405 research outputs found
Magnetic Field Evolution in Giant Radio Relics using the example of CIZA J2242.8+5301
Giant radio relics are the arc-shaped diffuse radio emission regions observed
in the outskirts of some merging galaxy clusters. They are believed to trace
shock-waves in the intra-cluster medium. Recent observations demonstrated that
some prominent radio relics exhibit a steepening above 2 GHz in their radio
spectrum. This challenges standard theoretical models because shock
acceleration is expected to accelerate electrons to very high energies with a
power-law distribution in momentum. In this work we attempt to reconcile these
data with the shock-acceleration scenario. We propose that the spectral
steepening may be caused by the highest energy electrons emitting
preferentially in lower magnetic fields than the bulk of synchrotron bright
electrons in relics. Here, we focus on a model with an increasing mag- netic
field behind the shock front, which quickly saturates and then declines. We
derive the time-evolution of cosmic-ray electron spectra in time variable
magnetic fields and an expanding medium. We then apply the formalism on the
large radio relic in the cluster CIZA J2242.8+5301 (the Sausage relic). We show
that under favourable circumstances of magnetic field amplification downstream,
our model can explain the observed radio spectrum, the brightness profile and
the spectral index profile of the relic. A possible interpretation for the
required amplification of the magnetic field downstream is a dynamo acting
behind the shock with an injection scale of magnetic turbulence of about 10
kpc. Our models require injection efficiencies of CRe - which are in tension
with simple diffusive shock acceleration from the thermal pool. We show that
this problem can likely be alleviated considering pre-existing CRe.Comment: 18 pages, 3 tables, 14 figure
RESEARCH ON THE PHENOLOGY OF THE VARIETIES CULTIVATED IN ECOLOGICAL AND CONVENTIONAL SYSTEM IN THE GROWING SEASONS 2018 IN THE MURFATLAR VITICULTURAL AREA
The study carried out in the vintage 2018 in the Murfatlar winegrowing area included 6 varieties and two culture systems: conventional and ecological. The evolution of the phenological stages in the 6 varieties showed that the duration of the growing season, from the budburst to the fall of the leaves was between 196 and 205 days, depending on the variety. The conventional or ecological culture system had no influence on the duration of the phenological stages
THE INFLUENCE OF AGEING ON LEES ON THE QUALITY OF WHITE WINES FROM THE MURFATLAR VINEYARD
Ageing of wines on lees allows the release of different compounds such as mannoproteins and polysaccharides into wines during yeast autolysis. Yeasts can release polysaccharides, mainly mannoproteins, from the cell wall, not only during autolysis but also during alcoholic fermentation of the must. The polysaccharides released and more particularly the mannoproteins are wall constituents of yeast. We followed the effect of ageing on lees in 3 white wines from the Mulrfatlar vineyard, vintage 2020. We adopted 3 different maturation periods on yeasts: 10, 20 and 30 days. The results show that this technique offers great prospects for improving the quality of white wines
THE INFLUENCE OF MACERATION DURATION ON THE QUALITY OF RED WINES FROM THE MURFATLAR VINEYARD
Maceration is the main technological stage in red vinification. The duration of maceration is the main technological factor that influences the intensity of extraction of phenolic compounds and aromas from grapes. In this study we applied different maceration times to the vinification of three red varieties from the Murfatlar vineyard and we found significant differences between wines in terms of composition and sensory properties
THE FAVORABILITY OF THE VITICOL YEAR 2018 FOR THE CULTURE OF WINE IN THE ECOLOGICAL SYSTEM IN THE MURFATLAR VITICULTURAL AREA
The culture of the vine in an ecological system requires particularly favorable climatic conditions that allow the growth, development and maturation of the grapes under optimal conditions. To do this, the climatic conditions must limit as much as possible the development of diseases and pests. Therefore, the temperature regime and the water regime are prime factors for the favorability of a wine-growing area. Research has shown that the year 2018 was particularly warm but also with a surplus of rainfall, especially during the growing season, which also led to a decrease in the duration of the sun's brightness. Therefore, the year 2018 was more favorable to the ecological system for the white varieties and less favorable for the red varieties
X-ray study of the double radio relic galaxy cluster CIZA J2242.8+5301
Content: We present the results from observations of the merging
cluster of galaxies CIZA J2242.8+5301 at =0.192. Aims. To study the physics
of gas heating and particle acceleration in cluster mergers, we investigated
the X-ray emission from CIZA J2242.8+5301, which hosts two giant radio relics
in the northern/southern part of the cluster. Methods. We analyzed data from
three-pointed Suzaku observations of CIZA J2242.8+5301 to derive the
temperature distribution in four different directions. Results: The
Intra-Cluster Medium (ICM) temperature shows a remarkable drop from
8.5 keV to 2.7 keV across the northern radio
relic. The temperature drop is consistent with a Mach number and a shock velocity
. We also confirm the
temperature drop across the southern radio relic. However, the ICM temperature
beyond this relic is much higher than beyond the northern one, which gives a
Mach number and shock velocity
. These results agree with
other systems showing a relationship between the radio relics and shock fronts
which are induced by merging activity. We compare the X-ray derived Mach
numbers with the radio derived Mach numbers from the radio spectral index under
the assumption of diffusive shock acceleration in the linear test particle
regime. For the northern radio relic, the Mach numbers derived from X-ray and
radio observations agree with each other. Based on the shock velocities, we
estimate that CIZA J2242.8+5301 is observed approximately 0.6 Gyr after core
passage. The magnetic field pressure at the northern relic is estimated to be
9% of the thermal pressure.Comment: 12 pages, 10 figures, A&A accepte
The rise and fall of star-formation in merging galaxy clusters
CIZA J2242.8+5301 (`Sausage') and 1RXS J0603.3+4213 (`Toothbrush') are two
low-redshift (), massive (), post-core
passage merging clusters, which host shock waves traced by diffuse radio
emission. To study their star-formation properties, we uniformly survey the
`Sausage' and `Toothbrush' clusters in broad and narrow band filters and select
a sample of and line emitters, down to a rest-frame equivalent
width ({\AA}). We robustly separate between H and higher redshift
emitters using a combination of optical multi-band (B, g, V, r, i, z) and
spectroscopic data. We build H luminosity functions for the entire
cluster region, near the shock fronts, and away from the shock fronts and find
striking differences between the two clusters. In the dynamically younger,
Gyr old `Sausage' cluster we find numerous () H emitters above a
star-formation rate (SFR) of M_{\sun} yr surprisingly located
in close proximity to the shock fronts, embedded in very hot intra-cluster
medium plasma. The SFR density for the cluster population is at least at the
level of typical galaxies at . Down to the same star-formation rate,
the possibly dynamically more evolved `Toothbrush' cluster has only
H galaxies. The cluster H galaxies fall on the SFR-stellar mass
relation for the field. However, the `Sausage' cluster has an
H emitter density times that of blank fields. If the shock passes
through gas-rich cluster galaxies, the compressed gas could collapse into dense
clouds and excite star-formation for a few Myr. This process ultimately
leads to a rapid consumption of the molecular gas, accelerating the
transformation of gas-rich field spirals into cluster S0s or ellipticals.Comment: Accepted for publication in MNRAS after minor referee report. 21
pages, 15 figures, 5 table
Exploring the multi-humped fission barrier of 238U via sub-barrier photofission
The photofission cross-section of 238U was measured at sub-barrier energies
as a function of the gamma-ray energy using, for the first time, a
monochromatic, high-brilliance, Compton-backscattered gamma-ray beam. The
experiment was performed at the High Intensity gamma-ray Source (HIgS) facility
at beam energies between E=4.7 MeV and 6.0 MeV and with ~3% energy resolution.
Indications of transmission resonances have been observed at gamma-ray beam
energies of E=5.1 MeV and 5.6 MeV with moderate amplitudes. The triple-humped
fission barrier parameters of 238U have been determined by fitting EMPIRE-3.1
nuclear reaction code calculations to the experimental photofission cross
section.Comment: 5 pages, 3 figure
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