Dust in galaxy clusters

The conditions for the destruction of dust in hot gas in galaxy clusters are investigated. It is argued that extinction measurements can be subject to selection effects, hindering their use in obtaining trustworthy estimates of dust masses in clusters. It is shown, in particular, that the ratio of the dust mass to the extinction M _d /S _d increases as dust grains are disrupted, due to the rapid destruction of small grains. Over long times, this ratio can asymptotically reach values a factor of three higher than the mean value in the interstellar medium in the Galaxy. This lowers dust-mass estimates based on measurements of extinction in galaxy clusters. The characteristic lifetime of dust in hot cluster gas is determined by its possible thermal isolation by the denser medium of gas fragments within which the dust is ejected from galaxies, and can reach 100–300 million years, depending on the kinematics and morphology of the fragments. As a result, the mass fraction of dust in hot cluster gas can reach 1–3% of the Galactic value. Over its lifetime, dust can also be manifest through its far-infrared emission. The emission characteristics of the dust change as it is disrupted, and the ratio of the fluxes at 350 and 850 μm can increase appreciably. This can potentially serve as an indicator of the state of the dust and ambient gas.     

Cosmological tests and the evolution of extragalactic objects

The results of several cosmographic tests of the standard ΛCDM model taking into account evolution and a “tired-light” model without evolution are compared. Physical tests and observations of the microwave background are also considered. Arguments supporting each of these models are presented. The general conclusion is that it is not possible to unambiguously identify a preferred cosmological model based on the currently available observational data. The nature of the redshift of spectral lines emitted by extragalactic objects is discussed. Possibilities for further studies are also briefly noted.     

The origin of intergalactic stars in galaxy clusters

The paper analyzes possible origins of stars located in intergalactic space that are not bound to specific galaxies, which comprise 15–50% of all stars in galaxy clusters. Some such stars can form in streams of intergalactic gas flowing around gas-rich disk galaxies moving in the cluster. Others may be the products of the decay of young, low-mass, spheroidal galaxies after the loss of their gaseous components during an initial burst of star formation. The decay of low-mass disk galaxies moving at high speeds after they have lost their gaseous components due to the pressure of the incident flow of dense intergalactic gas is possible in the cluster core. The largest fraction of intergalactic stars are probably produced by the partial disruption of galaxies as a result of close passages, collisions, or mergers. Collisions of low-mass, gas-rich galaxies are especially good suppliers of intergalactic stars. Both stars from decaying stellar components of galaxies and stars arising in the gaseous components of colliding galaxies can be supplied to the intergalactic medium. The merger of galaxies harboring supermassive black holes in their nuclei could lead to the partial or total disruption of these galaxies during the deceleration of the binary black hole that is formed during the merger. An enhanced density of intergalactic stars is observed in the cores of galaxy clusters, underscoring the role of galaxy collisions in the formation of the intergalactic stellar population, since the frequency of galaxy collisions grows with their density.     

Proper motions of open star clusters and the rotation rate of the galaxy

The mean proper motions of 167 Galactic open clusters with radial-velocity measurements are computed from the data of the Tycho-2 catalog using kinematic and photometric cluster membership criteria. The resulting catalog is compared to the results of other studies. The new proper motions are used to infer the Galactic rotation rate at the solar circle, which is found to be ω₀=+24.6±0.8 km s^?1 kpc^?1. Analysis of the dependence of the dispersion of ω₀ estimates on heliocentric velocity showed that even the proper motions of clusters with distances r>3 kpc contain enough useful information to be used in kinematic studies demonstrating that the determination of proper motions is quite justified even for very distant clusters.     

Supermassive black holes and central star clusters: Connection with the host galaxy kinematics and color

The relationship between the masses of the central, supermassive black holes (M _bh) and of the nuclear star clusters (M _nc) of disk galaxies with various parameters galaxies are considered: the rotational velocity at R = 2 kpc V ₍₂₎, the maximum rotational velocity V _max, the indicative dynamical mass M ₂₅, the integrated mass of the stellar populationM _*, and the integrated color index B-V. The rotational velocities andmasses of the central objects were taken from the literature. ThemassM _nc correlatesmore closely with the kinematic parameters and the disk mass than M _bh, including with the velocity V _max, which is closely related to the virial mass of the dark halo. On average, lenticular galaxies are characterized by higher massesM _bh compared to other types of galaxies with similar characteristics. The dependence of the blackhole mass on the color index is bimodal: galaxies of the red group (red-sequence) with B-V >0.6–0.7 which are mostly early-type galaxies with weak star formation, differ appreciably from blue galaxies, which have higher values of M _nc and M _bh. At the dependences we consider between the masses of the central objects and the parameters of the host galaxies (except for the dependence of M _bh on the central velocity dispersion), the red-group galaxies have systematically higher M _bh values, even when the host-galaxy parameters are similar. In contrast, in the case of nuclear star clusters, the blue and red galaxies form unified sequences. The results agree with scenarios in which most red-group galaxies form as a result of the partial or complete loss of interstellar gas in a stage of high nuclear activity in galaxies whose central black-hole masses exceed 10⁶?10⁷ M _⊙ (depending on the mass of the galaxy itself). The bulk of disk galaxies with M _bh > 10⁷ M _⊙ are lenticular galaxies (types S0, E/S0) whose disks are practically devoid of gas.     

The dynamical evolution of galaxy clusters taking into account the deceleration of disk galaxies by the gaseous component of the cluster

Numerical simulations of the dynamical evolution of a galaxy cluster in the framework of the N-body problem taking into account dark matter are presented. These simulations are aimed at studying the role of intergalactic gas in the cluster (the ICM) in the formation of a central, supermassive cD galaxy. The numerical models indicate that deceleration of the galaxies by intergalactic gas supports the observed high temperature of this gas, and accelerates the formation of a supermassive cD galaxy in the cluster core. The accretion of interstellar gas by the cluster core can support a high accretion rate by the central, supermassive black hole associated with the nucleus of the cD galaxy. As a result, this nucleus harbors a bright quasar. The mass of the black hole can grow with time to values 10¹⁰ M _⊙, as are observed for the brightest quasars.     

Cosmological Constraints on a Temporal Variation of the Proton-to-electron Mass Ratio based on the Red-shifted Lines of Extragalactic Argonium

Astronomy Reports - The sensitivity coefficients of the argonium ground $${{X}^{1}}{{\Sigma }^{ + }}$$ -state rotational lines with respect to the reduced molecular mass $$\mu $$ are evaluated...     

A revision of the meteorite based cosmic abundance of boron

Analyses of meteorites for B abundances have shown that many chondrites are contaminated with terrestrial B, producing erroneously high meteoritic abundances of this element. Boron concentrations in freshly prepared interior samples are significantly lower than they are in samples with unknown or unspecified terrestrial histories. An estimate of the cosmic abundance based upon the analyses of 8 interior samples of 2 carbonaceous chondrites and 1 interior sample of each of 8 ordinary chondrites is a factor of 6.7 less than the previous low estimate. Our revised value, 3.0 B/10¹⁰H, is in excellent agreement with estimates based on observations of the solar photosphere. There is no longer a need to consider processes that enrich B in carbonaceous chondrites or deplete it in the sun. Relative meteoritic abundances of Li, Be and B are now in general agreement with models of nucleosynthesis of these light elements by galactic cosmic ray induced spallation.     

基于电?磁法联合勘探的火烧区范围及富水性的预测

为精确查明矿区火烧岩体的分布范围及其富水程度,综合考虑地质体电?磁性特征,组合一套新型火烧区边界及富水性预测勘探手段。采用高精度磁测、瞬变电磁法、高密度电法3种物探方法联合勘探,将其应用于新疆沙吉海一号井田火烧区勘探,并与之前物探结果进行对比。结果表明,火烧区南部边界较原勘探边界发生较小移动;研究区总体富水性较弱,富水区主要集中在火烧区南部边界及以南,在B₁₀煤层附近圈定了9个火烧富水区,编号为Y1—Y9;拟设计钻孔位置均较合理,为下一步钻探施工提供可靠的物探资料依据。多种物探方法相互结合验证性较好,为今后火烧岩地区火烧范围及富水性探查提供实践依据。      

Significance tests for multivariate normality of clusters from branching patterns in dendrograms

A significance test is presented for whether, based on levels of branches in a dendrogram, a cluster is from a multivariate normal distribution. The method compares the observed cumulative graph of number of branches with a graph derived from a simple logistic function. Provided the number of objects or variables is not small, the difference between graphs can be tested by the Kolmogorov-Smirnov, Cramér-von Mises, and Lilliefors statistics.Logistic functions were obtained by simulation and are available for three similarity measures: (1) Euclidean distances, (2) squared Euclidean distances, and (3) simple matching coefficients, and for five cluster methods: (1) WPGMA, (2) UPGMA, (3) single linkage (or minimum spanning trees), (4) complete linkage, and (5) Ward's increase in sums of squares. For simple matching coefficient, the mean intracluster similarity also is required.The method allows a test of whether the dendrogram could be from a cluster of smaller dimensionality due to character correlations. Good fit of the data to abnormally large or small dimensionality provides an important warning to interpretation of the dendrogram. Quantiles of test statistics were found by simulation to be well-approximated by logistic functions. The Lilliefors test is recommended for general use; if a conservative test is required, the two-tailed Kolmogorov-Smirnov test is most suitable. The method is suitable for use with a hand calculator, and a computer program for it is available from the author.     

Comparison of the luminosity functions of open clusters based on USNO-A1 data

The luminosity and mass functions of a group of Galactic open clusters are constructed by applying a statistical method to photometric data from the USNO-A1 catalog. Despite some limitations, this catalog can be used for statistical analyses in Galactic astronomy. Pairwise comparisons of the derived cluster luminosity functions are performed for five age intervals. The differences between the luminosity functions of the open clusters are not statistically significant in most cases. It is concluded that the luminosity functions are approximately universal throughout a large volume in the solar neighborhood. Combined luminosity and mass functions are constructed for six age intervals. The slope of the mass spectrum may vary somewhat from cluster to cluster, and the mean slope may be somewhat higher than the Salpetervalue.     

基于光纤传感技术的地裂缝物理模型试验

苏南地区地裂缝成因机制较为复杂,且灾害活跃。以光纤光栅传感器为监测手段,建立基岩潜山条件下物理地质模型,模拟抽水差异性沉降过程,揭示地裂缝发育演化规律。试验结果表明:（1）地下水过量抽采导致的不均匀沉降是地裂缝发育的最直接因素,地下水水位降深越大、抽采速率越快,地面沉降越明显。（2）基岩潜山形态位置对地表沉降起控制作用;同时地面沉降最严重区域与地裂缝分布区域基本一致;基岩潜山的发育位置形态、地表的沉降曲线以及地裂缝分布情况基本一致。（3）模型试验结果与研究区地裂缝灾害发育规律基本一致。此次基于光纤技术的物理模型试验研究为地裂缝研究提供新的方法与手段。     

基于湿度应力场理论的硬石膏岩膨胀试验研究

传统的湿度应力场理论处理硬石膏围岩膨胀问题时,未反映膨胀特性与湿度状态之间的时变关系。以该理论为基础,设计硬石膏岩膨胀试验：不同初始湿度下的膨胀,不同浸水时间的膨胀,以及膨胀后的抗拉强度测试。试验发现：随初始湿度的增加,硬石膏岩膨胀持续的时间增长,最大膨胀应变和应力增大,终止时的吸水率和结晶水率增加,而自由水率近于0;相同初始湿度下,随浸水时间增加,其吸水率先快速后缓慢增加,结晶水率逐渐增大到接近于吸水率,自由水率逐渐减小到接近于0;随吸水率的增加,其最大轴向膨胀应变、最大侧向膨胀应力和抗拉强度都呈增大趋势。根据试验结果,建立了湿度状态时变系列方程以及含时间效应的膨胀本构模型。     

基于AquiferTest的抽水试验参数计算方法分析

抽水试验是水文地质勘查中最常用的水文地质试验,通过抽水试验,可准确计算水文地质参数。本文根据在河南豫东地区进行的抽水试验,分别用AquiferTest软件计算抽水试验参数和人工求参,进而进行对比分析得出:传统的人工求参,计算结果较为准确,可靠,但因人而异,有不唯一性;用AquiferTest软件计算抽水试验参数,规范、可比性好。本文最后还对参数取值问题进行了分析对比。     

Revisions of the M 8.0 Wenchuan earthquake seismic intensity map based on co-seismic landslide abundance

Natural Hazards - Hundreds of thousands of landslides were triggered by the May 12, 2008, Mw 7.9 Wenchuan earthquake in China. A detailed inventory of landslides triggered by the earthquake was...     

基于原位试验成果的地基非线性沉降分析

提出了利用小尺寸载荷试验（PLT）及标准贯入试验（SPT）成果准确求解地基非线性沉降的新方法。首先利用压板载荷试验成果经过双曲线拟合,确定出某一土层地基土的修正切线模量;然后根据不同深度的SPT标贯击数按照线性相关关系,确定该土层不同深度各分层土的修正切线模量;最后依据分层总和法求解地基或基础的非线性沉降。该方法的特点是能进行加载至极限状态的全过程非线性沉降分析,而计算原理简单,计算参数全部来自现场原位测试,附加应力依据压板试验成果进行自动修正。分析广东某大型油罐地基及某高层建筑筏板基础的沉降结果表明,该方法计算结果准确可靠,能满足以沉降控制为目标的地基基础工程设计要求。     

Relic Radiation and the Modern Cosmological Model

Astronomy Reports - The review considers the contribution of the results of measuring fluctuations of relic cosmic microwave background (CMB) radiation to cosmological model and the latest results...     

基于超前钻探测试的隧道地层智能识别方法

可靠地识别掌子面前方地层是保证隧道工程稳定与安全的重要因素之一。传统的超前地质预报方法不能同时保证有高识别精度、低实施成本和占用少的施工时间,对于不同地质情况的地层识别通用性不强。在传统超前钻孔的同时获取掌子面前方围岩钻探测试数据,实时获取不同深度岩层情况,将大大提高超前预报效率,方便快捷,不影响施工,但目前缺乏客观、准确的地层识别方法。提出了一种基于神经网络的钻探测试数据智能分析和地层识别方法,对楚大高速公路九顶山隧道超前钻探测试数据进行了深入分析,通过隧道开挖后所揭示地层对分析方法进行了验证。结果表明:单一钻进参数用于地层识别的错误率在35%左右,打击能和打击数、送水压力和送水流量的参数组合不能显著提升地层识别准确率;钻进速度、扭矩、回转数、推进力的参数组合可降低地层识别错误率至22%。在神经网络模型中引入钻进参数的标准差,可大幅降低错误率,可使地层划分错误率下降9%～12%;多参数组合下的神经网络钻探测试神经网络模型对随机抽样的地层识别错误率小于10%,对单个钻孔的地层识别错误率小于14%。     

Globular cluster subsystems in the galaxy

Data from the literature are used to construct a homogeneous catalog of fundamental astrophysical parameters for 145 globular clusters of the Milky Way Galaxy. The catalog is used to analyze the relationships between chemical composition, horizontal-branch morphology, spatial location, orbital elements, age, and other physical parameters of the clusters. The overall globular-cluster population is divided by a gap in the metallicity function at [Fe/H]=?1.0 into two discrete groups with well-defined maxima at [Fe/H]=?1.60±0.03 and ?0.60±0.04. The mean spatial-kinematic parameters and their dispersions change abruptly when the metallicity crosses this boundary. Metal-poor clusters occupy a more or less spherical region and are concentrated toward the Galactic center. Metal-rich clusters (the thick disk subsystem), which are far fewer in number, are concentrated toward both the Galactic center and the Galactic plane. This subsystem rotates with an average velocity of V _rot=165±28 km/s and has a very steep negative vertical metallicity gradient and a negligible radial gradient. It is, on average, the youngest group, and consists exclusively of clusters with extremely red horizontal branches. The population of spherical-subsystem clusters is also inhomogeneous and, in turn, breaks up into at least two groups according to horizontal-branch morphology. Clusters with extremely blue horizontal branches occupy a spherical volume of radius ～9 kpc, have high rotational velocities (V _rot=77±33 km/s), have substantial and equal negative radial and vertical metallicity gradients, and are, on average, the oldest group (the old-halo subsystem). The vast majority of clusters with intermediate-type horizontal branches occupy a more or less spherical volume ≈18 kpc in radius, which is slightly flattened perpendicular to the Z direction and makes an angle of ≈30° to the X-axis. On average, this population is somewhat younger than the old-halo clusters (the young-halo subsystem), and exhibits approximately the same metallicity gradients as the old halo. As a result, since their Galactocentric distance and distance from the Galactic plane are the same, the young-halo clusters have metallicities that are, on average, Δ[Fe/H] ≈0.3 higher than those for old-halo clusters. The young-halo subsystem, which apparently consists of objects captured by the Galaxy at various times, contains many clusters with retrograde orbits, so that its rotational velocity is low and has large errors, V _rot=?23±54 km/s. Typical parameters are derived for all the subsystems, and the mean characteristics of their member globular clusters are determined. The thick disk has a different nature than both the old and young halos. A scenario for Galactic evolution is proposed based on the assumption that only the thick-disk and old-halo subsystems are genetically associated with the Galaxy. The age distributions of these two subsystems do not overlap. It is argued that heavy-element enrichment and the collapse of the proto-Galactic medium occurred mainly in the period between the formation of the old-halo and thick-disk subsystems.