A polarimetric study of the B[e] star HD 45677

We aim to characterize the current status of knowledge on the accuracy of open-cluster parameters such as the age, reddening and distance. These astrophysical quantities are often used to study the global characteristics of the Milky Way down to the very local stellar phenomena. In general, the errors of these quantities are neglected or set to some kind of heuristic standard value. We attempt to give some realistic estimates for the accuracy of available cluster parameters by using the independently derived values published in the literature. In total, 6437 individual estimates for 395 open clusters were used in our statistical analysis. We discuss the error sources depending on theoretical as well as observational methods and compare our results with those parameters listed in the widely used catalogue by Dias et al. In addition, we establish a list of 72 open clusters with the most accurate known parameters which should serve as a standard table in the future for testing isochrones and stellar models.     

A Catalogue of previously unstudied Berkeley clusters

The main astrophysical parameters of 24 previously unstudied open clusters of Berkeley catalogue are presented here. JHK near-infrared (Two Micron All Sky Survey) photometry and the proper motions astrometry of Naval Observatory Merged Astrometric Dataset (NOMAD) are used. The clusters' centres, angular diameters, ages, distances and colour excesses for these clusters are estimated for the first time.     

疏散星团运动学资料汇集与若干统计分析

整理汇集了迄今最完整的同时具备绝对自行与视向速度数据的 14 4个疏散星团样本 ,计算得出这些星团的 3维空间速度。对银河系疏散星团的空间分布 (采用了更多样本 )和运动学性质进行了若干统计分析     

An extension of the Planck galaxy cluster catalogue

We present a catalogue of galaxy clusters detected in the Planck all-sky Compton parameter maps and identified using data from the WISE and SDSS surveys. The catalogue comprises about 3000 clusters in the SDSS fields. We expect the completeness of this catalogue to be high for clusters with masses larger than M ₅₀₀ ≈ 3 × 10¹⁴ M _⊙, located at redshifts z < 0.7. At redshifts above z ≈ 0.4, the catalogue contains approximately an order of magnitude more clusters than the 2nd Planck Catalogue of Sunyaev-Zeldovich sources in the same fields of the sky. This catalogue can be used for identification of massive galaxy clusters in future large cluster surveys, such as the SRG/eROSITA all-sky X-ray survey.     

UKIRT follow-up observations of the old open cluster FSR 0358 (Kirkpatrick 1)

We aim to characterize the properties of the stellar clusters in the Milky Way. Utilising an expectation-maximization method, we determined that the cluster FSR 0358, originally discovered by J.D. Kirkpatrick, is the most likely real cluster amongst the cluster candidates from Froebrich et al. Here, we present new deep high resolution near-infrared imaging of this object obtained with the United Kingdom Infrared Telescope (UKIRT). The analysis of the data reveals that FSR 0358 (Kirkpatrick 1) is a  5 ± 2 Gyr  old open cluster in the outer Milky Way. Its age, metallicity of   Z = 0.008  and distance from the Galactic Centre of 11.2 kpc are typical for the known old open galactic clusters. So far six of the FSR cluster candidates have been identified as having an age above 5 Gyr. This shows the significance of this catalogue in enhancing our knowledge of the oldest open clusters in the Galaxy.     

Two populations of open star clusters in the Galaxy

Based on our compiled catalogue of fundamental astrophysical parameters for 593 open clusters, we analyze the relations between the chemical composition, spatial positions, Galactic orbital elements, age, and other physical parameters of open star clusters. We show that the population of open clusters is heterogeneous and is divided into two groups differing by their mean parameters, properties, and origin. One group includes the Galactic clusters formed mainly from the interstellar matter of the thin disk with nearly solarmetallicities ([Fe/H] > ?0.2) and having almost circular orbits a short distance away from the Galactic plane, i.e., typical of the field stars of the Galactic thin disk. The second group includes the peculiar clusters formed through the interaction of extragalactic objects (such as high-velocity clouds, globular clusters, or dwarf galaxies) with the interstellar matter of the thin disk, which, as a result, derived abnormally low (for field thin-disk stars) metallicities and/or Galactic orbits typical of objects of the older Galactic subsystems. About 70% of the clusters older than 1Gyr have been found to be peculiar, suggesting a slower disruption of clusters with noncircular high orbits. Analysis of orbital elements has shown that the bulk of the clusters from both groups were formed within a Galactocentric radius of ??10.5 kpc and closer than ??180 pc from the Galactic plane, but owing to their high initial velocities, the peculiar clusters gradually took up the volumes occupied by the objects of the thick disk, the halo, and even the accreted halo of the Galaxy. Analysis of the relative abundances of magnesium (a representative of the ??-elements) in clusters that, according to their kinematical parameters, belong to different Galactic subsystems has shown that all clusters are composed of matter incorporating the interstellar matter of a single protogalactic cloud in different proportions, i.e., reprocessed in genetically related stars of the Galaxy. The [Mg/Fe] ratios for the clusters with thick-disk kinematics are, on average, overestimated, just as for the field stars of the socalled ??metal-rich wing?? of the thick disk. For the clusters with halo kinematics, these ratios exhibit a very large spread, suggesting that they were formed mainly from matter that experienced a history of chemical evolution different from the Galactic one. We point out that a large fraction of the open clusters with thindisk kinematics have also been formed from matter of an extragalactic nature within the last ??30 Myr.     

Spectroscopic Redshift Measurements for Galaxy Clusters Detected in the Planck All-Sky Survey

Astronomy Letters - We present the results of spectroscopic redshift measurements for galaxy clusters from the catalogue compiled previously from Planck all-sky survey data in combination with...     

Updated version of the ‘homogeneous catalog of open cluster parameters’

We report a new version of the “Homogeneous catalog of open cluster parameters” maintained by our team over the last decades. The catalog is based on redetermination of the main parameters of clusters (color excesses, heliocentric distances, and ages) based on published photometric measurements, in particular, those provided by the 2MASS point-source catalog. Currently, our catalog provides the parameters for 959 clusters. It also gives the estimates of cluster radial velocities for 496 clusters partly based on the data fromRAVE catalog. Estimates of proper-motion components are provided for all clusters included into the catalog. We analyze the distributions of the errors of the main cluster parameters and compare the distribution of cluster positions projected onto the Galactic plane with the distribution of cosmic masers thereby validating the distance scale of open clusters.     

Morphological analysis of open clusters’ properties: II. Relationships projected onto the galactic plane

A morphological analysis study of open clusters’ properties has been achieved for a sample of 160 UBVCCD open star clusters of approximately 128,000 stars near the galactic plane. The data was obtained and reduced from Tadross (2001) using the same reduction procedures, which makes this catalogue the largest homogeneous source of open clusters’ parameters.     

The Las Campanas/AAT rich cluster survey – I. Precision and reliability of the photometric catalogue

The Las Campanas Observatory and Anglo-Australian Telescope Rich Cluster Survey (LARCS) is a panoramic imaging and spectroscopic survey of an X-ray luminosity-selected sample of 21 clusters of galaxies at     . Charge-coupled device (CCD) imaging was obtained in B and R of typically 2° wide regions centred on the 21 clusters, and the galaxy sample selected from the imaging is being used for an on-going spectroscopic survey of the clusters with the 2dF spectrograph on the Anglo-Australian Telescope. This paper presents the reduction of the imaging data and the photometric analysis used in the survey. Based on an overlapping area of 12.3 deg² we compare the CCD-based LARCS catalogue with the photographic-based galaxy catalogue used for the input to the 2dF Galaxy Redshift Survey (2dFGRS) from the APM, to the completeness of the GRS/APM catalogue,     . This comparison confirms the reliability of the photometry across our mosaics and between the clusters in our survey. This comparison also provides useful information concerning the properties of the GRS/APM. The stellar contamination in the GRS/APM galaxy catalogue is confirmed as around     per cent, as originally estimated. However, using the superior sensitivity and spatial resolution in the LARCS survey evidence is found for four distinct populations of galaxies that are systematically omitted from the GRS/APM catalogue. The characteristics of the 'missing' galaxy populations are described, reasons for their absence examined and the impact they will have on the conclusions drawn from the 2dF Galaxy Redshift Survey are discussed.     

Predicting the clustering of X-ray selected galaxy clusters in flux-limited surveys

We present a model to predict the clustering properties of X-ray selected clusters in flux-limited surveys. Our technique correctly accounts for past light-cone effects on the observed clustering and follows the non-linear evolution in redshift of the underlying dark matter correlation function and cluster bias factor. The conversion of the limiting flux of a survey into the corresponding minimum mass of the hosting dark matter haloes is obtained by using theoretical and empirical relations between mass, temperature and X-ray luminosity of galaxy clusters. Finally, our model is calibrated to reproduce the observed cluster counts adopting a temperature–luminosity relation moderately evolving with redshift. We apply our technique to three existing catalogues: the ROSAT Brightest Cluster Sample (BCS); the X-ray Brightest Abell-type Cluster sample (XBACs); and the ROSAT –ESO Flux-Limited X-ray sample (REFLEX). Moreover, we consider an example of possible future space missions with fainter limiting flux. In general, we find that the amplitude of the spatial correlation function is a decreasing function of the limiting flux and that the Einstein–de Sitter models always give smaller correlation amplitudes than open or flat models with low matter density parameter Ω_0m. In the case of the XBACs catalogue, the comparison with previous estimates of the observational spatial correlation shows that only the predictions of models with Ω_0m=0.3 are in good agreement with the data, while the Einstein–de Sitter models have too low a correlation strength. Finally, we use our technique to discuss the best strategy for future surveys. Our results show that, to study the clustering properties of X-ray selected clusters, the choice of a wide area catalogue, even with a brighter limiting flux, is preferable to a deeper, but smaller area, survey.     

Optical Identifications of High-Redshift Galaxy Clusters from the Planck Sunyaev–Zeldovich Survey

We present the results of optical identifications and spectroscopic redshift measurements for galaxy clusters from the second Planck catalogue of Sunyaev–Zeldovich sources (PSZ2) located at high redshifts, z ≈ 0.7?0.9. We used the data of optical observations with the Russian–Turkish 1.5-mtelescope (RTT-150), the Sayan Observatory 1.6-m telescope, the Calar Alto 3.5-m telescope, and the 6-m SAO RAS telescope (BTA). The spectroscopic redshift measurements were obtained for seven galaxy clusters, including one cluster, PSZ2 G126.57+51.61, from the cosmological sample of the PSZ2 catalogue. In the central regions of two clusters, PSZ2 G069.39+68.05 and PSZ2 G087.39?34.58, we detected arcs of strong gravitational lensing of background galaxies, one of which is at redshift z = 4.262. The data presented below roughly double the number of known galaxy clusters in the second Planck catalogue of Sunyaev–Zeldovich sources at high redshifts, z ≈ 0.8.     

Mass selection bias in galaxy cluster peculiar velocities from the kinetic Sunyaev–Zel'dovich effect

Upcoming surveys for galaxy clusters using the Sunyaev–Zel'dovich effect are potentially sensitive enough to create a peculiar velocity catalogue. The statistics of these peculiar velocities are sensitive to cosmological parameters. We develop a method to explore parameter space using N -body simulations in order to quantify dark matter halo velocity statistics which will be useful for cluster peculiar velocity observations. We show that mass selection bias from a kinetic Sunyaev–Zel'dovich velocity catalogue forecasts rms peculiar velocities with a much more complicated  Ω_m  dependency than suggested by linear perturbation theory. In addition, we show that both two-point functions for velocities disagree with linear theory predictions out to  ∼40  h ⁻¹ Mpc  separations. A pedagogical appendix is included developing linear theory notation with respect to the two-point peculiar velocities functions.     

Catalogue of averaged stellar effective magnetic fields – II. Re-discussion of chemically peculiar A and B stars

This paper presents a catalogue and the method of determining averaged quadratic effective magnetic fields  〈 B _e〉  for 1212 main-sequence and giant stars, and 11 white dwarf stars. The catalogue includes stars that are members of several open clusters. We have compiled measurements of the longitudinal magnetic field for those stars, which were scattered in the existing literature. A new parameter, magnetization (MA), has been defined, and we present values of MA for stars of various spectral classes. Our sample includes a subset of 610 chemically peculiar early-type stars. We confirm the conclusion of our previous study that the number distribution of all chemically peculiar stars versus the averaged magnetic field strength is described by a decreasing exponential function. Relations of this type also hold for stars of all the analysed subclasses of chemical peculiarity. Magnetization tends to correlate with the effective temperature only at high MA, for He-weak and He-rich stars.     

Photoelectric catalogue of globular clusters in the Andromeda Nebula M31 and its companions NGC 147, NGC 185, and NGC 205

The photoelectric catalogue of the globular clusters (including the objects previously considered to be clusters) in the Andromeda Nebula M31 and its companions NGC 147, NGC185, and NGC 205 is presented. The catalogue based on all published data includes 338 objects withUBV, six objects withBV, and one object withV measurements.     

The 2dF Galaxy Redshift Survey: a targeted study of catalogued clusters of galaxies

We have carried out a study of known clusters within the 2dF Galaxy Redshift Survey (2dFGRS) observed areas and have identified 431 Abell, 173 APM and 343 EDCC clusters. Precise redshifts, velocity dispersions and new centroids have been measured for the majority of these objects, and this information is used to study the completeness of these catalogues, the level of contamination from foreground and background structures along the cluster's line of sight, the space density of the clusters as a function of redshift, and their velocity dispersion distributions. We find that the Abell and EDCC catalogues are contaminated at the level of about 10 per cent, whereas the APM catalogue suffers only 5 per cent contamination. If we use the original catalogue centroids, the level of contamination rises to approximately 15 per cent for the Abell and EDCC catalogues, showing that the presence of foreground and background groups may alter the richness of clusters in these catalogues. There is a deficiency of clusters at     that may correspond to a large underdensity in the Southern hemisphere. From the cumulative distribution of velocity dispersions for these clusters, we derive a space density of     clusters of     This result is used to constrain models for structure formation; our data favour low-density cosmologies, subject to the usual assumptions concerning the shape and normalization of the power spectrum.     

New open cluster candidates discovered in the XSTPS-GAC survey

The Xuyi Schmidt Telescope Photometric Survey of the Galactic Anti-center(XSTPS-GAC)is a photometric sky survey that covers nearly 6000 deg~2 towards the Galactic Anti-center(GAC) in the g,r,i bands. Half of its survey field is located on the Galactic Anti-center disk,which makes XSTPSGAC highly suitable to search for new open clusters in the GAC region. In this paper,we report new open cluster candidates discovered in this survey,as well as properties of these open cluster candidates,such as age,distance and reddening,derived by isochrone fitting in the color-magnitude diagram(CMD).These open cluster candidates are stellar density peaks detected in the star density maps by applying the method from Koposov et al. Each candidate is inspected in terms of its true color image composed from three XSTPS-GAC band images. Then its CMD is checked,in order to identify whether the central region stars have a clear isochrone-like trend differing from background stars. The parameters derived from isochrone fitting for these candidates are mainly based on three band photometry of XSTPS-GAC.Moreover,when these new candidates are able to be seen clearly in 2 MASS data,their parameters are also derived based on the 2 MASS(J-H,J) CMD. There are a total of 320 known open clusters rediscovered and 24 new open cluster candidates discovered in this work. Furthermore,the parameters of these new candidates,as well as another 11 previously known open clusters,are properly determined for the first time.     

Astrophysical supplements to the ASCC‐2.5. I. Radial velocity data

We present a catalogue of radial velocities of Galactic stars with high precision astrometric data CRVAD which is the result of the cross‐identification of star lists from the General Catalog of Average Radial Velocities (GCRV) and from the homogeneous All‐sky Compiled Catalogue of 2.5Million Stars (ASCC‐2.5). The CRVAD includes accurate J2000 equatorial coordinates, proper motions and trigonometric parallaxes in the Hipparcos system, Johnson's BV photometric data, spectral types, multiplicity and variability flags from the ASCC‐2.5, and radial velocities, stellar magnitudes and spectral types from the GCRV for 34553 ASCC‐2.5 stars. The CRVAD was used for the construction of a sample of standard stars with accurate astrometric, photometric and radial velocity data for the RAVE project. A second application of the CRVAD , the radial velocity determination for 292 open clusters (including 97 with previously unknown radial velocities), using their newly defined members from proper motions and photometry in the ASCC‐2.5, is briefly described. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Heiles星光偏振源表的距离更正

星光偏振是研究星际介质磁场的有力工具之一.Heiles源表收集了9286颗恒星的偏振信息,是目前最大的光学波段星光偏振源表,被广泛使用.但该表中恒星的距离参数是以前的测光距离,很不确定.把Heiles源表和Gaia第2次数据释放(DR2)源表进行交叉证认,以位置和星等作为判据,匹配了7613颗恒星,并获得了这些恒星的三角视差距离和误差,超过90%的恒星距离相对误差小于20%.基于新的距离,展示了星光偏振在银河系内的分布并讨论了可能的应用.     

Searching for Excess Rotation Measures in Galaxy Clusters with the NVSS

We present a statistical analysis of the rotation measure (RM) catalogue from the NVSS in search for a statistical excess of rotation measure through Abell clusters. After excluding the data known to be affected by the large-scale magnetic field of the Galaxy (b ≤ |30|), we consider RMs as a function of normalized Abell radius for 496 galaxy clusters. Despite that it is now well established that galaxy clusters contain magnetic fields, we find no evidence of an increase of the rotation measure for lines of sight toward Abell clusters. Additionally, we find no evidence for statistically different rotation measure values between cluster lines of sight and RMs up to 7 Abell radii from the cluster over that expected from the intrinsic variation of the NVSS dataset. We suggest this is the result of sparse spatial coverage of suitably polarized sources in the NVSS.