Naomi Ota

Hard X-ray Detector (HXD) on board Suzaku

The Hard X-ray Detector (HXD) on board Suzaku covers a wide energy range from 10 keV to 600 keV by combination of silicon PIN diodes and GSO scintillators. The HXD is designed to achieve an extremely low in-orbit back ground based on a combination of new techniques, including the concept of well-type active shield counter. With an effective area of 142 cm^2 at 20 keV and 273 cm2 at 150 keV, the background level at the sea level reached ~1x10^{-5} cts s^{-1} cm^{-2} keV^{-1} at 30 keV for the PI N diodes, and ~2x10^{-5} cts s^{-1} cm^{-2} keV^{-1} at 100 keV, and ~7x10^{-6} cts s^{-1} cm^{-2} keV^{-1} at 200 keV for the phoswich counter. Tight active shielding of the HXD results in a large array of guard counters surrounding the main detector parts. These anti-coincidence counters, made of ~4 cm thick BGO crystals, have a large effective area for sub-MeV to MeV gamma-rays. They work as an excellent gamma-ray burst monitor with limited angular resolution (~5 degree). The on-board signal-processing system and the data transmitted to the ground are also described.

A uniform X-ray analysis of 79 distant galaxy clusters with ROSAT and ASCA

We present a uniform analysis of the ROSAT HRI and the ASCA GIS/SIS data for 79 distant clusters of galaxies in the redshift range 0.1 < z < 0.82 to study the global structures of the intracluster medium. We have constructed an X-ray catalog consisting of the largest sample of clusters in the redshift range for which pointed X-ray observations were carried out with both the observatories. We determined the emission-weighted X-ray temperatures of the clusters with ASCA, while we studied surface brightness distribution with the ROSAT HRI utilizing the isothermal β model. We investigated the statistical properties and trends for redshift evolution of the X-ray parameters including the temperature, the density profile of the intracluster gas and the gas-mass fraction within r500. We also present correlations of the cluster parameters with the X-ray temperature and with the core radius and compare them with the predictions of the self-similar model, from which we discuss the possible origin of the double structure discovered in the core radius distribution.

CHANDRA ANALYSIS AND MASS ESTIMATION OF THE LENSING CLUSTER OF GALAXIES CL 0024+17

We present a detailed analysis of Chandra X-ray observations of the lensing cluster of galaxies CL0024+17 at z = 0.395. We found that the radial temperature profile is consistent with being isothermal out to ∼ 600 kpc and that the average X-ray temperature is 4.47 +0.83 −0.54 keV. The X-ray surface brightness profile is represented by the sum of extended emission centered at the central bright elliptical galaxy with a small core of 50 kpc and more extended emission which can be well described by a spherical β-model with a core radius of about 210 kpc. Assuming the X-ray emitting gas to be in hydrostatic equilibrium, we estimated the X-ray mass within the arc radius and found it is significantly smaller than the strong lensing mass by a factor of about 2–3. We detected a strong redshifted iron K line in the X-ray spectrum from the cluster for the first time and find the metal abundance to be 0.76 +0.37 −0.31 solar. Subject headings: galaxies: clusters: individual (CL0024+17) — X-rays: galaxies — gravitational lensing — dark matter

The Astro-H High Resolution Soft X-Ray Spectrometer

We present the overall design and performance of the Astro-H (Hitomi) Soft X-Ray Spectrometer (SXS). The instrument uses a 36-pixel array of x-ray microcalorimeters at the focus of a grazing-incidence x-ray mirror Soft X-Ray Telescope (SXT) for high-resolution spectroscopy of celestial x-ray sources. The instrument was designed to achieve an energy resolution better than 7 eV over the 0.3-12 keV energy range and operate for more than 3 years in orbit. The actual energy resolution of the instrument is 4-5 eV as demonstrated during extensive ground testing prior to launch and in orbit. The measured mass flow rate of the liquid helium cryogen and initial fill level at launch predict a lifetime of more than 4 years assuming steady mechanical cooler performance. Cryogen-free operation was successfully demonstrated prior to launch. The successful operation of the SXS in orbit, including the first observations of the velocity structure of the Perseus cluster of galaxies, demonstrates the viability and power of this technology as a tool for astrophysics.

Exploring Cluster Physics with High-Resolution Sunyaev-Zel'dovich Effect Images and X-Ray Data: The Case of the Most X-Ray-Luminous Galaxy Cluster RX J1347-1145

Foreseeing the era of high spatial resolution measurements of the Sunyaev–Zel’dovich effect (SZE) in clusters of galaxies, we present a prototype analysis of this sort combined with Chandra X-ray data. It is applied specifically to RX J1347–1145 at z = 0.451, the most X-ray-luminous galaxy cluster known, for which the highest resolution SZE and X-ray images are currently available. We demonstrate that the combined analysis yields a unique probe of complex structures in the intracluster medium, offering determinations of their temperature, density, and line-of-sight extent. For a subclump in RX J1347– 1145, previously discovered in our SZE map, the temperature inferred after removing the foreground and background components is well in excess of 20 keV, indicating that the cluster has recently undergone a violent merger. Excluding the region around this subclump, the SZE signals in submillimeter to centimeter bands (350, 150, and 21 GHz) are all consistent with those expected from Chandra X-ray observations. We further present a temperature deprojection technique based on the SZE and X-ray images, without any knowledge of spatially resolved X-ray spectroscopy. The methodology presented here will be applicable to a statistical sample of clusters available in the future SZE surveys.

Astro-E hard x-ray detector

Astro-E is the x-ray satellite to be launched in the year 2000 by Inst. of Space & Astronautical Science. This report deals with the design and expected performance of the hard x-ray detector (HXD), one of the 3 experiments aboard Astro- E. The HXD is a combination of GSO/BGO well-type phoswich counters and silicon PIN diodes: the two combined will cover a wide energy band of 10 - 700 keV. The detector is characterized by its low background of approximately 10-5/s/cm2/keV and its sensitivity higher than any past missions between a few 10 keV and several 100 keV. Combined with the other 2 experiments, a micro-calorimeter array (XRS) and 4 CCD arrays (XIS), both with x-ray mirrors, the mission will cover the soft and hard x-ray range at a highest sensitivity.

X-Ray Study of the Outer Region of Abell 2142 with Suzaku

We observed outer regions of a bright cluster of galaxies A2142 with Suzaku. Temperature and brightness structures were measured out to the virial radius (

Soft x-ray spectrometer (SXS): The high-resolution cryogenic spectrometer onboard ASTRO-H

r_{200}

Suzaku Observation of the Metallicity Distribution in the Intracluster Medium of the Fornax Cluster

) with good sensitivity. We confirmed the temperature drop from 9 keV around the cluster center to about 3.5 keV at

Suzaku observations of the Hydra A cluster out to the virial radius

r_{200}