An AKARI Search for Intracluster Dust of Globular Clusters

We report the observations of 12 globular clusters with the AKARI/FIS. Our goal is to search for emission from the cold dust within clusters. We detect diffuse emissions toward NGC 6402 and 2808, but the IRAS 100-micron maps show the presence of strong background radiation. They are likely emitted from the galactic cirrus, while we cannot rule out the possible association of a bump of emission with the cluster in the case of NGC 6402. We also detect 28 point-like sources mainly in the WIDE-S images (90 micron). At least several of them are not associated with the clusters but background galaxies based on some external catalogs. We present the SEDs by combining the near-and-mid infrared data obtained with the IRC if possible. The SEDs suggest that most of the point sources are background galaxies. We find one candidate of the intracluster dust which has no mid-infrared counterpart unlike the other point-like sources, although some features such as its point-like appearance should be explained before we conclude its intracluster origin. For most of the other clusters, we have confirmed the lack of the intracluster dust. We evaluate upper limits of the intracluster dust mass to be between 1.0E-05 and 1.0E-03 solar mass depending on the dust temperature. The lifetime of the intracluster dust inferred from the upper limits is shorter than 5 Myr (T=70K) or 50 Myr (35K). Such short lifetime indicates some mechanism(s) are at work to remove the intracluster dust. We also discuss its impact on the chemical evolution of globular clusters.Comment: Accepted for publication in PASJ AKARI special issue. 14 pages, 11 figure

Composition of primary cosmic rays at energies 10(15) to approximately 10(16) eV

The sigma epsilon gamma spectrum in 1 approx. 5 x 1000 TV observed at Mt. Fuji suggests that the flux of primary protons 10 to the 15 approx 10th eV is lower by a factor of 2 approx. 3 than a simple extrapolation from lower energies; the integral proton spectrum tends to be steeper than around to the power V and the spectral index tends to be steeper than Epsilon to the -17th power around 10 to the 14th power eV and the spectral index becomes approx. 2.0 around 10 to the 15th power eV. If the total flux of primary particles has no steepening up to approx 10 to the 15th power eV, than the fraction of primary protons to the total flux should be approx 20% in contrast to approx 45% at lower energies

AKARI Near- to Mid-Infrared Imaging and Spectroscopic Observations of the Small Magellanic Cloud. I. Bright Point Source List

We carried out a near- to mid-infrared imaging and spectroscopic observations of the patchy areas in the Small Magellanic Cloud using the Infrared Camera on board AKARI. Two 100 arcmin2 areas were imaged in 3.2, 4.1, 7, 11, 15, and 24 um and also spectroscopically observed in the wavelength range continuously from 2.5 to 13.4 um. The spectral resolving power (lambda/Delta lambda) is about 20, 50, and 50 at 3.5, 6.6 and 10.6 um, respectively. Other than the two 100 arcmin2 areas, some patchy areas were imaged and/or spectroscopically observed as well. In this paper, we overview the observations and present a list of near- to mid-infrared photometric results, which lists ~ 12,000 near-infrared and ~ 1,800 mid-infrared bright point sources detected in the observed areas. The 10 sigma limits are 16.50, 16.12, 13.28, 11.26, 9.62, and 8.76 in Vega magnitudes at 3.2, 4.1, 7, 11, 15, and 24 um bands, respectively.Comment: 16 pages, 7 figures, accepted for publication in PASJ. Full resolution version is available at http://www-irc.mtk.nao.ac.jp/%7Eyita/smc20100112.pd

Development of high current vapor-cooled current leads for large superconductor critical current measuring

Several programs to develop superconducting magnets for the Large Helical Device (LHD) are under way at the National Institute for Fusion Science in Japan. The development of large-scale superconductors for use in superconducting magnets is an important goal of these programs. To measure the critical current of such large-scale superconductors it is necessary to supply a very high current of up to 100 kA. For this purpose, very large current capacity, vapor-cooled current leads have been developed. As a first step in this development, a pair of current leads with a short-time rated current of 30 kA has been made and tested. Also developed was an analytical program to calculate the time-dependent characteristics of vapor-cooled current leads, and the results of calculations with the experimental results obtained with 30 kA current leads were compare

Magnetic structure of CeRhIn_5 as a function of pressure and temperature

We report magnetic neutron-diffraction and electrical resistivity studies on single crystals of the heavy-fermion antiferromagnet CeRhIn$_{5}$ at pressures up to 2.3 GPa. These experiments show that the staggered moment of Ce and the incommensurate magnetic structure change weakly with applied pressure up to 1.63 GPa, where resistivity, specific heat and NQR measurements confirm the presence of bulk superconductivity. This work places new constraints on an interpretation of the relationship between antiferromagnetism and unconventional superconductivity in CeRhIn$_{5}$.Comment: 6 pages, 6 figures, submitted to Phys. Rev.

Field-Induced Quantum Criticality of Systems with Ferromagnetically Coupled Structural Spin Units

The field-induced quantum criticality of compounds with ferromagnetically coupled structural spin units (as dimers and ladders) is explored by applying Wilson's renormalization group framework to an appropriate effective action. We determine the low-temperature phase boundary and the behavior of relevant quantities decreasing the temperature with the applied magnetic field fixed at its quantum critical point value. In this context, a plausible interpretation of some recent experimental results is also suggested.Comment: to be published in Physics Letters

New Superconducting and Magnetic Phases Emerge on the Verge of Antiferromagnetism in CeIn3_3

We report the discovery of new superconducting and novel magnetic phases in CeIn$_3$ on the verge of antiferromagnetism (AFM) under pressure ($P$) through the In-nuclear quadrupole resonance (NQR) measurements. We have found a $P$-induced phase separation of AFM and paramagnetism (PM) without any trace for a quantum phase transition in CeIn$_3$. A new type of superconductivity (SC) was found in $P=2.28-2.5$ GPa to coexist with AFM that is magnetically separated from PM where the heavy fermion SC takes place. We propose that the magnetic excitations such as spin-density fluctuations induced by the first-order magnetic phase transition might mediate attractive interaction to form Cooper pairs.Comment: 4 pages, 4 EPS figures, submitted to J. Phys. Soc. Jp

Contrasting Pressure Effects in Sr2VFeAsO3 and Sr2ScFePO3

We report the resistivity measurements under pressure of two Fe-based superconductors with a thick perovskite oxide layer, Sr2VFeAsO3 and Sr2ScFePO3. The superconducting transition temperature Tc of Sr2VFeAsO3 markedly increases with increasing pressure. Its onset value, which was Tc{onset}=36.4 K at ambient pressure, increases to Tc{onset}=46.0 K at ~4 GPa, ensuring the potential of the "21113" system as a high-Tc material. However, the superconductivity of Sr2ScFePO3 is strongly suppressed under pressure. The Tc{onset} of ~16 K decreases to ~5 K at ~4 GPa, and the zero-resistance state is almost lost. We discuss the factor that induces this contrasting pressure effect.Comment: 5 pages, 4 figures, to be published in J. Phys. Soc. Jpn. No.12 (2009