Gas, Iron and Gravitational Mass in Galaxy Clusters: The General Lack of Cluster Evolution at z < 1.0

We have analyzed the ASCA data of 29 nearby clusters of galaxies systematically, and obtained temperatures, iron abundances, and X-ray luminosities of their intracluster medium (ICM). We also estimate ICM mass using the beta model, and then evaluate iron mass contained in the ICM and derive the total gravitating mass. This gives the largest and most homogeneous information about the ICM derived only by the ASCA data. We compare these values with those of distant clusters whose temperatures, abundances, and luminosities were also measured with ASCA, and find no clear evidence of evolution for the clusters at z<1.0. Only the most distant cluster at z=1.0, AXJ2019.3+1127, has anomalously high iron abundance, but its iron mass in the ICM may be among normal values for the other clusters, because the ICM mass may be smaller than the other clusters. This may suggest a hint of evolution of clusters at z ~ 1.0.Comment: 23 pages including 5 figures. Using PASJ2.sty, and PASJ95.sty. Accepted by PAS

Suzaku observation of the metallicity distribution in the intracluster medium of the Fornax cluster

The metallicity distribution in the Fornax cluster was studied with the XIS instrument onboard the Suzaku satellite. K-shell lines of O and Mg were resolved clearly, and the abundances of O, Mg, Si, S and Fe were measured with good accuracy. The region within a 4' radius of NGC 1399 shows approximately solar abundances of Fe, Si and S, while the O/Fe and Mg/Fe abundance ratios are about 0.4--0.5 and 0.7 in solar units. In the outer region spanning radii between 6' and 23', the Fe and Si abundances drop to 0.4--0.5 solar and show no significant gradient within this region. The abundance ratios, O/Fe and Mg/Fe, are consistent with those in the central region. We also measured the Fe abundance around NGC 1404 to be approximately solar, and the O, Ne and Mg abundances to be 0.5--0.7 times the Fe level. The significant relative enhancement of Fe within 130 kpc of NGC 1399 and in NGC 1404 indicates an origin in SN Ia, in contrast to the species O, Ne, and Mg which reflect the stellar metallicity. The mass-to-light ratios for O and Fe within 130 kpc of NGC 1399 are over an order of magnitude lower than those in rich clusters, reflecting the metal enrichment history of this poor cluster.Comment: 13 pages, accepted to PAS

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

Operating

processor

3-Exomethylene Sialic Acid Disaccharides as Substrate-Type Mechanism-Based Sialidase Inhibitors

We designed α(2,3)- and α(2,6)-sialylgalactose analogues bearing an exomethylene unit at C3 of sialic acid (3-exoSia) as a novel type of mechanism-based inhibitors of sialidases. Regio- and stereo-selective substitution by vinylogous activation enabled simultaneous construction of the 3-exomethylene moiety and the O-sialoside linkage. Both types of 3-exoSia disaccharides potently inhibit Clostridium perfringens sialidase NanI and selectively inhibit NEU2 among human sialidases, whereas the corresponding monosaccharide analogue is inactive. These analogues initially work as competitive inhibitors, but are gradually cleaved as substrates to generate a reactive species that forms a covalent bond with sialidase