxy-like) radio structures in these six NLS1s, which can be understood in the framework of the unified scheme of radio-loud AGNs that considers radio galaxies as non-beamed parent populations of blazars. Five of the six NLS1s have (1) extended radio luminosities suggesting jet kinetic powers of 1044?erg s?1, which is sufficient to make jets escape from hosts' dense environments; (2) black holes of 107 M ?, which can generate the necessary jet powers from near-Eddington mass accretion; and (3) two-sided radio structures at kpc scales, requiring expansion rates of ~0.01c-0.3c and kinematic ages of 107?years. On the other hand, most typical NLS1s would be driven by black holes of 107 M ? in a limited lifetime of ~107?years. Hence, the kpc-scale radio structures may originate in a small window of opportunity during the final stage of the NLS1 phase just before growing into broad-line AGNs.
122 citations
••
TL;DR: In this article, the photopion threshold effects with BLR photons suppress neutrino production below ∼ 1 PeV, which implies that neutrinos from other sources would dominate over the diffuse neutrini intensity at sub-PeV energies.
121 citations
••
TL;DR: In this paper, the authors performed infrared imaging of the jet of the quasar 3C 273 at wavelengths of 3.6 and 5.8 μm with the Infrared Array Camera (IRAC) on the Spitzer Space Telescope.
Abstract: We have performed infrared imaging of the jet of the quasar 3C 273 at wavelengths of 3.6 and 5.8 μm with the Infrared Array Camera (IRAC) on the Spitzer Space Telescope. When combined with the radio, optical, and X-ray measurements, the IRAC photometry of the X-ray-bright jet knots clearly shows that the optical emission is dominated by the high-energy emission component of the jet, not by the radio synchrotron component, as had been assumed to date. The high-energy component, represented by a power law from the optical through X-ray, may be due to a second synchrotron component or to inverse Compton scattering of ambient photons. In the former case, we argue that the acceleration of protons exceeding energies of Ep ~ 1016 eV or possibly even to Ep ~ 1019 eV would be taking place in the jet knots of 3C 273, assuming that the acceleration time is proportional to the particle gyroradius. In contrast, the inverse Compton model, into which highly relativistic Doppler beaming has to be incorporated, requires very low energy electrons of Ee ~ 1 MeV in the jet knots. The present polarization data in the radio and optical would favor the former interpretation in the case of the 3C 273 jet. Sensitive and detailed measurements of optical polarization are important in order to establish the radiation mechanism responsible for the high-energy emission. The present study offers new clues as to the controversial origin of the X-ray emission seen in many quasar jets.
120 citations
••
Japan Aerospace Exploration Agency1, National Institute for Environmental Studies2, University of Aizu3, Hokkaido University4, University of Tokyo5, Japan Agency for Marine-Earth Science and Technology6, Osaka University7, National Institute of Advanced Industrial Science and Technology8, University of Münster9
TL;DR: In this article, the authors performed new crater size-frequency measurements for 49 young mare units in the Procellarum KREEP Terrane (PKT), in which the latest magma eruption of the Moon occurred.
120 citations
Authors
Showing all 4340 results
Name | H-index | Papers | Citations |
---|---|---|---|
Yasushi Fukazawa | 135 | 882 | 64424 |
Jun Kataoka | 121 | 603 | 54274 |
Tadayuki Takahashi | 112 | 932 | 57501 |
Takaaki Tanaka | 105 | 321 | 41804 |
Yasunobu Uchiyama | 105 | 373 | 39610 |
Satoshi Tanaka | 96 | 739 | 76264 |
Masashi Hazumi | 87 | 708 | 29603 |
K. Izumi | 84 | 229 | 53205 |
Carolus J. Schrijver | 81 | 297 | 29858 |
Satoru Takahashi | 79 | 589 | 28007 |
Chris Done | 79 | 457 | 23210 |
Yasuo Doi | 79 | 370 | 33445 |
Poshak Gandhi | 75 | 481 | 18419 |
Alan M. Title | 74 | 203 | 21923 |
Yoshihiro Ueda | 72 | 576 | 25787 |