We study relation between stellar mass and halo mass for high-mass halos using a sample of galaxy clusters with accurate measurements of stellar masses from optical and ifrared data and total masses ...from X-ray observations. We find that stellar mass of the brightest cluster galaxies (BCGs) scales as
M
*,BCG
∝ M
500
α
BCG
with the best fit slope of
α
BCG
≈ 0.4 ± 0.1. We measure scatter of
M
*,BCG
at a fixed
M
500
of ≈0.2 dex. We show that stellar mass-halo mass relations from abundance matching or halo modelling reported in recent studies underestimate masses of BCGs by a factor of ∼2−4. We argue that this is because these studies used stellar mass functions (SMF) based on photometry that severely underestimates the outer surface brightness profiles of massive galaxies. We show that
M
*
−M
relation derived using abundance matching with the recent SMF calibration by Bernardi et al. (2013) based on improved photometry is in a much better agreement with the relation we derive via direct calibration for observed clusters. The total stellar mass of galaxies correlates with total mass
M
500
with the slope of ≈0.6 ± 0.1 and scatter of 0.1 dex. This indicates that efficiency with which baryons are converted into stars decreases with increasing cluster mass. The low scatter is due to large contribution of satellite galaxies: the stellar mass in satellite galaxies correlates with
M
500
with scatter of ≈0.1 dex and best fit slope of α
sat
≈ 0.8 ± 0.1. We show that for a fixed choice of the initial mass function (IMF) total stellar fraction in clusters is only a factor of 3−5 lower than the peak stellar fraction reached in
M
≈ 10
12
M
⊙
halos. The difference is only a factor of ∼1.5−3 if the IMF becomes progressively more bottom heavy with increasing mass in early type galaxies, as indicated by recent observational analyses. This means that the overall efficiency of star formation in massive halos is only moderately suppressed compared to
L
*
galaxies and is considerably less suppressed than previously thought. The larger normalization and slope of the
M
*
−
M
relation derived in this study shows that feedback and associated suppression of star formation in massive halos should be weaker than assumed in most of the current semi-analytic models and simulations.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
ABSTRACT
We present the first sample of tidal disruption events (TDEs) discovered during the SRG all-sky survey. These 13 events were selected among X-ray transients detected in the 0° < l < 180° ...hemisphere by eROSITA during its second sky survey (2020 June 10 to December 14) and confirmed by optical follow-up observations. The most distant event occurred at z = 0.581. One TDE continued to brighten at least 6 months. The X-ray spectra are consistent with nearly critical accretion on to black holes of a few ×103 to $10^8\, \mathrm{ M}_\odot$, although supercritical accretion is possibly taking place. In two TDEs, a spectral hardening is observed 6 months after the discovery. Four TDEs showed an optical brightening apart from the X-ray outburst. The other nine TDEs demonstrate no optical activity. All 13 TDEs are optically faint, with Lg/LX < 0.3 (Lg and LX being the g band and 0.2–6 keV luminosity, respectively). We have constructed a TDE X-ray luminosity function, which can be fit by a power law with a slope of −0.6 ± 0.2, similar to the trend observed for optically selected TDEs. The total rate is estimated at (1.1 ± 0.5) × 10−5 TDEs per galaxy per year, an order of magnitude lower than inferred from optical studies. This suggests that X-ray bright events constitute a minority of TDEs, consistent with models predicting that X-rays can only be observed from directions close to the axis of a thick accretion disc formed from the stellar debris. Our TDE detection threshold can be lowered by a factor of ∼2, which should allow a detection of ∼700 TDEs by the end of the SRG survey.
The paper presents the simulation results of the mode propagation parameters in a circular waveguide consisting of two layers of right- and left-handed materials (Veselago media). The model tests ...allow to conclude that there are many magnetic modes with a significant deceleration of the phase velocity.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Abstract
The method of analytical modeling and simulation of technological processes is presented, which makes it possible to assess the influence of external factors on the operation of information ...and control systems. The application of this method to study the process of detecting pipeline defects by vibroacoustic control systems is considered. A mathematical model with automatic selection of the parameters of autocorrelation functions of random disturbances is proposed, which makes it possible to take into account the influence of natural and man-made noises on the detection process. The possibility of modeling the influence of random disturbances on the working processes of technological machines is also considered. The proposed simulation models are of practical value, since they allow one to study virtual prototypes of construction and road-building machinery in various modes and reduce the cost of performing expensive field experiments.
Abstract
The article deals with optimization issues in design of an automatic control system (ACS). The method of multicriteria optimization is presented, which combines simulation of ACS and ...optimization procedure based on a genetic algorithm and implemented by the MATLAB / Global Optimization Toolbox. The method of the generalized criterion composition based on the initial particular criteria is also proposed. The use of this generalized criterion makes it possible to reduce the complexity of determining the optimal parameters of the ACS and allows to take into account the constraints when searching for the optimal solution.
We present a probabilistic model built for the optical cross-match between the SRG/eROSITA X-ray sources and photometric data from the DESI Legacy Imaging Surveys. The model relies both on positional ...and photometric information on optical objects nearby X-ray sources and allows performing selection with precision and recall
(for
erg s
cm
). With this model, we calibrated positional error of the SRG/eROSITA sources detected in the Lockman Hole:
. The model will become a part of the SRGz system for data analysis of the X-ray data obtained from the all-sky SRG/eROSITA survey.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
For the first time, a fully neural approach has been proposed, capable of solving the optimization problem of routes of extremely large dimensions (~5000 points) with real-world constraints such as ...cargo capacity, time windows, and delivery sequencing. The proposed solution allows for rapid suboptimal problem solving for small and medium dimensions (<1000 points). Meanwhile, it outperforms heuristic approaches for tasks of extremely large dimensions (>1000 points), thereby representing a state-of-the-art (SotA) solution in the field of route optimization with real-world constraints and extremely large dimensions.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The vehicle routing problem with pickup and delivery is one of the most important problems in the context of global urban population growth. Although these kinds of small-size problems can be solved ...using various classical approaches, a fast (or real-time) route optimizer under real-world constraints (such as throughput and time window constraints) for medium- and large-size problems is still a challenge. In this work, we first successfully applied a deep reinforcement learning approach (a modified JAMPR model) to solve the capacitated pickup and delivery problem with time windows (CPDPTW). We obtained a robust model that gives a fast optimal solution for small- to medium-size problems and gives a fast suboptimal solution for large-size (>200) problems.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Recycled scrap and waste are used in the production of copper and copper alloys. Cable scrap containing impurities of non-ferrous and ferrous metals is often used as copper scrap. Herein, we propose ...a novel steam-air oxidation method for the purification of copper alloys. In this method, the melt surface was blown with a steam-air mixture supplied to the melting furnace using a specially manufactured device. Technological parameters ensuring the effective removal of iron, tin, lead, and zinc impurities from the copper melt were determined experimentally. The melt oxidation degree, oxidizer consumption, and duration of the transition of impurities into slag and the gas phase were found to be the key parameters affecting the remelting refining of copper scrap. The technological parameters for the oxidation refining of the melt were optimized using the evolutionary solution search method in order to improve the efficiency of the process and reduce the deoxidizer consumption. It was found that to achieve the maximum efficiency of copper refining, it is necessary to ensure the optimal steam-air oxidation of the melt with oxygen dissolved in it. The results demonstrated the applicability of steam-air oxidation in the refining of copper scrap containing more than 1.6% impurities (including iron, tin, lead, and zinc) to obtain copper melts with chemical compositions corresponding to grades M0 and M1.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The article describes an experimentally-based innovative technology for assessing the performance characteristic «Usability» of the information security system in the automated system of the digital ...educational environment. This characteristic consists of indicators: the structure of a typical operation, time index and probability rate. On the basis of the obtained results of the assessment of the listed indicators it is possible to choose an information security system for the designed digital educational environment.
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