- ID:
- ivo://CDS.VizieR/J/ApJS/238/32
- Title:
- 3rd MAXI/GSC X-ray cat at high Galactic latitude
- Short Name:
- J/ApJS/238/32
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the third MAXI/GSC catalog in the high Galactic latitude sky (|b|>10{deg}) based on the 7-year data from 2009 August 13 to 2016 July 31, complementary to that in the low Galactic latitude sky (|b|<10{deg}) (Hori+ 2018ApJS..235....7H). We compile 682 sources detected at significances of s_D,4-10keV_>=6.5 in the 4-10keV band. A two-dimensional image fit based on the Poisson likelihood algorithm (C-statistics) is adopted for the detections and constraints on their fluxes and positions. The 4-10keV sensitivity reaches ~0.48mCrab, or ~5.9x10^-12^erg/cm^2^/s, over half of the survey area. Compared with the 37-month Hiroi+ (2013, J/ApJS/207/36) catalog, which adopted a threshold of s_D,4-10keV_>=7, the source number increases by a factor of ~1.4. The fluxes in the 3-4keV and 10-20keV bands are further estimated, and hardness ratios (HRs) are calculated using the 3-4keV, 4-10keV, 3-10keV, and 10-20keV band fluxes. We also make the 4-10keV light curves in 1-year bins for all the sources and characterize their variabilities with an index based on a likelihood function and the excess variance. Possible counterparts are found from five major X-ray survey catalogs by Swift, Uhuru, RXTE, XMM-Newton, and ROSAT, as well as an X-ray galaxy cluster catalog (MCXC). Our catalog provides the fluxes, positions, detection significances, HRs, 1-year bin light curves, variability indices, and counterpart candidates.
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- ID:
- ivo://CDS.VizieR/J/MNRAS/366/171
- Title:
- Red AGN in XMM/SDSS fields
- Short Name:
- J/MNRAS/366/171
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper we combine archival and proprietary XMM-Newton observations (about 5deg^2^) that overlap with the Sloan Digital Sky Survey to explore the nature of the moderate-z X-ray population. We focus on X-ray sources with optically red colours (g-r>0.4), which we argue are important for understanding the origin of the X-ray background (XRB).
- ID:
- ivo://CDS.VizieR/J/ApJS/224/1
- Title:
- redMaPPer cluster catalog from DES data
- Short Name:
- J/ApJS/224/1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We describe updates to the redMaPPer algorithm, a photometric red-sequence cluster finder specifically designed for large photometric surveys. The updated algorithm is applied to 150deg^2^ of Science Verification (SV) data from the Dark Energy Survey (DES), and to the Sloan Digital Sky Survey (SDSS) DR8 photometric data set. The DES SV catalog is locally volume limited and contains 786 clusters with richness {lambda}>20 (roughly equivalent to M_500c_>~10^14^h_70_^-1^M_{sun}_) and 0.2<z<0.9. The DR8 catalog consists of 26311 clusters with 0.08<z<0.6, with a sharply increasing richness threshold as a function of redshift for z>~0.35. The photometric redshift performance of both catalogs is shown to be excellent, with photometric redshift uncertainties controlled at the {sigma}_z_/(1+z)~0.01 level for z<~0.7 , rising to ~0.02 at z~0.9 in DES SV. We make use of Chandra and XMM X-ray and South Pole Telescope Sunyaev-Zeldovich data to show that the centering performance and mass-richness scatter are consistent with expectations based on prior runs of redMaPPer on SDSS data. We also show how the redMaPPer photo-z and richness estimates are relatively insensitive to imperfect star/galaxy separation and small-scale star masks.
- ID:
- ivo://CDS.VizieR/J/A+A/468/807
- Title:
- Redshifts of galaxies associated with X emission
- Short Name:
- J/A+A/468/807
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of spectroscopic observations of galaxies associated with the diffuse X-ray emitting structure discovered by Zappacosta et al. (2002A&A...394....7Z). After measuring the redshifts of 161 galaxies, we confirm an overdensity of galaxies with projected dimensions of at least 2Mpc, determine its spectroscopic redshift in z=0.401+/-0.002, and show that it is spatially coincident with the diffuse X-ray emission. This confirms the original claim that this X-ray emission has an extragalactic nature and is due to the warm-hot intergalactic medium (WHIM). We used this value of the redshift to compute the temperature of the emitting gas. The resulting value depends on the metallicity that is assumed for the IGM, and is constrained to be between 0.3 and 0.6keV for metallicities between 0.05 and 0.3solar, in good agreement with the expectations from the WHIM.
- ID:
- ivo://CDS.VizieR/J/ApJ/658/865
- Title:
- Redshifts of galaxies in X-ray-luminous groups
- Short Name:
- J/ApJ/658/865
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the galaxy populations in seven X-ray-selected, intermediate-redshift groups (0.2<z<0.6). Overall, the galaxy populations in these systems are similar to those in clusters at the same redshift; they have large fractions of early-type galaxies (fe~70%) and small fractions of galaxies with significant star formation (f~30%).
- ID:
- ivo://CDS.VizieR/J/A+A/618/A66
- Title:
- Redshifts of obscured AGN
- Short Name:
- J/A+A/618/A66
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Redshifts are fundamental for our understanding of extragalactic X-ray sources. Ambiguous counterpart associations, expensive optical spectroscopy and/or multimission multiwavelength coverage to resolve degeneracies make estimation often difficult in practice. We attempt to constrain redshifts of obscured Active Galactic Nuclei (AGN) using only low-resolution X-ray spectra. Our XZ method fits AGN X-ray spectra with a moderately complex spectral model incorporating a corona, torus obscurer and warm mirror. Using the Bayesian X-ray Astronomy (BXA) package, we constrain redshift, column density, photon index and luminosity simultaneously. The redshift information primarily comes from absorption edges in Compton-thin AGN, and from the Fe K{alpha} fluorescent line in heavily obscured AGN. A new generic background fitting method allows us to extract more information from limited numbers of source counts. We derive redshift constraints for 74/321 hard-band detected sources in the Chandra deep field South. Comparing with spectroscopic redshifts, we find an outlier fraction of 8%, indicating that our model assumptions are valid. For three Chandra deep fields, we release our XZ redshift estimates. The independent XZ estimate is easy to apply and effective for a large fraction of obscured AGN in todays deep surveys without the need for any additional data. Comparing to different redshift estimation methods, XZ can resolve degeneracies in photometric redshifts, help to detect potential association problems and confirm uncertain single-line spectroscopic redshifts. With high spectral resolution and large collecting area, this technique will be highly effective for Athena/WFI observations.
- ID:
- ivo://CDS.VizieR/J/MNRAS/274/75
- Title:
- Redshifts of ROSAT X-ray brightest clusters
- Short Name:
- J/MNRAS/274/75
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report results from the second stage of an optical follow-up study aimed at determining new redshifts for clusters of galaxies selected from the ROSAT All-Sky Survey. We review the optical properties of all the clusters obtained so far in this programme, which comprises 71 clusters up to a redshift of 0.3. The fraction of central galaxies exhibiting optical line emission and an excess blue continuum is 34%, consistent with smaller, previous, X-ray samples. There is no trend for this fraction to increase with redshift, although we find a clear tendency for the strongest line emitters to have the bluest continua. The probability of the presence of line emission and an excess blue continuum is increased for those galaxies with associated radio sources, although the strength of these features does not appear to be related to the power of the radio emission.
- ID:
- ivo://CDS.VizieR/J/ApJ/607/202
- Title:
- Redshift survey of nearby galaxy groups
- Short Name:
- J/ApJ/607/202
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We constrain the mass profile and orbital structure of nearby groups and clusters of galaxies. Our method yields the joint probability distribution of the density slope n, the velocity anisotropy {beta}, and the turnover radius r_0_ for these systems. The measurement technique does not use results from N-body simulations as priors. We incorporate 2419 new redshifts (included here) in the fields of 41 systems of galaxies with z<0.04.
- ID:
- ivo://CDS.VizieR/J/A+A/425/367
- Title:
- REFLEX Galaxy Cluster Survey catalogue
- Short Name:
- J/A+A/425/367
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the catalogue of the REFLEX Cluster Survey providing information on the X-ray properties, redshifts, and some identification details of the clusters in the REFLEX sample. The catalogue describes a statistically complete X-ray flux-limited sample of 447 galaxy clusters above an X-ray flux of 3x10^-12^erg/s/cm^2^ (0.1 to 2.4keV) in an area of 4.24ster in the southern sky. The cluster candidates were first selected by their X-ray emission in the ROSAT-All Sky Survey and subsequently spectroscopically identified in the frame of an ESO key programme. Previously described tests have shown that the sample is more than 90% complete and there is a conservative upper limit of 9% on the fraction of clusters with a dominant X-ray contamination from AGN. In addition to the cluster catalogue we also describe the complete selection criteria as a function of the sky position and the conversion functions used to analyse the X-ray data. These are essential for the precise statistical analysis of the large-scale cluster distribution. This data set is at present the largest, statistically complete X-ray galaxy cluster sample. Together with these data set we also provide for the first time the full three-dimensional selection function. The sample forms the basis of several cosmological studies, one of the most important applications being the assessment of the statistics of the large-scale structure of the universe and the test of cosmological models. Part of these cosmological results have already been published.
- ID:
- ivo://CDS.VizieR/J/MNRAS/429/3272
- Title:
- REFLEX II flux-limited supercluster sample
- Short Name:
- J/MNRAS/429/3272
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first supercluster catalogue constructed with the extended ROSAT-ESO Flux-Limited X-ray (REFLEX II) Galaxy Cluster survey data, which comprises 919 X-ray selected galaxy clusters with a flux limit of 1.8x10^-12^erg/s/cm2. Based on this cluster catalogue we construct a supercluster catalogue using a friends-of-friends algorithm with a linking length depending on the (local) cluster density, which thus varies with redshift. The resulting catalogue comprises 164 superclusters at redshift z<=0.4. The choice of the linking length in the friends-of-friends method modifies the properties of the superclusters. We study the properties of different catalogues such as the distributions of the redshift, extent and multiplicity by varying the choice of parameters. In addition to the supercluster catalogue for the entire REFLEX II sample, we compile a large volume-limited cluster sample from REFLEX II with the redshift and luminosity constraints of z<=0.1 and L_X_>=5x10^43^erg/s. With this catalogue we construct a volume-limited sample of superclusters. This sample is built with a homogeneous linking length, and hence selects effectively the same type of superclusters. By increasing the luminosity cut we can build a hierarchical tree structure of the volume-limited samples, where systems at the top of the tree are only formed via the most luminous clusters. This allows us to test if the same superclusters are found when only the most luminous clusters are visible, comparable to the situation at higher redshift in the REFLEX II sample. We find that the selection of superclusters is very robust, independent of the luminosity cut, and the contamination of spurious superclusters among cluster pairs is expected to be small. Numerical simulations and observations of the substructure of clusters suggest that regions of high cluster number density provide an astrophysically different environment for galaxy clusters, where the mass function and X-ray luminosity function are shifted to higher cut-off values and an increased merger rate may also boost some of the cluster X-ray luminosities. We therefore compare the X-ray luminosity function for the clusters in superclusters with that for the field clusters with the flux- and volume-limited catalogues. The results mildly support the theoretical suggestion of a top-heavy X-ray luminosity function of galaxy clusters in regions of high cluster density.
