Fumie Akimoto

Characterization of the supermirror hard-x-ray telescope for the InFOCμS balloon experiment

A hard-x-ray telescope is successfully produced for balloon observations by making use of depth-graded multilayers, or so-called supermirrors, with platinum-carbon (Pt/C) layer pairs. It consists of four quadrant units assembled in an optical configuration with a diameter of 40 cm and a focal length of 8 m. Each quadrant is made of 510 pieces of coaxially and confocally aligned supermirrors that significantly enhance the sensitivity in an energy range of 20-40 keV. The configuration of the telescope is similar to the x-ray telescope onboard Astro-E, but with a longer focal length. The reflectivity of supermirrors is of the order of 40% in the energy range concerned at a grazing angle of 0.2 deg. The effective area of a fully assembled telescope is 50 cm2 at 30 keV. The angular resolution is 2.37 arc min at half-power diameter 8.0 keV. The field of view is 12.6 arc min in the hard-x-ray region, depending somewhat on x-ray energies. We discuss these characteristics, taking into account the figure errors of reflectors and their optical alignment in the telescope assembly. This hard-x-ray telescope is unanimously afforded in the International Focusing Optics Collaboration for muCrab Sensitivity balloon experiment.

The Observed Mass Profiles of Dark Halos and the Formation Epoch of Galaxies

We have determined the mass profiles of dark halos in 83 objects observed by ASCA. The point-spread function of the X-ray telescope was deconvoled by the Richardson-Lucy algorithm, and the temperature profiles were calculated to obtain the mass profiles. The derived mass profiles are consistent with the Navarro, Frenk, & White model in (0.01-1.0)rvirial. We found a good correlation between the scale radius rs and the characteristic mass density δc, which indicates the self-similarity of dark halos. The spectrum index of primordial density fluctuation, P(k) ∝ kn, was determined from the slope of the rs-δc relation. For M200 = 1012-1015 M☉, our analysis gives n = -1.2 ± 0.3 with a confidence level of 90%. The mass density of dark halos is a good indicator of the mean mass density of the universe at the time when the halos were assembled, z = zf. Assuming δc ∝ (1 + zf)3, we have determined the epoch when each dark halo was assembled. Our analysis indicates that the field elliptical galaxies and groups of galaxies formed approximately at 1 + zf 15 and at 1 + zf 7-10, respectively.

InFOCμS balloon-borne hard x-ray experiment with multilayer supermirror x-ray telescope

We have been developing the high throughput hard X-ray telescope, using reflectors coated with the depth graded multilayer known as supermirror, which is considered to be a key technology for future satellite hard X-ray imaging missions. InFOC(mu)

Characterization and performance of the InFOCμS 20-40 keV x-ray focusing mirror

S, the International Focusing Optics Collaboration for (mu) -Crab Sensitivity is the project of the balloon observation of a cosmic hard X-ray source with this type of hard X-ray telescope and CdZnTe pixel detector as a focal plane imager. For the fist InFOC(mu) S balloon experiment, we developed the hard X-ray telescope with outermost diameter of 40cm, focal length of 8m and energy band pass of 20-40 keV, for which Pt/C multilayer was used. From the pre-flight X-ray calibration, we confirmed its energy band and imaging capability of 2 arcmin HPD and 10 arcmin FOV of FWHM, and a effective area of 50 cm2 for 20-40 keV X-ray. We report the current status of our balloon borne experiment and performance of our hard X-ray telescope.

Spectroscopic Measurements of High Emissivity Materials Using Two-Dimensional Two-Color Thermometry

Mass production of replicated thin aluminum x-ray reflecting foils for the InFOC(mu) S (International Focusing Optics Collaboration for Micro-Crab Sensitivity) balloon payload is complete, and the full mirror has been assembled. InFOC(mu) S is an 8-meter focal length hard x-ray telescope scheduled for first launch in July 2001 and will be the first instrument to focus and image x-rays at high energies (20-40 keV) using multilayer-based reflectors. The individual reflecting elements are replicated thin aluminum foils, in a conical approximation Wolter-I system similar to those built for ASCA and ASTRO-E. These previous imaging systems achieved half-power-diameters of 3.5 and 1.7-2.1 arcminutes respectively. The InFOC(mu) S mirror is expected to have angular resolution similar to the ASTRO-E mirror. The reflecting foils for InFOC(mu) S, however, utilize a vertically graded Pt/C multilayer to provide broad-band high-energy focusing. We present the results of our pre-flight characterization of the full mirror, including imaging and sensitivity evaluations. If possible, we will include imaging results from the first flight of a multilayer-based high-energy focusing telescope.

Iron K-line analysis of clusters of galaxies with the resonance scattering effect

Radiative heat transfer characteristics from the surface of a substance coated with a high-emissivity material have been examined from the measured two-dimensional (2D) temperature distribution using two-color thermometry principle. The technique utilized a charge coupled device camera and optical filters having either wide or narrow wavelength bandpass filters. The results obtained were compared to evaluate the accuracy of the temperature measurements. The 2D emissivity distributions were also derived from the measured 2D temperature distributions. The results indicate that the substrate coated with high-emissivity material exhibit high emission of radiation, resulting in effective cooling. The enhanced emissivity of materials also results in improved radiative heat transfer in heating furnaces and other high-temperature applications. The emissivity measured with the wide-bandpass filters increased with temperature. Atmospheric absorption, mainly due to humidity, made a negligible contribution to the total spectral intensity and to the temperature measurements. The small discrepancies are attributed to the dependence of emissivity on wavelength. Thus, the use of narrow-bandpass filters in thermometry is advantageous over the wide-bandpass ones.

Two-Dimensional Temperature Distributions of the Surface of Heated Materials by Spectroscopic Measurements

Abstract The spectral analysis was carried out in the central core and outer envelope region of each of 50 galaxy clusters observed with ASCA . Among them, we investigated iron K-lines of 8 targets which have large iron line intensities. Iron K-lines were separately observed as He-like K α , H-like K α by SIS and their blend and K β blended with nickel K α lines by GIS. Their energies and intensities were derived from spectral fittings of continuum and Gaussian lines in the energy range of 3 10keV. The intensity ratio of He-like K α to H-like K α has the tendency to be smaller than that estimated from a thin hot plasma model. The intensity ratio of K α to K β has the same tendency as well, and seems to be increasing from the core to the envelope for some clusters. These discrepancies would be due to the reduction of K α , especially He-like K α intensity. The optical depth of He-like iron K α is estimated to be around unity in the core, so that the line would be suppressed in the core and enhanced in the envelope by the resonance scattering effect. This observational evidence of the resonance scattering is critically important to determine the abundance and to investigate the origin of heavy elements in an intra-cluster medium (ICM).

X-Ray Properties of ASCA Observed 43 Clusters of Galaxies

In order to investigate the characteristics of the surface of substrates without destroying and touching them, two-dimensional (2D) surface brightness distributions have been measured with a CCD camera equipped with optical filter (700-800 nm). The images measured with each wavelength gave 2D temperature distributions by two-color thermometry. In addition 2D emissivity distributions were also derived from the derived 2D temperature distribution and the measured images. We demonstrate the convenience and usefulness of this method for heated materials with different surface roughness or with and without coasting of high emissivity material. Subject headings: 2D-temperature distribution, two color method, high temperature, emissivity

Measurements of surface temperature and emissivity by two-dimensional four-color thermometry with narrow bandwidth

Much attempts of statistical approach have been made to study the origin of heavy elements, distribution of dark matter and evolution of clusters of galaxies. Henry et al. (1991) reported a power-law relation; Lx ∝ kTγ, γ ∼ 2.7. Edge and Stwert(1991) found significant scatter in the correlation using 45 clusters. David at al.(1993) reported γ ∼ 3.4 using 104 clusters.