Orbital evolution of Saturn's satellites due to the interaction between the moons and massive Saturn's rings

Saturn's mid-sized moons (satellites) have a puzzling orbital configuration with trapping in mean-motion resonances with every other pairs (Mimas-Tethys 4:2 and Enceladus-Dione 2:1). To reproduce their current orbital configuration on the basis of Crida & Charnoz's model of satellite formation from a hypothetical ancient massive rings, adjacent pairs must pass 1st-order mean-motion resonances without being trapped. The trapping could be avoided by fast orbital migration and/or excitation of the satellite's eccentricity caused by gravitational interactions between the satellites and the rings (the disk), which are still unknown. In our research, we investigate the satellite orbital evolution due to interactions with the disk through full N-body simulations. We performed global high-resolution N-body simulations of a self-gravitating particle disk interacting with a single satellite. We used $N \sim 10^5$ particles for the disk. Gravitational forces of all the particles and their inelastic collisions are taken into account. As a result, dense short-wavelength wake structure is created by the disk self-gravity and global spiral arms with $m \sim$ a few is induced by the satellite. The self-gravity wakes regulate the orbital evolution of the satellite, which has been considered as a disk spreading mechanism but not as a driver for the orbital evolution. The self-gravity wake torque to the satellite is so effective that the satellite migration is much faster than that was predicted with the spiral arms torque. It provides a possible model to avoid the resonance capture of adjacent satellite pairs and establish the current orbital configuration of Saturn's mid-sized satellites.Comment: (6 pages, 4 figures, Accepted in A&A

Ferroic quadrupolar ordering in CeCoSi revealed using 59^{59}Co-NMR measurements

A nonmagnetic phase transition at $T_0 \sim 12$ K in the tetragonal system CeCoSi with a Kramers doublet ground state is reminiscent of an electric quadrupole ordering, even though its well-separated crystal-electric-field (CEF) levels are unlikely to acquire higher-order multipole degrees of freedom. Here, we report $^{59}$Co nuclear magnetic resonance (NMR) studies that are highly compatible with a ferroic quadrupole ordering below $T_0$. Changes in the NMR spectra below $T_0$ suggest that an external magnetic field induces ferroic Ce dipole moments orthogonal to the field, enabling domain selection in the nonmagnetic phase. Our findings suggest the presence of a ferroic $O_{zx}$-type quadrupole component in CeCoSi and demonstrate that quadrupole ordering may occur under well-separated CEF levels in tetragonal systems.Comment: 7 pages, 6 figures, 1 tabl

Torus Constraints in ANEPD-CXO245: A Compton-thick AGN with Double-peaked Narrow Lines

We report on the torus constraints of the Compton-thick active galactic nucleus (AGN) with double-peaked optical narrow-line region emission lines, ANEPD-CXO245, at z = 0.449 in the AKARI NEP Deep Field. The unique infrared data on this field, including those from the nine-band photometry over 2–24 μm with the AKARI Infrared Camera, and the X-ray spectrum from Chandra allow us to constrain torus parameters such as the torus optical depth, X-ray absorbing column, torus angular width (σ), and viewing angle (i). We analyze the X-ray spectrum as well as the UV–optical–infrared spectral energy distribution (UOI-SED) with clumpy torus models in X-ray (XCLUMPY) and infrared (CLUMPY), respectively. From our current data, the constraints on σ–i from both X-rays and UOI show that the line of sight crosses the torus as expected for a type 2 AGN. We obtain a small X-ray scattering fraction (NH from the X-ray spectrum, we find that the gas-to-dust ratio is <4 times larger than the Galactic value

Are common names becoming less common? The rise in uniqueness and individualism in Japan.

個性的な名前を与える傾向が増加している -日本文化の個人主義化を示唆-. 京都大学プレスリリース. 2015-10-22.We examined whether Japanese culture has become more individualistic by investigating how the practice of naming babies has changed over time. Cultural psychology has revealed substantial cultural variation in human psychology and behavior, emphasizing the mutual construction of socio-cultural environment and mind. However, much of the past research did not account for the fact that culture is changing. Indeed, archival data on behavior (e.g., divorce rates) suggest a rise in individualism in the U.S. and Japan. In addition to archival data, cultural products (which express an individual’s psyche and behavior outside the head; e.g., advertising) can also reveal cultural change. However, little research has investigated the changes in individualism in East Asia using cultural products. To reveal the dynamic aspects of culture, it is important to present temporal data across cultures. In this study, we examined baby names as a cultural product. If Japanese culture has become more individualistic, parents would be expected to give their children unique names. Using two databases, we calculated the rate of popular baby names between 2004 and 2013. Both databases released the rankings of popular names and their rates within the sample. As Japanese names are generally comprised of both written Chinese characters and their pronunciations, we analyzed these two separately. We found that the rate of popular Chinese characters increased, whereas the rate of popular pronunciations decreased. However, only the rate of popular pronunciations was associated with a previously validated collectivism index. Moreover, we examined the pronunciation variation of common combinations of Chinese characters and the written form variation of common pronunciations. We found that the variation of written forms decreased, whereas the variation of pronunciations increased over time. Taken together, these results showed that parents are giving their children unique names by pairing common Chinese characters with uncommon pronunciations, which indicates an increase in individualism in Japan