280 research outputs found
Weak Lensing Light-Cones in Modified Gravity simulations with and without Massive Neutrinos
We present a novel suite of cosmological N-body simulations called the
DUSTGRAIN-pathfinder, implementing simultaneously the effects of an extension
to General Relativity in the form of gravity and of a non-negligible
fraction of massive neutrinos. We describe the generation of simulated weak
lensing and cluster counts observables within a past light-cone extracted from
these simulations. The simulations have been performed by means of a
combination of the MG-GADGET code and a particle-based implementation of
massive neutrinos, while the light-cones have been generated using the MapSim
pipeline allowing us to compute weak lensing maps through a ray-tracing
algorithm for different values of the source plane redshift. The mock
observables extracted from our simulations will be employed for a series of
papers focussed on understanding and possibly breaking the well-known
observational degeneracy between gravity and massive neutrinos, i.e. the
fact that some specific combinations of the characteristic parameters for these
two phenomena (the scalar amplitude and the total neutrino mass
) may result indistinguishable from the standard
cosmology through several standard observational probes.
In particular, in the present work we show how a tomographic approach to weak
lensing statistics could allow - especially for the next generation of
wide-field surveys - to disentangle some of the models that appear
statistically indistinguishable through standard single-redshift weak lensing
probe.Comment: accepted for publication in MNRAS, added theoretical comparisons to
the simulation measurement
Characterizing dark interactions with the halo mass accretion history and structural properties
We study the halo mass accretion history (MAH) and its correlation with the
internal structural properties in coupled dark energy cosmologies (cDE). To
accurately predict all the non-linear effects caused by dark interactions, we
use the COupled Dark Energy Cosmological Simulations (CoDECS). We measure the
halo concentration at z=0 and the number of substructures above a mass
resolution threshold for each halo. Tracing the halo merging history trees back
in time, following the mass of the main halo, we develope a MAH model that
accurately reproduces the halo growth in term of M_{200} in the {\Lambda}CDM
Universe; we then compare the MAH in different cosmological scenarios. For cDE
models with a weak constant coupling, our MAH model can reproduce the
simulation results, within 10% of accuracy, by suitably rescaling the
normalization of the linear matter power spectrum at z=0, {\sigma}_8. However,
this is not the case for more complex scenarios, like the "bouncing" cDE model,
for which the numerical analysis shows a rapid growth of haloes at high
redshifts, that cannot be reproduced by simply rescaling the value of
{\sigma}_8. Moreover, at fixed value of {\sigma}_8, cold dark matter (CDM)
haloes in these cDE scenarios tend to be more concentrated and have a larger
amount of substructures with respect to {\Lambda}CDM predictions. Finally, we
present an accurate model that relates the halo concentration to the time at
which it assembles half or 4% of its mass. Combining this with our MAH model,
we show how halo concentrations change while varying only {\sigma}_8 in a
{\Lambda}CDM Universe, at fixed halo mass.Comment: 18 pages, 14 figures, accepted for publication in MNRA
Weak Lensing Peaks in Simulated Light-Cones: Investigating the Coupling between Dark Matter and Dark Energy
In this paper, we study the statistical properties of weak lensing peaks in
light-cones generated from cosmological simulations. In order to assess the
prospects of such observable as a cosmological probe, we consider simulations
that include interacting Dark Energy (hereafter DE) models with coupling term
between DE and Dark Matter. Cosmological models that produce a larger
population of massive clusters have more numerous high signal-to-noise peaks;
among models with comparable numbers of clusters those with more concentrated
haloes produce more peaks. The most extreme model under investigation shows a
difference in peak counts of about with respect to the reference
CDM model. We find that peak statistics can be used to
distinguish a coupling DE model from a reference one with the same power
spectrum normalisation. The differences in the expansion history and the growth
rate of structure formation are reflected in their halo counts, non-linear
scale features and, through them, in the properties of the lensing peaks. For a
source redshift distribution consistent with the expectations of future
space-based wide field surveys, we find that typically seventy percent of the
cluster population contributes to weak-lensing peaks with signal-to-noise
ratios larger than two, and that the fraction of clusters in peaks approaches
one-hundred percent for haloes with redshift z0.5. Our analysis
demonstrates that peak statistics are an important tool for disentangling DE
models by accurately tracing the structure formation processes as a function of
the cosmic time.Comment: accepted in MNRAS, figures improved and text update
The mass accretion rate of galaxy clusters: a measurable quantity
We explore the possibility of measuring the mass accretion rate (MAR) of
galaxy clusters from their mass profiles beyond the virial radius . We
derive the accretion rate from the mass of a spherical shell whose inner radius
is , whose thickness changes with redshift, and whose infall velocity
is assumed to be equal to the mean infall velocity of the spherical shells of
dark matter halos extracted from -body simulations. This approximation is
rather crude in hierarchical clustering scenarios where both smooth accretion
and aggregation of smaller dark matter halos contribute to the mass accretion
of clusters.Nevertheless, in the redshift range , our prescription
returns an average MAR within of the average rate derived from the
merger trees of dark matter halos extracted from -body simulations. The MAR
of galaxy clusters has been the topic of numerous detailed numerical and
theoretical investigations, but so far it has remained inaccessible to
measurements in the real universe. Since the measurement of the mass profile of
clusters beyond their virial radius can be performed with the caustic technique
applied to dense redshift surveys of the cluster outer regions, our result
suggests that measuring the mean MAR of a sample of galaxy clusters is actually
feasible. We thus provide a new potential observational test of the
cosmological and structure formation models.Comment: 11 pages, 7 figures, 5 tables, minor text modifications to match the
published version, typos correcte
Disentangling dark sector models using weak lensing statistics
We perform multi-plane ray-tracing using the GLAMER gravitational lensing
code within high-resolution light-cones extracted from the CoDECS simulations:
a suite of cosmological runs featuring a coupling between Dark Energy and Cold
Dark Matter. We show that the presence of the coupling is evident not only in
the redshift evolution of the normalisation of the convergence power spectrum,
but also in differences in non-linear structure formation with respect to
{\Lambda}CDM. Using a tomographic approach under the assumption of a
{\Lambda}CDM cosmology, we demonstrate that weak lensing measurements would
result in a {\sigma}8 value that changes with the source redshift if the true
underlying cosmology is a coupled Dark Energy one. This provides a generic null
test for these types of models. We also find that different models of coupled
Dark Energy can show either an enhanced or a suppressed correlation between
convergence maps with differing source redshifts as compared to {\Lambda}CDM.
This would provide a direct way to discriminate between different possible
realisations of the coupled Dark Energy scenario. Finally, we discuss the
impact of the coupling on several lensing observables for different source
redshifts and angular scales with realistic source redshift distributions for
current ground-based and future space-based lensing surveys.Comment: 17 pag. and 14 fig. replaced to match the accepted version (increased
the number of light-cone realisations
The stellar-to-halo mass relation over the past 12 Gyr
Understanding how galaxy properties are linked to the dark matter halos they
reside in, and how they co-evolve is a powerful tool to constrain the processes
related to galaxy formation. The stellar-to-halo mass relation (SHMR) and its
evolution over the history of the Universe provides insights on galaxy
formation models and allows to assign galaxy masses to halos in N-body dark
matter simulations. We use a statistical approach to link the observed galaxy
stellar mass functions on the COSMOS field to dark matter halo mass functions
from the DUSTGRAIN simulation and from a theoretical parametrization from z=0
to z=4. We also propose an empirical model to describe the evolution of the
stellar-to-halo mass relation as a function of redshift. We calculate the
star-formation efficiency (SFE) of galaxies and compare results with previous
works and semi-analytical models.Comment: accepted for publication in A&A, matching version in pres
Comparative Effectiveness of DPP-4 Inhibitors Versus Sulfonylurea for the Treatment of Type 2 Diabetes in Routine Clinical Practice: A Retrospective Multicenter Real-World Study
Introduction: DPP-4 inhibitors (DPP4i) and sulfonylureas are popular second-line therapies for type 2 diabetes (T2D), but there is a paucity of real-world studies comparing their effectiveness in routine clinical practice. Methods: This was a multicenter retrospective study on diabetes outpatient clinics comparing the effectiveness of DPP4i versus gliclazide extended release. The primary endpoint was change from baseline in HbA1c. Secondary endpoints were changes in fasting plasma glucose, body weight, and systolic blood pressure. Automated software extracted data from the same clinical electronic chart system at all centers. Propensity score matching (PSM) was used to generate comparable cohorts to perform outcome analysis. Results: We included data on 2410 patients starting DPP4i and 1590 patients starting gliclazide (mainly 30–60 mg/day). At baseline, the two groups differed in disease duration, body weight, blood pressure, HbA1c, fasting glucose, HDL cholesterol, triglycerides, liver enzymes, eGFR, prevalence of microangiopathy, and use of metformin. Among DPP4i molecules, no difference in glycemic effectiveness was detected. In matched cohorts (n = 1316/group), patients starting DPP4i, as compared with patients starting gliclazide, experienced greater reductions in HbA1c (− 0.6% versus − 0.4%; p < 0.001), fasting glucose (− 14.1 mg/dl versus − 8.8 mg/dl; p = 0.007), and body weight (− 0.4 kg versus − 0.1 kg; p = 0.006) after an average 6 months follow-up. DPP4i improved glucose control more than gliclazide, especially in patients who had failed with other glucose-lowering medications or were on basal insulin. Conclusions: This large retrospective real-world study shows that, in routine clinical practice, starting a DPP4i allows better glycemic control than starting low-dose gliclazide. Funding: The Italian Diabetes Society, with external support from AstraZeneca
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