1,407 research outputs found
(E)-2-{[1-(3,11-Dimethyl-4-methylene- 10-oxo-1-phenyl-4,5,10,11-tetrahydro-1H-benzo[b]pyrazolo[3,4-f][1,5]diazocin- 5-yl)ethylidene]amino}-N-methyl-N-(3-methyl-1-phenyl-1H-pyrazol-5-yl)-benzamide
The central eight-membered ring of the title compound,C40H36N8O2, deviates from the ideal boat conformation
because the bond between the
exo-ethylene group and the
adjacent N atom is twisted by 60.0 (4)°
due to steric hindrance.
Its adjacent benzene and pyrazole rings are oriented almost
perpendicular to each other, making a dihedral angle of
85.8 (3)°. In the crystal, the molecules are linked by C(ar)—
H...O hydrogen bonds, generating a three-dimensional
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Arc sensitivity to cluster ellipticity, asymmetries and substructures
We investigate how ellipticity, asymmetries and substructures separately
affect the ability of galaxy clusters to produce strong lensing events, i.e.
gravitational arcs, and how they influence the arc morphologies and fluxes.
This is important for those studies aiming, for example, at constraining
cosmological parameters from statistical lensing, or at determining the inner
structure of galaxy clusters through gravitational arcs. We do so by creating
two-dimensional gradually smoothed, differently elliptical and asymmetric
versions of some numerical models. On average, we find that the contributions
of ellipticity, asymmetries and substructures amount to ~40%, ~10% and ~30% of
the total strong lensing cross section, respectively. However, our analysis
shows that substructures play a more important role in less elliptical and
asymmetric clusters, even if located at large distances from the cluster
centers (~1Mpc/h). Conversely, their effect is less important in highly
asymmetric lenses. The morphology, position and flux of individual arcs are
strongly affected by the presence of substructures in the clusters. Removing
substructures on spatial scales <~50kpc/h, roughly corresponding to mass scales
<~5 10^{10}M_\odot/h, alters the image multiplicity of ~35% of the sources used
in the simulations and causes position shifts larger than 5'' for ~40% of the
arcs longer than 5''. We conclude that any model for cluster lens cannot
neglect the effects of ellipticity, asymmetries and substructures. On the other
hand, the high sensitivity of gravitational arcs to deviations from regular,
smooth and symmetric mass distributions suggests that strong gravitational
lensing is potentially a powerfull tool to measure the level of substructures
and asymmetries in clusters.Comment: 16 pages, 18 figures. Accepted version. Version with full resolution
images can be found at
http://www.ita.uni-heidelberg.de/~massimo/sub/publications.htm
Strong lensing in the MareNostrum Universe: biases in the cluster lens population
Strong lensing is one of the most direct probes of the mass distribution in
the inner regions of galaxy clusters. It can be used to constrain the density
profiles and to measure the mass of the lenses. Moreover, the abundance of
strong lensing events can be used to constrain the structure formation and the
cosmological parameters through the so-called "arc-statistics" approach.
However, several issues related to the usage of strong lensing clusters in
cosmological applications are still controversial, leading to the suspect that
several biases may affect this very peculiar class of objects. With this study
we aim at better understanding the properties of galaxy clusters which can
potentially act as strong lenses. We do so by investigating the properties of a
large sample of galaxy clusters extracted from the N-body/hydrodynamical
simulation MareNostrum Universe. We explore the correlation between the cross
section for lensing and many properties of clusters, like the mass, the
three-dimensional and projected shapes, their concentrations, the X-ray
luminosity and the dynamical activity. We find that the probability of strong
alignments between the major axes of the lenses and the line of sight is a
growing function of the lensing cross section. In projection, the strong lenses
appear rounder within R200, but we find that their cores tend to be more
elliptical as the lensing cross section increases. We also find that the
cluster concentrations estimated from the projected density profiles tend to be
biased high. The X-ray luminosity of strong lensing clusters is higher than
that of normal lenses of similar mass and redshift. This is particular
significant for the least massive lenses. Finally, we find that the strongest
lenses generally exhibit an excess of kinetic energy within the virial radius,
indicating that they are more dynamically active than usual clusters.Comment: 22 pages, 18 figures, accepted for publication on A&
Accuracy of photometric redshifts for future weak lensing surveys from space
Photometric redshifts are a key tool to extract as much information as
possible from planned cosmic shear experiments. In this work we aim to test the
performances that can be achieved with observations in the near-infrared from
space and in the optical from the ground. This is done by performing realistic
simulations of multi-band observations of a patch of the sky, and submitting
these mock images to software usually applied to real images to extract the
photometry and then a redshift estimate for each galaxy. In this way we mimic
the most relevant sources of uncertainty present in real data analysis,
including blending and light pollution between galaxies. As an example we adopt
the infrared setup of the ESA-proposed Euclid mission, while we simulate
different observations in the optical, modifying filters, exposure times and
seeing values. Finally, we consider directly some future ground-based
experiments, such as LSST, Pan-Starrs and DES. The results highlight the
importance of u-band observations, especially to discriminate between low (z <
0.5) and high (z ~ 3) redshifts, and the need for good observing sites, with
seeing FWHM < 1. arcsec. The former of these indications clearly favours the
LSST experiment as a counterpart for space observations, while for the other
experiments we need to exclude at least 15 % of the galaxies to reach a
precision in the photo-zs equal to < 0.05.Comment: 11 pages, to be published in MNRAS. Minor changes to match the
published versio
Mass profiles and concentration-dark matter relation in X-ray luminous galaxy clusters
(Abriged) Assuming that the hydrostatic equilibrium holds between the
intracluster medium and the gravitational potential, we constrain the NFW
profiles in a sample of 44 X-ray luminous galaxy clusters observed with
XMM-Newton in the redshift range 0.1-0.3. We evaluate several systematic
uncertainties that affect our reconstruction of the X-ray masses. We measure
the concentration c200, the dark mass M200 and the gas mass fraction within
R500 in all the objects of our sample, providing the largest dataset of mass
parameters for galaxy clusters in this redshift range. We confirm that a tight
correlation between c200 and M200 is present and in good agreement with the
predictions from numerical simulations and previous observations. When we
consider a subsample of relaxed clusters that host a Low-Entropy-Core (LEC), we
measure a flatter c-M relation with a total scatter that is lower by 40 per
cent. From the distribution of the estimates of c200 and M200, with associated
statistical (15-25%) and systematic (5-15%) errors, we use the predicted values
from semi-analytic prescriptions calibrated through N-body numerical runs and
measure sigma_8*Omega_m^(0.60+-0.03)= 0.45+-0.01 (at 2 sigma level, statistical
only) for the subsample of the clusters where the mass reconstruction has been
obtained more robustly, and sigma_8*Omega_m^(0.56+-0.04) = 0.39+-0.02 for the
subsample of the 11 more relaxed LEC objects. With the further constraint from
the fgas distribution in our sample, we break the degeneracy in the
sigma_8-Omega_m plane and obtain the best-fit values sigma_8~1.0+-0.2
(0.75+-0.18 when the subsample of the more relaxed objects is considered) and
Omega_m = 0.26+-0.01.Comment: 21 pages. A&A in press. Minor revisions to match accepted version.
Corrected 2nd and 3rd column in Table 3, and equation (A.4
Weighing simulated galaxy clusters using lensing and X-ray
We aim at investigating potential biases in lensing and X-ray methods to
measure the cluster mass profiles. We do so by performing realistic simulations
of lensing and X-ray observations that are subsequently analyzed using
observational techniques. The resulting mass estimates are compared among them
and with the input models. Three clusters obtained from state-of-the-art
hydrodynamical simulations, each of which has been projected along three
independent lines-of-sight, are used for this analysis. We find that strong
lensing models can be trusted over a limited region around the cluster core.
Extrapolating the strong lensing mass models to outside the Einstein ring can
lead to significant biases in the mass estimates, if the BCG is not modeled
properly for example. Weak lensing mass measurements can be largely affected by
substructures, depending on the method implemented to convert the shear into a
mass estimate. Using non-parametric methods which combine weak and strong
lensing data, the projected masses within R200 can be constrained with a
precision of ~10%. De-projection of lensing masses increases the scatter around
the true masses by more than a factor of two due to cluster triaxiality. X-ray
mass measurements have much smaller scatter (about a factor of two smaller than
the lensing masses) but they are generally biased low by 5-20%. This bias is
ascribable to bulk motions in the gas of our simulated clusters. Using the
lensing and the X-ray masses as proxies for the true and the hydrostatic
equilibrium masses of the simulated clusters and averaging over the cluster
sample we are able to measure the lack of hydrostatic equilibrium in the
systems we have investigated.Comment: 27 pages, 21 figures, accepted for publication on A&A. Version with
full resolution images can be found at
http://pico.bo.astro.it/~massimo/Public/Papers/massComp.pd
Arc Statistics in Cosmological Models with Dark Energy
We investigate how the probability of the formation of giant arcs in galaxy
clusters is expected to change in cosmological models dominated by dark energy
with an equation of state p=w rho c^2 compared to cosmological-constant or open
models. To do so, we use a simple analytic model for arc cross sections based
on the Navarro-Frenk-White density profile which we demonstrate reproduces
essential features of numerically determined arc cross sections. Since analytic
lens models are known to be inadequate for accurate absolute quantifications of
arc probabilities, we use them only for studying changes relative to
cosmological-constant models. Our main results are (1) the order of magnitude
difference between the arc probabilities in low density, spatially flat and
open CDM models found numerically is reproduced by our analytic model, and (2)
dark-energy cosmologies with w>-1 increase the arc optical depth by at most a
factor of two and are thus unlikely to reconcile arc statistics with spatially
flat cosmological models with low matter density.Comment: 8 pages, accepted by A&
Testing the reliability of weak lensing cluster detections
We study the reliability of dark-matter halo detections with three different
linear filters applied to weak-lensing data. We use ray-tracing in the multiple
lens-plane approximation through a large cosmological simulation to construct
realizations of cosmic lensing by large-scale structures between redshifts zero
and two. We apply the filters mentioned above to detect peaks in the
weak-lensing signal and compare them with the true population of dark matter
halos present in the simulation. We confirm the stability and performance of a
filter optimized for suppressing the contamination by large-scale structure. It
allows the reliable detection of dark-matter halos with masses above a few
times 1e13 M_sun/h with a fraction of spurious detections below ~10%. For
sources at redshift two, 50% of the halos more massive than ~7e13 M_sun/h are
detected, and completeness is reached at ~2e14 M_sun/h.Comment: 14 pages, 13 figures, accepted on A&
Trajectories across the healthy adult lifespan on sense of direction, spatial anxiety, and attitude in exploring places
Introduction: Self-evaluations about orientation and navigation in the environment contribute to individual differences in spatial cognition. Evidence suggests that they may change, even slightly, with the progression of adulthood. It is necessary to improve the framing of environment-related subjective self-evaluations in adulthood and aging by examining how they change and the factors related to them. Therefore, this study aimed to examine the developmental trajectories of sense of direction, spatial anxiety, and attitude in exploring place across the adult lifespan while also considering gender and education. Materials and methods: A sample of 1,946 participants (1,068 women), aged 18–87 years, completed the sense of direction and spatial representation, spatial anxiety, and attitude in exploring scales. Results: The regression models showed a linear increase in sense of direction with age, stable spatial anxiety until age 66 years when anxiety began increasing, and a stable attitude in exploring with a deflection by age 71 years. Gender played a role in all three types of self-evaluations, with men reporting higher ratings in sense of direction and attitude toward exploring (especially in older men), and lower levels of spatial anxiety than women did. Education also played a role, with higher education years associated with lower ratings in spatial anxiety and a higher sense of direction, nullifying gender differences in the latter. Discussion: These results offer, in the spatial cognition framework, a better understanding of how specific environment-related self-evaluations develop with age and related factors, such as education. This underscores the importance of enhancing them, particularly in women and older adults
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