Search Publications
AGN number fraction in galaxy groups and clusters at z < 1.4 from the Subaru Hyper Suprime-Cam survey
Goto, Tomotsugu; Imanishi, Masatoshi; Schramm, Malte +20 more
One of the key questions on active galactic nuclei (AGN) in galaxy clusters is how AGN could affect the formation and evolution of member galaxies and galaxy clusters in the history of the Universe. To address this issue, we investigate the dependence of AGN number fraction (fAGN) on cluster redshift (zcl) and distance from t…
MeerKAT's view of double radio relic galaxy cluster Abell 3376
Nakanishi, Hiroyuki; Akamatsu, Hiroki; Takeuchi, Tsutomu T. +10 more
We present the initial results of our MeerKAT L-band observations of Abell 3376. We achieved higher (5″) angular resolution and better (~4 µ Jy beam-1) sensitivity compared to the previous observations. Our achieved sensitivity is only a factor of 2 larger than the thermal noise of MeerKAT. Astrometric and flux comparison of discr…
X-ray and optical spectroscopic study of a γ Cassiopeiae analog source π Aquarii
Tsujimoto, Masahiro; Hayashi, Takayuki; Morihana, Kumiko +1 more
γ Cas analog sources are a subset of Be stars that emit intense and hard X-ray emission. Two competing ideas for their X-ray production mechanism are (a) the magnetic activities of the Be star and its disk and (b) the accretion from the Be star to an unidentified compact object. Among such sources, π Aqr plays a pivotal role as it is one of the on…
CO multi-line imaging of nearby galaxies (COMING). XII. CO-to-H2 conversion factor and dust-to-gas ratio
Kobayashi, Masato I. N.; Kuno, Nario; Miyamoto, Yusuke +8 more
We simultaneously measured the spatially resolved CO-to-H2 conversion factor (αCO) and dust-to-gas ratio (DGR) in nearby galaxies on a kiloparsec scale. In this study, we used 12CO(J = 1-0) data obtained by the Nobeyama 45 m radio telescope with H I and dust mass surface densities. We obtained the values of global …
Magnetic-field structure of the Crab pulsar wind nebula revealed with IXPE
Weisskopf, Martin C.; Slane, Patrick; Mizuno, Tsunefumi +5 more
We report a detailed study of the magnetic-field structure of the Crab pulsar wind nebula, using the X-ray polarization data in 2-8 keV obtained with the Imaging X-ray Polarimetry Explorer. Contamination of the data for the nebula region by the pulsar emission was removed through application of a stringent pulsation phase cut, extracting a phase r…
Revisiting planetary systems in the Okayama Planet Search Program: A new long-period planet, RV astrometry joint analysis, and a multiplicity-metallicity trend around evolved stars
Izumiura, Hideyuki; Sato, Bun'ei; Yoshida, Michitoshi +15 more
In this study, we revisit 32 planetary systems around evolved stars observed within the framework of the Okayama Planet Search Program (OPSP) and its collaborative framework of the East Asian Planet Search Network to search for additional companions and investigate the properties of stars and giant planets in multiple-planet systems. With our late…
The soft X-ray background with Suzaku. II. Supervirial temperature bubbles?
Sato, Kosuke; Yamasaki, Noriko Y.; Matsushita, Kyoko +4 more
Observations of the hot X-ray emitting interstellar medium in the Milky Way are important for studying the stellar feedback and for understanding the formation and evolution of galaxies. We present measurements of the soft X-ray background emission for 130 Suzaku observations at 75° < l < 285° and |b| > 15°. With the standard soft X-ray b…
XMM-Newton view of the shock heating in an early merging cluster, CIZA J1358.9-4750
Sato, Kosuke; Nakazawa, Kazuhiro; Gu, Liyi +10 more
CIZA J1358.9-4750 is a nearby galaxy cluster in the early phase of a major merger. The two-dimensional temperature map using XMM-Newton EPIC-PN observation confirms the existence of a high-temperature region, which we call the "hot region," in the "bridge region" connecting the two clusters. The ~500 kpc wide region between the south-east and nort…
Seimei/KOOLS-IFU mapping of the gas and dust distributions in Galactic PNe: Unveiling the origin and evolution of the Galactic halo PN H4-1
Ueta, Toshiya; Otsuka, Masaaki; Tajitsu, Akito
H4-1 is a planetary nebula (PN) located in the Galactic halo, and is notably carbon-rich and one of the most metal-deficient PNe in the Milky Way. To unveil its progenitor evolution through accurate measurement of the gas mass, we conducted a comprehensive investigation of H4-1, using the newly obtained Seimei/KOOLS-IFU spectra and multiwavelength…
Spectral analysis of the Galactic supernova remnant Kesteven 69 with Suzaku
Yamauchi, Shigeo; Pannuti, Thomas G.
The results of a Suzaku observation of the supernova remnant (SNR) Kesteven 69 = G21.8-0.6 are presented. To estimate the sky background precisely, we conducted a simultaneous fit of the source region spectrum with the background region spectrum and found that the SNR spectrum is well represented by a two-component ionizing plasma model composed o…