XMM-Newton temperature maps for five intermediate redshift clusters of galaxies

We have analyzed XMM-Newton archive data for five clusters of galaxies (redshifts 0.223–0.313) covering a wide range of dynamical states, from relaxed objects to clusters undergoing several mergers. We present here temperature maps of the X-ray gas together with a preliminary interpretation of the formation history of these clusters.     

X-ray measurements of the dark matter distribution in clusters of galaxies with Chandra

We investigate the dark matter distributions in the central region of two clusters of galaxies (A1835 and MKW3S) using Chandra data. N-body simulations in the standard cold dark matter (CDM) model predict the dark matter distribution shows a cuspy dark matter profile: ρ(r) ∝ r, with in the range 1–2, while observations of dwarf and low surface brightness galaxies seem to favor the presence of a relatively flat core: 0 <  < 1. To investigate the dark matter distributions in the central region of clusters of galaxies, we analyze the Chandra data of A1835 and MKW3S with a deprojection method. We derive the mass profiles without the assumption of analytical models. We examine the inner slope of derived mass profiles assuming the dark matter profile is described with a power-law expression. The values of the slope are 0.95 ± 0.10 for A1835 and 1.33 ± 0.12 for MKW3S within the radius of 200 kpc. These are consistent with the result of the CDM simulations. However, within the radius of 100 kpc, the value of is less than unity for A1835 (0.47 ± 0.31). Our result implies that the central dark matter profile of some clusters cannot be described by CDM halos.     

BAX: a dedicated X-rays galaxy clusters database

We present BAX, Base de Données amas de galaxies X (http://webast.ast.obs-mip.fr/bax), a project aiming at building a comprehensive database dedicated to X-rays clusters of galaxies allowing detailed information retrieval. BAX provides the user with basic data published in the literature on X-rays clusters of galaxies as well as with information concerning the physical properties in the X-rays domain or at other wavelengths. BAX allows individual studies on selected clusters as well as building up homogenous samples, from known X-rays clusters for which selection criteria are chosen through web interfaces. We expect BAX to become a useful tool for astronomy community in order to optimize the cluster science return using data from both ground based facilities like MEGACAM (CFHT), VIRMOS (VLT) and space missions like XMM, Chandra and Planck.     

XMM-Newton study of soft excess X-ray emission in clusters of galaxies

We discuss the detection of soft excess X-ray emission in a sample of 19 clusters of galaxies observed by XMM-Newton. In 6/19 clusters evidence for a soft X-ray excess is found. Four of these clusters show soft X-ray and O VII line emission from gas with a temperature of 0.2 keV. The centroid of this oxygen line is consistent with the redshift of the cluster. The intensity and spatial extend of the soft excess agrees with previous PSPC measurements. These observations are interpreted as emission from warm-hot intergalactic medium filaments, with density enhancements near the cluster centers, consistent with theoretical predictions. In the other two soft excess clusters a non-thermal origin is consistent with the data.     

The dust content of clusters of galaxies

We have statistically investigated the infrared luminosity of clusters of galaxies in comparison with the known tracers of the cluster mass like the X-ray luminosity and the cluster richness (e.g. the number of member galaxies). Our results show that there is a clear positive correlation of the infrared luminosity with the cluster mass. Quantitatively speaking, the infrared luminosity is on average 20 times higher than the X-ray luminosity. Moreover, the infrared luminosity increases with the redshift. This probably shows that a major part of this infrared luminosity is due to star formation in the member galaxies. Another possible contribution would be the thermal emission from dust particles in the diffuse intracluster medium. However our method does not allow us to infer conclusions about this second hypothesis. Depending on their size and abundance, such particles would contribute to the infrared luminosity of galaxy cluster and have an impact on the cooling function of the baryons and thus on the formation of the large scale structures. This is an important cosmological question which still remains open.     

High resolution X-ray spectroscopy and chemical evolution in elliptical galaxies

We discuss the elemental composition in the hot ISM of elliptical galaxies derived from new and recent X-ray spectral analysis in the context of new phenomenological models of their chemical evolution. Star formation histories, the IMF, the astrophysics of supernovae, and the nature of galactic winds impact the metal content and relative abundances in the hot ISM. We evaluate how X-ray spectroscopy may be utilized to deconstruct how elliptical galaxies, and the stellar populations that compose them, form and evolve, with an emphasis on present and future high resolution spectroscopic analysis.     

How well do available data describe the distribution of galaxies in the nearby universe?

To study the distribution of galaxies in the Universe data on their positions magnitudes and redshifts are needed. A review of all large samples of galaxy counts, galaxy catalogues and redshift surveys as well as catalogues and redshifts of clusters is given. It is shown that the sky has been unevenly studied, the strongest asimmetry being between the Northern and Southern hemispheres. Particular attention is paid to the Zwicky near clusters. It is shown that only 14% have a well determined redshift and at least 28% are not single clusters but superposition of two or more groups.From an analysis of the available literature it appears that 1) there is more data about redshifts and positions of galaxies than are normally used. 2) The available data are far from uniform and complete.It is argued that a lot more new observations are needed before one can confidently draw conclusions about the structure of the Universe.     

Hi content in cluster and supercluster galaxies

In this lecture I review part of the published and unpublished observational evidence showing that cluster spiral galaxies are hydrogen deficient. Always using observational data, it is argued that the deficiency is due to the interaction between the galaxies and the intergalactic medium. Furthermore it is shown that the stellar population of deficient galaxies has also been affected and a brief discussion is given of the mechanisms at work.     

基于PSF相关的星点定位算法

为提高非高斯分布星点定位的精度,提出了一种新的PSFC (point spread function correlation)星点定位算法,具有很好的抗噪性能和精度水平,易于工程实现.该算法利用互相关中的定义,通过确定系统所测定的PSF与星像灰度值之间的最大相似度来定位星点位置,PSF的测定是在作互相关计算之前全视场范围内可按照整像素和亚像素两种方式完成的.仿真实验结果表明：在带有噪声的星像图条件下,本文PSF相关法的定位精度最高可达到0.034像素,比质心法的精度提高1个数量级,比曲面拟合法的精度提高约20%.     

Walsh相关函数的研究

研究了既有波形畸变又有时间位移时的Ｗａｌｓｈ互相关函数,并在Ｈａｒｎｕｔｈ ＨＦ给出的Ｗａｌｓｈ互相关函数误差矩阵定性结果的基础上进一步给出了定量结果,依据这个结果,提出了选择Ｗａｌｓｈ副载波的原则。     

The X-ray evolution of galaxies: implications for future X-ray observatories

The X-ray evolution of the luminosity of normal galaxies is primarily driven by the evolution of their X-ray binary populations. The imprints left by a cosmological evolution of the star formation rate (SFR) will cause the average X-ray luminosity of galaxies to appear higher in the redshift range 1–3. As reported by White and Ghosh [ApJ, 504 (1998) L31] the profile of X-ray luminosity with redshift can both serve as a diagnostic probe of the SFR profile and constrain evolutionary models for X-ray binaries. In order to observe the high redshift (z>3) universe in the X-ray band, it is necessary to avoid confusion from foreground field galaxies. We report on the predictions of these models of the X-ray flux expected from galaxies and the implications for the telescope parameters of future deep universe X-ray observatories.     

On kinematics of gas clouds in the broad-line region of active galactic nuclei and quasars

The kinematics of gas clouds in broad-line region of active galactic nuclei and quasars is considered. The motion of the clouds is governed by three forces — gravitational influence from the central supermassive body, radiational pressure from the continuum radiation, and resistance of the intercloud medium. Clouds moves radial but only outward motion gives a velocity field, which is in accordance with the observational data. The profiles of the permited lines are obtained in some simplify assumptions for the emissive capacity of the gas in clouds, and are in good agreement with the observational data. In the framework of the model under consideration there is a possibility to estimate some physical parameters of the nuclei such as mass of the central body and density of the intercloud medium.     

The dark matter halo structure of “fossil” groups candidates

We investigated properties of four isolated giant elliptical galaxies with extended X-ray halo using ASCA data. The derived size of X-ray halo, X-ray luminosity, and gravitational mass of the dark halo are unusually large those of X-ray halo of a single galaxy, but are typical for X-ray halos of groups and poor clusters of galaxies. The measured temperatures and abundances of the X-ray halo gas in these galaxies are also similar to those of the groups and poor clusters. Based on these results we identified these galaxies as “isolated X-ray overluminous elliptical galaxy” (IOLEG). The radial profiles of dark halo in these objects were derived from X-ray data. It is found that some are similar to those of compact groups while others are the same as those of normal ellipticals. The dark halos of lOLEGs are thus indistinguishable from those of groups (and poor clusters), which appears to be consistent with a widely believed idea that lOLEGs are a product of dynamical evolution of a compact group. However, mass-to-light ratios of IOLEGs (M₂₀₀/L_B  100–1000) are far greater than those of Hickson compact groups M₂₀₀/L_B  40–60). Since it is hard to consider that total optical luminosity of a compact group decreases by an order of magnitude in the course of dynamical evolution, such difference in the observed mass-to-light ratio between IOLEGs and Hickson compact groups strongly suggests that most IOLEGs have not evolved from compact groups which are observed at present.     

Catalogue of ionized emission line spectra in obscured AGN

High-energy, high-resolution in the spatial and energy domains is crucial to derive the geometrical distribution and the physical properties of gas and dust surrounding Active Galactic Nuclei (AGN). These are, in turn, basic ingredients of any serious attempt to build an AGN structure model. We present in this paper CIELO-AGN, the first catalogue of ionized emission lines detected in the soft X-ray spectra of a sample of 69 nearby obscured AGN. This catalogue has been implemented according to an IVOA data model, and can be accessed through VO-compatible applications.     

基于CCA与POD的气动光学畸变分析

利用典型相关分析和本征正交分解方法,对计算流体力学得到的导弹红外窗口绕流三维密度场数据进行研究.取三维密度场沿展向两个相邻截面的数据先进行典型相关分析提取出两个截面的相关性最强部分,再利用本征正交分解消除两个截面之间数据的冗余信息,获得了能够包含两个截面密度场主要的信息部分.利用提取出的数据重构流场,并进行气动光学畸变仿真分析,仿真结果能较好地近似原始流场的情况.     

X-rays from the first massive black holes

X-ray studies of high-redshift (z > 4) active galaxies have advanced substantially over the past few years, largely due to results from the new generation of X-ray observatories. As of this writing X-ray emission has been detected from nearly 60 high-redshift active galaxies. This paper reviews the observational results and their implications for models of the first massive black holes, and it discusses future prospects for the field.