Distribution of Si, Fe, and Ni in the Intracluster Medium of the Coma Cluster

We studied the distributions of Si, Fe, and Ni in the intracluster medium (ICM) of the Coma cluster, one of the largest clusters in the nearby universe, using XMM-Newton data up to 0.5 r180 and Suzaku data of the central region up to 0.16 r180. Using the flux ratios of Ly alpha of H-like Si and 7.8 keV blend to K alpha of He-like Fe, the abundance ratios of Si to Fe and Ni to Fe of the ICM were derived using APEC model v2.0.1. The Si/Fe ratio in the ICM of the Coma cluster shows no radial gradient. The emission weighted averages of the Si/Fe ratio in the ICM within 0.0--0.2 r180, 0.2--0.5 r180, and 0.0--0.5 r180 are 0.97 +- 0.11, 1.05 +- 0.36 and 0.99 +- 0.13, respectively, in solar units using the solar abundance of Lodders (2003). These values are close to those of smaller clusters and groups of galaxies. Using the Suzaku data of the central region, the derived Ni/Fe ratio of the ICM is 0.6--1.5 in solar units, according to the same solar abundance table. The systematic difference in the derived abundance ratios by different plasma codes are about 10%. Therefore, for the ICM in the Coma cluster, the abundance pattern of Si, Fe, and Ni is consistent with the same mixture of the yields of SN II and SN Ia in our Galaxy. Within 0.5 r180}, the cumulative iron-mass-to-light ratio increases with radius, and its radial profile is similar to those of relaxed smaller clusters with cD galaxies at their center. Considering the observed Si/Fe ratio, the cumulative metal-mass-to-light ratios at 0.5 r180 are compared with theoretical expectations.Comment: 10 pages, 7 figures, accepted for publication in PAS

Temperature and Metallicity in the Intra-cluster Medium of ABELL 262 observed with Suzaku

We studied the temperature and abundance distributions of intra-cluster medium (ICM) in the Abell 262 cluster of galaxies observed with Suzaku. Abell 262 is a bright, nearby poor cluster with ICM temperature of ~2 keV, thus providing useful information about the connection of ICM properties between groups and clusters of galaxies. The observed spectrum of the central region was well-represented by two temperature models, and the spectra for the outer regions were described by single temperature model. With the XIS instrument, we directly measured not only Si, S, and Fe lines but also O and Mg lines and obtained those abundances to an outer region of ~0.43 r_180 for the first time. We found steep gradients for Mg, Si, S, and Fe abundances, while O showed almost flat abundance distribution. Abundance ratios of alpha-elements to Fe were found to be similar to those of the other clusters and groups. We calculated the number ratio of type II to type Ia supernovae for the ICM enrichment to be 3.0 +- 0.6 within 0.1 r_180, and the value was consistent with those for other clusters and groups. We also calculated metal mass-to-light ratios (MLRs) for Fe, O and Mg (IMLR, OMLR, MMLR) with B-band and K-band luminosities of the member galaxies of Abell 262. The derived MLRs were comparable to those for other clusters with kT = 3-4 keV.Comment: 12 pages, 8 figures, accepted for publication in PAS

Suzaku observations of subhalos in the Coma cluster

We observed three massive subhalos in the Coma cluster with {\it Suzaku}. These subhalos, labeled "ID 1", "ID 2", and "ID 32", were detected with a weak-lensing survey using the Subaru/Suprime-Cam (Okabe et al. 2014a), and are located at the projected distances of 1.4 $r_{500}$, 1.2 $r_{500}$, and 1.6 $r_{500}$ from the center of the Coma cluster, respectively. The subhalo "ID 1" has a compact X-ray excess emission close to the center of the weak-lensing mass contour, and the gas mass to weak-lensing mass ratio is about 0.001. The temperature of the emission is about 3 keV, which is slightly lower than that of the surrounding intracluster medium (ICM) and that expected for the temperature vs. mass relation of clusters of galaxies. The subhalo "ID 32" shows an excess emission whose peak is shifted toward the opposite direction from the center of the Coma cluster. The gas mass to weak-lensing mass ratio is also about 0.001, which is significantly smaller than regular galaxy groups. The temperature of the excess is about 0.5 keV and significantly lower than that of the surrounding ICM and far from the temperature vs. mass relation of clusters. However, there is no significant excess X-ray emission in the "ID 2" subhalo. Assuming an infall velocity of about 2000 $\rm km~s^{-1}$, at the border of the excess X-ray emission, the ram pressures for "ID 1" and "ID 32" are comparable to the gravitational restoring force per area. We also studied the effect of the Kelvin-Helmholtz instability to strip the gas. Although we found X-ray clumps associated with the weak-lensing subhalos, their X-ray luminosities are much lower than the total ICM luminosity in the cluster outskirts.Comment: 19 pages, 8 figures, ApJ in pres

Measurements of Thermodynamic Data of Water in Ca-Bentonite by Relative Humidity Method

Buffer material (compacted bentonite), one of the engineered barrier elements in the geological disposal of a high-level radioactive waste, develops swelling stress due to groundwater penetration from the surrounding rock mass. Montmorillonite is the major clay mineral component of bentonite. Even previous studies provide few mechanical and thermodynamic data on Ca-montmorillonite. In this study, thermodynamic data on Ca-montmorillonite were obtained as a function of water content by measuring relative humidity (RH) and temperature. The activities of water and the relative partial molar Gibbs free energies of water were determined from the experimental results, and the swelling stress of Ca-bentonite was calculated using the thermodynamic model and compared with measured data. The activities of water and the relative partial molar Gibbs free energies obtained in the experiments decreased with decreasing water content in water contents lower than about 25%. This trend was similar to that of Na-montmorillonite. The swelling stress calculated based on the thermodynamic model was approximately 200 MPa at a montmorillonite partial density of 2.0 Mg/m3 and approximately 10 MPa at a montmorillonite partial density of 1.4 Mg/m3. The swelling stresses in the high-density region (around 2.0 Mg/m3) were higher than that of Na-montmorillonite and were similar levels in the low-density region (around 1.5 Mg/m3). Comparison with measured data showed the practicality of the thermodynamic model

Responsive-ExtendedHand: Adaptive Visuo-Haptic Feedback Recognizing Object Property With RGB-D Camera for Projected Extended Hand

Sato Y., Iwai D., Sato K.. Responsive-ExtendedHand: Adaptive Visuo-Haptic Feedback Recognizing Object Property With RGB-D Camera for Projected Extended Hand. IEEE Access 12, 38247 (2024); https://doi.org/10.1109/ACCESS.2024.3375917.The ExtendedHand interface displays computer graphics (CG) hand images in real space from a projector, allowing the user to visually point at and touch real objects that are out of their physical reach. Furthermore, when the projected CG hand (extended hand) touches an object, the user can feel the tactile sensation of the object through pseudo-haptics by giving the extended hand visual effects that emphasize the action. In the previous psychological study, the human operator had to manually assign the location and shape of objects and the intensities of their visual effects in advance in order to emphasize the appropriate visual effect for the object touched by the extended hand. To increase practical feasibility, we propose an adaptive system that utilizes an RGB-D camera and deep neural networks to generate the appropriate visual effects automatically and apply them to the projected extended hand. By employing U-Net to generate the appropriate intensities of the visual effects from the captured color and depth images, the system can estimate the appropriate visual effects for objects without pre-setting them. The user evaluation results showed that the proposed system allowed users to naturally perceive the tactile sensation of objects at a rate of 44%, instead of the manual rate of 49%

Sound Texture Feedback for a Projected Extended Hand Interface

Sato Y., Iwai D., Sato K.. Sound Texture Feedback for a Projected Extended Hand Interface. IEEE Access 12, 27673 (2024); https://doi.org/10.1109/ACCESS.2024.3367601.The ExtendedHand interface projects a computer graphics (CG) hand that synchronizes with a user's physical hand movements onto a real environment, visually extending the user's reach. This paper focuses on enhancing the user's tactile perception of an object through cross-modal phenomena by providing a sound texture (auditory information that matches the object) when the CG hand touches it. Here, ExtendedHand enables users to touch objects beyond their physical reach, an experience that cannot be achieved with their physical body. In such situations, the appropriateness of adjusting sound pressure based on physical laws according to distance for users is unclear. Additionally, we have empirical knowledge that the speed at which we touch objects with our hands results in different sounds. Within ExtendedHand, since the movement of the user's physical hand is amplified and reflected in the CG hand's movement, the physical hand's speed does not match the CG hand's speed. This raises the question of whether sound texture feedback should align with the visual information of the CG hand or the proprioceptive sensory information of the physical hand. In this paper, we conducted two user studies to explore appropriate sound texture feedback for the projected CG hand. The results indicate that when the CG hand touches objects at various distances, the sound pressure should follow the same sound pressure attenuation as observed in physical phenomena. Additionally, the results suggest that despite swift tracing actions with the CG hand, users perceive sounds produced at a slower pace to be more suitable