23 research outputs found
CODEX clusters - Survey, catalog, and cosmology of the X-ray luminosity function
No full textInternational audienceContext. Large area catalogs of galaxy clusters constructed from ROSAT All-Sky Survey provide the basis for our knowledge of the population of clusters thanks to long-term multiwavelength efforts to follow up observations of these clusters.Aims. The advent of large area photometric surveys superseding previous, in-depth all-sky data allows us to revisit the construction of X-ray cluster catalogs, extending the study to lower cluster masses and higher redshifts and providing modeling of the selection function.Methods. We performed a wavelet detection of X-ray sources and made extensive simulations of the detection of clusters in the RASS data. We assigned an optical richness to each of the 24 788 detected X-ray sources in the 10 382 square degrees of the Baryon Oscillation Spectroscopic Survey area using red sequence cluster finder redMaPPer version 5.2 run on Sloan Digital Sky Survey photometry. We named this survey COnstrain Dark Energy with X-ray (CODEX) clusters.Results. We show that there is no obvious separation of sources on galaxy clusters and active galactic nuclei (AGN) based on the distribution of systems on their richness. This is a combination of an increasing number of galaxy groups and their selection via the identification of X-ray sources either by chance or by groups hosting an AGN. To clean the sample, we use a cut on the optical richness at the level corresponding to the 10% completeness of the survey and include it in the modeling of the cluster selection function. We present the X-ray catalog extending to a redshift of 0.6.Conclusions. The CODEX suvey is the first large area X-ray selected catalog of northern clusters reaching fluxes of 10−13 ergs s−1 cm−2. We provide modeling of the sample selection and discuss the redshift evolution of the high end of the X-ray luminosity function (XLF). Our results on z < 0.3 XLF agree with previous studies, while we provide new constraints on the 0.3 < z < 0.6 XLF. We find a lack of strong redshift evolution of the XLF, provide exact modeling of the effect of low number statistics and AGN contamination, and present the resulting constraints on the flat ΛCDM.Key words: surveys / catalogs / large-scale structure of Universe⋆ The catalog of clusters is only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/638/A11
Offset between X-ray and optical centers in clusters of galaxies: Connecting eROSITA data with simulations
No full textContext. The characterization of the dynamical state of galaxy clusters is key to studying their evolution, evaluating their selection, and using them as a cosmological probe. In this context, the offsets between different definitions of the center have been used to estimate the cluster disturbance.
Aims. Our goal is to study the distribution of the offset between the X-ray and optical centers in clusters of galaxies. We study the offset for clusters detected by the extended ROentgen Survey with an Imaging Telescope Array (eROSITA) on board the Spectrum-Roentgen-Gamma (SRG) observatory. We aim to connect observations to predictions by hydrodynamical simulations and N-body models. We assess the astrophysical effects affecting the displacements.
Methods. We measured the offset for clusters observed in the eROSITA Final Equatorial-Depth Survey (eFEDS) and the first eROSITA all-sky survey (eRASS1). We focus on a subsample of 87 massive eFEDS clusters at low redshift, with M500c > 1×1014 M⊙ and 0.15 < z < 0.4. We compared the displacements in such sample to those predicted by the TNG and the Magneticum simulations. We additionally link the observations to the offset parameter Xoff measured for dark matter halos in N-body simulations, using the hydrodynamical simulations as a bridge.
Results. We find that, on average, the eFEDS clusters show a smaller offset compared to eRASS1 because the latter contains a larger fraction of massive and disturbed structures. We measured an average offset of kpc, when focusing on the subsample of 87 eFEDS clusters. This is in agreement with the predictions from TNG and Magneticum, and the distribution of Xoff from dark matter only (DMO) simulations. However, the tails of the distributions are different. Using ΔX − O to classify relaxed and disturbed clusters, we measured a relaxed fraction of 31% in the eFEDS subsample. Finally, we found a correlation between the offset measured on hydrodynamical simulations and Xoff measured on their parent dark-matter-only run and we calibrated the relation between them.
Conclusions. We conclude that there is good agreement between the offsets measured in eROSITA data and the predictions from simulations. Baryonic effects cause a decrement (increment) in the low (high) offset regime compared to the Xoff distribution from dark matter-only simulations. The offset–Xoff relation provides an accurate prediction of the true Xoff distribution in Magneticum and TNG. It allows for the offsets to be introduced in a cosmological context with a new method in order to marginalize over selection effects related to the cluster dynamical state
SPIDERS: overview of the X-ray galaxy cluster follow-up and the final spectroscopic data release
No full text19 pages, 21 figures. Accepted for publication in MNRASInternational audienceSPIDERS (The SPectroscopic IDentification of eROSITA Sources) is a large spectroscopic programme for X-ray selected galaxy clusters as part of the Sloan Digital Sky Survey-IV (SDSS-IV). We describe the final dataset in the context of SDSS Data Release 16 (DR16): the survey overall characteristics, final targeting strategies, achieved completeness and spectral quality, with special emphasis on its use as a galaxy cluster sample for cosmology applications. SPIDERS now consists of about 27,000 new optical spectra of galaxies selected within 4,000 photometric red sequences, each associated with an X-ray source. The excellent spectrograph efficiency and a robust analysis pipeline yield a spectroscopic redshift measurement success rate exceeding 98%, with a median velocity accuracy of 20 km s^{-1} (at z=0.2). Using the catalogue of 2,740 X-ray galaxy clusters confirmed with DR16 spectroscopy, we reveal the three-dimensional map of the galaxy cluster distribution in the observable Universe up to z ~ 0.6. We highlight the homogeneity of the member galaxy spectra among distinct regions of the galaxy cluster phase space. Aided by accurate spectroscopic redshifts and by a model of the sample selection effects, we compute the galaxy cluster X-ray luminosity function and we present its lack of evolution up to z=0.6. Finally we discuss the prospects of forthcoming large multiplexed spectroscopic programmes dedicated to follow up the next generation of all-sky X-ray source catalogues
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
Cosmological constraints from CODEX galaxy clusters spectroscopically confirmed by SDSS-IV/SPIDERS DR16
No full textThis is a pre-copyedited, author-produced PDF of an article accepted for publication in Monthly Notices of the Royal Astronomical Society following peer review. The version of record Monthly Notices of the Royal Astronomical Society, Volume 499, Issue 4, December 2020, Pages 4768–4784 is available online at: https://doi.org/10.1093/mnras/staa3044International audienceThis paper presents a cosmological analysis based on the properties of X-ray selected clusters of galaxies from the CODEX survey which have been spectroscopically followed up within the SPIDERS programme as part of the sixteenth data release (DR16) of SDSS-IV. The cosmological sub-sample contains a total of 691 clusters over an area of 5350 deg2 with newly measured optical properties provided by a reanalysis of the CODEX source catalogue using redMaPPer and the DESI Legacy Imaging Surveys (DR8). Optical richness is used as a proxy for the cluster mass, and the combination of X-ray, optical, and spectroscopic information ensures that only confirmed virialized systems are considered. Clusters are binned in observed redshift, z̃ ∈[0.1,0.6) and optical richness, λ̃ ∈[25,148) and the number of clusters in each bin is modelled as a function of cosmological and richness–mass scaling relation parameters. A high-purity sub-sample of 691 clusters is used in the analysis and best-fitting cosmological parameters are found to be Ωm0=0.34+0.09−0.05 and σ8=0.73+0.03−0.03. The redshift evolution of the self-calibrated richness–mass relation is poorly constrained due to the systematic uncertainties associated with the X-ray component of the selection function (which assumes a fixed X-ray luminosity–mass relation with h = 0.7 and Ωm0=0.30). Repeating the analysis with the assumption of no redshift evolution is found to improve the consistency between both cosmological and scaling relation parameters with respect to recent galaxy cluster analyses in the literature
CODEX: Role of velocity substructure in the scaling relations of galaxy clusters
No full textContext. The use of galaxy clusters as cosmological probes relies on a detailed understanding of their properties. They define cluster selection and ranking linked to a cosmologically significant cluster mass function. Previous studies have employed small samples of clusters, concentrating on achieving the first calibrations of cluster properties with mass, while the diversity of cluster properties has been revealed via detailed studies. Aims. The large spectroscopic follow-up on the CODEX cluster sample with SDSS and NOT enables a detailed study of hundreds of clusters, lifting the limitations of previous samples. We aim to update the spectroscopic cluster identification of CODEX by running the spectroscopic group finder on the follow-up spectroscopy results and connecting the dynamical state of clusters to their scaling relations. Methods. We implemented a reproducible spectroscopic membership determination and cleaning procedures, based on the redMaPPer membership, running the spectroscopic group finder on the follow-up spectroscopy results and cleaning the membership for spectroscopic outliers. We applied the Anderson-Darling test for velocity substructure and analysed its influence on the scaling relations. We also tested the effect of the X-ray-to-optical centre offset on the scaling relations. Results. We report on the scaling relations between richness, X-ray luminosity, and velocity dispersion for a complete sample of clusters with at least 15 members. Clusters with velocity substructure exhibit enhanced velocity dispersion for a given richness and are characterized by 2.5 times larger scatter. Clusters that have a strong offset in X-ray-to-optical centres have comparable scaling relations as clusters with substructure. We demonstrate that there is a consistency in the parameters of the scaling relations for the low- and high-richness galaxy clusters. Splitting the clusters by redshift, we note a decrease in scatter with redshift in all scaling relations. We localize the redshift range where a high scatter is observed to z < 0.15, which is in agreement with the literature results on the scatter. We note that the increase in scatter for both high- and low-luminosity clusters is z < 0.15, suggesting that both cooling and the resulting active galactic nucleus feedback are at the root of this scatter
CODEX: Role of velocity substructure in the scaling relations of galaxy clusters
No full textThe use of galaxy clusters as cosmological probes relies on a detailed
understanding of their properties. We aim to update the spectroscopic cluster
identification of CODEX by running the spectroscopic group finder on the
follow-up spectroscopy results and connecting the dynamical state of clusters
to their scaling relations. We implemented a reproducible spectroscopic
membership determination and cleaning procedures, based on the redMaPPer
membership, running the spectroscopic group finder on the follow-up
spectroscopy results and cleaning the membership for spectroscopic outliers. We
applied the Anderson-Darling test for velocity substructure and analysed its
influence on the scaling relations. We also tested the effect of the
X-ray-to-optical centre offset on the scaling relations. We report on the
scaling relations between richness, X-ray luminosity, and velocity dispersion
for a complete sample of clusters with at least 15 members. Clusters with
velocity substructure exhibit enhanced velocity dispersion for a given richness
and are characterized by 2.5 times larger scatter. Clusters that have a strong
offset in X-ray-to-optical centres have comparable scaling relations as
clusters with substructure. We demonstrate that there is a consistency in the
parameters of the scaling relations for the low- and high-richness galaxy
clusters. Splitting the clusters by redshift, we note a decrease in scatter
with redshift in all scaling relations. We localize the redshift range where a
high scatter is observed to , which is in agreement with the literature
results on the scatter. We note that the increase in scatter for both high- and
low-luminosity clusters is , suggesting that both cooling and the
resulting active galactic nucleus feedback are at the root of this scatter.
Abridged.Comment: 23 pages, A&A in press, catalogs are released through CD
CODEX: Role of velocity substructure in the scaling relations of galaxy clusters
No full textContext. The use of galaxy clusters as cosmological probes relies on a detailed understanding of their properties. They define cluster selection and ranking linked to a cosmologically significant cluster mass function. Previous studies have employed small samples of clusters, concentrating on achieving the first calibrations of cluster properties with mass, while the diversity of cluster properties has been revealed via detailed studies.
Aims. The large spectroscopic follow-up on the CODEX cluster sample with SDSS and NOT enables a detailed study of hundreds of clusters, lifting the limitations of previous samples. We aim to update the spectroscopic cluster identification of CODEX by running the spectroscopic group finder on the follow-up spectroscopy results and connecting the dynamical state of clusters to their scaling relations.
Methods. We implemented a reproducible spectroscopic membership determination and cleaning procedures, based on the redMaPPer membership, running the spectroscopic group finder on the follow-up spectroscopy results and cleaning the membership for spectroscopic outliers. We applied the Anderson-Darling test for velocity substructure and analysed its influence on the scaling relations. We also tested the effect of the X-ray-to-optical centre offset on the scaling relations.
Results. We report on the scaling relations between richness, X-ray luminosity, and velocity dispersion for a complete sample of clusters with at least 15 members. Clusters with velocity substructure exhibit enhanced velocity dispersion for a given richness and are characterized by 2.5 times larger scatter. Clusters that have a strong offset in X-ray-to-optical centres have comparable scaling relations as clusters with substructure. We demonstrate that there is a consistency in the parameters of the scaling relations for the low- and high-richness galaxy clusters. Splitting the clusters by redshift, we note a decrease in scatter with redshift in all scaling relations. We localize the redshift range where a high scatter is observed to z < 0.15, which is in agreement with the literature results on the scatter. We note that the increase in scatter for both high- and low-luminosity clusters is z < 0.15, suggesting that both cooling and the resulting active galactic nucleus feedback are at the root of this scatter
The mass function dependence on the dynamical state of dark matter haloes
No full textContext. Galaxy clusters are luminous tracers of the most massive dark matter haloes in the Universe. To use them as a cosmological probe, a detailed description of the properties of dark matter haloes is required. Aims. We characterize how the dynamical state of haloes impacts the dark matter halo mass function at the high-mass end (i.e., for haloes hosting clusters of galaxies). Methods. We used the dark matter-only MultiDark suite of simulations and the high-mass objects M > 2.7 × 1013 M⊙ h−1 therein. We measured the mean relations of concentration, offset, and spin as a function of dark matter halo mass and redshift. We investigated the distributions around the mean relations. We measured the dark matter halo mass function as a function of offset, spin, and redshift. We formulated a generalized mass function framework that accounts for the dynamical state of the dark matter haloes. Results. We confirm the recent discovery of the concentration upturn at high masses and provide a model that predicts the concentration for different values of mass and redshift with one single equation. We model the distributions around the mean values of concentration, offset, and spin with modified Schechter functions. We find that the concentration of low-mass haloes shows a faster redshift evolution compared to high-mass haloes, especially in the high-concentration regime. We find that the offset parameter is systematically smaller at low redshift, in agreement with the relaxation of structures at recent times. The peak of its distribution shifts by a factor of ∼1.5 from z = 1.4 to z = 0. The individual models are combined into a comprehensive mass function model, which predicts the mass function as a function of spin and offset. Our model recovers the fiducial mass function with ∼3% accuracy at redshift 0 and accounts for redshift evolution up to z ∼ 1.5. Results. This new approach accounts for the dynamical state of the halo when measuring the halo mass function. It offers a connection with dynamical selection effects in galaxy cluster observations. This is key toward precision cosmology using cluster counts as a probe
