Does Metallicity Affect the Protoplanetary Disk Fraction? Answers from the Outer Milky Way

Abstract

Abstract The role of metallicity in shaping protoplanetary disk evolution remains poorly comprehended. This study analyzes the disk fraction of 10 young (0.9–2.1 Myr) and low-metallicity (0.34–0.83 Z ⊙) clusters located in the outer Milky Way with Galactocentric distances between 10 and 13 kpc. Using JHK data obtained from UKIDSS, the calculated disk fraction values for low-mass stars (0.2–2 M ⊙) ranged from 42% to 7%. To enhance the statistical reliability of our analysis, eight additional low-metallicity clusters are sourced from previous studies with metallicity range 0.25–0.85 Z ⊙ along with our sample, resulting in a total of 18 regions with low metallicity. We find that low-metallicity clusters exhibit on average a 2.6 ± 0.2 times lower disk fraction compared to solar-metallicity clusters in all the age bins we have. Within the age range we can probe, our study does not find evidence of faster disk decay in subsolar-metallicity regions compared to solar-metallicity regions. Furthermore, we observe a positive correlation between cluster disk fraction and metallicity for two different age groups of 0.3–1.4 and 1.4–2.5 Myr. We emphasize that both cluster age and metallicity significantly affect the fraction of stars with evidence of inner disks.