The Quiescent Intracluster Medium in the Core of the Perseus Cluster

Clusters of galaxies are the most massive gravitationally-bound objects in the Universe and are still forming. They are thus important probes of cosmological parameters and a host of astrophysical processes. Knowledge of the dynamics of the pervasive hot gas, which dominates in mass over stars in a cluster, is a crucial missing ingredient. It can enable new insights into mechanical energy injection by the central supermassive black hole and the use of hydrostatic equilibrium for the determination of cluster masses. X-rays from the core of the Perseus cluster are emitted by the 50 million K diffuse hot plasma filling its gravitational potential well. The Active Galactic Nucleus of the central galaxy NGC1275 is pumping jetted energy into the surrounding intracluster medium, creating buoyant bubbles filled with relativistic plasma. These likely induce motions in the intracluster medium and heat the inner gas preventing runaway radiative cooling; a process known as Active Galactic Nucleus Feedback. Here we report on Hitomi X-ray observations of the Perseus cluster core, which reveal a remarkably quiescent atmosphere where the gas has a line-of-sight velocity dispersion of 164+/-10 km/s in a region 30-60 kpc from the central nucleus. A gradient in the line-of-sight velocity of 150+/-70 km/s is found across the 60 kpc image of the cluster core. Turbulent pressure support in the gas is 4% or less of the thermodynamic pressure, with large scale shear at most doubling that estimate. We infer that total cluster masses determined from hydrostatic equilibrium in the central regions need little correction for turbulent pressure.Comment: 31 pages, 11 Figs, published in Nature July

Hitomi (ASTRO-H) X-ray Astronomy Satellite

The Hitomi (ASTRO-H) mission is the sixth Japanese x-ray astronomy satellite developed by a large international collaboration, including Japan, USA, Canada, and Europe. The mission aimed to provide the highest energy resolution ever achieved at E  >  2  keV, using a microcalorimeter instrument, and to cover a wide energy range spanning four decades in energy from soft x-rays to gamma rays. After a successful launch on February 17, 2016, the spacecraft lost its function on March 26, 2016, but the commissioning phase for about a month provided valuable information on the onboard instruments and the spacecraft system, including astrophysical results obtained from first light observations. The paper describes the Hitomi (ASTRO-H) mission, its capabilities, the initial operation, and the instruments/spacecraft performances confirmed during the commissioning operations for about a month

Hitomi X-Ray Studies of Giant Radio Pulses from the Crab Pulsar

To search for giant X-ray pulses correlated with the giant radio pulses (GRPs) from the Crab pulsar, we performed a simultaneous observation of the Crab pulsar with the X-ray satellite Hitomi in the 2300 keV band and the Kashima NICT radio telescope in the 1.41.7 GHz band with a net exposure of about 2 ks on 2016 March 25, just before the loss of the Hitomi mission. The timing performance of the Hitomi instruments was confirmed to meet the timing requirement and about 1000 and 100 GRPs were simultaneously observed at the main pulse and inter-pulse phases, respectively, and we found no apparent correlation between the giant radio pulses and the X-ray emission in either the main pulse or inter-pulse phase. All variations are within the 2 fluctuations of the X-ray fluxes at the pulse peaks, and the 3 upper limits of variations of main pulse or inter-pulse GRPs are 22% or 80% of the peak flux in a 0.20 phase width, respectively, in the 2300 keV band. The values for main pulse or inter-pulse GRPs become 25% or 110%, respectively, when the phase width is restricted to the 0.03 phase. Among the upper limits from the Hitomi satellite, those in the 4.510 keV and 70300 keV bands are obtained for the first time, and those in other bands are consistent with previous reports. Numerically, the upper limits of the main pulse and inter-pulse GRPs in the 0.20 phase width are about (2.4 and 9.3) 10(exp 11) erg cm(exp 2), respectively. No significant variability in pulse profiles implies that the GRPs originated from a local place within the magnetosphere. Although the number of photon-emitting particles should temporarily increase to account for the brightening of the radio emission, the results do not statistically rule out variations correlated with the GRPs, because the possible X-ray enhancement may appear due to a >0.02% brightening of the pulse-peak flux under such conditions

VBC-Cul2 ユビキチン リガーゼ フクゴウタイ ニ オケル Rbx1 ノ タヨウナ ヤクワリ

京都大学0048新制・課程博士博士(医学)甲第11983号医博第2927号新制||医||912(附属図書館)23796UT51-2006-C663京都大学大学院医学研究科外科系専攻(主査)教授 戸口田 淳也, 教授 瀬原 淳子, 教授 藤井 信吾学位規則第4条第1項該当Doctor of Medical ScienceKyoto UniversityDA

Molecular Mechanism of the Reaction Specificity in Threonine Synthase: Importance of the Substrate Conformations

Threonine synthase (ThrS) catalyzes the final chemical reaction of l-threonine biosynthesis from its precursor, <i>O</i>-phospho-l-homoserine. As the phosphate ion generated in its former half reaction assists its latter reaction, ThrS is recognized as one of the best examples of product-assisted catalysis. In our previous QM/MM study, the chemical reactions for the latter half reactions, which are critical for the product-assisted catalysis, were revealed. However, accurate free energy changes caused by the conformational ensembles and entrance of water molecules into the active site are unknown. In the present study, by performing long-time scale MD simulations, the free energy changes by the divalent anions (phosphate or sulfate ions) and conformational states of the intermediate states were theoretically investigated. We found that the calculated free energy double differences are in good agreement with the experimental results. We also revealed that the phosphate ion contributes to forming hydrogen bonds that are suitable for the main reaction progress. This means that the conformation of the active site amino acid residues and the substrate, and hence, the tunable catalysis, are controlled by the product phosphate ion, and this clearly demonstrates a molecular mechanism of the product-assisted catalysis in ThrS