We search for isolated galaxies based on the automatic identification of isolated sources from the Two Micron All-Sky Survey (2MASS) followed by a visual inspection of their surroundings. We use the modified Karachentseva criterion to compile a catalog of 3227 isolated galaxies (2MIG), which contains 6% of 2MASS Extended Sources Catalog (or 2MASX) sources brighter than Ks = 12 mag with angular diameters a_K > 30 arcsec. The catalog covers the entire sky and has an effective depth of z = 0.02. The 2493 very isolated objects of the catalog, which we include into the 2MVIG catalog, can be used as a reference sample to investigate the effects of the environment on the structure and evolution of galaxies located in regions with extremely low density of matter.
A Public, K-Selected, Optical-to-Near-Infrared Catalog of the Extended Chandra Deep Field South (ECDFS) from the MUltiwavelength Survey by Yale-Chile (MUSYC)
Using a mapping from dark matter halos to galaxy properties based on hydrodynamical simulations, we explore the impact of galaxy properties on the void size function and the void-galaxy correlation function. We replicate the properties of galaxies from Illustris on MassiveNus halos, to perform both luminosity and star formation rate cuts on MassiveNus halos. We compare the impact of such cuts on voids properties with respect to cuts on halo mass (as usually performed on halo catalogs driven from N-body simulations). We find that void catalogs built from luminosity-selected galaxies and halos a…
There is a known tension between cosmological parameter constraints obtained from the primary CMB and those from galaxy cluster samples. One possible explanation could be certain types of groups or clusters of galaxy have been missed in the past. We aim to search for galaxy groups and clusters with particularly extended surface brightness distributions, by creating a new X-ray selected catalog of extended galaxy clusters from the ROSAT All-Sky Survey, using a dedicated algorithm optimized for extended sources. Through extensive simulations, the detection efficiency and sample purity are invest…
Weak-Lensing Shear-Selected Galaxy Clusters from the Hyper Suprime-Cam Subaru Strategic Program: I. Cluster Catalog, Selection Function and Mass--Observable Relation
We present the results of a systematic analysis of the XMM-Newton spectra of nearby optically bright QSOs. The objects have been selected from X-ray Galaxy Catalog Xgal20. It is a catalog of 1172 manually identified and classified galaxies, obtained as a cross-correlation between the 4XMM-DR9 catalog and the Hyper-Linked Extragalactic Databases and Archives (HyperLeda) with an X-ray flux greater than 1E-13 erg/cm^2/s. The goal of this work is to characterize the X-ray spectral properties of selected QSOs in the 0.1 - 10 keV energy band. The majority of the sources (6 out of 11), are classified…
Quasars are very important in materializing the reference frame. The excess emission of AGNs (active galactic nuclei) in the mid infrared band can be used to identify quasar candidates. As extremely distant and point like objects, quasars also could be further selected by astrometry method. Increasing the number of reliable quasar candidates is necessary in characterizing the properties of Gaia astrometric solution and evaluating the reliability of Gaia own quasars classification. We identify quasars by using appropriate AllWISE [W1-W2] color and different combinations of astrometric criteria.…
On the measurements of assembly bias and splashback radius using optically selected galaxy clusters
我们批判性地研究了Miyatake et al.(2016)和More et al.(2016)声称的使用光学选择的星系团观测检测晕组装偏差的方法。我们模仿的光学集群检测算法,并将其应用到两个不同的模拟目录产生的千年模拟星系目录,其中一个是晕组装偏置信号存在,而另一个组装偏置信号已明确删除。我们分裂成两个这些集群样本的成员星系的平均集群中心距离,以衡量在集群强度的子样本相对于彼此的差异。我们观察到,由集群中心半径分裂的子样本显示集群强度的差异,即使在真正的组装偏差信号被删除的目录。我们表明,这是由于污染的成员星系样本从闯入者沿视线。这无疑表明,在以前的研究中采用的特定方法不能用于声称检测到组装偏倚信号。我们找出了这种污染的迹象,并表明观测数据也显示出类似的特征。此外,我们还发现光学星系团中的投影效应会使对星系团三维边缘(回溅半径)的推断产生偏差,因此在解释光学星系团的回溅半径时应给予适当的注意。
We use the Hyper Suprime-Cam Subaru Strategic Program S19A shape catalog to construct weak lensing shear-selected cluster samples. From aperture mass maps covering $\sim 510$~deg$^2$ created using a truncated Gaussian filter, we construct a catalog of 187 shear-selected clusters that correspond to mass map peaks with the signal-to-noise ratio larger than 4.7. Most of the shear-selected clusters have counterparts in optically-selected clusters, from which we estimate the purity of the catalog to be higher than 95\%. The sample can be expanded to 418 shear-selected clusters with the same signal-…
We present a catalog of physical properties for galaxies hosting active galactic nuclei (AGN) detected by the Wide-field Infrared Survey Explorer (WISE). By fitting broadband spectral energy distributions of sources in the WISE AGN Catalog (Assef et al. 2018) with empirical galaxy and AGN templates, we derive photometric redshifts, AGN bolometric luminosities, measures of AGN obscuration, host galaxy stellar masses, and host galaxy star formation rates (SFRs) for 695,273 WISE AGN. The wide-area nature of this catalog significantly augments the known number of obscured AGN out to redshifts of z…
Cosmological probes based on galaxy clusters rely on cluster number counts and large-scale structure information. X-ray cluster surveys are well suited for this purpose, since they are far less affected than optical surveys by projection effects, and cluster properties can be predicted with good accuracy. The XMM Cluster Archive Super Survey, X-CLASS, is a serendipitous search of X-ray-detected galaxy clusters in 4176 XMM-Newton archival observations until August 2015. All observations are clipped to exposure times of 10 and 20 ks to obtain uniformity and they span ~269 deg$^2$ across the high…
Ultra-Flat Galaxies Selected from RFGC Catalog. I. The Sample Properties
我们使用修订的扁平星系目录(RFGC)创建了一个超扁平星系(UFG)的样本,覆盖了除银河系区域外的整个北部和南部天空。它包含了817个从侧面看去的旋涡星系,根据它们在蓝色和红色波段的视轴比分别为$(a/b)_B\geq10.0$和$(a/b)_R\geq8.53$而被选入UFG样本。在这个基本样本中,我们固定了441个UFG星系的示例性样本,其径向速度为$V_{LG} < 10000$ km s $^{-1}$,银河纬度为$\mid b\mid>10^{\circ}$,蓝色角直径为$a_B > 1.0^{\prime}$。根据Schmidt检验,441个星系的典型样本具有约(80-90)%的完整性,这足以研究超扁平星系的不同性质。我们发现,超过3/4的UFG具有$T= 7\pm1$窄范围内的形态类型,即最薄的星盘出现在Scd、Sd和Sdm类型中。UFG星系的平均表面亮度趋向于向最平坦的无膨胀星系减小。没有不对称迹象的规则形状的圆盘在所有RFGC星系和UFG样本天体中约占2/3。大约60%的超扁平星系可以被称为动力学孤立的物体,而其中30%可能属于分散的协会(细丝,壁),只有大约10%的它们是相对于邻居的动力学主导星系。
Ultra-Flat Galaxies Selected from RFGC Catalog. II. Orbital Estimates of Halo Masses
我们使用修订的扁平星系表(RFGC),选择817个超扁平(UF)的边缘盘星系的蓝色和红色的视轴比$(a/b)_B > 10.0$和$(a/b)_R > 8.5$。样本覆盖了整个天空,除了银河系区域,包含490个具有测量径向速度的UF星系。我们对它们周围的邻近星系的检查显示,在$R_p < 250$ kpc的投影分离内,只有30个径向速度差为$^{-1}$ km s的伴星。其中,在$R_p < 750$ kpc范围内,UF星系周围的较宽区域不包含其他比UF星系本身更亮的邻居。所得的样本星系大多属于Sc、Scd、Sd形态类型。它们有一个中等的自转速度曲线振幅约为$120$ km s $^{-1}$和一个中等的K带光度约为$10^{10}L_{\odot}$。它们的伴星径向速度的中位差为$87$ km s $^{-1}$,产生的中位轨道质量估计值约为$5\times10^{11}M_{\odot}$。排除6个可能的非孤立星系对后,我们得到了一个典型的UF星系晕-恒星质量比,大约为$30$,这与最近星系群中的主要旋涡星系M31和M81几乎相同。我们还注意到,超平星系看起来比其他同样光度的螺旋星系少两倍的“尘埃”。