4,293 research outputs found
The turbulent pressure support in galaxy clusters revisited
Due to their late formation in cosmic history, clusters of galaxies are not
fully in hydrostatic equilibrium and the gravitational pull of their mass at a
given radius is expected not to be entirely balanced by the thermal gas
pressure. Turbulence may supply additional pressure, and recent (X-ray and SZ)
hydrostatic mass reconstructions claim a pressure support of of
the total pressure at . In this work we show that, after carefully
disentangling bulk from small-scale turbulent motions in high-resolution
simulations of galaxy clusters, we can constrain which fraction of the gas
kinetic energy effectively provides pressure support in the cluster's
gravitational potential. While the ubiquitous presence of radial inflows in the
cluster can lead to significant bias in the estimate of the non-thermal
pressure support, we report that only a part of this energy effectively acts as
a source of pressure, providing a support of the order of of the
total pressure at .Comment: 5 pages, 5 pages, accepted, to appear in MNRAS Letter
Guide to the processing, storage, and retrieval of bibliographic information at the NASA Scientific and Technical Information Facility
Handbook of bibliographic and subject information processing, storage, and retrieval at NASA SCIENTIFIC and Technical Information Facilit
Turbulent pressure support and hydrostatic mass-bias in the intracluster medium
The degree of turbulent pressure support by residual gas motions in galaxy
clusters is not well known. Mass modelling of combined X-ray and Sunyaev
Zel'dovich observations provides an estimate of turbulent pressure support in
the outer regions of several galaxy clusters. Here, we test two different
filtering techniques to disentangle bulk from turbulent motions in
non-radiative high-resolution cosmological simulations of galaxy clusters using
the cosmological hydro code ENZO. We find that the radial behavior of the ratio
of non-thermal pressure to total gas pressure as a function of cluster-centric
distance can be described by a simple polynomial function. The typical
non-thermal pressure support in the centre of clusters is 5%, increasing
to 15% in the outskirts, in line with the pressure excess found in recent
X-ray observations. While the complex dynamics of the ICM makes it impossible
to reconstruct a simple correlation between turbulent motions and hydrostatic
bias, we find that a relation between them can be established using the median
properties of a sample of objects. Moreover, we estimate the contribution of
radial accelerations to the non-thermal pressure support and conclude that it
decreases moving outwards from 40% (in the core) to 15% (in the cluster's
outskirts). Adding this contribution to one provided by turbulence, we show
that it might account for the entire observed hydrostatic bias in the innermost
regions of the clusters, and for less than 80% of it at .Comment: 20 pages; 21 figures; Substantial Revision; MNRAS in pres
High rate production of polarized 3He with meta-stability exchange method
Keywords: polarized 3He, meta-stability exchange, infrared laserComment: 4 figures, submitted to J. Phys. Soc. Jpn
The stripping of a galaxy group diving into the massive cluster A2142
Structure formation in the current Universe operates through the accretion of
group-scale systems onto massive clusters. The detection and study of such
accreting systems is crucial to understand the build-up of the most massive
virialized structures we see today. We report the discovery with XMM-Newton of
an irregular X-ray substructure in the outskirts of the massive galaxy cluster
Abell 2142. The tip of the X-ray emission coincides with a concentration of
galaxies. The bulk of the X-ray emission of this substructure appears to be
lagging behind the galaxies and extends over a projected scale of at least 800
kpc. The temperature of the gas in this region is 1.4 keV, which is a factor of
~4 lower than the surrounding medium and is typical of the virialized plasma of
a galaxy group with a mass of a few 10^13M_sun. For this reason, we interpret
this structure as a galaxy group in the process of being accreted onto the main
dark-matter halo. The X-ray structure trailing behind the group is due to gas
stripped from its original dark-matter halo as it moves through the
intracluster medium (ICM). This is the longest X-ray trail reported to date.
For an infall velocity of ~1,200 km s-1 we estimate that the stripped gas has
been surviving in the presence of the hot ICM for at least 600 Myr, which
exceeds the Spitzer conduction timescale in the medium by a factor of >~400.
Such a strong suppression of conductivity is likely related to a tangled
magnetic field with small coherence length and to plasma microinstabilities.
The long survival time of the low-entropy intragroup medium suggests that the
infalling material can eventually settle within the core of the main cluster.Comment: 11 pages, 7 figures, accepted for publication in A&
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Eyewear for rugby union: wearer characteristics and experience with rugby goggles
YesUnlike many other sports, Rugby Union has not permitted players
to wear spectacles or eye protection. With an industrial
partner, World Rugby developed goggles suitable for use while
playing rugby for the purposes of growing participation
amongst those that need to wear corrective lenses. This study
reports on the profile and experiences of goggle wearers. 387
players received the goggles. Data were obtained from 188
(49 %) using an online, 75-item questionnaire. 87 % “strongly
agreed/agreed” that goggles are beneficial and 75 % are happy
with goggle performance. Common problems reported by 49.7
and 32.6 % of respondents were issues with fogging-up and
getting dirty. 15 (8 %) players stopped wearing the goggles
because of fogging-up, limits to peripheral vision and poor
comfort/fit. Injuries were reported in 3 % of respondents. In
none of these cases did the player stop wearing the goggles.
From the positive experience of players in the trial, the goggles
were adopted into the Laws of the game on July 1, 2019. As the
need to correct vision with spectacles is common, and contact
lenses are not worn by 80 % + of spectacle wearers, the new
Rugby goggles will widen participation for those that need to
wear refractive correction, or have an existing/increased risk
of uniocular visual impairment
Expressão de proteína capsídica recombinante do Apple stem pitting virus e produção de antissoro policlonal.
O objetivo deste trabalho foi a expressão do gene da proteína capsidíca do ASPV em bactérias e a produção do antissoro policlonal contra a proteína expressada.Resumo
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