- ID:
- ivo://CDS.VizieR/J/MNRAS/449/199
- Title:
- Relaxed galaxy clusters sample
- Short Name:
- J/MNRAS/449/199
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This is the first in a series of papers studying the astrophysics and cosmology of massive, dynamically relaxed galaxy clusters. Here we present a new, automated method for identifying relaxed clusters based on their morphologies in X-ray imaging data. While broadly similar to others in the literature, the morphological quantities that we measure are specifically designed to provide a fair basis for comparison across a range of data quality and cluster redshifts, to be robust against missing data due to point source masks and gaps between detectors, and to avoid strong assumptions about the cosmological background and cluster masses. Based on three morphological indicators - symmetry, peakiness, and alignment - we develop the symmetry-peakiness-alignment (SPA) criterion for relaxation. This analysis was applied to a large sample of cluster observations from the Chandra and ROSAT archives. Of the 361 clusters which received the SPA treatment, 57 (16 per cent) were subsequently found to be relaxed according to our criterion. We compare our measurements to similar estimators in the literature, as well as projected ellipticity and other image measures, and comment on trends in the relaxed cluster fraction with redshift, temperature, and survey selection method. Code implementing our morphological analysis will be made available on the web (http://www.slac.stanford.edu/amantz/work/morph14/).
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Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/448/2644
- Title:
- REXCESS sample optical and X-ray profiles
- Short Name:
- J/MNRAS/448/2644
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Galaxy clusters' structure, dominated by dark matter, is traced by member galaxies in the optical and hot intracluster medium (ICM) in X-rays. We compare the radial distribution of these components and determine the mass-to-light ratio versus system mass relation. We use 14 clusters from the REXCESS sample which is representative of clusters detected in X-ray surveys. Photometric observations with the Wide Field Imager on the 2.2m Max-Planck-Gesellschaft/European Southern Observatory telescope are used to determine the number density profiles of the galaxy distribution out to r_200_. These are compared to electron density profiles of the ICM obtained using XMM-Newton, and dark matter profiles inferred from scaling relations and a Navarro-Frenk-White model. While red sequence galaxies trace the total matter profile, the blue galaxy distribution is much shallower. We see a deficit of faint galaxies in the central regions of massive and regular clusters, and strong suppression of bright and faint blue galaxies in the centres of cool-core clusters, attributable to ram pressure stripping of gas from blue galaxies in high-density regions of ICM and disruption of faint galaxies due to galaxy interactions. We find a mass-to-light ratio versus mass relation within r_200_ of (3.0+/-0.4)x10^2^hM_{sun}_/L_{sun} at 10^15^M_{sun}_ with slope 0.16+/-0.14, consistent with most previous results.
- ID:
- ivo://CDS.VizieR/J/A+A/640/A31
- Title:
- R-Gamma correlation of Swift/BAT AGN
- Short Name:
- J/A+A/640/A31
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The reflection hump is a prominent feature in the hard X-ray spectrum of active galactic nuclei (AGN). Its exact shape and its correlation to other quantities provide valuable information about the inner and outer regions of an AGN. Our main goal is to study the reflection hump in a large sample of nearby AGN. We aim to investigate the evolution of reflection with absorption and its correlation with the spectral index. We analysed archived NuSTAR observations of the 70-month BAT catalogue AGN. By performing a detailed spectral analysis, we were able to constrain the spectral parameters and to investigate the reflection emission in a large sample of individual sources. The reflection strength was found to be strongly correlated with the power-law slope in unabsorbed sources, pointing towards disc reflection for these sources. Different possible explanations were tested and the most likely one is that the corona is moving either towards or away from the disc with a moderately relativistic velocity. An R-Gamma correlation was not detected for absorbed sources. In addition, these AGN feature harder spectra, suggesting intrinsic differences between the two classes or a slab geometry for the X-ray source.
- ID:
- ivo://CDS.VizieR/J/ApJ/525/127
- Title:
- RGB sample of BL Lacertae objects
- Short Name:
- J/ApJ/525/127
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Combining newly identified and previously known BL Lacertae objects from the ROSAT All-Sky Survey-Green Bank (RGB) catalog, we present a sample of 127 BL Lacertae objects, the largest ever derived from a single uniform survey. A complete sample of 33 objects brighter than O=18.0 mag is also presented. These samples are compared to other known BL Lac samples and are generally found to exhibit properties intermediate between those of the previously disparate classes of high- and low-energy-peaked BL Lacertae objects (HBLs and LBLs, respectively). This result is most dramatic in the distribution of the X-ray to radio logarithmic flux ratios, where the RGB BL Lacertae objects are shown to peak precisely where the sharp dichotomy between the two subclasses was previously seen.
- ID:
- ivo://CDS.VizieR/J/MNRAS/311/456
- Title:
- RIXOS source catalogue
- Short Name:
- J/MNRAS/311/456
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We describe the ROSAT International X-ray/Optical Survey (RIXOS), a medium-sensitivity survey and optical identification of X-ray sources discovered in ROSAT high Galactic latitude fields (|b|>280) and observed with the Position Sensitive Proportional Counter (PSPC) detector. We presents a catalogue of the RIXOS sources and their optical identifications.
- ID:
- ivo://CDS.VizieR/J/MNRAS/308/233
- Title:
- RIXOS source sample X-ray spectra
- Short Name:
- J/MNRAS/308/233
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results of an extensive study of the X-ray spectral properties of sources detected in the RIXOS survey, which is a large, nearly complete sample of objects detected serendipitously in ROSAT PSPC fields down to a flux limit of 3x10^-14^erg/cm2/s (0.5-2keV). We show that for X-ray surveys containing sources with low count rate, such as RIXOS, spectral slopes estimated using simple hardness ratios in the ROSAT band can be biased. Instead, we analyse three-colour X-ray data using statistical techniques appropriate to the Poisson regime which remove the effects of this bias. We also show that the use of three-colour data enables some discrimination between thermal and non-thermal spectra. We have then applied this technique to the RIXOS survey to study the spectral properties of the sample. For the AGN we find an average energy index of 1.05+/-0.05, with no evidence for spectral evolution with redshift. Individual AGN are shown to have a range of properties, including soft X-ray excesses and intrinsic absorption. Narrow-emission-line galaxies (NLLGs) also seem to fit to a power-law spectrum, which may indicate a non-thermal origin for their X-ray emission. We infer that most of the clusters in the sample have a bremsstrahlung temperature >3keV, although some show evidence for a cooling flow. The stars deviate strongly from a power-law model but fit to a thermal model. Finally, we have analysed the whole RIXOS sample (extending the flux cut-off to the sensitivity threshold of each individual observation) containing 1762 sources to study the relationship between spectral slope and flux. We find that the mean spectral slope of the sources hardens at lower fluxes, in agreement with results from other samples. However, a study of the individual sources demonstrates that the majority have relatively soft spectra even at faint flux levels, and the hardening of the mean is caused by the appearance of a population of very hard sources at the lowest fluxes. This has implications for the nature of the soft X-ray background.
- ID:
- ivo://CDS.VizieR/J/ApJ/617/192
- Title:
- ROSAT AGN Catalog in North Ecliptic Pole
- Short Name:
- J/ApJ/617/192
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a detailed description of the first direct measurement of the spatial correlation function of X-ray-selected active galactic nuclei (AGNs). This result is based on an X-ray flux-limited sample of 219 AGNs discovered in the contiguous 80.7{deg}^2^ region of the ROSAT North Ecliptic Pole (NEP) Survey (Cat. <J/ApJS/149/29>).
- ID:
- ivo://CDS.VizieR/IX/10A
- Title:
- ROSAT All-Sky Bright Source Catalogue (1RXS)
- Short Name:
- IX/10A
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The ROSAT All-Sky Survey Bright Source Catalogue (RASS-BSC, revision 1RXS) is derived from the all-sky survey performed during the first half year (1990/91) of the ROSAT mission. 18,806 sources are catalogued (five sources were removed compared to the 18,811 sources of the 1996 version), down to a limiting ROSAT PSPC count-rate of 0.05cts/s in the 0.1-2.4keV energy band, with a detection likelihood of at least 15 and with at least 15 source photons. For 94% of the sources visual inspection confirmed the results of the standard processing with respect to existence and position; the remaining 6% were re-analysed and appropriately flagged. At a brightness limit of 0.1cts/s (8,547 sources) the catalogue represents a sky coverage of 92%. Broad band images are available for a subset of the flagged sources from http://www.rosat.mpe-garching.mpg.de/survey/rass-bsc . Questions or comments may be directed to <xray-info(at)mpe.mpg.de>
- ID:
- ivo://CDS.VizieR/J/A+AS/118/481
- Title:
- ROSAT all-sky survey catalogue of OB stars
- Short Name:
- J/A+AS/118/481
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- For the detailed statistical analysis of the X-ray emission of hot stars we selected all stars of spectral type O and B listed in the Yale Bright Star Catalogue and searched for them in the ROSAT All-Sky Survey. In this paper we describe the selection and preparation of the data and present a compilation of the derived X-ray data for a complete sample of bright OB stars.
- ID:
- ivo://CDS.VizieR/IX/29
- Title:
- ROSAT All-Sky Survey Faint Source Catalog
- Short Name:
- IX/29
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The ROSAT All-Sky Survey Faint Source Catalogue (RASS-FSC) is derived from the all-sky survey performed during the ROSAT mission in the energy band 0.1-2.4 keV. 105,924 sources are catalogued and represent the faint extension to the RASS bright source catalogue (RASS-BSC, 1999A&A...349..389V, See Cat. <IX/10>). The sources have a detection likelihood of at least 7 and contain at least 6 source photons. (The likelihood of source detection is defined as L = -ln(1-P), with P = probability of source detection). For each source we provide the ROSAT name, the position in equatorial coordinates, the positional error, the source countrate and error, the background countrate, exposure time, date of observation, hardness-ratios HR1 and HR2 and errors, extent and likelihood of extent, and likelihood of detection. Questions or comments may be directed to xray-info(at)mpe.mpg.de
