20 research outputs found
The Quiescent Intracluster Medium in the Core of the Perseus Cluster
Clusters of galaxies are the most massive gravitationally-bound objects in
the Universe and are still forming. They are thus important probes of
cosmological parameters and a host of astrophysical processes. Knowledge of the
dynamics of the pervasive hot gas, which dominates in mass over stars in a
cluster, is a crucial missing ingredient. It can enable new insights into
mechanical energy injection by the central supermassive black hole and the use
of hydrostatic equilibrium for the determination of cluster masses. X-rays from
the core of the Perseus cluster are emitted by the 50 million K diffuse hot
plasma filling its gravitational potential well. The Active Galactic Nucleus of
the central galaxy NGC1275 is pumping jetted energy into the surrounding
intracluster medium, creating buoyant bubbles filled with relativistic plasma.
These likely induce motions in the intracluster medium and heat the inner gas
preventing runaway radiative cooling; a process known as Active Galactic
Nucleus Feedback. Here we report on Hitomi X-ray observations of the Perseus
cluster core, which reveal a remarkably quiescent atmosphere where the gas has
a line-of-sight velocity dispersion of 164+/-10 km/s in a region 30-60 kpc from
the central nucleus. A gradient in the line-of-sight velocity of 150+/-70 km/s
is found across the 60 kpc image of the cluster core. Turbulent pressure
support in the gas is 4% or less of the thermodynamic pressure, with large
scale shear at most doubling that estimate. We infer that total cluster masses
determined from hydrostatic equilibrium in the central regions need little
correction for turbulent pressure.Comment: 31 pages, 11 Figs, published in Nature July
Hitomi (ASTRO-H) X-ray Astronomy Satellite
The Hitomi (ASTRO-H) mission is the sixth Japanese x-ray astronomy satellite developed by a large international collaboration, including Japan, USA, Canada, and Europe. The mission aimed to provide the highest energy resolution ever achieved at E > 2 keV, using a microcalorimeter instrument, and to cover a wide energy range spanning four decades in energy from soft x-rays to gamma rays. After a successful launch on February 17, 2016, the spacecraft lost its function on March 26, 2016, but the commissioning phase for about a month provided valuable information on the onboard instruments and the spacecraft system, including astrophysical results obtained from first light observations. The paper describes the Hitomi (ASTRO-H) mission, its capabilities, the initial operation, and the instruments/spacecraft performances confirmed during the commissioning operations for about a month
Performance of prototype Dual Gain Multilayer Thick GEM with high-intensity heavy-ion beam injections in low-pressure hydrogen gas
A prototype Dual Gain Multilayer Thick Gas Electron Multilyer (DG-M-THGEM)
with an active area of 10 cm 10 cm was manufactured aiming at the
production of a large-volume active-target time projection chamber which can
work under the condition of high-intensity heavy-ion beam injections. The
DG-M-THGEM has a alternating structure of electrodes and insulators. Effective
gas gains of two regions, which are called beam and recoil regions, are
separately controlled. Performance of the prototype DG-M-THGEM in hydrogen gas
at a pressure of 40 kPa was evaluated. Irradiating a Xe beam, an
effective gas gain lower than 100 with a charge resolution of 3% was achieved
in the beam region while the effective gas gain of 2000 was maintained in the
recoil region. Position distributions of measured charges along the beam axis
were investigated in order to evaluate gain uniformity in the high intensity
beam injection. The gain shift was estimated by simulations considering space
charges in the drift region. The gain shift was suppressed within 3% even at
the beam intensity of 2.5 10 particles per second.Comment: 19 pages, 14 figures, 3 table