We present ALMA [CII] line and far-infrared (FIR) continuum observations of seven z > 6 low-luminosity quasars (M1450 > −25 mag) discovered by our on-going Subaru Hyper Suprime-Cam survey. The [CII] line was detected in all targets with luminosities of ∼(2−10) × 108 L⊙, about one order of magnitude smaller than optically luminous quasars. Also found was a wide scatter of FIR continuum luminosity, ranging from LFIR < 1011L⊙ to ∼2 × 1012L⊙. With the [CII]-based dynamical mass, we suggest that a significant fraction of low-luminosity quasars are located on or even below the local Magorrian relation, particularly at the massive end of the galaxy mass distribution. This is a clear contrast to the previous finding that luminous quasars tend to have overmassive black holes relative to the relation. Our result is expected to show a less-biased nature of the early co-evolution of black holes and their host galaxies.

X-ray surveys provide us with one of the least biased samples of Active Galactic Nuclei (AGNs) against obscuration. Here we present the most up-to-date AGN X-ray luminosity function (XLF) and absorption function over the redshift range from 0 to 5, using the largest, highly complete sample ever available obtained from surveys of various depth, depth, and energy bands. We utilize a maximum likelihood method to reproduce the count-rate versus redshift distribution for each survey, by taking into account the evolution of the absorbed fraction, contribution from Compton-thick AGNs, and AGN broad band X-ray spectra including reflection components from tori based on the luminosity and redshift dependent unified scheme. We find that the shape of the XLF at z ~ 1–3 is significantly different from that in the local universe, for which the luminosity dependent density evolution (LDDE) model gives the best description. These results establish the standard population synthesis model of the X-Ray Background (XRB), which well reproduces the source counts in both soft and hard bands, the observed fractions of Compton-thick AGNs, and the spectrum of the XRB.

We report our recent results from multiwavelengths studies of microquasars, focusing on X-ray data of GX 339–4 and GRS 1915+105 obtained with Suzaku and other observatories. The broad band coverage and high energy resolution achieved with Suzaku (or a combination of Chandra/HETGS and RXTE) enable us to perform the most reliable spectral analysis both on iron-K features and continuum, and thus to best constrain the accretion disk structure of microquasars and its relation to the jet formation at various mass accretion rates.

We present the results of six Suzaku observations of the recurrent black hole transient 4U 1630–472 during its decline from its most recent outburst in 2006. All observations show the typical high/soft state spectral shape in the 2–50 keV band, roughly described by an optically thick disk spectrum in the soft energy band plus a weak power-law tail.

The disk temperature decreases from 1.4 keV to 1.2 keV as the flux decreases by a factor 2, consistent with a constant radius as expected for disk-dominated spectra. All the observations reveal significant absorption lines from highly ionized (H-like and He-like) iron Kα at 7.0 keV and 6.7 keV.

The energies of these absorption lines suggest a blue shift with an outflow velocity of ∼1000 km s−1. The H–like iron Kα equivalent width remains approximately constant at ∼30 eV over all the observations, while that of the He–like Kα line increases from 7 eV to 20 eV. Thus the ionization state of the material decreases, as expected from the decline in flux.

The data constrain the velocity dispersion of the absorber to 200–2000 km s−1, and the size of the plasma as ∼1010 cm assuming a source distance of 10 kpc.

Although CI Cam, which showed an outburst in April 1998, has been regarded as a soft X-ray transient (SXT) harboring a, black hole, it has some characteristics that can hardly be reconciled with the SXT picture. In this paper, we propose a white dwarf as the central accreting star in CI Cam.

The effects of the dietary oligosaccharide raffinose on immune responses, with special reference to its anti-allergic functions, were examined in vivo. First, feeding a diet supplemented with 50 g raffinose/kg to BALB/c mice significantly (P<0·05) increased interleukin (IL) 12 secretion from isolated Peyer's patch (PP) cells in vitro compared with feeding control diet. When isolated PP cells were used as antigen-presenting cells (APC) for CD4+ T-splenocytes isolated from ovalbumin (OVA)-specific T-cell receptor transgenic (Tg) mice in the presence of OVA as antigen, significantly (P<0·05) higher levels of interferon-γ were observed in the cultures using APC from raffinose-fed mice than those cultures using APC from control mice. Second, the diet containing 50 g raffinose/kg or control diet was fed to OVA Tg mice, and subsequently, OVA was added to each diet to prime T cells in vivo. CD4+ T-cells from the mesenteric lymph nodes of the raffinose-fed mice secreted significantly (P<0·05) higher levels of IL-2 and significantly (P<0·05) lower levels of IL-4 following in vitro antigenic stimulation compared with those of the control mice. These present results suggest that feeding raffinose may suppress differentiation of naïve T-helper (Th) cells into Th2 cells in the mesenteric lymphoid nodes. Last, feeding raffinose suppressed rises of serum immunoglobulin E levels in the Tg mice treated with long-term ingestion of OVA. In conclusion, it is suggested that dietary raffinose suppresses serum immunoglobulin E response through suppression of Th2-type immune response against oral antigen in the lymphoid organs located in or near the intestine.

To understand luminous AGNs in the z < 1 universe, the ASCA AGN samples are the best at present. Combining the identified sample of AGNs from the ASCA Large Sky Survey and Medium Sensitivity Survey, the sample of hard X-ray selected AGNs has been expanded up to 108 AGNs above a flux limit of 10-13 erg s-1 cm-2 in the 2-10 keV hard X-ray band. We discuss the fraction of absorbed AGNs in the hard X-ray selected AGN sample, and the nature of absorbed luminous AGNs.

We present the ASCA/GIS results of the transient source GRO J1744-28, the bursting X-ray pulsar, for the two times observations about one year apart. (the first and the second observations are on Feb.27th 1996 and Mar.16th 1997 respectively.) Since the discovery of GRO J1744-28 on Dec. 2 1995 with the BATSE observatory (Fishman et al. 1995; Kouveliotou et al.), thousands of Type II X-ray bursts, and sinusoidal pulsations have been observed in the X-ray band. No other source has ever been found to exhibit such unusual characteristics. Following each burst the flux decreases below, and recovers to the pre-burst persistent level (here after the dip) within a few seconds to a few minutes, depending on the total flux of the burst. We examined the spectrum of GRO J1744-28 during each persistent, dip, burst phases at the two observations. This is the first detail study of the spectra (1-10keV band) of GRO J1744-28.

We investigated the conduction mechanism and performance of GaAs-A1GaAs quantum-well infrared photodetectors and proposed a conduction model consisting of Poole-Frenkel-like emission from wells and carrier relaxation wells. The model agrees with the measured photocurrent and dark current. The detector's noise current is given by a simple shot noise formula. Analysis has shown that the photocurrent and the noise current are inversely proportional to the barrier width, while the dark current is inversely proportional to the square of the barrier width.

In recent years, the heteroepitaxial growth of GaAs layers on Si substrates has been gained an increasing interest [1 - 14]. GaAs is one of the most important III-V materials and has been well studied and used for optical and electrical devices. On the other hand, with Si we have large size wafers of superior quality and sophisticated technologies and Si is a main material for semiconductor industries. Therefore, GaAs/Si system has possibilities for realizing new types of functional devices or ICs with GaAs and Si devices. This system, however, has two serious problems. One is the large lattice mismatch of about 4 % between these materials and the other is the polar on nonpolar problem i.e., the formation of an antiphase domain disorder. It was reported that when (211)-oriented Si substrates were used, there was no problem of the formation of an antiphase domain structure 5. For growing materials on lattice mismatched substrates, it was reported that the thin layers deposited at low temperatures were effective to relax the lattice mismatches for the systems such as SiC on Si[15] and Si on saphire [16]. In GaAs/Si system, the Ge buffer layer has been used to relax the lattice mismatch[17 - 22] It was also reported that the composite strained layer superlattice with GaP/GaAsP and GaAsP/GaAs was very effective as a buffer layer[23 - 25].