Exploring the contamination of the DES-Y1 cluster sample with SPT-SZ selected clusters

• Published in: Monthly Notices of the Royal Astronomical Society
• Main Authors: Grandis, S., Mohr, J. J., Costanzi, M., Saro, A., Bocquet, S., Klein, M., Aguena, M., Allam, S., Annis, J., Ansarinejad, B., Bacon, D., Bertin, E., Bleem, L., Brooks, D., Burke, D. L., Carnero Rosel, A., Carrasco Kind, M., Carretero, J., Castander, F. J., Choi, A., da Costa, L. N., de Vincente, J., Desai, S., Diehl, H. T., Dietrich, J. P., Doel, P., Eifler, T. F., Everett, S., Ferrero, I., Floyd, B., Fosalba, P., Frieman, J., García-Bellido, J., Gaztanaga, E., Gruen, D., Gruendl, R. A., Gschwend, J., Gupta, N., Gutierrez, G., Hinton, S. R., Hollowood, D. L., Honscheid, K., James, D. J., Jeltema, T., Kuehn, K., Lahav, O., Lidman, C., Lima, M., Maia, M. A. G., March, M., Marshall, J. L., Melchior, P., Menanteau, F., Miquel, R., Morgan, R., Myles, J., Ogando, R., Palmese, A., Paz-Chinchón, F., Plazas, A. A., Reichardt, C. L., Romer, A. K., Sanchez, E., Scarpine, V., Serrano, S., Sevilla-Noarbe, I., Singh, P., Smith, M., Suchyta, E., Swanson, M. E. C., Tarle, G., Thomas, D., To, C., Weller, J., Wilkinson, R. D., Wu, H.
• Other Authors: Institut d'Astrophysique de Paris (IAP), Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2021
• Subjects: methods: statistical; galaxies: clusters: general; large-scale structure of Universe; Astrophysics - Cosmology and Nongalactic Astrophysics; [SDU]Sciences of the Universe [physics]; [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph]; South pole
• Online Access: https://insu.hal.science/insu-03748203; https://insu.hal.science/insu-03748203/document; https://insu.hal.science/insu-03748203/file/stab869.pdf; https://doi.org/10.1093/mnras/stab869

International audience We perform a cross validation of the cluster catalogue selected by the red-sequence Matched-filter Probabilistic Percolation algorithm (redMaPPer) in Dark Energy Survey year 1 (DES-Y1) data by matching it with the Sunyaev-Zel'dovich effect (SZE) selected cluster catalogue from the South Pole Telescope SPT-SZ survey. Of the 1005 redMaPPer selected clusters with measured richness $\hat{\lambda } 40$ in the joint footprint, 207 are confirmed by SPT-SZ. Using the mass information from the SZE signal, we calibrate the richness-mass relation using a Bayesian cluster population model. We find a mass trend λ ∝ M B consistent with a linear relation (B ~ 1), no significant redshift evolution and an intrinsic scatter in richness of σ λ = 0.22 ± 0.06. By considering two error models, we explore the impact of projection effects on the richness-mass modelling, confirming that such effects are not detectable at the current level of systematic uncertainties. At low richness SPT-SZ confirms fewer redMaPPer clusters than expected. We interpret this richness dependent deficit in confirmed systems as due to the increased presence at low richness of low-mass objects not correctly accounted for by our richness-mass scatter model, which we call contaminants. At a richness $\hat{\lambda }=40$, this population makes up ${}12{{\ \rm per\ cent}}$ (97.5 percentile) of the total population. Extrapolating this to a measured richness $\hat{\lambda }=20$ yields ${}22{{\ \rm per\ cent}}$ (97.5 percentile). With these contamination fractions, the predicted redMaPPer number counts in different plausible cosmologies are compatible with the measured abundance. The presence of such a population is also a plausible explanation for the different mass trends (B ~ 0.75) obtained from mass calibration using purely optically selected clusters. The mean mass from stacked weak lensing (WL) measurements suggests that these low-mass contaminants are galaxy groups with masses ~3-5 × 10 13 M ⊙ which are beyond the sensitivity of current ...