The end of the white dwarf cooling sequence in M 67

TL;DR

This study presents the first proper-motion-selected white dwarf sample in the old open cluster M 67, enabling precise comparison of the white dwarf cooling sequence with models to confirm the cluster's age.

Contribution

It provides the first proper-motion-based white dwarf sample in M 67, extending to the bottom of the cooling sequence, and compares observations with theoretical models.

Findings

White dwarf cooling sequence matches the cluster's age derived from turn-off.

Proper motions effectively separate cluster members from field stars.

The observed WD sequence confirms the age estimate from other methods.

Abstract

In this paper, we present for the first time a proper-motion-selected white dwarf (WD) sample of the old Galactic open cluster M 67, down to the bottom of the WD cooling sequence (CS). The color-magnitude diagram is based on data collected with the LBC-Blue camera at the prime focus of LBT. As first epoch data, we used CFHT-archive images collected 10 years before LBC data. We measured proper motions of all the identified sources. Proper motions are then used to separate foreground and background objects from the cluster stars, including WDs. Finally, the field-object cleaned WD CS in the V vs. B-I color-magnitude diagram is compared with the models. We confirm that the age derived from the location of the bottom of the WD CS is consistent with the turn off age.