Kyoto University · Physics and Astronomy
Professor Satoshi Yamada's research lab specializes in astrobiology and high-energy astrophysics, focusing on active galactic nuclei (AGNs), X-ray winds, and the multiwavelength properties of ultraluminous and luminous infrared galaxies. The lab conducts systematic X-ray spectroscopic and SED (spectral energy distribution) analyses using advanced space telescopes such as NuSTAR, Swift, Chandra, and XMM-Newton to study obscured AGNs, clumpy torus models, and the role of circumnuclear dust and gas in galaxy evolution. A key focus is identifying and characterizing 'buried' AGNs—especially Compton-thick systems—through X-ray and infrared indicators like [O IV] and [Ne V] emission lines.
Figures are computed from collected data and may differ slightly.
L-cysteine is an important amino acid in terms of its industrial applications. We previously found a marked production of L-cysteine from glucose in recombinant Escherichia coli cells expressing an altered cysE gene encoding feedback inhibition-insensitive serine acetyltransferase. Also, a lower level of cysteine desulfhydrase (CD) activity, which is involved in L-cysteine degradation, increased L-cysteine productivity in E. coli. The use of an L-cysteine efflux system could be promising for bre
Abstract We perform a systematic X-ray spectroscopic analysis of 57 local luminous and ultraluminous infrared galaxy systems (containing 84 individual galaxies) observed with the Nuclear Spectroscopic Telescope Array and/or Swift/BAT. Combining soft X-ray data obtained with Chandra, XMM-Newton, Suzaku, and/or Swift/XRT, we identify 40 hard (>10 keV) X-ray–detected active galactic nuclei (AGNs) and constrain their torus parameters with the X-ray clumpy torus model XCLUMPY. Among the AGNs at z
Fusion of vesicular stomatitis virus with some cells (HELR 66, KB, and human erythrocytes, both intact and trypsinized) and liposomes made of various natural and synthetic lipids was studied with spin-labeled phospholipid. Binding of virus was assayed separately with radiolabeled and spin-labeled virus. Binding to cells and liposomes was small at neutral pH but enhanced at acidic pHs. Fusion with cells and liposomes was negligibly small at neutral pH but greatly activated at acidic pHs lower tha
Abstract We conduct hard X-ray to radio multiwavelength spectral energy distribution (SED) decomposition for 57 local luminous and ultraluminous infrared galaxies observed with the Nuclear Spectroscopic Telescope Array and/or Swift/Burst Alert Telescope in the GOALS sample. We modify the latest SED-fitting code X-CIGALE by implementing the infrared (IR) CLUMPY model, allowing us to conduct the multiwavelength study with the X-ray torus model XCLUMPY self-consistently. Adopting the torus paramete
Abstract As an inaugural investigation under the X-ray Winds In Nearby-to-distant Galaxies (X-WING) program, we assembled a data set comprising 132 active galactic nuclei (AGNs) spanning redshifts z ∼ 0–4 characterized by blueshifted absorption lines indicative of X-ray winds. Through an exhaustive review of previous research, we compiled the outflow parameters for 583 X-ray winds, encompassing key attributes such as outflow velocities ( V out ), ionization parameters ( ξ ), and hydrogen column
Abstract We study “buried” active galactic nuclei (AGNs) almost fully covered by circumnuclear material in ultra/luminous infrared galaxies (U/LIRGs), which show weak ionized lines from narrow-line regions. Employing an indicator of a [O iv ] 25.89 or [Ne v ] 14.32 μ m line to 12 μ m AGN luminosity ratio, we find 17 buried AGN candidates that are [O iv ]-weak ( L [O IV ] / L 12,AGN ≤ −3.0) or [Ne v ]-weak ( L [Ne V] / L 12,AGN ≤ −3.4) among 30 AGNs in local U/LIRGs. For the [O iv ]-weak AGNs, we
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