Globular cluster absolute ages from cooling brown dwarfs

Publication Type
Year of Publication
Jeremy S. Heyl
Harvey Richer
Jason Kalirai
Astrophysics - Solar and Stellar Astrophysics; Astrophysics - Cosmology and Nongalactic Astrophysics; Astrophysics - Astrophysics of Galaxies

Globular clusters are the oldest conglomerates of stars in our Galaxyand can be useful laboratories to test theories from stellar evolutionto cosmology. In this paper, we present a new method to estimate theabsolute age of a globular cluster from observations of its browndwarfs. The transition region between the end of the main sequence andthe brown dwarf regime is characterized by a dearth of objects asfunction of magnitude. The brightest of the cooling brown dwarfs iseasily identified by an increase in density in the color-magnitudediagram as you go fainter in magnitudes, and these brightest browndwarfs get fainter with age. By identifying the brightest brown dwarfs,it is thus possible to determine the age of a globular cluster within a1 Gyr precision with four-sigma confidence. This new method, which isindependent of current methods of age estimation and which does not relyon the knowledge of the cluster's distance from Earth, will becomefeasible thanks to the high spatial resolution and incredible infraredsensitivity of the James Webb Space Telescope.