344 research outputs found
Cross-cutting Perspective Freshwater
One singularity of northwestern Europe (NWE) is that severe droughts are rare events in the region and water scarcity has hardly been experienced in its history. The DROP pilot sites are not exceptions to this context. Although the lack of a drought history in wet areas can explain why drought and water scarcity are not necessarily the focus of (if ever considered in) river basin management plans, it must be noted that freshwater availability for drinking water provision remains a priority stake in both quantitative and qualitative aspects. Providing a reliable and safe supply of drinking water may thus be a leading entryway to the development of drought risk awareness and drought adaptation measures in a river basin. When such essential resource is threatened and the competition for water among users increases, there is a good chance that reflections and changes will be triggered. Water use conflicts and drinking water supply threats may arise due to increased water demand, but also due to decreased water availability. The later may occur because of natural climate variability, i.e., drier years than average, or as the result of the impact of climate change on local water resources. Climate change awareness is then an important asset to manage water availability. Where climate change awareness is low and adaptation measures are basically inexistent, social and political responses to drought adaptation may be slow and inefficient. However, even in those cases where climate change awareness is still low in general society, water authorities and other stakeholders are conscious that water demand tends to intensify with population and economic growth, rendering water scarcity conceivable and even foreseeable. Freshwater availability for drinking water supply is therefore an issue that can motivate the introduction of drought and water scarcity risks into the political and public agenda , even in “ drought-scarce ” regions. This chapter highlights the links between drought governance and the vulnerability of freshwater for drinking water supply, with a focus on drought adaptation. The main issues presented here are illustrated with how freshwater issues are managed in the DROP project cases with a particular focus on the two “ freshwater reservoir ” pilot sites: the Arzal dam in Brittany France (see Chap. 6 ) and the Eifel-Rur in Germany (see Chap. 4 ). Those two cases deal with reservoir management not only for drinking water supply (Fig. 11.1 ) but also for other uses, with various priority sets
Chandra observation of the central galaxies in A1060 cluster of galaxies
Chandra observation of the central region of the A1060 cluster of galaxies
resolved X-ray emission from two giant elliptical galaxies, NGC 3311 and NGC
3309. The emission from these galaxies consists of two components, namely the
hot interstellar medium (ISM) and the low-mass X-ray binaries (LMXBs). We found
the spatial extent of the ISM component was much smaller than that of stars for
both galaxies, while the ratios of X-ray to optical blue-band luminosities were
rather low but within the general scatter for elliptical galaxies. After
subtracting the LMXB component, the ISM is shown to be in pressure balance with
the intracluster medium of A1060 at the outer boundary of the ISM. These
results imply that the hot gas supplied from stellar mass loss is confined by
the external pressure of the intracluster medium, with the thermal conduction
likely to be suppressed. The cD galaxy NGC 3311 does not exhibit the extended
potential structure which is commonly seen in bright elliptical galaxies, and
we discuss the possible evolution history of the very isothermal cluster A1060.Comment: 12 pages, 7 figures, Latex2e(emulateapj5), accepted in Ap
Locating the Warm-Hot Intergalactic Medium in the Simulated Local Universe
We present an analysis of mock spectral observation of warm-hot intergalactic
medium (WHIM) using a constrained simulation of the local universe. The
simulated map of oxygen emission lines from local WHIM reproduces well the
observed structures traced by galaxies in the real local universe. We further
attempt to perform mock observations of outer parts of simulated Coma cluster
and A3627 adopting the expected performance of DIOS (Diffuse Intergalactic
Oxygen Surveyor), which is proposed as a dedicated soft X-ray mission to search
for cosmic missing baryons. We find that WHIMs surrounding nearby clusters are
detectable with a typical exposure time of a day, and thus constitute realistic
and promising targets for DIOS. We also find that an X-ray emitting clump in
front of Coma cluster, recently reported in the XMM-Newton observation, has a
counterpart in the simulated local universe, and its observed spectrum can be
well reproduced in the simulated local universe if the gas temperature is set
to the observationally estimated value.Comment: 25 pages, 3 tables, 16 figures. Accepted for publication in PASJ.
High resolution PS/PDF files are available at
http://www-utap.phys.s.u-tokyo.ac.jp/~kohji/research/x-ray/index.htm
Detection of Bulk Motions in the ICM of the Centaurus Cluster
Several recent numerical simulations of off-center cluster mergers predict
that significant angular momentum with associated velocities of a few x 10^{3}
km/s can be imparted to the resulting cluster. Such gas bulk velocities can be
detected by the Doppler shift of X-ray spectral lines with ASCA spectrometers.
Using two ASCA observations of the Centaurus cluster, we produced a velocity
map for the gas in the cluster's central regions. We also detected radial and
azimuthal gradients in temperature and metal abundance distributions, which
seem to be associated with the infalling sub-group centered at NGC 4709 (Cen
45). More importantly, we found a significant (>99.8% confidence level)
velocity gradient along a line near-perpendicular to the direction of the
incoming sub-group and with a maximum velocity difference of ~3.4+-1.1 x 10^{3}
km/s. It is unlikely (P < 0.002) that the observed velocity gradient is
generated by gain fluctuations across the detectors. While the observed
azimuthal temperature and abundance variations can be attributed to the
interaction with Cen 45, we argue that the intracluster gas velocity gradient
is more likely due to a previous off-center merging event in the main body of
the Centaurus cluster.Comment: 13 pages in emulateapj5 style, 8 postscript figures; Accepted by ApJ;
Revised version with minor change
Recommended from our members
Near-realtime quantitative precipitation estimation and prediction (RealPEP)
Flash floods in small- to medium-sized catchments and intense precipitation over cities
caused by severe local storms pose increasing threats to our society. For the timely prediction of such events, the value of high-resolution and high-quality QPE and corresponding
forecasts cannot be overrated. Seamless predictions harmonizing nowcasting and numerical
weather prediction (NWP) across forecast lead times from minutes to days would greatly help
to improve the value and efficiency of warnings. Organized by the Research Unit on Near-Realtime Precipitation Estimation and Prediction (RealPEP, www2.meteo.uni-bonn.de/realpep)
and supported by the Project on Seamless Integrated Forecasting System (SINFONY, www.dwd
.de/DE/forschung/forschungsprogramme/sinfony_iafe/sinfony_node.html) of the German Meteorological Service (DWD), an international 3-day online conference was held from 5 to 7 October 2020,
dedicated to Precipitation and Flash-Flood Predictions from Minutes to Days (https://indico
.scc.kit.edu/event/883/). Most speakers agreed to have their presentations recorded, which we
uploaded to YouTube for further distribution (see, e.g., on the conference homepage, https://
indico.scc.kit.edu/event/883/page/588-recorded-talks).
The speakers were both invited experts in the respective research fields and researchers
from the RealPEP and SINFONY projects. Talks and discussions could be followed on video
stream. Interaction between the about 250 participants was enabled by entering written questions and comments via a dedicated tool, which allowed for voting and thus also ranking
questions. Registered participants could enter chat rooms from where they could be moved to
the speaker room for posing the questions directly to the speakers and the auditorium. On the
last day of the conference podium discussions with selected speakers summarized talks and
discussions and elaborated on overarching problems, ideas, and developments in the fields
of quantitative precipitation estimation (QPE), quantitative precipitation nowcasting (QPN),
quantitative precipitation forecasting (QPF), flash-flood prediction (FFP), and their organization into seamless prediction systems, which also constituted the topics of the five sessions
during the conference. We report here in particular on the outcomes of the panel discussions
Detection of an X-Ray Hot Region in the Virgo Cluster of Galaxies with ASCA
Based on mapping observations with ASCA, an unusual hot region with a spatial
extent of 1 square degree was discovered between M87 and M49 at a center
coordinate of R. A. = 12h 27m 36s and Dec. = (J2000). The X-ray
emission from the region has a 2-10 keV flux of ergs
s cm and a temperature of keV, which is
significantly higher than that in the surrounding medium of keV. The
internal thermal energy in the hot region is estimated to be ergs with a gas density of cm. A power-law
spectrum with a photon index is also allowed by the data. The hot
region suggests there is an energy input due to a shock which is probably
caused by the motion of the gas associated with M49, infalling toward the M87
cluster with a velocity km s.Comment: 12 pages, 3 figures, accepted to ApJ
Radio Bubbles in Clusters
We extend our earlier work on cluster cores with distinct radio bubbles,
adding more active bubbles, i.e. those with Ghz radio emission, to our sample,
and also investigating ``ghost bubbles,'' i.e. those without GHz radio
emission. We have determined k, which is the ratio of the total particle energy
to that of the electrons radiating between 10 MHz and 10 GHz. Constraints on
the ages of the active bubbles confirm that the ratio of the energy factor, k,
to the volume filling factor, f lies within the range 1 < k/f < 1000. In the
assumption that there is pressure equilibrium between the radio-emitting plasma
and the surrounding thermal X-ray gas, none of the radio lobes has
equipartition between the relativistic particles and the magnetic field. A
Monte-Carlo simulation of the data led to the conclusion that there are not
enough bubbles present in the current sample to be able to determine the shape
of the population. An analysis of the ghost bubbles in our sample showed that
on the whole they have higher upper limits on k/f than the active bubbles,
especially when compared to those in the same cluster. A study of the Brightest
55 cluster sample shows that 17, possibly 20, clusters required some form of
heating as they have a short central cooling time, t_cool < 3 Gyr, and a large
central temperature drop, T_centre/T_outer< 1/2. Of these between 12 (70 per
cent) and 15 (75 per cent), contain bubbles. This indicates that the duty cycle
of bubbles is large in such clusters and that they can play a major role in the
heating process.Comment: 12 pages, Accepted for publication in MNRA
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