392 research outputs found
Evolution of galaxy groups in the Illustris simulation
We present the first study of evolution of galaxy groups in the Illustris
simulation. We focus on dynamically relaxed and unrelaxed galaxy groups
representing dynamically evolved and evolving galaxy systems, respectively. The
evolutionary state of a group is probed from its luminosity gap and separation
between the brightest group galaxy and the center of mass of the group members.
We find that the Illustris simulation, over-produces large luminosity gap
galaxy systems, known as fossil systems, in comparison to observations and the
probed semi-analytical predictions. However, this simulation is equally
successful in recovering the correlation between luminosity gap and luminosity
centroid offset, in comparison to the probed semi-analytic model. We find
evolutionary tracks based on luminosity gap which indicate that a large
luminosity gap group is rooted in a small luminosity gap group, regardless of
the position of the brightest group galaxy within the halo. This simulation
helps, for the first time, to explore the black hole mass and its accretion
rate in galaxy groups. For a given stellar mass of the brightest group
galaxies, the black hole mass is larger in dynamically relaxed groups with a
lower rate of mass accretion. We find this consistent with the latest
observational studies of the radio activities in the brightest group galaxies
in fossil groups. We also find that the IGM in dynamically evolved groups is
hotter for a given halo mass than that in evolving groups, again consistent
with earlier observational studies.Comment: 10 pages, 10 figures. Accepted for publication in Ap
Effect of drying process on antioxidant properties of date palm fruits
Aim. In order to identify antioxidant activities and phenolic compound, two varieties of date palm (Mazfati and Kalute varieties) (Phoenix dactylifera) fruits (DPF) from Iran systematically evaluated. Methods. Antioxidant activity determined using typical methods such as DPPH, reducing power and total antioxidant method. The total phenolic content of the dates was measured using Folin-Ciocalteau method. The included samples were gathered at three stages of khalaal, rutab, tamr and dried date from Sam and Jiroft date. The total phenolic content ranged from 1074, 856.4 and 723.8 in Mozafati variety and 921.5, 723.5 and 785.3 mg gallic acid equivalents (GAE/100-g-dw sample) in Kalute variety for khalal, rutab and tamr stage, respectively. Results. In both varieties antioxidant activities and total phenolic content decreased by ripening stages. Result of drying process showed that total phenolic content and antioxidant activities varied from temperature and decreased by increase of drying temperature. Conclusion. This research demonstrates Iranian dates could be potential rich resources of natural antioxidants, and could be developed into functional foods or drug for the prevention and treatment of diseases caused by oxidative stress
Evolution of the galaxy luminosity function in progenitors of fossil groups
Using the semi-analytic models based on the Millennium simulation, we trace
back the evolution of the luminosity function of galaxies residing in
progenitors of groups classified by the magnitude gap at redshift zero. We
determine the luminosity function of galaxies within , and for galaxy groups/clusters. The bright end of the galaxy
luminosity function of fossil groups shows a significant evolution with
redshift, with changes in by 1-2 mag between and
(for the central ), suggesting that the formation of the most
luminous galaxy in a fossil group has had a significant impact on the
galaxies e.g. it is formed as a result of multiple mergers of the
galaxies within the last Gyr. In contrast, the slope of the faint end,
, of the luminosity function shows no considerable redshift evolution
and the number of dwarf galaxies in the fossil groups exhibits no evolution,
unlike in non-fossil groups where it grows by towards low
redshifts. In agreement with previous studies, we also show that fossil groups
accumulate most of their halo mass earlier than non-fossil groups. Selecting
the fossils at a redshift of 1 and tracing them to a redshift 0, we show that
of the fossil groups () will lose their large magnitude gaps. However, about
of fossil clusters () will retain their large
gaps.Comment: Accepted for publication in A&A. 13 pages, 15 figure
The mass assembly of galaxy groups and the evolution of the magnitude gap
We investigate the assembly of groups and clusters of galaxies using the
Millennium dark matter simulation and the associated gas simulations and
semi-analytic catalogues of galaxies. In particular, in order to find an
observable quantity that could be used to identify early-formed groups, we
study the development of the difference in magnitude between their brightest
galaxies to assess the use of magnitude gaps as possible indicators. We select
galaxy groups and clusters at redshift z=1 with dark matter halo mass M(R200) >
1E13/h Msun, and trace their properties until the present time (z=0). We
consider only the systems with X-ray luminosity L_X> 0.25E42/h^2 erg/s at z=0.
While it is true that a large magnitude gap between the two brightest galaxies
of a particular group often indicates that a large fraction of its mass was
assembled at an early epoch, it is not a necessary condition. More than 90% of
fossil groups defined on the basis of their magnitude gaps (at any epoch
between 0<z<1) cease to be fossils within 4 Gyr, mostly because other massive
galaxies are assembled within their cores, even though most of the mass in
their haloes might have been assembled at early times. We show that, compared
to the conventional definition of fossil galaxy groups based on the magnitude
gap Delta m(12)> 2 (in the R-band, within 0.5R200 of the centre of the group),
an alternative criterion Delta m(14)>2.5 (within the same radius) finds 50%
more early-formed systems, and those that on average retain their fossil phase
longer. However, the conventional criterion performs marginally better at
finding early-formed groups at the high-mass end of groups. Nevertheless, both
criteria fail to identify a majority of the early-formed systems.Comment: 16 pages, 11 figures, 2 tables. Accepted for publication in MNRA
Young stellar populations in early-type dwarf galaxies; occurrence, radial extent and scaling relations
To understand the stellar population content of dwarf early-type galaxies
(dEs) and its environmental dependence, we compare the slopes and intrinsic
scatter of color-magnitude relations (CMRs) for three nearby clusters, Fornax,
Virgo and Coma. Additionally we present and compare internal color profiles of
these galaxies to identify central blue regions with younger stars.
We use the imaging of the HST/ACS Fornax cluster in the magnitude range of
-18.7 <= M_g' <= -16.0, to derive magnitudes, colors and color profiles, which
we compare with literature measurements.
Based on analysis of the color profiles, we report a large number of dEs with
young stellar populations in their center in all three clusters. While for
Virgo and Coma the number of blue-cored dEs is found to be 85 +/- 2% and 53 +/-
3% respectively, for Fornax, we find that all galaxies have a blue core. We
show that bluer cores reside in fainter dEs, similar to the trend seen in
nucleated dEs. We find no correlation between the luminosity of the galaxy and
the size of its blue core. Moreover, a comparison of the CMRs of the three
clusters shows that the scatter in Virgo's CMR is considerably larger than in
the Fornax and Coma clusters. Presenting adaptive smoothing we show that the
galaxies on the blue side of the CMR often show evidence for dust extinction,
which strengthens the interpretation that the bluer colors are due to young
stellar populations. We also find that outliers on the red side of the CMR are
more compact than expected for their luminosity. We find several of these red
outliers in Virgo, often close to more massive galaxies. No red outlying
compact early-types are found in Fornax and Coma in this magnitude range while
we find three in the Virgo cluster. We suggest that the large number of
outliers and larger scatter found for the Virgo cluster CMR is a result of
Virgo's different assembly history.Comment: 24 pages, accepted for publication in Astronomy and Astrophysic
Security Technology by Using Firewall for Smart Grid
Due to the increasing development of computer systems and information networks, power grids should change extensively too. Nowadays, substantial movement has begun to implement the Smart Grid industry around the world. Since with the creation of smart electricity grids, it is possible to access the internal network from the external spaces, it is also necessary to protect information and data against unauthorized access. Therefore, a firewall should be used for information security. The firewall based on existing security regulations, decides which data is incoming to the network or going out of the network. Considering the discussions of passive defense topics at the national level and also the high importance of information security in Smart Grids, in this paper, in addition to examining the Firewalls, its advantages and disadvantages are also stated. Although the firewall has a major role in establishing security, and its installation and appropriate configuration can only be one of the primary activities in this field, we should also take advantage of other security mechanisms to enhance the security of the Smart Grid
Optically selected fossil groups; X-ray observations and galaxy properties
We report on the X-ray and optical observations of galaxy groups selected
from the 2dfGRS group catalog, to explore the possibility that galaxy groups
hosting a giant elliptical galaxy and a large optical luminosity gap present
between the two brightest group galaxies, can be associated with an extended
X-ray emission, similar to that observed in fossil galaxy groups. The X-ray
observations of 4 galaxy groups were carried out with Chandra telescope with
10-20 ksec exposure time. Combining the X-ray and the optical observations we
find evidences for the presence of a diffuse extended X-ray emission beyond the
optical size of the brightest group galaxy. Taking both the X-ray and the
optical criteria, one of the groups is identified as a fossil group and one is
ruled out because of the contamination in the earlier optical selection. For
the two remaining systems, the X-ay luminosity threshold is close to the
convention know for fossil groups. In all cases the X-ray luminosity is below
the expected value from the X-ray selected fossils for a given optical
luminosity of the group. A rough estimation for the comoving number density of
fossil groups is obtained and found to be in broad agreement with the
estimations from observations of X-ray selected fossils and predictions of
cosmological simulations.Comment: Accepted for publication in MNRA
Expression of complete rhoptry protein 2 (ROP2) gene of Toxoplasma gondii in eukaryotic cell
Toxoplasma gondii is the intracellular protozoan parasite responsible for animal and human toxoplasmosis. In immunodeficient patients, chronic infection with T. gondii can reactivate and produceencephalitis, which is often lethal. ROP2 (rhoptry protein of T. gondii) is one of the most important interferer in organelle and PVM blending. ROP2 protein is recognized by clone T-cell (Tcc32) in humanbody and also has epitope for B-cell. All of these characteristics of ROP2 makes it a candidate for cocktail vaccine and recombinant vaccine against toxoplasmosis. We described the expression of thegene which encodes the complete rhoptry protein 2 (ROP2) of T. gondii in CHO cells and confirmed it by SDS-PAGE and Western blot analysis. In the present work, genomic DNA of T. gondii was extractedand used for amplifying of ROP2 gene as a template. Then PCR product was cloned into pTZ57R/T vector, and plasmid containing ROP2 gene (pT-ROP2) was extracted from transformed bacteria andsequenced. We hope to use from this recombinant plasmid (pT-ROP2) to make DNA vaccine against toxoplasmosis
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