A possible route to spontaneous reduction of the heat conductivity by a temperature gradient driven instability in electron-ion plasmas

We have shown that there exists low-frequency growing modes driven by a global temperature gradient in electron and ion plasmas, by linear perturbation analysis within the frame work of plasma Kinetic theory. The driving force of the instability is the local deviation of the distribution function from the Maxwell-Boltzmann due to global temperature gradient. Application to the intracluster medium shows that scattering of the particles due to waves excited by the instability is possible to reduce mean free paths of electron and ion down to five to seven order of magnitude than the mean free paths due to Coulomb collisions. This may provide a hint to explain why hot and cool gas can co-exist in the intracluster medium in spite of the very short evaporation time scale due to thermal conduction if the conductivity is the classical Spitzer value. Our results suggest that the realization of the global thermal equilibrium is postponed by the local instability which is induced for quicker realization of local thermal equilibrium state in plasmas. The instability provides a new possibility to create and grow cosmic magnetic fields without any seed magnetic field.Comment: Accepted for publication in ApJ: 16 pages, 1figur

Can One Distinguish Tau Neutrinos from Antineutrinos in Neutral-Current Pion Production Processes?

A potential way to distinguish tau-neutrinos from antineutrinos, below the tau-production threshold, but above the pion production one, is presented. It is based on the different behavior of the neutral current pion production off the nucleon, depending on whether it is induced by neutrinos or antineutrinos. This procedure for distinguishing tau-neutrinos from antineutrinos neither relies on any nuclear model, nor it is affected by any nuclear effect (distortion of the outgoing nucleon waves, etc...). We show that neutrino-antineutrino asymmetries occur both in the totally integrated cross sections and in the pion azimuthal differential distributions. To define the asymmetries for the latter distributions we just rely on Lorentz-invariance. All these asymmetries are independent of the lepton family and can be experimentally measured by using electron or muon neutrinos, due to the lepton family universality of the neutral current neutrino interaction. Nevertheless and to estimate their size, we have also used the chiral model of hep-ph/0701149 at intermediate energies. Results are really significant since the differences between neutrino and antineutrino induced reactions are always large in all physical channels.Comment: Revised version. 8 pages, 3 figures. The abstract has been changed and discussion extende

Manifestations of fine features of the density of states in the transport properties of KOs2O6

We performed high-pressure transport measurements on high-quality single crystals of KOs2O6, a beta-pyrochlore superconductor. While the resistivity at high temperatures might approach saturation, there is no sign of saturation at low temperatures, down to the superconducting phase. The anomalous resistivity is accompanied by a nonmetallic behavior in the thermoelectric power (TEP) up to temperatures of at least 700 K, which also exhibits a broad hump with a maximum at 60 K. The pressure influences mostly the low-energy electronic excitations. A simple band model based on enhanced density of states in a narrow window around the Fermi energy (EF) explains the main features of this unconventional behavior in the transport coefficients and its evolution under pressure

A massive star origin for an unusual helium-rich supernova in an elliptical galaxy

The unusual helium-rich (type Ib) supernova SN 2005E is distinguished from any supernova hitherto observed by its faint and rapidly fading light curve, prominent calcium lines in late-phase spectra and lack of any mark of recent star formation near the supernova location. These properties are claimed to be explained by a helium detonation in a thin surface layer of an accreting white dwarf (Perets et al. 2010). Here we report on observations of SN 2005cz appeared in an elliptical galaxy, whose observed properties resemble those of SN 2005E in that it is helium-rich and unusually faint, fades rapidly, shows much weaker oxygen emission lines than those of calcium in the well-evolved spectrum. We argue that these properties are best explained by a core-collapse supernova at the low-mass end ($8-12 M_{\odot}$) of the range of massive stars that explode (Smartt 2009). Such a low mass progenitor had lost its hydrogen-rich envelope through binary interaction, having very thin oxygen-rich and silicon-rich layers above the collapsing core, thus ejecting a very small amount of radioactive $^{56}$Ni and oxygen. Although the host galaxy NGC 4589 is an elliptical, some studies have revealed evidence of recent star-formation activity (Zhang et al. 2008), consistent with the core-collapse scenario.Comment: Accepted by Nature (24 March 2010), 32 pages including Supplementary Informatio

Far-infrared all sky diffuse mapping with AKARI

We discuss the capability of AKARI in recovering diffuse far-infrared emission, and examine the achieved reliability. Critical issues in making images of diffuse emission are the transient response and long-term stability of the far-infrared detectors. Quantitative evaluation of these characteristics are the key to achieving sensitivity comparable to or better than that for point sources (< 20 -- 95 MJy sr-1). We describe current activity and progress toward the production of high quality images of the diffuse far-infrared emission using the AKARI all-sky survey data.Comment: 4 pages, 8 figures, to appear in the Proceedings of the Conference "AKARI, a light to illuminate the misty Universe", Fukutake Hall, The University of Tokyo, Japan, 16-19 February 200

Evolution of Multiphase Hot Interstellar Medium in Elliptical Galaxies

We present the results of a variety of simulations concerning the evolution of multiphase (inhomogeneous) hot interstellar medium (ISM) in elliptical galaxies. We assume the gases ejected from stars do not mix globally with the circumferential gas. The ejected gas components evolve separately according to their birth time, position, and origin. We consider cases where supernova remnants (SNRs) mix with local ISM. The components with high metal abundance and/or high density cool and drop out of the hot ISM gas faster than the other components because of their high metal abundance and/or density. This makes the average metal abundance of the hot ISM low. Furthermore, since the metal abundance of mass-loss gas decreases with radius, gas inflow from outer region makes the average metal abundance of the hot ISM smaller than that of mass-loss gas in the inner region. As gas ejection rate of stellar system decreases, mass fraction of mass-loss gas ejected at outer region increases in a galaxy. If the mixing of SNRs is ineffective, our model predicts that observed [Si/Fe] and [Mg/Fe] should decrease towards the galactic center because of strong iron emission by SNRs. In the outer region, where the cooling of time of the ISM is long, the selective cooling is ineffective and most of gas components remain hot. Thus, the metal abundance of the ISM in this region directly reflects that of the gas ejected from stars. Our model shows that supernovae are not effective heating sources in the inner region of elliptical galaxies, because most of the energy released by them radiates. Therefore, cooling flow is established even if the supernova rate is high. Mixing of SNRs with ambient ISM makes the energy transfer between supernova explosion and ambient ISM more effective.Comment: 21 pages (AASTeX), 14 figures, accepted for publication in The Astrophysical Journa

SZ and X-ray combined analysis of a distant galaxy cluster, RX J2228+2037.

We have performed a combined analysis of X-ray and Sunyaev-Zel'dovich data in the direction of the distant galaxy cluster, RX J2228+2037. Fitting a $\beta$-model to the high-resolution HRI data gives $r_c = 103 \pm 12 h_{70}^{-1}$ kpc and $\beta=0.54 \pm 0.03$. The dependency of the Sunyaev-Zel'dovich effect with respect to the gas temperature allows us, through the additional use of the 21 GHz data of the cluster, to determine $k_B T_e=10.4 \pm 1.8 h_{70}^{1/2}$ keV. Extrapolating the gas density profile out to the virial radius ($R_v=r_{178}=2.9$ Mpc), we derived a gas mass of $M_{g}(r<R_v)=(4.0\pm 0.2)\times 10^{14} h_{70}^{-5/2} \rm{M}_\odot$. Within the hypothesis of hydrostatic equilibrium, the corresponding extrapolated total mass for this source is: $M_{tot}(r<R_v)=(1.8 \pm 0.4)\times 10^{15} h^{-1} \rm{M}_\odot$, which corresponds to a gas fraction of $f_{gas}=0.22\pm 0.06 h_{70}^{-3/2}$. Our results on the temperature and on the cluster mass classify RX J2228+2037 among the distant, hot and very massive galaxy clusters. Our work highlights the power of the association of galaxy cluster mapping observations in X-ray and the SZ effect to derive the cluster's physical properties, even without X-ray spectroscopy.Comment: 7 pages, 4 figures, accepted for publication in A&

Cooperative Effect of Coulomb Interaction and Electron-Phonon Coupling on the Heavy Fermion State in the Two-Orbital Periodic Anderson Model

We investigate the two-orbital periodic Anderson model, where the local orbital fluctuations of f-electrons couple with a two-fold degenerate Jahn-Teller phonon, by using the dynamical mean-field theory. It is found that the heavy fermion state caused by the Coulomb interaction between f-electrons U is largely enhanced due to the electron-phonon coupling g, in contrast to the case with the single-orbital periodic Anderson model where the effects of U and g compete to each other. In the heavy fermion state for large $U$ and g, both the orbital and lattice fluctuations are enhanced, while the charge (valence) and spin fluctuations are suppressed. In the strong coupling regime, a sharp soft phonon mode with a large spectral weight is observed for small U, while a broad soft phonon mode with a small spectral weight is observed for large U. The cooperative effect of U and g for half-filling with two f-electrons per atom $n_f=2$ is more pronounced than that for quarter-filling with $n_f=1$.Comment: 8 pages, 11 figures, accepted for publication in JPS

An anatomic study of the accessory anterolateral talar facet

Background: A small accessory facet with articular surface morphology is occasionally seen on the talus, bordering on the lateral end of the sinus tarsi. This facet has been named the accessory anterolateral talar facet. However, few anatomical studies have addressed this facet. Here we present the precise morphology of accessory anterolateral talar facet with emphasis on anatomical correlation between the presence of this facet and the angle of the infero-lateral surface of the talus (talar infero-lateral surface — TILS angle). Materials and methods: A total of 22 (11 male, 11 female) adult cadavers with no known pathological conditions in the talocalcaneal joints were examined during educational dissection at Nagoya City University Medical School in 2013. After exclusion of 1 joint due to the poor condition of the talus, 43 talus (22 right, 21 left) were analysed. We judged the presence of the accessory anterolateral talar facet and measured TILS angle. We performed statistical analysis on the point of laterality, gender difference and the difference in the TILS angles in tali with or without the accessory anterolateral talar facets. Results: An accessory anterolateral talar facet was identified in 11 (26%) of the 43 specimens. Of the 21 cadavers with paired talar specimens, 5 displayed the facet bilaterally. Conclusions: There was no sex difference and no significant laterality, however we found that TILS angle was significantly larger in accessory anterolateral talar facet positive samples than in negative ones

AKARI Far-Infrared All Sky Survey

We demonstrate the capability of AKARI for mapping diffuse far-infrared emission and achieved reliability of all-sky diffuse map. We have conducted an all-sky survey for more than 94 % of the whole sky during cold phase of AKARI observation in 2006 Feb. -- 2007 Aug. The survey in far-infrared waveband covers 50 um -- 180 um with four bands centered at 65 um, 90 um, 140 um, and 160 um and spatial resolution of 3000 -- 4000 (FWHM).This survey has allowed us to make a revolutionary improvement compared to the IRAS survey that was conducted in 1983 in both spatial resolution and sensitivity after more than a quarter of a century. Additionally, it will provide us the first all-sky survey data with high-spatial resolution beyond 100 um. Considering its extreme importance of the AKARI far-infrared diffuse emission map, we are now investigating carefully the quality of the data for possible release of the archival data. Critical subjects in making image of diffuse emission from detected signal are the transient response and long-term stability of the far-infrared detectors. Quantitative evaluation of these characteristics is the key to achieve sensitivity comparable to or better than that for point sources (< 20 -- 95 [MJy/sr]). We describe current activities and progress that are focused on making high quality all-sky survey images of the diffuse far-infrared emission.Comment: To appear in Proc. Workshop "The Space Infrared Telescope for Cosmology & Astrophysics: Revealing the Origins of Planets and Galaxies". Eds. A.M. Heras, B. Swinyard, K. Isaak, and J.R. Goicoeche