1704.05843
Properties of the cosmological filament between two clusters: a possible detection of a large-scale accretion shock by $Suzaku$
Akamatsu, et al
Report on the results of a Suzaku observation of the plasma in the filament located between the two massive clusters of galaxies Abell 399 and Abell 401. Abell 399 (z=0.0724) and 401 (z=0.0737) are expected to be in the initial phase of a cluster merger. In the region between the two clusters, find a clear enhancement in the temperature of the filament plasma from 4 keV (expected value from a typical cluster temperature profile) to kT~6.5 keV. The analysis also shows that filament plasma is present out to a radial distance of 15' (1.3 Mpc) from a line connecting the two clusters. The temperature profile is characterized by an almost flat radial shape with kT~6-7 keV within 10' or ~0.8 Mpc. Across r=8' from the axis, the temperature of the filament plasma shows a drop from 6.3 keV to 5.1 keV, indicating the presence of a shock front. The Mach number based on the temperature drop is estimated to be M~1.3. Also successfully determined the abundance profile up to 15' (1.3 Mpc), showing an almost constant value (Z=0.3 solar) at the cluster outskirt. Estimated the Compton y-parameter to be ~14.5±1.3e-6, which is in agreement with Planck's results (14-17e-6 on the filament). The line of sight depth of the filament is ell~1.1 Mpc, indicating that the geometry of filament is likely a pancake shape rather than cylindrical. The total mass of the filamentary structure is ~7.7e13 Msun. Discuss a possible interpretation of the drop of X-ray emission at the rim of the filament, which was pushed out by the merging activity and formed by the accretion flow induced by the gravitational force of the filament.
1704.05858
The Hyper Suprime-Cam SSP Survey: Overview and survey design
Aihara, et al
HSC is a wide-field imaging camera on the prime focus of the 8.2m Subaru telescope on the summit of Maunakea. A team of scientists from Japan, Taiwan and Princeton University is using HSC to carry out a 300-night multi-band imaging survey of the high-latitude sky. The survey includes 3 layers: the Wide layer will cover 1400 deg^2 in 5 broad bands (grizy), with a 5 sigma point-source depth of r~26. The Deep layer covers a total of 26 deg^2 in 4 fields, going roughly a magnitude fainter, while the Ultra Deep layer goes almost a magnitude fainter still in 2 pointings of HSC (a total of 3.5 deg^2). Describe the instrument, the science goals of the survey, and the survey strategy and data processing. This paper serves as an introduction to a special issue of the Publications of the Astronomical Society of Japan, which includes a large number of technical and scientific papers describing results from the early phases of this survey.
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