10 research outputs found
Clustering of CODEX clusters
No full textContext. The clustering of galaxy clusters links the spatial nonuniformity of dark matter halos to the growth of the primordial spectrum of perturbations. The amplitude of the clustering signal is widely used to estimate the halo mass of astrophysical objects. The advent of cluster mass calibrations enables using clustering in cosmological studies.
Aims. We analyze the autocorrelation function of a large contiguous sample of galaxy clusters, the Constrain Dark Energy with X-ray (CODEX) sample, in which we take particular care of cluster definition. These clusters were X-ray selected using the ROentgen SATellite All-Sky Survey and then identified as galaxy clusters using the code redMaPPer run on the photometry of the Sloan Digital Sky Survey. We develop methods for precisely accounting for the sample selection effects on the clustering and demonstrate their robustness using numerical simulations.
Methods. Using the clean CODEX sample, which was obtained by applying a redshift-dependent richness selection, we computed the two-point autocorrelation function of galaxy clusters in the 0.1 < z < 0.3 and 0.3 < z < 0.5 redshift bins. We compared the bias in the measured correlation function with values obtained in numerical simulations using a similar cluster mass range.
Results. By fitting a power law, we measured a correlation length r0 = 18.7 ± 1.1 and slope γ = 1.98 ± 0.14 for the correlation function in the full redshift range. By fixing the other cosmological parameters to their nine-year Wilkinson Microwave Anisotropy Probe values, we reproduced the observed shape of the correlation function under the following cosmological conditions: and with estimated additional systematic errors of σΩm0 = 0.02 and σS8 = 0.20. We illustrate the complementarity of clustering constraints by combining them with CODEX cosmological constraints based on the X-ray luminosity function, deriving Ωm0 = 0.25 ± 0.01 and with an estimated additional systematic error of σΩm0 = 0.07 and σσ8 = 0.04. The mass calibration and statistical quality of the mass tracers are the dominant source of uncertainty
Characterisation of the X-ray point source variability in the eROSITA south ecliptic pole field
No full textAims: During the Spectrum Roentgen Gamma (SRG)/ eROSITA all-sky surveys, X-ray sources close to the South Ecliptic Pole (SEP) are observed almost every 4 hours. We aim to identify the sources exhibiting the most significant long-term X-ray variability within 3 degrees of the SEP in the first three surveys, and investigate their properties.
Methods: We determined the variability significance of all sources observed by eROSITA within 3 degrees of the SEP by using thresholds on the Bayesian excess variance (SCATT_LO) and the maximum amplitude deviation (AMPL_SIG). Sources exhibiting a variability significance above were subdivided into likely Galactic and extragalactic sources, by using spectral and photometric information of their optical counterparts. We quantified the X-ray normalised excess variances of all variable sources, and also calculated the periodograms of the brightest ones.
Results: Out of more than X-ray sources detected by eROSITA within 3 degrees of the SEP, we identified 453 that exhibit significant X-ray variability. SCATT_LO is significantly more sensitive to detecting variable sources in this field, but AMPL_SIG helps provide a more complete variability sample. Of those variable sources, 168 were classified as likely extragalactic, and 235 as likely Galactic. The periodograms of most bright and variable extragalactic sources are approximately described by an aliased power law () with an index of . We identified a potential tidal disruption event, and long-term transient sources. The stellar X-ray variability was predominantly caused by bright X-ray flares from coronally active stars.22 pages, 29 figure
The eROSITA Final Equatorial-Depth Survey (eFEDS): Catalog of galaxy clusters and groups
No full textThe eROSITA Final Equatorial-Depth Survey has been carried out during the PV
phase of the SRG/eROSITA telescope and completed in November 2019. This survey
is designed to provide the first eROSITA-selected sample of galaxy clusters and
groups and to test the predictions for the all-sky survey in the context of
cosmological studies with clusters. In the 140 deg area covered by eFEDS,
542 candidate clusters and groups are detected as extended X-ray sources, down
to a flux of erg/s/cm in the soft band (0.5-2 keV) within
1'. In this work, we provide the catalog of candidate galaxy clusters and
groups in eFEDS. We perform imaging and spectral analysis on the eFEDS clusters
with eROSITA X-ray data, and study the properties of the sample. The clusters
are distributed in the redshift range [0.01, 1.3], with the median redshift at
0.35. We obtain the ICM temperature measurement with c.l. for
1/5 (102/542) of the sample. The average temperature of these clusters is
2 keV. Radial profiles of flux, luminosity, electron density, and gas
mass are measured from the precise modeling of the imaging data. The selection
function, the purity and completeness of the catalog are examined and discussed
in detail. The contamination fraction is in this sample, dominated by
misidentified point sources. The X-ray Luminosity Function of the clusters
agrees well with the results obtained from other recent X-ray surveys. We also
find 19 supercluster candidates in eFEDS, most of which are located at
redshifts between 0.1 and 0.5. The eFEDS cluster and group catalog provides a
benchmark proof-of-concept for the eROSITA All-Sky Survey extended source
detection and characterization. We confirm the excellent performance of eROSITA
for cluster science and expect no significant deviations from our pre-launch
expectations for the final All-Sky Survey.Comment: Submitted to A&A for the Special Issue: The Early Data Release of
eROSITA and Mikhail Pavlinsky ART-XC on the SRG Mission. 25 pages, 13 figure
The eROSITA Final Equatorial-Depth Survey (eFEDS): Galaxy Clusters and Groups in Disguise
No full textThe eROSITA Final Equatorial-Depth Survey (eFEDS), executed during the
performance verification phase of the Spectrum-Roentgen-Gamma (SRG)/eROSITA
telescope, was completed in Nov. 2019. One of the science goals of this survey
is to demonstrate the ability of eROSITA to detect samples of clusters and
groups at the final depth of the eROSITA all-sky survey. Because of the
sizeable point-spread function of eROSITA, high-redshift clusters of galaxies
or compact nearby groups hosting bright active galactic nuclei (AGN) can be
misclassified as point sources by the source detection algorithms. A total of
346 galaxy clusters and groups in the redshift range of 0.1<z<1.3 were
identified based on their red sequence in the point source catalog. We examine
the multiwavelength properties of these clusters and groups to understand the
potential biases in our selection process and the completeness of the
extent-selected sample. The majority of the clusters and groups in the point
source sample are indeed underluminous and compact compared to the
extent-selected sample. Their faint X-ray emission, well below the flux limit
of the extent-selected eFEDS clusters, and their compact X-ray emission are
likely to be the main reason for this misclassification. In the sample, we
confirm that 10% of the sources host AGN in their brightest cluster galaxies
(BCGs) through optical spectroscopy and visual inspection. By studying their
X-ray, optical, infrared, and radio properties, we establish a method for
identifying clusters and groups that host AGN in their BCGs. We successfully
test this method on the current point source catalog through the Sloan Digital
Sky Survey optical spectroscopy and find eight clusters and groups with active
radio-loud AGN that are particularly bright in the infrared. They include
eFEDSJ091437.8+024558, eFEDSJ083520.1+012516, and eFEDSJ092227.1+043339 at
redshifts 0.3-0.4. [ABRIDGED]Comment: 31 pages, 13 figures, 3 tables. Accepted for publication in A&A for
the Special Issue: The Early Data Release of eROSITA and Mikhail Pavlinsky
ART-XC on the SRG Missio
Full-sky photon simulation of clusters and active galactic nuclei in the soft X-rays for eROSITA
No full textInternational audienceThe eROSITA X-ray telescope on board the Spectrum-Roentgen-Gamma (SRG) mission will measure the position and properties of about 100,000 clusters of galaxies and 3 million active galactic nuclei over the full sky. To study the statistical properties of this ongoing survey, it is key to estimate the selection function accurately. We create a set of full sky light-cones using the MultiDark and UNIT dark matter only N-body simulations. We present a novel method to predict the X-ray emission of galaxy clusters. Given a set of dark matter halo properties (mass, redshift, ellipticity, offset parameter), we construct an X-ray emissivity profile and image for each halo in the light-cone. We follow the eROSITA scanning strategy to produce a list of X-ray photons on the full sky. We predict scaling relations for the model clusters, which are in good agreement with the literature. The predicted number density of clusters as a function of flux also agrees with previous measurements. Finally, we obtain a scatter of 0.21 (0.07, 0.25) for the X-ray luminosity -- mass (temperature -- mass, luminosity -- temperature) model scaling relations. We provide catalogues with the model photons emitted by clusters and active galactic nuclei. These catalogues will aid the eROSITA end to end simulation flow analysis and in particular the source detection process and cataloguing methods
The eROSITA Final Equatorial-Depth Survey (eFEDS) - Characterization of morphological properties of galaxy groups and clusters
No full textInternational audienceContext. Morphological parameters are the estimators for the dynamical state of clusters of galaxies. Surveys performed at different wavelengths through their selection effects may be biased toward, different populations of clusters. For example, X-ray surveys are biased to detecting cool-core clusters as opposed to Sunyaev-Zel’dovich (SZ) surveys being more biased toward non-cool-core systems. Understanding the underlying population of clusters of galaxies in surveys is of the utmost importance when these samples are to be used in astrophysical and cosmological studies.Aims. We present an in-depth analysis of the X-ray morphological parameters of the galaxy clusters and groups detected in the eROSITA Final Equatorial-Depth Survey (eFEDS). The eFEDS, completed during the performance verification phase of the Spectrum-Roentgen-Gamma(SRG)/eROSITA telescope, is designed to provide the first eROSITA X-ray selected sample of galaxy clusters and groups.Methods. We studied the eROSITA X-ray imaging data for a sample of 325 clusters and groups that were significantly detected in the eFEDS field. We characterized their dynamical properties by measuring a number of dynamical estimators: concentration, central density, cuspiness, centroid shift, ellipticity, power ratios, photon asymmetry, and the Gini coefficient. The galaxy clusters and groups detected in eFEDS cover a luminosity range of more than three orders of magnitude and a wide redshift range out to 1.2. They provide an ideal sample on which the redshift and luminosity evolution of the morphological parameters can be studied and the underlying dynamical state of the sample can be characterized. Based on these measurements, we constructed a new dynamical indicator, the relaxation score, for all the clusters in the sample.Results. We find no evidence for a bimodality in the distribution of the morphological parameters of our clusters. We instead observe a smooth transition from the cool core to non-cool core and from relaxed to disturbed states, with a preference for skewed distributions or log-normal distributions. A significant evolution in redshift and luminosity is also observed in the morphological parameters we examined after taking the selection effects into account.Conclusions. We determine that in contrast do ROSAT-based cluster samples, our eFEDS-selected cluster sample is not biased toward cool-core clusters, but contains a similar fraction of cool-cores as SZ surveys.Key words: galaxies: clusters: intracluster medium / galaxies: clusters: general / X-rays: galaxies: cluster
CODEX Weak Lensing Mass Catalogue and implications on the mass-richness relation
No full textInternational audienceThe COnstrain Dark Energy with X-ray clusters (CODEX) sample contains the largest flux limited sample of X-ray clusters at , with , and . We find a slope , normalization and using CFHT richness estimates. In comparison to other weak lensing richness-mass relations, we find the normalization of the richness statistically agreeing with the normalization of other scaling relations from a broad redshift range () and with different cluster selection (X-ray, Sunyaev-Zeldovich, and optical)
The Seventeenth Data Release of the Sloan Digital Sky Surveys: Complete Release of MaNGA, MaStar and APOGEE-2 Data
No full textThis paper documents the seventeenth data release (DR17) from the Sloan Digital Sky Surveys; the fifth and final release from the fourth phase (SDSS-IV). DR17 contains the complete release of the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey, which reached its goal of surveying over 10,000 nearby galaxies. The complete release of the MaNGA Stellar Library (MaStar) accompanies this data, providing observations of almost 30,000 stars through the MaNGA instrument during bright time. DR17 also contains the complete release of the Apache Point Observatory Galactic Evolution Experiment 2 (APOGEE-2) survey which publicly releases infra-red spectra of over 650,000 stars. The main sample from the Extended Baryon Oscillation Spectroscopic Survey (eBOSS), as well as the sub-survey Time Domain Spectroscopic Survey (TDSS) data were fully released in DR16. New single-fiber optical spectroscopy released in DR17 is from the SPectroscipic IDentification of ERosita Survey (SPIDERS) sub-survey and the eBOSS-RM program. Along with the primary data sets, DR17 includes 25 new or updated Value Added Catalogs (VACs). This paper concludes the release of SDSS-IV survey data. SDSS continues into its fifth phase with observations already underway for the Milky Way Mapper (MWM), Local Volume Mapper (LVM) and Black Hole Mapper (BHM) surveys.40 pages, 8 figures, 6 tables. In press at ApJSS (arxiv v2 corrects some minor typos and updates references
The 16th data release of the Sloan Digital Sky Surveys:first release from the APOGEE-2 Southern Survey and full release of eBOSS Spectra
No full textInternational audienceThis paper documents the sixteenth data release (DR16) from the Sloan Digital Sky Surveys; the fourth and penultimate from the fourth phase (SDSS-IV). This is the first release of data from the southern hemisphere survey of the Apache Point Observatory Galactic Evolution Experiment 2 (APOGEE-2); new data from APOGEE-2 North are also included. DR16 is also notable as the final data release for the main cosmological program of the Extended Baryon Oscillation Spectroscopic Survey (eBOSS), and all raw and reduced spectra from that project are released here. DR16 also includes all the data from the Time Domain Spectroscopic Survey (TDSS) and new data from the SPectroscopic IDentification of ERosita Survey (SPIDERS) programs, both of which were co-observed on eBOSS plates. DR16 has no new data from the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey (or the MaNGA Stellar Library "MaStar"). We also preview future SDSS-V operations (due to start in 2020), and summarize plans for the final SDSS-IV data release (DR17)
