out. In the following, we provide details for the data from ground-based facilities and [*HST*]{}.

Ground-based dataset
--------------------

We used the catalogues obtained by @stetson2019, which provide high-precision photometry of stars in the $U$, $B$, $V$ and $I$ bands over a wide field of view. Details on the dataset and on the data reduction are provided by @stetson2005 [@monelli2013; @stetson2019]. $U$-band photometry of M22 is taken from @marino2015 and was derived from images collected with the Wide Field Imager of the ESO/MPI telescope at Cerro Tololo Inter-American Observatory (WFI@2.2m). We refer to the paper by Marino and collaborators for details on their photometric catalogue. The photometry is calibrated on the photometric system by @landolt1992.\
@bellini2009 used multi-epoch data acquired by WFI@2.2m to derive proper motions of stars in the field of view of $\omega\,$Centauri, which are suitable to separate field stars from cluster members. Due to crowding, stellar proper motions from GAIA DR2 are not available for most of the stars in the central region of $\omega\,$Centauri. To increase the sample size, we identified the stars without Gaia DR2 proper motions that according to @bellini2009 have membership probabilities larger than $90\,\%$ and included these stars in the analysis of the 