Browsing by Author "Clerc, N."

Now showing 1 - 7 of 7
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    Active galactic nuclei and their large-scale structure: an eROSITA mock catalogue
    (2019) Comparat, J.; Merloni, A.; Salvato, M.; Nandra, K.; Boller, T.; Georgakakis, A.; Finoguenov, A.; Dwelly, T.; Buchner, J.; Del Moro, A.; Clerc, N.; Wang, Y.; Zhao, G.; Prada, F.; Yepes, G.; Brusa, M.; Krumpe, M.; Liu, T.
    In the context of the upcoming SRG/eROSITA survey, we present an N-body simulation-based mock catalogue for X-ray-selected active galactic nucleus (AGN) samples. The model reproduces the observed hard X-ray AGN luminosity function (XLF) and the soft X-ray logN-logS from redshift 0 to 6. The XLF is reproduced to within +/- 5 per cent and the logN-logS to within +/- 20 per cent. We develop a joint X-ray - optical extinction and classification model. We adopt a set of empirical spectral energy distributions to predict observed magnitudes in the UV, optical, and NIR. With the latest eROSITA all sky survey sensitivity model, we create a high-fidelity full-sky mock catalogue of X-ray AGN. It predicts their distributions in right ascension, declination, redshift, and fluxes. Using empirical medium resolution optical spectral templates and an exposure time calculator, we find that 1.1 x 10(6) (4 x 10(5)) fibre-hours are needed to follow-up spectroscopically from the ground the detected X-ray AGN with an optical magnitude 21 < r < 22.8 (22.8 < r < 25) with a 4-m (8-m) class multiobject spectroscopic facility. We find that future clustering studies will measure the AGN bias to the per cent level at redshift z < 1.2 and should discriminate possible scenarios of galaxy-AGN co-evolution. We predict the accuracy to which the baryon acoustic oscillation standard ruler will be measured using X-ray AGN: better than 3 per cent for AGN between redshift 0.5 to 3 and better than 1 per cent using the Ly alpha forest of X-ray QSOs discovered between redshift 2 and 3. eROSITA will provide an outstanding set of targets for future galaxy evolution and cosmological studies.
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    Clustering of CODEX clusters
    (2021) Lindholm, V.; Finoguenov, A.; Comparat, J.; Kirkpatrick, C. C.; Rykoff, E.; Clerc, N.; Collins, C.; Damsted, S.; Chitham, J. Ider; Padilla, N.
    Context. 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
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    Gravitational redshifting of galaxies in the SPIDERS cluster catalogue
    (2021) Mpetha, C. T.; Collins, C. A.; Clerc, N.; Finoguenov, A.; Peacock, J. A.; Comparat, J.; Schneider, D.; Capasso, R.; Damsted, S.; Furnell, K.; Merloni, A.; Padilla, N. D.; Saro, A.
    Data from the SPectroscopic IDentification of ERosita Sources (SPIDERS) are searched for a detection of the gravitational redshifting of light from similar to 20 000 galaxies in similar to 2500 galaxy clusters using three definitions of the cluster centre: its Brightest Cluster Galaxy (BCG), the redMaPPer identified Central Galaxy (CG), or the peak of X-ray emission. Distributions of velocity offsets between galaxies and their host cluster's centre, found using observed redshifts, are created. The quantity (Delta) over cap, the average of the radial velocity difference between the cluster members and the cluster systemic velocity, reveals information on the size of a combination of effects on the observed redshift, dominated by gravitational redshifting. The change of (Delta) over cap with radial distance is predicted for SPIDERS galaxies in General Relativity (GR), and f(R) gravity, and compared to the observations. The values of (Delta) over cap = -13.5 +/- 4.7 kms(-1), (Delta) over cap = -12.5 +/- 5.1 kms(-1), and (Delta) over cap = -18.6 +/- 4.8 kms(-1) for the BCG, X-ray, and CG cases, respectively, broadly agree with the literature. There is no significant preference of one gravity theory over another, but all cases give a clear detection (>2.5 sigma) of (Delta) over cap. The BCG centroid is deemed to be the most robust method in this analysis, due to no well-defined central redshift when using an X-ray centroid, and CGs identified by redMaPPer with no associated spectroscopic redshift. For future gravitational redshift studies, an order-of-magnitude more galaxies, similar to 500 000, will be required - a possible feat with the forthcoming Vera C. Rubin Observatory, Euclid and eROSITA.
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    Precision cosmology with a wide area XMM cluster survey
    (2011) Pierre, M.; Pacaud, F.; Juin, J. B.; Melin, J. B.; Valageas, P.; Clerc, N.; Corasaniti, P. S.
    We explore the cosmological constraints expected from wide area XMM-type cluster surveys covering 50-200 deg(2), under realistic observing conditions. We perform a Fisher matrix analysis, based on cluster number counts in combination with estimates of the two-point cluster correlation function. The effect of the survey design is implemented through an observationally well-tested cluster selection function. Special attention is given to the modelling of the shot noise and sample variance, which we estimate by applying our selection function to numerically simulated surveys. We then infer the constraints on the equation of state of the dark energy, considering various survey configurations. We quantitatively investigate the respective impact of the cluster mass measurements, of the correlation function and of the 1 < z < 2 cluster population. We show that, with some 20 Ms XMM observing time, it is possible to constrain the dark energy parameters at a level comparable to that expected from the next generation of cosmic probes. Such a survey also has the power to provide unique insights into the physics of high-redshift clusters and the properties of active galactic nuclei.
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    SPIDERS : overview of the X-ray galaxy cluster follow-up and the final spectroscopic data release
    (2020) Clerc, N.; Kirkpatrick, C. C.; Finoguenov, A.; Capasso, R.; Comparat, J.; Damsted, S.; Furnell, K.; Kukkola, A. E.; Chitham, J. I.; Padilla, Nelson; Merloni, A.; Salvato, M.; Gueguen, A.; Dwelly, T.; Collins, C.; Saro, A.; Erfanianfar, G.; Schneider, D. P.; Brownstein, J.; Mamon, G. A.; Jullo, E.; Bizyaev, D.
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    SPIDERS: an overview of the largest catalogue of spectroscopically confirmed x-ray galaxy clusters
    (2021) Kirkpatrick, C. C.; Clerc, N.; Finoguenov, A.; Damsted, S.; Chitham, J. Ider; Kukkola, A. E.; Gueguen, A.; Furnell, K.; Rykoff, E.; Comparat, J.; Saro, A.; Capasso, R.; Padilla, N.; Erfanianfar, G.; Mamon, G. A.; Collins, C.; Merloni, A.; Brownstein, J. R.; Schneider, D. P.
    SPIDERS is the spectroscopic follow-up effort of the Sloan Digital Sky Survey IV (SDSS-IV) project for the identification of X-ray selected galaxy clusters. We present our catalogue of 2740 visually inspected galaxy clusters as part of the SDSS Data Release 16 (DR16). Here we detail the target selection, our methods for validation of the candidate clusters, performance of the survey, the construction of the final sample, and a full description of what is found in the catalogue. Of the sample, the median number of members per cluster is approximately 10, with 818 having 15 or greater. We find that we are capable of validating over 99 per cent of clusters when five redshifts are obtained below z < 0.3 and when nine redshifts are obtained above z > 0.3. We discuss the improvements in this catalogue's identification of cluster using 33 340 redshifts, with Delta Z(phot)/Delta Z(spec) similar to 100, over other photometric and spectroscopic surveys, as well as presenting an update to previous (sigma-L-X) and (sigma-lambda) relations. Finally, we present our cosmological constraints derived using the velocity dispersion function.
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    SPIDERS: selection of spectroscopic targets using AGN candidates detected in all-sky X-ray surveys
    (OXFORD UNIV PRESS, 2017) Dwelly, T.; Salvato, M.; Merloni, A.; Brusa, M.; Buchner, J.; Anderson, S. F.; Boller, Th.; Brandt, W. N.; Budavari, T.; Clerc, N.; Coffey, D.; Del Moro, A.; Georgakakis, A.; Green, P. J.; Jin, C.; Menzel, M. L.; Myers, A. D.; Nandra, K.; Nichol, R. C.; Ridl, J.; Schwope, A. D.; Simm, T.
    SPIDERS (SPectroscopic IDentification of eROSITA Sources) is a Sloan Digital Sky Survey IV (SDSS-IV) survey running in parallel to the Extended Baryon Oscillation Spectroscopic Survey (eBOSS) cosmology project. SPIDERS will obtain optical spectroscopy for large numbers of X-ray-selected active galactic nuclei (AGN) and galaxy cluster members detected in wide-area eROSITA, XMM-Newton and ROSAT surveys. We describe the methods used to choose spectroscopic targets for two sub-programmes of SPIDERS X-ray selected AGN candidates detected in the ROSAT All Sky and the XMM-Newton Slew surveys. We have exploited a Bayesian cross-matching algorithm, guided by priors based on mid-IR colourmagnitude information from the Wide-field Infrared Survey Explorer survey, to select the most probable optical counterpart to each X-ray detection. We empirically demonstrate the high fidelity of our counterpart selection method using a reference sample of bright welllocalized X-ray sources collated from XMM-Newton, Chandra and Swift-XRT serendipitous catalogues, and also by examining blank-sky locations. We describe the down-selection steps which resulted in the final set of SPIDERS-AGN targets put forward for spectroscopy within the eBOSS/TDSS/SPIDERS survey, and present catalogues of these targets. We also present catalogues of similar to 12 000 ROSAT and similar to 1500 XMM-Newton Slew survey sources that have existing optical spectroscopy from SDSS-DR12, including the results of our visual inspections. On completion of the SPIDERS programme, we expect to have collected homogeneous spectroscopic redshift information over a footprint of similar to 7500 deg(2) for > 85 per cent of the ROSAT and XMM-Newton Slew survey sources having optical counterparts in the magnitude range 17 < r < 22.5, producing a large and highly complete sample of bright X-ray-selected AGN suitable for statistical studies of AGN evolution and clustering.