572 research outputs found
A joint SZ-X-ray-optical analysis of the dynamical state of 288 massive galaxy clusters
No full textWe use imaging from the first three years of the Dark Energy Survey to characterize the dynamical state of 288 galaxy clusters at 0.1 ≲ z ≲ 0.9 detected in the South Pole Telescope (SPT) Sunyaev-Zeldovich (SZ) effect survey (SPT-SZ). We examine spatial offsets between the position of the brightest cluster galaxy (BCG) and the centre of the gas distribution as traced by the SPT-SZ centroid and by the X-ray centroid/peak position from Chandra and XMM data. We show that the radial distribution of offsets provides no evidence that SPT SZ-selected cluster samples include a higher fraction of mergers than X-ray-selected cluster samples. We use the offsets to classify the dynamical state of the clusters, selecting the 43 most disturbed clusters, with half of those at z ≳ 0.5, a region seldom explored previously. We find that Schechter function fits to the galaxy population in disturbed clusters and relaxed clusters differ atz >0.55 but not at lower redshifts. Disturbed clusters atz >0.55 have steeper faint-end slopes and brighter characteristic magnitudes. Within the same redshift range, we find that the BCGs in relaxed clusters tend to be brighter than the BCGs in disturbed samples, while in agreement in the lower redshift bin. Possible explanations includes a higher merger rate, and a more efficient dynamical friction at high redshift. The red-sequence population is less affected by the cluster dynamical state than the general galaxy population. © 2020 The Author(s)
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The mass and galaxy distribution around SZ-selected clusters
No full textWe present measurements of the radial profiles of the mass and galaxy number density around Sunyaev–Zel’dovich (SZ)-selected clusters using both weak lensing and galaxy counts. The clusters are selected from the Atacama Cosmology Telescope Data Release 5 and the galaxies from the Dark Energy Survey Year 3 data set. With signal-to-noise ratio of 62 (45) for galaxy (weak lensing) profiles over scales of about 0.2–20 h-1 Mpc, these are the highest precision measurements for SZ-selected clusters to date. Because SZ selection closely approximates mass selection, these measurements enable several tests of theoretical models of the mass and light distribution around clusters. Our main findings are: (1) The splashback feature is detected at a consistent location in both the mass and galaxy profiles and its location is consistent with predictions of cold dark matter N-body simulations. (2) The full mass profile is also consistent with the simulations. (3) The shapes of the galaxy and lensing profiles are remarkably similar for our sample over the entire range of scales, from well inside the cluster halo to the quasilinear regime. We measure the dependence of the profile shapes on the galaxy sample, redshift, and cluster mass. We extend the Diemer & Kravtsov model for the cluster profiles to the linear regime using perturbation theory and show that it provides a good match to the measured profiles. We also compare the measured profiles to predictions of the standard halo model and simulations that include hydrodynamics. Applications of these results to cluster mass estimation, cosmology, and astrophysics are discussed. © 2021 The Author(s).Immediate accessThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]
The mass and galaxy distribution around SZ-selected clusters
No full textWe present measurements of the radial profiles of the mass and galaxy number density around Sunyaev–Zel’dovich (SZ)-selected clusters using both weak lensing and galaxy counts. The clusters are selected from the Atacama Cosmology Telescope Data Release 5 and the galaxies from the Dark Energy Survey Year 3 data set. With signal-to-noise ratio of 62 (45) for galaxy (weak lensing) profiles over scales of about 0.2–20 h-1 Mpc, these are the highest precision measurements for SZ-selected clusters to date. Because SZ selection closely approximates mass selection, these measurements enable several tests of theoretical models of the mass and light distribution around clusters. Our main findings are: (1) The splashback feature is detected at a consistent location in both the mass and galaxy profiles and its location is consistent with predictions of cold dark matter N-body simulations. (2) The full mass profile is also consistent with the simulations. (3) The shapes of the galaxy and lensing profiles are remarkably similar for our sample over the entire range of scales, from well inside the cluster halo to the quasilinear regime. We measure the dependence of the profile shapes on the galaxy sample, redshift, and cluster mass. We extend the Diemer & Kravtsov model for the cluster profiles to the linear regime using perturbation theory and show that it provides a good match to the measured profiles. We also compare the measured profiles to predictions of the standard halo model and simulations that include hydrodynamics. Applications of these results to cluster mass estimation, cosmology, and astrophysics are discussed. © 2021 The Author(s)
Refined modelling of the radio SZ signal: kinematic terms, relativistic temperature corrections, and anisotropies in the radio background
No full textA significant cosmological radio background will inevitably lead to a radio Sunyaev-Zeldovich (SZ) effect. In the simplest limit, the combined signal from the scattered radio and cosmic microwave background exhibits a null at around ν 735 MHz. Here, we show that kinematic and relativistic temperature corrections to this radio SZ signal are easily calculable. We treat both the cluster and observer motion, and the scattering of anisotropies in the radio background, highlighting how the spectrum of the radio SZ effect is affected in each case. Although relativistic temperature corrections only enter at the level of a few per cent, our expressions allow high-precision modelling of these terms. By measuring the SZ signal around the radio null, one is in principle able to place constraints on the properties of a cosmological radio background. A combination with standard SZ measurements from large cluster samples could provide a promising avenue towards breaking degeneracies between different contributions. Stacking analyses can reduce the effect of kinematic corrections and dipolar anisotropies in the radio background, thereby providing a way to constrain the redshift dependence of the average radio background. Our qualitative discussion is meant to give an analytic understanding of the various effects and also motivate further studies with the aim to obtain quantitative forecasts of their observability. At this stage, a detection of the corrections seems rather futuristic, but the advent of large SZ and X-ray cluster samples could drastically improve our ability to disentangle various effects. © 2022 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society
Minimizing the condition number of a positive definite matrix by completion
No full textElsner L, He C, Mehrmann V. Minimizing the condition number of a positive definite matrix by completion. Numerische Mathematik. 1994;69(1):17-23.We consider the problem of minimizing the spectral condition number of a positive definite matrix by completion: [GRAPHICS] where A is an n x n Hermitian positive definite matrix, B a p x n matrix and X is a free p x p Hermitian matrix. We reduce this problem to an optimization problem for a convex function in one variable. Using the minimal solution of this problem we characterize the complete set of matrices that give the minimum condition number
Az „Sz Programpont" : Teleki Pál egy kevésbé ismert reformtervezete
No full textThe present study strives to examine a less know reform plan, the so-called „SZ agenda” from the second term (1939–1941) of PM Pál Teleki. The file labeled as „highly classified”, which turned up in the secretary of the foreign office, Elemér Újpétey’s legacy, encompasses a series of papers comprising a complete plan to reform the public administration, the government, and the economy. None of these papers indicates neither the name of its author nor the date of its creation, nonetheless it is fair to assume that they were laid down around November/December of 1940, and that the Service for National Policy, which used to orchestrate Teleki’s secret domestic actions, was hugely involved in their making. The most important piece of these papers concentrates on the so-called State Staff, which, at its core, would have been an organization akin to the Council of Ministers assisting the PM and the government. An organization of this kind could have worked as a kind of shadow government in the event of a possible German occupation. By and large, these papers reveal that the outlined reforms were interrelated with Teleki’s corporatist ideas, nevertheless their paramount importance was to beef up an independent and sovereign Hungary first and foremost vis-à-vis the Third Reich. It is uncharted, which stage of its realization the „SZ agenda” arrived at, but it is fairly feasible that the main hurdle to its implementation was Pál Teleki’s death on April 3, 1941
Author Correction: Differential epigenetic reprogramming in response to specific endocrine therapies promotes cholesterol biosynthesis and cellular invasion
No full textThis Article omits a declaration from the Competing Interests statement, which should have included the following: ‘One of the authors, Y.L., is an editor on the staff of Nature Communications, but was not in any way involved in the journal review process. The other authors declare no competing interests.’ Also, the Article contains an error in the name of the author Alba Rodriguez-Meira, which is incorrectly given as Alba Meira. These errors have not been corrected in either the PDF or HTML versions of the Article. © 2019, The Author(s)
Agent Based Test and Repair of Distributed Systems
No full textThis article demonstrates how to use intelligent agents for testing and repairing a distributed system, whose elements may or may not have embedded BIST (Built-In Self-Test) and BISR (Built-In Self-Repair) facilities. Agents are software modules that perform monitoring, diagnosis and repair of the faults. They form together a society whose members communicate, set goals and solve tasks. An experimental solution is presented, and future developments of the proposed approach are explore
CHANGES IN THE STRUCTURE OF AGRICULTURAL PRODUCTION, FARM STRUCTURE AND INCOME IN HUNGARY IN THE PERIOD OF 2004-2006
No full textThis study reviews the major changes in Hungarian agriculture that occurred between 2004 and 2006. Subjects investigated will include the structural shift towards crop production, the drastic decrease in the foreign food trade balance, and agricultures deteriorating capacity to sustain and retain a rural population. (Hereinafter: sustaining and retaining capacity of agriculture). The author will diagnose related problems, but will not offer any solutions. Nevertheless, he will present a perspective stipulating that Hungarian agricultures chronic problems require an agricultural strategy based on political consensus.EU accession, structural change, foreign food trade, sustaining and retaining capacity of agriculture, agricultural strategy, Farm Management,
[[alternative]]The Effects of Web-Assisted Instruction of LEGO Dacta on Elementary Students' Problem- Solving
No full text[[abstract]]The purpose of this study was to explore the effects of the Web- assisted instruction of LEGO Dacta on elementary students' problem- solving attitude. The author-designed Web-assisted course of Lego Dacta were developed according to the related references. A pre- and post-test quasi-experimental design was employed to measure the differences of students' problem- solving attitude under the conditions of two different teaching methods. The major results of this research were as follows:
1. There was a significant improvement in problem solving attitude of the experimental group students who received the Web-assisted course of Lego Dacta.
2. There was no difference in problem solving attitude between the experimental group students and the control group students.
3. Most of the experimental group students thought that the Web-assisted course of Lego Dacta was good and could promote their learning motivation.
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