We present an analysis of the relation between the masses of cluster- and group-sized haloes, extracted from Λ cold dark matter (ΛCDM) cosmological N-body and hydrodynamic simulations, and their ...velocity dispersion at different redshifts from z = 2 to 0. The main aim of this analysis is to understand how the implementation of baryonic physics in simulations affects such relations, i.e. to what extent the use of the velocity dispersion as a proxy for cluster mass determination is hampered by the imperfect knowledge of the baryonic physics. In our analysis, we use several sets of simulations with different physics implemented: one DM-only simulation, one simulation with non-radiative gas, and two radiative simulations, one of which with feedback from active galactic nuclei. Velocity dispersions are determined using three different tracers: DM particles, subhaloes and galaxies.
We confirm that DM particles trace a relation that is fully consistent with the theoretical expectations based on the virial theorem, σv ∝ M
α with α = 1/3, and with previous results presented in the literature. On the other hand, subhaloes and galaxies trace steeper relations, with velocity dispersion scaling with mass with α > 1/3, and with larger values of the normalization. Such relations imply that galaxies and subhaloes have a ∼10 per cent velocity bias relative to the DM particles, which can be either positive or negative, depending on the halo mass, redshift and physics implemented in the simulation.
We explain these differences as due to dynamical processes, namely dynamical friction and tidal disruption, acting on substructures and galaxies, but not on DM particles. These processes appear to be more or less effective, depending on the halo masses and the importance of baryon cooling, and may create a non-trivial dependence of the velocity bias and the σ1D-M
200 relation on the tracer, the halo mass and its redshift.
These results are relevant in view of the application of velocity dispersion as a proxy for cluster masses in ongoing and future large redshift surveys.
Aims. We aim to compute the mass and velocity anisotropy profiles of Abell 2142 and, from there, the pseudo phase–space density profile Q(r) and the density slope − velocity anisotropy β − γ ...relation, and then to compare them with theoretical expectations. Methods. The mass profiles were obtained by using three techniques based on member galaxy kinematics, namely the caustic method, the method of dispersion-kurtosis, and MAMPOSSt. Through the inversion of the Jeans equation, it was possible to compute the velocity anisotropy profiles. Results. The mass profiles, as well as the virial values of mass and radius, computed with the different techniques agree with one another and with the estimates coming from X-ray and weak lensing studies. A combined mass profile is obtained by averaging the lensing, X-ray, and kinematics determinations. The cluster mass profile is well fitted by an NFW profile with c = 4.0 ± 0.5. The population of red and blue galaxies appear to have a different velocity anisotropy configuration, since red galaxies are almost isotropic, while blue galaxies are radially anisotropic, with a weak dependence on radius. The Q(r) profile for the red galaxy population agrees with the theoretical results found in cosmological simulations, suggesting that any bias, relative to the dark matter particles, in velocity dispersion of the red component is independent of radius. The β − γ relation for red galaxies matches the theoretical relation only in the inner region. The deviations might be due to the use of galaxies as tracers of the gravitational potential, unlike the non–collisional tracer used in the theoretical relation.
We present a detailed mass reconstruction and a novel study on the substructure properties in the core of the Cluster Lensing And Supernova survey with Hubble (CLASH) and Frontier Fields galaxy ...clusterMACS J0416.1-2403. We reproduce the measured positions of a set of 30 multiple images with a remarkable median offset of only 0.3 by means of a comprehensive strong lensing model comprised of two cluster dark-matter halos, represented by cored elliptical pseudo-isothermal mass distributions, and the cluster member components, parameterized with dual pseudo-isothermal total mass profiles. We investigate the galaxy contribution, both in terms of total and stellar mass, to the total mass budget of the cluster. Our findings of the location and shape of the cluster dark-matter halo density profiles and on the cluster substructures provide intriguing tests of the assumed collisionless, cold nature of dark matter and of the role played by baryons in the process of structure formation.
ABSTRACT
We present a new numerical method to determine second-order Lagrangian displacement fields in presence of modified gravity (MG). We start from the extension of Lagrangian perturbation theory ...(LPT) to a class of MG models, which can be described by a parametrized Poisson equation. We exploit Fast Fourier transforms to compute the full source term of the differential equation for the second-order Lagrangian displacement field. We compare its mean to the source term computed for specific configurations, for which a k-dependent solution can be found numerically. We choose the configuration that best matches the full source term, thus obtaining an approximate factorization of the second-order displacement field as the space term valid for Λ Cold Dark Matter (ΛCDM) times a k-dependent, second-order growth factor. Such approximation is used to compute second-order displacements for particles. The method is tested against N-body simulations run with standard and f(R) gravity: we rely on the results of a friends-of-friends code run on the N-body snapshots to assign particles to haloes, then compute the halo power spectrum. We find very consistent results for the two gravity theories: second-order LPT (2LPT) allows to recover the N-body halo power spectrum within ∼10 per cent precision to k ∼ 0.2–0.4 h Mpc−1, as well as halo positions. We show that the performance of 2LPT with MG is the same (within 1 per cent) as the one obtained for standard ΛCDM case. This formulation of 2LPT can quickly generate dark matter distributions with f(R) gravity, and can easily be extended to other MG theories.
Innate lymphoid cells (ILCs) have a central role in innate defenses against pathogens, lymphoid organogenesis, and tissue remodeling. They have been detected in human decidua, however, their role in ...this tissue remains unclear. Successful pregnancy requires an early inflammatory phase favoring implantation and tissue remodeling as well as a subsequent regulatory phase to prevent fetal rejection and supporting neoangiogenesis. Here, we show that, during the first trimester of pregnancy, neutrophils infiltrate decidua basalis and are more abundant in normal pregnancy than in spontaneous miscarriages. Decidual neutrophils localize in proximity of NCR
ILC3, which may influence neutrophil migration and survival given their production of CXCL8 and granulocyte macrophage colony-stimulating factor (GM-CSF). Moreover, NCR
ILC3-derived GM-CSF was found to induce the expression of heparin-binding EGF-like growth factor and IL1ra in neutrophils, two proteins/cytokines involved in tissue remodeling and maintenance of pregnancy. Our data suggest that the simultaneous presence of NCR
ILC3 and neutrophils in decidual tissues and their possible cross talk, may have a role in the early phases of pregnancy.
The epidemiological research benefits from an accurate characterization of both spatial and temporal variability of exposure to air pollution. This work aims at proposing a method to combine the high ...spatial resolution of Land Use Regression (LUR) models with the high temporal resolution of fixed site monitoring data, to model spatiotemporal variability of NO2 over a wide geographical area in Northern Italy. We developed seasonal LUR models to reconstruct the spatial distribution of a scaling factor that relates local concentrations to those measured at two reference central sites, one for the northern flat area and one for the southern mountain area. We calculated the daily average concentrations at 19 locations spread over the study areas as the product of the local scaling factor and the reference central site concentrations. We evaluated model performance comparing modeled and measured NO2 data. LUR model's R2 ranges from 0.76 to 0.92. The main predictors refers substantially to traffic, industrial land use, buildings volume and altitude a.s.l. The model's performance in reproducing measured concentrations was satisfactory. The temporal variability of concentrations was well captured: Spearman correlation between model and measures was >0.7 for almost all sites. Model's average absolute errors were in the order of 10μgm−3. The model for the southern area tends to overestimate measured concentrations. Our modeling framework was able to reproduce spatiotemporal differences in NO2 concentrations. This kind of model is less data-intensive than usual regional atmospheric models and it may be very helpful to assess population exposure within studies in which individual relevant exposure occurs along periods of days or months.
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•We combined land use regression (LUR) models and central site continuous monitoring.•We reconstructed NO2 spatiotemporal variability over a wide geographical area.•The model performed well in reproducing measured daily concentrations.•The model is very useful for both long and short term exposure assessment.
We present a multiwavelength study of the massive ( M 200 c ( 1 - 2 ) × 10 15 M ) galaxy clusters RXC J2248.7−4431, MACS J0416.1−2403, and MACS J1206.2−0847 at z 0.4. Using the X-ray surface ...brightness of the clusters from the deep Chandra data to model their hot gas, we are able to disentangle this mass term from the diffuse dark matter (DM) in our new strong-lensing analysis, with approximately 50-100 secure multiple images per cluster, effectively separating the collisional and collisionless mass components of the clusters. At a radial distance of 10% of R200c (approximately 200 kpc), we measure a projected total mass of (0.129 0.001), (0.131 0.001) and (0.137 0.001) × M200c, for RXC J2248, MACS J0416 and MACS J1206, respectively. These values are surprisingly similar considering the large differences in the merging configurations and, consequently, in the mass models of the clusters. Interestingly, at the same radii, the hot gas over total mass fractions differ substantially, ranging from 0.082 0.001 to 0.133 0.001, which reflects the various dynamical states of the clusters. Moreover, we do not find a statistically significant offset between the positions of the peak of the diffuse DM component and of the BCG in the more complex clusters of the sample. We extend the previous findings of a number of massive sub-halos that are higher than in numerical simulations to this sample of clusters. Our results highlight the importance of a proper separation of the different mass components to study the properties of DM in galaxy clusters in detail.
Context.
Studies of cluster mass and velocity anisotropy profiles are useful tests of dark matter models and of the assembly history of clusters of galaxies. These studies might be affected by ...unknown systematics caused by projection effects.
Aims.
We aim to test observational methods for the determination of mass and velocity anisotropy profiles of clusters of galaxies. Particularly, we focus on the MAMPOSSt technique
Methods.
We used results from two semi-analytic models of galaxy formation, coupled with high-resolution
N
-body cosmological simulations, the DLB07 catalog, and the FIRE catalog based on the new GAlaxy Evolution and Assembly model. We tested the reliability of the Jeans equation in recovering the true mass profile when full projected phase-space information is available. We examined the reliability of the MAMPOSSt method in estimating the true mass and velocity anisotropy profiles of the simulated halos when only projected phase-space information is available, as in observations.
Results.
The spherical Jeans equation provides a reliable tool to determine cluster mass profiles, both when considering the whole population of cluster galaxies, and when considering subsamples of tracers separated by galaxy color; the exception to this is for the central region, where deviations may be attributed to dynamical friction effects or galaxy mergers. The results are equally good for prolate and oblate clusters. Using only projected phase-space information, MAMPOSSt provides estimates of the mass profile with a standard deviation of 35–69% and a negative bias of 7–17%, nearly independent of radius, which we attribute to the presence of interlopers in the projected samples. The bias changes sign; that is, the mass is over-estimated, for prolate clusters with their major axis aligned along the line of sight. The MAMPOSSt method measures the velocity anisotropy profiles accurately in the inner cluster regions and there is a slight overestimate in the outer regions for the whole sample of observationally identified cluster members, and, separately, for red and blue galaxies.
Aims. We perform a comprehensive study of the total mass distribution of the galaxy cluster RXC J2248.7−4431 (z = 0.348) with a set of high-precision strong lensing models, which take advantage of ...extensive spectroscopic information on many multiply lensed systems. In the effort to understand and quantify inherent systematics in parametric strong lensing modelling, we explore a collection of 22 models in which we use different samples of multiple image families, different parametrizations of the mass distribution and cosmological parameters. Methods. As input information for the strong lensing models, we use the Cluster Lensing And Supernova survey with Hubble (CLASH) imaging data and spectroscopic follow-up observations, with the VIsible Multi-Object Spectrograph (VIMOS) and Multi Unit Spectroscopic Explorer (MUSE) on the Very Large Telescope (VLT), to identify and characterize bona fide multiple image families and measure their redshifts down to mF814W ≃ 26. A total of 16 background sources, over the redshift range 1.0−6.1, are multiply lensed into 47 images, 24 of which are spectroscopically confirmed and belong to ten individual sources. These also include a multiply lensed Lyman-α blob at z = 3.118. The cluster total mass distribution and underlying cosmology in the models are optimized by matching the observed positions of the multiple images on the lens plane. Bayesian Markov chain Monte Carlo techniques are used to quantify errors and covariances of the best-fit parameters. Results. We show that with a careful selection of a large sample of spectroscopically confirmed multiple images, the best-fit model can reproduce their observed positions with a rms scatter of 0.̋3 in a fixed flat ΛCDM cosmology, whereas the lack of spectroscopic information or the use of inaccurate photometric redshifts can lead to biases in the values of the model parameters. We find that the best-fit parametrization for the cluster total mass distribution is composed of an elliptical pseudo-isothermal mass distribution with a significant core for the overall cluster halo and truncated pseudo-isothermal mass profiles for the cluster galaxies. We show that by adding bona fide photometric-selected multiple images to the sample of spectroscopic families, one can slightly improve constraints on the model parameters. In particular, we find that the degeneracy between the lens total mass distribution and the underlying geometry of the Universe, which is probed via angular diameter distance ratios between the lens and sources and the observer and sources, can be partially removed. Allowing cosmological parameters to vary together with the cluster parameters, we find (at 68% confidence level) Ωm = 0.25+ 0.13-0.16 and w = −1.07+ 0.16-0.42 for a flat ΛCDM model, and Ωm = 0.31+ 0.12-0.13 and ΩΛ = 0.38+ 0.38-0.27 for a Universe with w = −1 and free curvature. Finally, using toy models mimicking the overall configuration of multiple images and cluster total mass distribution, we estimate the impact of the line-of-sight mass structure on the positional rms to be 0.̋3 ± 0. We argue that the apparent sensitivity of our lensing model to cosmography is due to the combination of the regular potential shape of RXC J2248, a large number of bona fide multiple images out to z = 6.1, and a relatively modest presence of intervening large-scale structure, as revealed by our spectroscopic survey.
We present a high-resolution dissection of the two-dimensional total mass distribution in the core of the Hubble Frontier Fields galaxy cluster MACS J0416.1−2403, at z = 0.396. We exploit HST/WFC3 ...near-IR (F160W) imaging, VLT/Multi Unit Spectroscopic Explorer spectroscopy, and Chandra data to separate the stellar, hot gas, and dark-matter mass components in the inner 300 kpc of the cluster. We combine the recent results of our refined strong lensing analysis, which includes the contribution of the intracluster gas, with the modeling of the surface brightness and stellar mass distributions of 193 cluster members, of which 144 are spectroscopically confirmed. We find that, moving from 10 to 300 kpc from the cluster center, the stellar to total mass fraction decreases from 12% to 1% and the hot gas to total mass fraction increases from 3% to 9%, resulting in a baryon fraction of approximatively 10% at the outermost radius. We measure that the stellar component represents ∼30%, near the cluster center, and 15%, at larger clustercentric distances, of the total mass in the cluster substructures. We subtract the baryonic mass component from the total mass distribution and conclude that within 30 kpc (∼3 times the effective radius of the brightest cluster galaxy) from the cluster center the surface mass density profile of the total mass and global (cluster plus substructures) dark-matter are steeper and that of the diffuse (cluster) dark-matter is shallower than an NFW profile. Our current analysis does not point to a significant offset between the cluster stellar and dark-matter components. This detailed and robust reconstruction of the inner dark-matter distribution in a larger sample of galaxy clusters will set a new benchmark for different structure formation scenarios.
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