[Show abstract][Hide abstract] ABSTRACT: We present both the observations and the data reduction procedures of the Subaru COSMOS 20 project, an optical imaging survey
of the HST COSMOS field, carried out by using Suprime-Cam on the Subaru Telescope with the following 20 optical filters: six
broad-band (B, g′, V, r′, i′, and z′), two narrow-band (NB711 and NB816), and 12 intermediate-band filters (IA427, IA464, IA484, IA505, IA527, IA574, IA624, IA679, IA709, IA738, IA767, and IA827). Part of this project is described in Taniguchi et al. (2007, ApJS, 172, 9) and Capak et al. (2007, ApJS, 172, 99) for the six broad-band and one narrow-band (NB816) filter data. In this paper, we present details of the observations and data reduction for the remaining 13 filters (the
12 IA filters and NB711). In particular, we describe the accuracy of both the photometry and astrometry in all the filter bands. We also present
the optical properties of the Suprime-Cam IA filter system in appendices.
Full-text · Article · Oct 2015 · Publications- Astronomical Society of Japan
[Show abstract][Hide abstract] ABSTRACT: A brief history is given of wide area optical surveys of galaxies and resulting catalogs, starting from the Shapley-Ames Catalog through POSS and CfA surveys to modern surveys. Scientific impacts of large surveys are described in terms of the complete sample, large homogeneous samples, and new discoveries. Upcoming and future ambitious surveys are also mentioned. A recent review of surveys in various wavelength regions is given by Djorgovski et al. (2012).
No preview · Article · Feb 2015 · Proceedings of the International Astronomical Union
[Show abstract][Hide abstract] ABSTRACT: A scenario for non-inductive current ramp-up has been demonstrated using electron cyclotron waves in the spherical tokamak QUEST. The configuration was characterized by a high toroidal magnetic mirror ratio of 2 and a steady vertical magnetic field of more than 10% of the toroidal magnetic field. The generation and confinement of energetic electrons having energy greater than 10 keV were studied using hard x-rays. Because of the energetic electron pressure, a natural divertor formed with an inboard poloidal field null at the high poloidal beta (approximately 3–4).
[Show abstract][Hide abstract] ABSTRACT: We investigate the diffuse light in the outer regions of the nearby
elliptical galaxy M87 in the Virgo cluster, using planetary nebulas (PNs) as
tracers. The surveyed areas (0.43 squared degrees) cover M87 up to a radial
distance of 150 kpc, in the ransition region between galaxy halo and
intracluster light (ICL). All PNs are identified through the on-off band
technique using automatic selection criteria based on the distribution of the
detected sources in the colour-magnitude diagram and the properties of their
point-spread function. We extract a catalogue of 688 objects down to
m_5007=28.4, with an estimated residual contamination from foreground stars and
background Lyalpha galaxies, which amounts to ~35% of the sample. This is one
of the largest extragalactic PN samples in number of candidates, magnitude
depth, and radial extent, which allows us to carry out an unprecedented
photometric study of the PN population in the outer regions of M87. We find
that the logarithmic density profile of the PN distribution is shallower than
the surface brightness profile at large radii. This behaviour is consistent
with the superposition of two components associated with the halo of M87 and
with the ICL, which have different luminosity specific PN numbers, the ICL
contributing three times more PNs per unit light. Because of the depth of this
survey we are also able to study the shape of the PN luminosity function (PNLF)
in the outer regions of M87. We find a slope for the PNLF that is steeper at
fainter magnitudes than the standard analytical PNLF formula and adopt a
generalised model that treats the slope as a free parameter. Comparing the PNLF
of M87 and the M31 bulge, both normalised by the sampled luminosity, the M87
PNLF contains fewer bright PNs and has a steeper slope towards fainter
Preview · Article · Aug 2013 · Astronomy and Astrophysics
[Show abstract][Hide abstract] ABSTRACT: The luminosity function of planetary nebulae populations in galaxies within
10-15 Mpc distance has a cut-off at bright magnitudes and a functional form
that is observed to be invariant in different galaxy morphological types. Thus
it is used as a secondary distance indicator in both early and late-type
galaxies. Recent deep surveys of planetary nebulae populations in brightest
cluster galaxies (BCGs) seem to indicate that their luminosity functions
deviate from those observed in the nearby galaxies. We discuss the evidence for
such deviations in Virgo, and indicate which physical mechanisms may alter the
evolution of a planetary nebula envelope and its central star in the halo of
BCGs. We then discuss preliminary results for distances for the Virgo, Hydra I
and Coma clusters based on the observed planetary nebulae luminosity functions.
Preview · Article · Dec 2012 · Proceedings of the International Astronomical Union
[Show abstract][Hide abstract] ABSTRACT: Non-inductive current start-up via relativistic electron cyclotron resonance interaction is investigated for the high ratio (~10 %) of vertical Bv to toroidal Bt fields and the concave field lines in the QUEST spherical tokamak. In the start-up scenario with an internal poloidal field null (IPN), the fast current start-up rate of 0.3-0.5 MA/sec and correlation with mildly relativistic electrons accelerated due to multiple ECR interaction are observed. In steady state high p equilibrium characterized by the inboard null (Rs ~ 0.7×R0) and p of 1.5 is achieved, where p are the inverse aspect ratio and poloidal beta, respectively. Relaxation oscillations in this equilibrium and confinement of the energetic electrons are discussed.
[Show abstract][Hide abstract] ABSTRACT: Laser phase contrast is a powerful diagnostic method to determine the spatial distribution of electron density fluctuations in magnetically confined plasmas, although its applicability depends on magnetic field configurations. The spatial resolution of fluctuations is linked with the resolution of the propagation direction that is derived from the two-dimensional spectral analysis of the wavenumber for the fluctuations. The method was applied to fluctuation measurements in a compact helical system. In order to improve the resolution of the propagation direction with a relatively small number of data points, the maximum entropy method with polar coordinates was employed. A spatial resolution of the order of 1 cm was obtained, which is satisfactory in a plasma with a 20 cm minor radius.
No preview · Article · Jan 2012 · The Review of scientific instruments
[Show abstract][Hide abstract] ABSTRACT: A method of plasma production by ion cyclotron wave heating has been developed in RFC-XX. Nagoya Type-III antennas were used for wave excitation, and gas was supplied through a gas box. The effect of the rotating field excitation on plasma production and heating was investigated. In the m = − 1 rotational mode (rotation in the direction of ion cyclotron motion), the plasma density profile is flat within the gas box bore with a line integrated density nℓ = 3 × 1013cm−2, and the ion temperature is Ti ≈ 150 eV. For the m = +1 mode, a high density plasma was obtained with a different profile having a peak at the centre. In this mode, the line integrated density is nℓ = 3 × 1014cm−2, with the peak density n(0) = 7 × 1013cm−3.
[Show abstract][Hide abstract] ABSTRACT: The loss flux to an azimuthally segmented limiter in the central cell of the cusp end cell stabilized, axisymmetric mirror machine, RFC-XX, shows that non-axisymmetric illumination by either ICH or ECH can induce azimuthal non-uniformities in the plasma. Measurements of the floating potential in the vicinity of the limiter and by the limiter itself suggest that a large stationary azimuthal electric field is induced which can convectively transport plasma across magnetic field lines. The local radial component of the electric drift velocity is as large as 7 × 104 cms−1. Examinatio n of the plasma end loss versus azimuth and probe measurements deep in the plasma show that the non-uniformities extend into the plasma and are not localized near the outer boundary. The data suggest that the RF fields are driving an anomalous radial loss.
[Show abstract][Hide abstract] ABSTRACT: Experimental data for ion cyclotron resonance heating in the RFC-XX machine in IPP-Nagoya are presented. The achieved ion temperature is as high as 100 eV at n = 1013 cm−3 and 1 keV at n = 1012 cm−3. The ion energy confinement becomes worse by the application of a longer pulse, which is found to be due to the enhanced charge-exchange loss and/or electron drag. Axially and azimuthally arrayed antennas are used in the heating, and the importance of the phasing is demonstrated. A simple model of the multiple-antenna problem is also given and used to interpret the experimental data.
[Show abstract][Hide abstract] ABSTRACT: A tangential Fast Ion Charge eXchange Spectroscopy is newly applied on a Large Helical Device (LHD) for co/countercirculating fast ions, which are produced by high energy tangential negative-ion based neutral beam injection. With this new observation geometry, both the tangential-neutral beam (NB) and a low-energy radial-NB based on positive ions can be utilized as probe beams of the measurement. We have successfully observed Doppler-shifted H-alpha lights due to the charge exchange process between the probing NB and circulating hydrogen ions of around 100 keV in LHD plasmas.
Full-text · Article · Nov 2010 · Review of Scientific Instruments
[Show abstract][Hide abstract] ABSTRACT: Recurrent bursting energetic-particle modes (EPMs) are observed in an l = 2 helical plasma heated by second harmonic electron cyclotron resonance heating (ECRH) without neutral beam injection. The observed instabilities are characterized by a rapid frequency downshift, propagating in the ion-diamagnetic drift direction. Such bursting MHD instabilities are seen only in fairly low-density plasmas with off-axis second harmonic ECRH. A soft x-ray detector operating in the counting mode indicates that there exist suprathermal electrons in low-density ECRH plasmas where EPMs are destabilized. The excitation of EPMs is supposed to be due to the helically trapped suprathermal electrons produced by the second harmonic ECRH.
[Show abstract][Hide abstract] ABSTRACT: A virtual laboratory system for nuclear fusion researches in Japan known as SNET run by the National Institute for Fusion Science has been in development for the past seven years. Twenty-one remote sites have participated in SNET, which reached a speed of 1 Gbps in April 2009. The SNET is a closed network system based on L2 and L3VPN provided by SINET3, which is a national academic network operated by the National Institute of Informatics. SNET has been successfully supporting the remote participation of various sizes and types of experimental equipments and has also been supporting the remote use of a supercomputer. In this paper, we describe the configuration of SNET, which is overcoming the challenges that arise in virtual laboratories; we mainly explain the remote participation in the experiment. Remarks about the remote participation regarding the ITER activity, massive data transfer, and GRID are also discussed. A data transfer experiment between Japan and France was performed, with the average throughput reaching 880 Mbps on 1 Gbps of bandwidth.
No preview · Article · Jul 2010 · Fusion Engineering and Design
[Show abstract][Hide abstract] ABSTRACT: We performed slitless spectroscopy of small bodies with Subaru Telescope
+ Suprime-Cam attached grism filters using a dark cloud as a curtain for
avoiding contamination from background stars. Spectra of 50 objects with
R < 23 mag will be on the poster.
[Show abstract][Hide abstract] ABSTRACT: The role of energetic electrons during the non-inductive current ramp-up is investigated in electron cyclotron heated plasma (≤ 60kW) in the spherical tokamak QUEST. The pulse height analysis of the hard X-ray (HX) is carried out with a fast time resolution of ≥1 ms, and acceleration of the electrons are studied by measuring the evolution of spectrum. It is found that wall recycling condition affects the formation of the tokamak configuration from an initial open magnetic field configuration. The vertical magnetic field Bz dependence of driven current Ip (~ 11 kA) is compared with those of HXs for studying contribution of fast electron. For high recycling case, Ip and HXs show peaks at an optimal low value of Bz/Bt = 7 ×10-3, however, for low recycling case, both increase monotonically with B z/Bt = 7 ×10-3 - 21×10 -3.