The impact of the white dwarf initial-final mass relation on star clusters' ages inferred from their cooling sequence

Abstract: We have investigated and quantified how the choice of the white dwarf (WD) initial-final mass relation (IFMRs) affects the age determination of star clusters from the luminosity function of their cooling sequences. We have performed a purely theoretical differential analysis using recent semi-empirical IFMRs across three age regimes: ~ 10 Gyr (old ages), ~ 1 Gyr (intermediate ages), and ~ 100 Myr (young ages), respectively. For each regime, we have considered the age of a representative cluster whose entire WD sequence has already been observed and analysed, and calculated theoretical luminosity functions (varying the IFMR) that include realistic observational errors and binning. We have found that for old ages (as those of globular clusters), the choice of the semi-empirical IFMR introduces age offsets of at most ~0.6 +- 0.2 Gyr, while for intermediate ages the impact is reduced to 0.2 +- 0.1 Gyr, and it becomes negligible at young ages. Additionally, we have employed the metallicity-dependent IFMR derived by a recent grid of theoretical stellar evolution models to study whether the predicted metallicity dependence impacts the ages of old clusters with subsolar metal content. We found that neglecting this predicted metallicity dependence in old metal-poor globular clusters can lead to an age underestimate of up to 0.8 +-0.2 Gyr. All these age offsets should be interpreted as a systematic uncertainty associated with the choice of the IFMR.