The X-Ray Imaging and Spectroscopy Mission (XRISM) is a joint mission between the Japan Aerospace Exploration Agency (JAXA) and the National Aeronautics and Space Administration (NASA) in collaboration with the European Space Agency (ESA). In addition to the three space agencies, universities and research institutes from Japan, North America, and Europe have joined to contribute to developing satellite and onboard instruments, data-processing software, and the scientific observation program. XRISM is the successor to the ASTRO-H (Hitomi) mission, which ended prematurely in 2016. Its primary science goal is to examine astrophysical problems with precise, high-resolution X-ray spectroscopy. XRISM promises to discover new horizons in X-ray astronomy. It carries a 6 × 6 pixelized X-ray microcalorimeter on the focal plane of an X-ray mirror assembly (Resolve) and a co-aligned X-ray CCD camera (Xtend) that covers the same energy band over a large field of view. XRISM utilizes the Hitomi heritage, but all designs were reviewed. The attitude and orbit control system was improved in hardware and software. The spacecraft was launched from the JAXA Tanegashima Space Center on 2023 September 6 (UTC). During the in-orbit commissioning phase, the onboard components were activated. Although the gate valve protecting the Resolve sensor with a thin beryllium X-ray entrance window was not yet opened, scientific observation started in 2024 February with the planned performance verification observation program. The nominal observation program commenced with the following guest observation program beginning in 2024 September.

We present a weak-lensing analysis of X-ray galaxy groups and clusters selected from the XMM-XXL survey using the first-year data from the Hyper Suprime-Cam (HSC) Subaru Strategic Program. Our joint weak-lensing and X-ray analysis focuses on 136 spectroscopically confirmed X-ray-selected systems at 0.031 ≤ z ≤ 1.033 detected in the 25 deg² XXL-N region, which largely overlaps with the HSC-XMM field. With high-quality HSC weak-lensing data, we characterize the mass distributions of individual clusters and establish the concentration–mass (c–M) relation for the XXL sample, by accounting for selection bias and statistical effects and marginalizing over the remaining mass calibration uncertainty. We find the mass-trend parameter of the c–M relation to be and the normalization to be at and z = 0.3. We find no statistical evidence for redshift evolution. Our weak-lensing results are in excellent agreement with dark-matter-only c–M relations calibrated for recent ΛCDM cosmologies. The level of intrinsic scatter in c ₂₀₀ is constrained as ( CL), which is smaller than predicted for the full population of ΛCDM halos. This is likely caused in part by the X-ray selection bias in terms of the cool-core or relaxation state. We determine the temperature–mass (T _X–M ₅₀₀) relation for a subset of 105 XXL clusters that have both measured HSC lensing masses and X-ray temperatures. The resulting T _X–M ₅₀₀ relation is consistent with the self-similar prediction. Our T _X–M ₅₀₀ relation agrees with the XXL DR1 results at group scales but has a slightly steeper mass trend, implying a smaller mass scale in the cluster regime. The overall offset in the T _X–M ₅₀₀ relation is at the ∼1.5σ level, corresponding to a mean mass offset of . We also provide bias-corrected, weak-lensing-calibrated M ₂₀₀ and M ₅₀₀ mass estimates of individual XXL clusters based on their measured X-ray temperatures.

We present an analysis of a Suzaku observation of the link region between the galaxy clusters A 399 and A 401. We obtained the metallicity of the intracluster medium (ICM) up to the cluster virial radii for the first time. We determined the metallicity where the virial radii of the two clusters cross each other ($\sim 2$ Mpc away from their centers) and found that it is comparable to that in their inner regions ($\sim 0.2\: Z_\odot$). It is unlikely that the uniformity of metallicity up to the virial radii is due to mixing caused by a cluster collision. Since the ram-pressure is too small to strip the interstellar medium of galaxies around the virial radius of a cluster, the fairly high metallicity that we found there indicates that the metals in the ICM are not transported from member galaxies by ram-pressure stripping. Instead, the uniformity suggests that the proto-cluster region was extensively polluted with metals by extremely powerful outflows (superwinds) from galaxies before the clusters formed. We also searched for the oxygen emission from the warm-hot intergalactic medium in that region and obtained a strict upper limit of the hydrogen density ($n_{\rm H}<4.1\times 10^{-5}$ cm$^{-3}$).

We present observations using the Atacama Large Millimeter/submillimeter Array of the CO(2−1), HCN(3−2), and HCO⁺(3−2) lines in the nearby radio galaxy/brightest cluster galaxy (BCG) NGC 1275 with a spatial resolution of ∼20 pc. In previous observations, the CO(2−1) emission was detected as radial filaments lying in the east–west direction on a kiloparsec scale. We resolved the inner filament and found that it cannot be represented by a simple infalling stream on a sub-kiloparsec scale. The observed complex nature of the filament resembles the cold gas structure predicted by numerical simulations of cold chaotic accretion. Within the central 100 pc, we detected a rotational disk of molecular gas whose mass is ∼10⁸ M _⊙. This is the first evidence of the presence of a massive cold gas disk on this spatial scale for BCGs. A crude estimate suggests that the accretion rate of the cold gas can be higher than that of hot gas. The disk rotation axis is approximately consistent with the radio-jet axis. This probably suggests that the cold gas disk is physically connected to the innermost accretion disk, which is responsible for jet launching. We also detected absorption features in the HCN(3−2) and HCO⁺(3−2) spectra against the radio continuum emission mostly radiated by a jet of size ∼1.2 pc. The absorption features are blueshifted from the systemic velocity by ∼300–600 km s⁻¹, suggesting the presence of outflowing gas from the active galactic nucleus (AGN). We discuss the relation of the AGN feeding with cold accretion, the origin of blueshifted absorption, and an estimate of the black hole mass using molecular gas dynamics.

We present an analysis of the first two XRISM/Resolve spectra of the well-known Seyfert-1.5 active galactic nucleus (AGN) in NGC 4151, obtained in 2023 December. Our work focuses on the nature of the narrow Fe K _α emission line at 6.4 keV, the strongest and most common X-ray line observed in AGN. The total line is found to consist of three components. Even the narrowest component of the line is resolved with evident Fe K _α,1 (6.404 keV) and K _α,2 (6.391 keV) contributions in a 2:1 flux ratio, fully consistent with neutral gas with negligible bulk velocity. Subject to the limitations of our models, the narrowest and intermediate-width components are consistent with emission from optically thin gas, suggesting that they arise in a disk atmosphere and/or wind. Modeling the three line components in terms of Keplerian broadening, they are readily associated with (1) the inner wall of the “torus,” (2) the innermost optical “broad-line region” (or “X-ray BLR”), and (3) a region with a radius of r ≃ 100 GM/c ² that may signal a warp in the accretion disk. Viable alternative explanations of the broadest component include a fast-wind component and/or scattering; however, we find evidence of variability in the narrow Fe K _α line complex on timescales consistent with small radii. The best-fit models are statistically superior to simple Voigt functions, but when fit with Voigt profiles the time-averaged lines are consistent with a projected velocity broadening of FWHM = 1600 − 200 + 400 km s − 1 . Overall, the resolution and sensitivity of XRISM show that the narrow Fe K line in AGN is an effective probe of all key parts of the accretion flow, as it is currently understood. We discuss the implications of these findings for our understanding of AGN accretion, future studies with XRISM, and X-ray-based black hole mass measurements.

We report on the detection of a new feature at the centre of NGC 1275 in the Perseus cluster, hosting the radio source 3C 84. This feature emerges ∼2 mas (∼0.8 pc) north of the central core in recent 15- and 43-GHz Very Long Baseline Array images, and it seems to be the counterjet to a known radio jet expanding to the south of the core. Apparently, the two jets were born through an outburst around 2005. From the ratio of the apparent lengths of the two jets from the core, we have found that the jet angle to the line of sight is θ = 65° ± 16°, which is not much different from the angle of the outer jets generated by an activity around 1959 and constrains theories on gamma-ray emission from jets. The new northern jet has a strongly inverted spectrum in contrast to the southern jet. This suggests that the central black hole is surrounded by a subparsec-scale accretion disc with the density of ≳ 10⁵ cm⁻³. The brightness of the counterjet suggests that the disc is highly inhomogeneous. The ambient gas density in the direction of the jet is ∼8 cm⁻³ if the current jet activity is similar to the past average.