Grandis, S., Klein, M., Mohr, J. J., Bocquet, S., Paulus, M., Abbott, T. M. C., Aguena, M., Allam, S., Annis, J., Benson, B. A., Bertin, E., Bhargava, S., Brooks, D., Burke, D. L., Carnero Rosell, A., Carrasco Kind, M., Carretero, J., Capasso, R., Costanzi, M., da Costa, L. N., De Vicente, J., Desai, S., Dietrich, J. P., Doel, P., Eifler, T. F. et al. 2020. "Validation of selection function, sample contamination and mass calibration in galaxy cluster samples." Monthly Notices of the Royal Astronomical Society, 498 771–798. https://doi.org/10.1093/mnras/staa2333.
We construct and validate the selection function of the MARD-Y3 galaxy cluster sample. This sample was selected through optical follow-up of the 2nd ROSAT faint source catalogue with Dark Energy Survey year 3 data. The selection function is modelled by combining an empirically constructed X-ray selection function with an incompleteness model for the optical follow-up. We validate the joint selection function by testing the consistency of the constraints on the X-ray flux-mass and richness-mass scaling relation parameters derived from different sources of mass information: (1) cross-calibration using South Pole Telescope Sunyaev-Zel'dovich (SPT-SZ) clusters, (2) calibration using number counts in X-ray, in optical and in both X-ray and optical while marginalizing over cosmological parameters, and (3) other published analyses. We find that the constraints on the scaling relation from the number counts and SPT-SZ cross-calibration agree, indicating that our modelling of the selection function is adequate. Furthermore, we apply a largely cosmology independent method to validate selection functions via the computation of the probability of finding each cluster in the SPT-SZ sample in the MARD-Y3 sample and vice versa. This test reveals no clear evidence for MARD-Y3 contamination, SPT-SZ incompleteness or outlier fraction. Finally, we discuss the prospects of the techniques presented here to limit systematic selection effects in future cluster cosmological studies.
