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17691. X-ray cavities from isolated gal. to clusters
ID:
ivo://CDS.VizieR/J/ApJS/227/31
Title:
X-ray cavities from isolated gal. to clusters
Short Name:
J/ApJS/227/31
Date:
21 Oct 2021
Publisher:
CDS
Description:
We perform a comprehensive study of X-ray cavities using a large sample of X-ray targets selected from the Chandra archive. The sample is selected to cover a large dynamic range including galaxy clusters, groups, and individual galaxies. Using {beta}-modeling and unsharp masking techniques, we investigate the presence of X-ray cavities for 133 targets that have sufficient X-ray photons for analysis. We detect 148 X-ray cavities from 69 targets and measure their properties, including cavity size, angle, and distance from the center of the diffuse X-ray gas. We confirm the strong correlation between cavity size and distance from the X-ray center similar to previous studies. We find that the detection rates of X-ray cavities are similar among galaxy clusters, groups and individual galaxies, suggesting that the formation mechanism of X-ray cavities is independent of environment.
17692. X-ray classification of young star clusters
ID:
ivo://CDS.VizieR/J/ApJ/659/585
Title:
X-ray classification of young star clusters
Short Name:
J/ApJ/659/585
Date:
21 Oct 2021
Publisher:
CDS
Description:
A large volume of low signal-to-noise, multidimensional data is available from the CCD imaging spectrometers aboard the Chandra X-Ray Observatory and the X-Ray Multimirror Mission (XMM-Newton). To make progress analyzing this data, it is essential to develop methods to sort, classify, and characterize the vast library of X-ray spectra in a nonparametric fashion (complementary to current parametric model fits). We have developed a spectral classification algorithm that handles large volumes of data and operates independently of the requirement of spectral model fits. We use proven multivariate statistical techniques including principal component analysis and an ensemble classifier consisting of agglomerative hierarchical clustering and K-means clustering applied for the first time for spectral classification. The algorithm positions the sources in a multidimensional spectral sequence and then groups the ordered sources into clusters based on their spectra. These clusters appear more distinct for sources with harder observed spectra. The apparent diversity of source spectra is reduced to a three-dimensional locus in principal component space, with spectral outliers falling outside this locus. The algorithm was applied to a sample of 444 strong sources selected from the 1616 X-ray emitting sources detected in deep Chandra imaging spectroscopy of the Orion Nebula Cluster.
17693. X-ray cluster of galaxies behind the Milky way
ID:
ivo://CDS.VizieR/J/ApJ/580/774
Title:
X-ray cluster of galaxies behind the Milky way
Short Name:
J/ApJ/580/774
Date:
21 Oct 2021
Publisher:
CDS
Description:
We report on the design and status of the Clusters in the Zone of Avoidance (CIZA) project, the first systematic X-ray search for clusters of galaxies behind the Milky Way. Our project, Clusters in the Zone of Avoidance (CIZA), uses X-ray data from the RASS for the initial cluster candidate selection and subsequent optical and NIR observations to confirm or refute the cluster nature of all selected candidates. We demonstrate that an X-ray survey can find galaxy clusters at low Galactic latitude where optical searches are inefficient because of massive obscuration and extinction problems. We discuss the rationale for such a survey in the context of large-scale structure studies and describe in detail the combined X-ray/optical/NIR approach used by CIZA to identify clusters of galaxies at |b|<20{deg}, a region of the sky that has traditionally been excluded from earlier cluster catalogs. So far, CIZA has identified and spectroscopically confirmed 137 galaxy clusters in what used to be the zone of avoidance; additional clusters have been confirmed in imaging observations and await spectroscopic observation. We present a catalog of the 73 X-ray brightest CIZA clusters, 53 (73%) of which are new discoveries.
17694. X-ray clusters from XMM
ID:
ivo://CDS.VizieR/J/MNRAS/423/3561
Title:
X-ray clusters from XMM
Short Name:
J/MNRAS/423/3561
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have processed 2774 high galactic observations from the XMM archive (as of 2010 May) and extracted a serendipitous catalogue of some 850 clusters of galaxies based on purely X-ray criteria, following the methodology developed for the XMM-Large-Scale Survey. Restricting the sample to the highest signal-to-noise ratio objects (347 clusters), we perform a cosmological analysis using only the X-ray information. The analysis consists in the modelling of the observed colour-magnitude [count rate and hardness ratio (CR-HR)] diagram constructed from cluster instrumental count rates measured in the [0.5-2], [1-2] and [0.5-1] keV bands. A Monte Carlo Markov chain procedure simultaneously fits the cosmological parameters, the evolution of the cluster scaling laws and the selection effects.
17695. X-ray clusters of galaxies
ID:
ivo://CDS.VizieR/J/A+A/420/61
Title:
X-ray clusters of galaxies
Short Name:
J/A+A/420/61
Date:
21 Oct 2021
Publisher:
CDS
Description:
A new method for a simultaneous search for clusters of galaxies in X-ray photon maps and optical galaxy maps is described. The method appears ideally suited for the analysis of the recently proposed wide-angle X-ray missions like DUO and ROSITA. As a first application, clusters are extracted from the 3rd version of the ROSAT All-Sky Survey (<IX/10>) and the Early Date Release of the Sloan Digital Sky Survey (SDSS, <J/AJ/123/567>). The time-consuming computations are performed within the German Astrophysical Virtual Observatory (GAVO). On a test area of 140 square degrees, 75 X-ray clusters are detected down to an X-ray flux limit of 3-5*10^-13^erg/s/cm^2^ in the ROSAT energy band 0.1-2.4keV. The clusters have redshifts z<0.5.
17696. X-ray clusters with radio emission
ID:
ivo://CDS.VizieR/J/MNRAS/379/260
Title:
X-ray clusters with radio emission
Short Name:
J/MNRAS/379/260
Date:
21 Oct 2021
Publisher:
CDS
Description:
By combining the REFLEX and NORAS cluster data sets with the NVSS radio catalogue, we obtain a sample of 145, z<0.3, X-ray-selected clusters brighter than 3x10^-12^erg/s/cm^-2^ that show a central radio emission above 3mJy. For virial masses M_vir_<10^14.5^M_{sun}_, 11 clusters out of 12 (corresponding to 92 per cent of the systems) are inhabited by a central radio source.
17697. X-ray data for IC 348 young stars
ID:
ivo://CDS.VizieR/J/A+A/539/A64
Title:
X-ray data for IC 348 young stars
Short Name:
J/A+A/539/A64
Date:
21 Oct 2021
Publisher:
CDS
Description:
The physical origin of the strong magnetic activity in T Tauri stars and its relation to stellar rotation is not yet well-understood. We investigate the relation between the X-ray activity, rotation, and Rossby number for a sample of young stars in the ~3Myr old cluster IC 348. We use the data of four Chandra observations of IC 348 to derive the X-ray luminosities of the young stars. Basic stellar parameters and rotation rates are collected from the literature. This results in a sample of 82 X-ray detected stars with known rotation periods. We determine the Rossby numbers (i.e. the ratio of rotation period to convective turnover time) of 76 of these stars from stellar structure- and evolution-models for pre-main sequence stars.
17698. X-ray data for 56 protoplanetary disk sources
ID:
ivo://CDS.VizieR/J/A+A/625/A66
Title:
X-ray data for 56 protoplanetary disk sources
Short Name:
J/A+A/625/A66
Date:
21 Oct 2021
Publisher:
CDS
Description:
Consistent modeling of protoplanetary disks requires the simultaneous solution of both continuum and line radiative transfer, heating and cooling balance between dust and gas and, of course, chemistry. Such models depend on panchromatic observations that can provide a complete description of the physical and chemical properties and energy balance of protoplanetary systems. Along these lines we present a homogeneous, panchromatic collection of data on a sample of 85 T Tauri and Herbig Ae objects for which data cover a range from X-rays to centimeter wavelengths. Datasets consist of photometric measurements, spectra, along with results from the data analysis such as line fluxes from atomic and molecular transitions. Additional properties resulting from modeling of the sources such as disc mass and shape parameters, dust size and PAH properties are also provided for completeness. The purpose of this data collection is to provide a solid base that can enable consistent modeling of the properties of protoplan- etary disks. To this end, we performed an unbiased collection of publicly available data that were combined to homogeneous datasets adopting consistent criteria. Targets were selected based on both their properties but also on the availability of data. Data from more than 50 different telescopes and facilities were retrieved and combined in homogeneous datasets directly from public data archives or after being extracted from more than 100 published articles. X-ray data for a subset of 56 sources represent an exception as they were reduced from scratch and are presented here for the first time. Compiled datasets along with a subset of continuum and emission-line models are stored in a dedicated database and distributed through a publicly accessible online system. All datasets contain metadata descriptors that allow to backtrack them to their original resources. The graphical user interface of the online system allows the user to visually inspect individual objects but also compare between datasets and models. It also offers to the user the possibility to download any of the stored data and metadata for further processing.
17699. X-ray detection of radio-selected SF galaxies
ID:
ivo://CDS.VizieR/J/A+A/542/A16
Title:
X-ray detection of radio-selected SF galaxies
Short Name:
J/A+A/542/A16
Date:
21 Oct 2021
Publisher:
CDS
Description:
X-ray surveys contain sizable numbers of star forming galaxies, beyond the AGN which usually make the majority of detections. Many methods to separate the two populations are used in the literature, based on X-ray and multiwavelength properties. We aim at a detailed test of the classification schemes and to study the X-ray properties of the resulting samples. We build on a sample of galaxies selected at 1.4GHz in the VLA-COSMOS survey, classified by Smolcic et al. (2008ApJS..177...14S) according to their optical colours and observed with Chandra. A similarly selected control sample of AGN is also used for comparison. We review some X-ray based classification criteria and check how they affect the sample composition. The efficiency of the classification scheme devised by Smolcic et al. (2008ApJS..177...14S) is such that ~30% of composite/misclassified objects are expected because of the higher X-ray brightness of AGN with respect to galaxies. The latter fraction is actually 50% in the X-ray detected sources, while it is expected to be much lower among X-ray undetected sources. Indeed, the analysis of the stacked spectrum of undetected sources shows, consistently, strongly different properties between the AGN and galaxy samples. X-ray based selection criteria are then used to refine both samples. The radio/X-ray luminosity correlation for star forming (SF) galaxies is found to hold with the same X-ray/radio ratio valid for nearby galaxies. Some evolution of the ratio may be possible for sources at high redshift or high luminosity, tough it is likely explained by a bias arising from the radio selection. Finally, we discuss the X-ray number counts of star forming galaxies from the VLA- and C-COSMOS surveys according to different selection criteria, and compare them to the similar determination from the Chandra Deep Fields. The classification scheme proposed here may find application in future works and surveys.
17700. X-ray detections in the {sigma} Ori cluster
ID:
ivo://CDS.VizieR/J/A+A/521/A45
Title:
X-ray detections in the {sigma} Ori cluster
Short Name:
J/A+A/521/A45
Date:
21 Oct 2021
Publisher:
CDS
Description:
We investigated the X-ray emission from young stars and brown dwarfs in the {sigma} Orionis cluster ({tau}=~3Ma, d=~385pc) and its relation to mass, the presence of circumstellar discs, and separation to the cluster centre by taking advantage of the superb spatial resolution of the Chandra X-ray Observatory.

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