scholarly journals Morphology of relaxed and merging galaxy clusters: analytical models for monolithic Minkowski functionals

2021 ◽  
Vol 502 (3) ◽  
pp. 3911-3921
Author(s):  
C Schimd ◽  
M Sereno
Keyword(s):  
Galaxy Clusters ◽  
Classification Scheme ◽  
Morphological Diversity ◽  
Analytical Models ◽  
Minkowski Functionals ◽  
Geometric Models ◽  
Analytical Formulas ◽  
Mass Assembly ◽  
Cluster Pair

ABSTRACT Galaxy clusters exhibit a rich morphology during the early and intermediate stages of mass assembly, especially beyond their boundary. A classification scheme based on shapefinders deduced from the Minkowski functionals is examined to fully account for the morphological diversity of galaxy clusters, including relaxed and merging clusters, clusters fed by filamentary structures, and cluster-pair bridges. These configurations are conveniently treated with idealized geometric models and analytical formulas, some of which are novel. Examples from CLASH and LC2 clusters and observed cluster-pair bridges are discussed.

scholarly journals On the accretion history of galaxy clusters: temporal and spatial distribution

2020 ◽  
Vol 499 (2) ◽  
pp. 2303-2318
Author(s):  
David Vallés-Pérez ◽  
Susana Planelles ◽  
Vicent Quilis
Keyword(s):  
Dark Matter ◽  
Galaxy Clusters ◽  
Adaptive Mesh Refinement ◽  
Adaptive Mesh ◽  
Temporal And Spatial Distribution ◽  
Mass Growth ◽  
Accretion Flows ◽  
Novel Approach ◽  
Mass Assembly ◽  
Gas Accretion

ABSTRACT We analyse the results of an Eulerian adaptive mesh refinement cosmological simulation in order to quantify the mass growth of galaxy clusters, exploring the differences between dark matter and baryons. We have determined the mass assembly histories (MAHs) of each of the mass components and computed several proxies for the instantaneous mass accretion rate (MAR). The mass growth of both components is clearly dominated by the contribution of major mergers, but high MARs can also occur during smooth accretion periods. We explored the correlations between MARs, merger events, and clusters’ environments, finding the mean densities in 1 ≤ r/R200m ≤ 1.5 to correlate strongly with Γ200m in massive clusters that undergo major mergers through their MAH. From the study of the dark matter velocity profiles, we find a strong anticorrelation between the MAR proxies Γ200m and α200m. Last, we present a novel approach to study the angularly resolved distribution of gas accretion flows in simulations, which allows to extract and interpret the main contributions to the accretion picture and to assess systematic differences between the thermodynamical properties of each of these contributions using multipolar analysis. We have preliminarily applied the method to the best numerically resolved cluster in our simulation. Amongst the most remarkable results, we find that the gas infalling through the cosmic filaments has systematically lower entropy compared to the isotropic component, but we do not find a clear distinction in temperature.

scholarly journals A giant radio bridge connecting two clusters in Abell 1758

2020 ◽  
Author(s):  
A Botteon ◽  
R J van Weeren ◽  
G Brunetti ◽  
F de Gasperin ◽  
H T Intema ◽  
...  
Keyword(s):  
Radio Emission ◽  
Galaxy Clusters ◽  
Large Scale ◽  
Synchrotron Emission ◽  
X Ray ◽  
Compressed Gas ◽  
Order Of Magnitude ◽  
Thermal Phenomena ◽  
Cluster Pair ◽  
Radio Halos

Abstract Collisions between galaxy clusters dissipate enormous amounts of energy in the intra-cluster medium (ICM) through turbulence and shocks. In the process, Mpc-scale diffuse synchrotron emission in form of radio halos and relics can form. However, little is known about the very early phase of the collision. We used deep radio observations from 53 MHz to 1.5 GHz to study the pre-merging galaxy clusters A1758N and A1758S that are ∼2 Mpc apart. We confirm the presence of a giant bridge of radio emission connecting the two systems that was reported only tentatively in our earlier work. This is the second large-scale radio bridge observed to date in a cluster pair. The bridge is clearly visible in the LOFAR image at 144 MHz and tentatively detected at 53 MHz. Its mean radio emissivity is more than one order of magnitude lower than that of the radio halos in A1758N and A1758S. Interestingly, the radio and X-ray emissions of the bridge are correlated. Our results indicate that non-thermal phenomena in the ICM can be generated also in the region of compressed gas in-between infalling systems.

The dependence of coordinate measurements error of the geometric elements shape characteristics of products on the control points number

Metrologiya ◽  
2021 ◽  
pp. 4-21
Author(s):  
M. F. Danilov ◽  
A. P. Ivanova
Keyword(s):  
A Priori ◽  
Analytical Models ◽  
Confidence Probability ◽  
Control Points ◽  
Regular Structures ◽  
Coordinate Metrology ◽  
Analytical Formulas ◽  
Coordinate Measurements ◽  
Shape Characteristics ◽  
Geometric Elements

The issues of estimating the error of coordinate measurements of the shape characteristics of geometric elements of products depending on the number of control points, taking into account a given confidence probability, are considered. Analytical models are proposed for estimating the error based on a priori data, similar to estimating uncertainty by type B. The correspondence of model and experimental results is verified by the Monte Carlo method using a specially developed program in VBA and the library functions of the Statistical Analysis package of the Microsoft Excel program. Such a characteristic of the shape of the part as roundness is investigated. The influence of the parameters of regular structures associated with the features of the technological processes of manufacturing the part on the parameters of the distribution function of the coordinates of the control points is revealed. Fourier analysis is used to identify and quantify regular structures on the surface of the part. The sources of error that have a significant impact on the results of measurements of the shape characteristics of geometric elements of products are given. Based on the results of statistical calculations, the dependence of the measurement error of the shape characteristics on the number of control points is analyzed, the scope of application of analytical formulas for estimating the error of single measurements for a given confidence probability is determined. The article is intended for specialists in the field of practical coordinate metrology and related fields.

scholarly journals An analytical model for predicting the natural frequency of retaining structures

2020 ◽  
Vol 15 (1) ◽  
pp. 7-12
Author(s):  
Lyazid Guechi ◽  
Smaïn Belkacemi
Keyword(s):  
Natural Frequency ◽  
Analytical Model ◽  
Current Model ◽  
Accurate Determination ◽  
Analytical Models ◽  
Retaining Structures ◽  
The Earth ◽  
Earth Pressures ◽  
Analytical Formulas ◽  
Failure Wedge

Abstract The importance of the retaining structures is crucial in geotechnical engineering and the accurate determination of static and seismic earth pressures and natural frequency is important for study the dynamic behavior of these structures. Usually analytical formulas which do not consider the earth pressures behind retaining structure are used. An analytical model for predicting the natural frequency of retaining structures including the earth pressures by failure wedges is proposed in the present analysis. The model considers the effect of Coulomb and Mononobe Okabe failure wedges. Backfill material is considered in the analysis as cohesionless. The failure wedge is an important factor which should be considered in determining the natural frequency of retaining structures. As the weight of failure wedge increases the natural frequency decreases significantly. The current model is validated using several analytical models reported in the literature of the earlier researcher.

scholarly journals The past history of galaxy clusters told by their present neighbours

2020 ◽  
Vol 496 (4) ◽  
pp. 5139-5148
Author(s):  
Jenny G Sorce ◽  
Stefan Gottlöber ◽  
Gustavo Yepes
Keyword(s):  
Galaxy Clusters ◽  
Past History ◽  
Virgo Cluster ◽  
Coma Cluster ◽  
The Past ◽  
Formation History ◽  
History Of ◽  
Observable Data ◽  
The Mean ◽  
Mass Assembly

ABSTRACT Galaxy clusters can play a key role in modern cosmology, provided their evolution is properly understood. However, observed clusters give us only a single timeframe of their dynamical state. Therefore, finding present observable data of clusters that are well correlated to their assembly history constitutes an inestimable tool for cosmology. Former studies correlating environmental descriptors of clusters to their formation history are dominated by halo mass–environment relations. This paper presents a mass-free correlation between the present neighbour distribution of cluster-size haloes and the latter mass assembly history. From the Big Multidark simulation, we extract two large samples of random haloes with masses ranging from Virgo to Coma cluster sizes. Additionally, to find the main environmental culprit for the formation history of the Virgo cluster, we compare the Virgo-size haloes to 200 Virgo-like haloes extracted from simulations that resemble the local Universe. The number of neighbours at different cluster-centric distances permits discriminating between clusters with different mass accretion histories. Similarly to Virgo-like haloes, clusters with numerous neighbours within a distance of about two times their virial radius experience a transition at z ≈ 1 between an active period of mass accretion, relative to the mean, and a quiet history. In contrary, clusters with few neighbours share an opposite trend: from passive to active assembly histories. Additionally, clusters with massive companions within about four times their virial radius tend to have recent active merging histories. Therefore, the radial distribution of cluster neighbours provides invaluable insights into the past history of these objects.

scholarly journals New calculation method for tube cross-flow heat exchangers

2021 ◽  
Vol 323 ◽  
pp. 00032
Author(s):  
Katarzyna Węglarz ◽  
Dawid Taler ◽  
Jan Taler ◽  
Mateusz Marcinkowski
Keyword(s):  
Heat Exchangers ◽  
Cross Flow ◽  
Analytical Models ◽  
Temperature Dependent ◽  
Flow Tube ◽  
Thermal Calculations ◽  
Analytical Formulas ◽  
Flow Heat ◽  
Control Volumes ◽  
Good Agreement

A new method for thermal calculations of the cross-flow tube heat exchangers was proposed. The temperature of both fluids and the wall temperature are determined. The heat exchanger is divided into control volumes, in which outlet fluid temperatures are calculated by closed analytical formulas. Two examples of the application of the method for the calculation of two-pass cross-co-current and cross-countercurrent superheaters were presented. An exact analytical model was also developed for both superheaters to estimate the accuracy of the proposed method. The results of the superheater calculations using the developed method are in good agreement with the results obtained by the exact analytical models. The proposed method can be used to calculate heat exchangers with a complicated flow system in which the physical properties of fluids are temperature-dependent.

Analytical model of the diffuse sound transmission loss of finite double panel structures

2021 ◽  
Vol 263 (5) ◽  
pp. 1723-1732
Author(s):  
Javier Vazquez Torre ◽  
Jonas Brunskog ◽  
Vicente Cutanda Henriquez
Keyword(s):  
Analytical Model ◽  
Transmission Loss ◽  
Sound Transmission ◽  
Analytical Models ◽  
Sound Insulation ◽  
Variational Technique ◽  
Sound Transmission Loss ◽  
Single Leaf ◽  
Audible Frequency ◽  
Analytical Formulas

An analytical model for the forced sound transmission loss of finite single-leaf walls using a variational technique was previously developed and validated. As the double panel is one of the most used structures in building acoustics, the aim of this paper is to extend the analytical model to consider double panel structures. Analytical formulas for the forced part of the airborne sound insulation of finite sized double panel structures are derived using a variational technique based on the integral-differential equation of the fluid loaded panels. The formulas are valid in the entire audible frequency range. The results are compared to alternative analytical models and measurements, with reasonable agreement.

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