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- Mpetha, C. T., et al.
(författare)
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Gravitational redshifting of galaxies in the SPIDERS cluster catalogue
- 2021
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 503:1, s. 669-678
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Tidskriftsartikel (refereegranskat)abstract
- Data from the SPectroscopic IDentification of ERosita Sources (SPIDERS) are searched for a detection of the gravitational redshifting of light from ∼20000 galaxies in ∼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 ˆΔ, 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 ˆΔ with radial distance is predicted for SPIDERS galaxies in General Relativity (GR), and f(R) gravity, and compared to the observations. The values of ˆΔ=−13.5±4.7 km s−1, ˆΔ=−12.5±5.1 km s−1, and ˆΔ=−18.6±4.8 km s−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 (>2.5σ) of ˆΔ. 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, ∼500000, will be required – a possible feat with the forthcoming Vera C. Rubin Observatory, Euclid and eROSITA.
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| 2. |
- Kirkpatrick, C. C., et al.
(författare)
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SPIDERS : an overview of the largest catalogue of spectroscopically confirmed x-ray galaxy clusters
- 2021
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 503:4, s. 5763-5777
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Tidskriftsartikel (refereegranskat)abstract
- 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 Δzphot/Δzspec ∼ 100, over other photometric and spectroscopic surveys, as well as presenting an update to previous (σ–LX) and (σ–λ) relations. Finally, we present our cosmological constraints derived using the velocity dispersion function.
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