16 research outputs found
Exploring the cosmological synergy between galaxy cluster and cosmic void number counts
Galaxy clusters and cosmic voids are the most extreme objects of our Universe
in terms of mass and size, tracing two opposite sides of the large-scale matter
density field. By studying their abundance as a function of their mass and
radius, respectively, i.e. the halo mass function (HMF) and void size function
(VSF), it is possible to achieve fundamental constraints on the cosmological
model. While the HMF has already been extensively exploited providing robust
constraints on the main cosmological model parameters (e.g. ,
and ), the VSF is still emerging as a viable and effective
cosmological probe. Given the expected complementarity of these statistics, in
this work we aim at estimating the costraining power deriving from their
combination. To achieve this goal, we exploit realistic mock samples of galaxy
clusters and voids extracted from state-of-the-art large hydrodynamical
simulations, in the redshift range . We perform an accurate
calibration of the free parameters of the HMF and VSF models, needed to take
into account the differences between the types of mass tracers used in this
work and those considered in previous literature analyses. Then, we obtain
constraints on and by performing a Bayesian Markov
Chain Monte Carlo analysis. We find that cluster and void counts represent
powerful independent and complementary probes to test the cosmological
framework. In particular, we found that the constraining power of the HMF on
and improves drastically with the VSF contribution,
increasing the constraint precision by a factor of about .Comment: 12 pages, 7 figures, submitted to MNRA
Slumped glass foils as substrate for adjustable x-ray optics
Thin glass modular mirrors are a viable solution to build future X-ray telescopes with high angular resolution and large collecting area. In our laboratories, we shape thin glass foils by hot slumping and we apply pressure to assist the replication of a cylindrical mould figure; this technology is coupled with an integration process able to damp low frequency errors and produces optics in the Wolter I configuration, typical for the X-ray telescopes. From the point of view of the hot slumping process, the efforts were focused in reducing low-, mid- and high- frequency errors of the formed Eagle glass foils. Some of our slumped glass foils were used for the development of active X-ray optics, where piezoelectric actuators are used to correct the slumped glass foil deviations from the ideal shape. In particular, they were used for the Adjustable X-raY optics for astrOnoMy project (AXYOM) developed in Italy, and the X-ray Surveyor mission, as developed at the Smithsonian Astrophysical Observatory / Center for Astrophysics (SAO/CfA) in USA. In this paper we describe the optimisation of the hot slumping process, comparing the results with the requirements of the considered active optics projects. Finally, since the present configuration of the Pennsylvania State University (PSU) coating equipment is limited to 100 x 100 mm2, the slumped glass foils used for the SAO project were cut from 200 x 200 mm2 to 100 x 100 mm2, and a low-frequency change was observed. A characterisation of the profile change upon cutting is presented
Performance Testing of a Large-Format Reflection Grating Prototype for a Suborbital Rocket Payload
The soft X-ray grating spectrometer on board the Off-plane Grating Rocket
Experiment (OGRE) hopes to achieve the highest resolution soft X-ray spectrum
of an astrophysical object when it is launched via suborbital rocket. Paramount
to the success of the spectrometer are the performance of the reflection
gratings populating its reflection grating assembly. To test current grating
fabrication capabilities, a grating prototype for the payload was fabricated
via electron-beam lithography at The Pennsylvania State University's Materials
Research Institute and was subsequently tested for performance at Max Planck
Institute for Extraterrestrial Physics' PANTER X-ray Test Facility. Bayesian
modeling of the resulting data via Markov chain Monte Carlo (MCMC) sampling
indicated that the grating achieved the OGRE single-grating resolution
requirement of at the 94% confidence level.
The resulting posterior probability distribution suggests that this
confidence level is likely a conservative estimate though, since only a finite
parameter space was sampled and the model could not constrain the upper
bound of to less than infinity. Raytrace simulations of the system found
that the observed data can be reproduced with a grating performing at
. It is therefore postulated that the behavior of the obtained
posterior probability distribution can be explained by a finite
measurement limit of the system and not a finite limit on . Implications
of these results and improvements to the test setup are discussed.Comment: 25 pages, 16 figures, preprint of an article accepted for publication
in the Journal of Astronomical Instrumentation \copyright 2020 [copyright
World Scientific Publishing Company]
[https://www.worldscientific.com/worldscinet/jai
Calibration of X-ray telescope prototypes at PANTER
We report a ground X-ray calibration of two X-ray telescope prototypes at the
PANTER X-ray Test Facility, of the Max-Planck-Institute for Extraterrestrial
Physics, in Neuried, Germany. The X-ray telescope prototypes were developed by
the Institute of Precision Optical Engineering (IPOE) of Tongji University, in
a conical Wolter-I configuration, using thermal glass slumping technology.
Prototype #1 with 3 layers and Prototype #2 with 21 layers were tested to
assess the prototypes' on-axis imaging performance. The measurement of
Prototype #1 indicates a Half Power Diameter (HPD) of 82" at 1.49 keV. As for
Prototype #2, we performed more comprehensive measurements of on-axis angular
resolution and effective area at several energies ranging from 0.5-10 keV. The
HPD and effective area are 111" and 39 cm^2 at 1.49 keV, respectively, at which
energy the on-axis performance of the prototypes is our greatest concern.Comment: 11 pages, 9 figure
Design and advancement status of the Beam Expander Testing X-ray facility (BEaTriX)
The BEaTriX (Beam Expander Testing X-ray facility) project is an X-ray apparatus under construction at INAF/OAB to generate a broad (200Ì60 mm2), uniform and low-divergent X-ray beam within a small lab (6Ì15 m2). BEaTriX will consist of an X-ray source in the focus a grazing incidence paraboloidal mirror to obtain a parallel beam, followed by a crystal monochromation system and by an asymmetrically-cut diffracting crystal to perform the beam expansion to the desired size. Once completed, BEaTriX will be used to directly perform the quality control of focusing modules of large X-ray optics such as those for the ATHENA X-ray observatory, based on either Silicon Pore Optics (baseline) or Slumped Glass Optics (alternative), and will thereby enable a direct quality control of angular resolution and effective area on a number of mirror modules in a short time, in full X-ray illumination and without being affected by the finite distance of the X-ray source. However, since the individual mirror modules for ATHENA will have an optical quality of 3-4 arcsec HEW or better, BEaTriX is required to produce a broad beam with divergence below 1-2 arcsec, and sufficient flux to quickly characterize the PSF of the module without being significantly affected by statistical uncertainties. Therefore, the optical components of BEaTriX have to be selected and/or manufactured with excellent optical properties in order to guarantee the final performance of the system. In this paper we report the final design of the facility and a detailed performance simulation
X-ray tests of the ATHENA mirror modules in BEaTriX: from design to reality
The BEaTriX (Beam Expander Testing X-ray) facility is now operative at the INAF-Osservatorio Astronomico Brera (Merate, Italy). This facility has been specifically designed and built for the X-ray acceptance tests (PSF and Effective Area) of the ATHENA Silicon Pore Optics (SPO) Mirror Modules (MM). The unique setup creates a parallel, monochromatic, large X-ray beam, that fully illuminates the aperture of the MMs, generating an image at the ATHENA focal length of 12 m. This is made possible by a microfocus X-ray source followed by a chain of optical components (a paraboloidal mirror, 2 channel cut monochromators, and an asymmetric silicon crystal) able to expand the X-ray beam to a 6 cm Ă 17 cm size with a residual divergence of 1.5 arcsec (vertical) Ă 2.5 arcsec (horizontal). This paper reports the commissioning of the 4.5 keV beam line, and the first light obtained with a Mirror Module
Optical simulations for the BEaTriX X-ray facility: a brief performance and alignment tolerance study
Parameter identification of degrading and pinched hysteretic systems using a modified BoucâWen model
The BoucâWen (BW) model is a successful differential equations model used to describe a wide range of nonlinear hysteretic systems. However, it is unable to describe force degradation, stiffness degradation and pinching effects. Therefore, Baber and Noori proposed a generalisation, developing the BoucâWenâBaberâNoori (BWBN) model. Nevertheless, it is composed of many parameters and complex pinching and degrading functions. Thus, it is necessary to develop a simpler and reliable model to be used for practical applications. In this paper, a modified BW model is proposed. It involves a more direct physical meaning of each parameter and allows achieving a substantial reduction of computational effort and numerical deficiencies. This is obtained through simpler pinching and degrading functions that entail a decrease of the number of parameters. The result is a straightforward model, capable of predicting the behaviour of degrading and pinched hysteretic systems. An application of the proposed scheme to a real case is also presented, in which reinforced concrete bridge piers that were physically tested in the laboratory are considered. The forceâdisplacement data are used to perform the identification process of the model parameters via a Genetic Algorithm. The numerical results are accurate since they coincide with the experimental ones
Development and Validation of New Bouc-Wen Data-Driven Hysteresis Model for Masonry Infilled RC Frames
During the last years, several mechanics-based macromodels have been proposed to assess the cyclic response of infilled RC frames. However, the uncertainties behind the assumptions on damage and failure mechanisms compromise the reliability of such approaches. For this reason, this paper proposes a new data-driven hysteresis model for the cyclic response of infilled RC frames. The infill panel is schematized as a single-degree-of-freedom element, whose constitutive law is given by the proposed hysteresis model. The model combines a degrading Bouc-Wen element with a slip-lock element, which is introduced specifically to reproduce the pinching effect due to crack openings in the masonry panel. The parameters governing the model have clear physical meanings and are calibrated on the basis of an experimental data set of cyclic responses of single-story single-bay RC infilled frames. The calibrations are carried out by means of a genetic algorithm-based optimization. Analytical correlation laws linking the model parameters with geometric and mechanical properties of the RC infilled frame are proposed and validated by blind validation tests. Results show adequate accuracy of the model in reproducing the cyclic response of infilled frames characterized by significantly different geometrical and mechanical features. The model is defined by a smooth analytical hysteresis law, with great advantages regarding numerical stability and computational effort. This makes it suitable for dynamic and stochastic simulations