EPJ Web of Conferences 228, 00011 (2020)
https://doi.org/10.1051/epjconf/202022800011

Biases in the estimation of velocity dispersions and dynamical masses for galaxy clusters

¹ Instituto de Astrofísica de Canarias (IAC), C/ Vía Láctea s/n, E-38205 La Laguna, Tenerife, Spain
² Universidad de La Laguna, Departamento de Astrofísica, C/ Astrofísico Francisco Sánchez s/n, E-38206 La Laguna, Tenerife, Spain
³ Dipartimento di Fisica, Sezione di Astronomia, Università di Trieste, Via Tiepolo 11, I-34143 Trieste, Italy
⁴ INAF/Osservatorio Astronomico di Trieste, Via Tiepolo 11, I-34143 Trieste, Italy

^* e-mail: ferragamo_ext@iac.es

Published online: 27 January 2020

Abstract

Using a set of 73 numerically simulated galaxy clusters, we have characterised the statistical and physical biases for three velocity dispersion and mass estimators, namely biweight, gapper and standard deviation, in the small number of galaxies regime (N_gal ≤ 75), both for the determination of the velocity dispersion and the dynamical mass of the clusters via the σ–M relation. These results are used to define a new set of unbiased estimators, that are able to correct for those statistical biases. By applying these new estimators to a subset of simulated observations, we show that they can retrieve bias-corrected values for both the mean velocity dispersion and the mean mass.