336 research outputs found
Investigating the hard X-ray emission from the hottest Abell cluster A2163 with Suzaku
We present the results from Suzaku observations of the hottest Abell galaxy
cluster A2163 at . To study the physics of gas heating in cluster
mergers, we investigated hard X-ray emission from the merging cluster A2163,
which hosts the brightest synchrotron radio halo. We analyzed hard X-ray
spectra accumulated from two-pointed Suzaku observations. Non-thermal hard
X-ray emission should result from the inverse Compton (IC) scattering of
relativistic electrons by the CMB photons. To measure this emission, the
dominant thermal emission in the hard X-ray band must be modeled in detail. To
this end, we analyzed the combined broad-band X-ray data of A2163 collected by
Suzaku and XMM-Newton, assuming single- and multi-temperature models for
thermal emission and the power-law model for non-thermal emission. From the
Suzaku data, we detected significant hard X-ray emission from A2163 in the
12-60 keV band at the level (or at the level if a
systematic error is considered). The Suzaku HXD spectrum alone is consistent
with the single-T thermal model of gas temperature keV. From the XMM
data, we constructed a multi-T model including a very hot ( keV)
component in the NE region. Incorporating the multi-T and the power-law models
into a two-component model with a radio-band photon index, the 12-60 keV energy
flux of non-thermal emission is constrained within . The 90% upper limit of detected IC
emission is marginal ( in the
12-60 keV). The estimated magnetic field in A2163 is .
While the present results represent a three-fold increase in the accuracy of
the broad band spectral model of A2163, more sensitive hard X-ray observations
are needed to decisively test for the presence of hard X-ray emission due to IC
emission.Comment: 7 pages, 7 figures, A&A accepted. Minor correctio
Development of an advanced Compton camera with gaseous TPC and scintillator
A prototype of the MeV gamma-ray imaging camera based on the full
reconstruction of the Compton process has been developed. This camera consists
of a micro-TPC that is a gaseous Time Projection Chamber (TPC) and
scintillation cameras. With the information of the recoil electrons and the
scattered gamma-rays, this camera detects the energy and incident direction of
each incident gamma-ray. We developed a prototype of the MeV gamma-ray camera
with a micro-TPC and a NaI(Tl) scintillator, and succeeded in reconstructing
the gamma-rays from 0.3 MeV to 1.3 MeV. Measured angular resolutions of ARM
(Angular Resolution Measure) and SPD (Scatter Plane Deviation) for 356 keV
gamma-rays were and , respectively.Comment: 4 pages, 5 figures. Proceedings of the 6th International Workshop On
Radiation Imaging Detector
The circumstellar disk of AB Aurigae: evidence for envelope accretion at late stages of star formation?
The circumstellar disk of AB Aurigae has garnered strong attention owing to
the apparent existence of spirals at a relatively young stage and also the
asymmetric disk traced in thermal dust emission. However, the physical
conditions of the spirals are still not well understood. The origin of the
asymmetric thermal emission is unclear.
We observed the disk at 230 GHz (1.3 mm) in both the continuum and the
spectral line ^12CO J=2-1 with IRAM 30-m, the Plateau de Bure interferometer,
and the Submillimeter Array to sample all spatial scales from 0.37" to about
50". To combine the data obtained from these telescopes, several methods and
calibration issues were checked and discussed.
The 1.3 mm continuum (dust) emission is resolved into inner disk and outer
ring. Molecular gas at high velocities traced by the CO line is detected next
to the stellar location. The inclination angle of the disk is found to decrease
toward the center. On a larger scale, based on the intensity weighted
dispersion and the integrated intensity map of ^12CO J=2-1, four spirals are
identified, where two of them are also detected in the near infrared. The total
gas mass of the 4 spirals (M_spiral) is 10^-7 < M_spiral < 10^-5 M_sun, which
is 3 orders of magnitude smaller than the mass of the gas ring. Surprisingly,
the CO gas inside the spiral is apparently counter-rotating with respect to the
CO disk, and it only exhibits small radial motion.
The wide gap, the warped disk, and the asymmetric dust ring suggest that
there is an undetected companion with a mass of 0.03 M_sun at a radius of 45
AU. Although an hypothetical fly-by cannot be ruled out, the most likely
explanation of the AB Aurigae system may be inhomogeneous accretion well above
or below the main disk plane from the remnant envelope, which can explain both
the rotation and large-scale motions detected with the 30-m image.Comment: 17 pages, 13 figures, accepted for publication in A&A journal. Typos
are correcte
Millimeter- and Submillimeter-Wave Observations of the OMC-2/3 Region. III. An Extensive Survey for Molecular Outflows
Using the ASTE 10 m submillimeter telescope and the 1.4 m Infrared Survey
Facility (IRSF), we performed an extensive outflow survey in the Orion
Molecular Cloud -2 and -3 region. Our survey, which includes 41 potential
star-forming sites, has been newly compiled using multi-wavelength data based
on millimeter- and submillimeter-continuum observations as well as radio
continuum observations. From the CO (3-2) observations performed with the ASTE
10 m telescope, we detected 14 CO molecular outflows, seven of which were newly
identified. This higher detection rate, as compared to previous CO (1-0)
results in the same region, suggests that CO (3-2) may be a better outflow
tracer. Physical properties of these outflows and their possible driving
sources were derived. Derived parameters were compared with those of CO
outflows in low- and high-mass starforming regions. We show that the CO outflow
momentum correlates with the bolometric luminosity of the driving source and
with the envelope mass, regardless of the mass of the driving sources. In
addition to these CO outflows, seven sources having NIR features suggestive of
outflows were also identified.Comment: Accepted to Astrophysical Journal, high resolution images at
http://www.asiaa.sinica.edu.tw/~satoko_t/papers/ms.ST.pd
DIOS: the dark baryon exploring mission
DIOS (Diffuse Intergalactic Oxygen Surveyor) is a small satellite aiming for
a launch around 2020 with JAXA's Epsilon rocket. Its main aim is a search for
warm-hot intergalactic medium with high-resolution X-ray spectroscopy of
redshifted emission lines from OVII and OVIII ions. The superior energy
resolution of TES microcalorimeters combined with a very wide field of view
(30--50 arcmin diameter) will enable us to look into gas dynamics of cosmic
plasmas in a wide range of spatial scales from Earth's magnetosphere to
unvirialized regions of clusters of galaxies. Mechanical and thermal design of
the spacecraft and development of the TES calorimeter system are described. We
also consider revising the payload design to optimize the scientific capability
allowed by the boundary conditions of the small mission.Comment: 10 pages, 11 figures, Proceedings of the SPIE Astronomical
Instrumentation : Space Telescopes and Instrumentation 2014: Ultraviolet to
Gamma Ra
Studies of the performance of different front-end systems for flat-panel multi-anode PMTs with CsI(Tl) scintillator arrays
We have studied the performance of two different types of front-end systems
for our gamma camera based on Hamamatsu H8500 (flat-panel 64 channels
multi-anode PSPMT) with a CsI(Tl) scintillator array. The array consists of 64
pixels of which corresponds to the anode pixels of
H8500. One of the system is based on commercial ASIC chips in order to readout
every anode. The others are based on resistive charge divider network between
anodes to reduce readout channels. In both systems, each pixel (6mm) was
clearly resolved by flood field irradiation of Cs. We also investigated
the energy resolution of these systems and showed the performance of the
cascade connection of resistive network between some PMTs for large area
detectors.Comment: 9 pages, 6 figures, proceedings of the 7th International Workshop on
Radiation Imaging Detectors (IWORID7), submitted to NIM
Development of Large area Gamma-ray Camera with GSO(Ce) Scintillator Arrays and PSPMTs
We have developed a position-sensitive scintillation camera with a large area
absorber for use as an advanced Compton gamma-ray camera. At first we tested
GSO(Ce) crystals. We compared light output from the GSO(Ce) crystals under
various conditions: the method of surface polishing, the concentration of Ce,
and co-doping Zr. As a result, we chose the GSO(Ce) crystals doped with only
0.5 mol% Ce, and its surface polished by chemical etching as the scintillator
of our camera. We also made a 1616 cm scintillation camera which
consisted of 9 position-sensitive PMTs (PSPMTs Hamamatsu flat-panel H8500), the
each of which had 88 anodes with a pitch of 6 mm and coupled to
88 arrays of pixelated 613 mm GSO(Ce) scintillators.
For the readout system of the 576 anodes of the PMTs, we used chained resistors
to reduce the number of readout channels down to 48 to reduce power
consumption. The camera has a position resolution of less than 6mm and a
typical energy resolution of 10.5% (FWHM) at 662 keV at each pixel in a large
area of 1616 cm. %to choose the best scintillator for our project.
Furthermore we constructed a 1616 array of 313 mm
pixelated GSO(Ce) scintillators, and glued it to a PMT H8500. This camera had
the position resolution of less than 3mm, over an area of 55 cm,
except for some of the edge pixels; the energy resolution was typically 13%
(FWHM) at 662 keV.Comment: Proceedings of PSD7 appear in NIM
- …