Circumstellar Disk Lifetimes In Numerous Galactic Young Stellar Clusters

TL;DR

This study analyzes the lifetimes of circumstellar disks in 69 young stellar clusters using homogeneous photometric data, revealing that disk longevity estimates depend heavily on the choice of pre-main sequence models and find no significant variation with stellar mass below 2 solar masses.

Contribution

It provides the largest homogeneous dataset for disk longevity, compares different PMS models, and assesses the influence of initial conditions and environment on disk lifetimes.

Findings

Disk half-life varies from 1.3 to 3.5 Myr depending on PMS model used.

No significant disk fraction variation with stellar mass below 2 solar masses.

Disk longevity estimates are sensitive to the choice of PMS evolutionary models.

Abstract

Photometric detections of dust circumstellar disks around pre-main sequence (PMS) stars, coupled with estimates of stellar ages, provide constraints on the time available for planet formation. Most previous studies on disk longevity, starting with Haisch, Lada & Lada (2001), use star samples from PMS clusters but do not consider datasets with homogeneous photometric sensitivities and/or ages placed on a uniform timescale. Here we conduct the largest study to date of the longevity of inner dust disks using X-ray and 1--8 micrometre infrared photometry from the MYStIX and SFiNCs projects for 69 young clusters in 32 nearby star-forming regions with ages t<=5 Myr. Cluster ages are derived by combining the empirical AgeJX method with PMS evolutionary models, which treat dynamo-generated magnetic fields in different ways. Leveraging X-ray data to identify disk-free objects, we impose similar stellar mass sensitivity limits for disk-bearing and disk-free YSOs while extending the analysis to stellar masses as low as M~0.1 Mo. We find that the disk longevity estimates are strongly affected by the choice of PMS evolutionary model. Assuming a disk fraction of 100% at zero age, the inferred disk half-life changes significantly, from t1/2 ~ 1.3--2 Myr to t1/2 ~ 3.5 Myr when switching from non-magnetic to magnetic PMS models. In addition, we find no statistically significant evidence that disk fraction varies with stellar mass within the first few Myr of life for stars with masses <2 Mo, but our samples may not be complete for more massive stars. The effects of initial disk fraction and star-forming environment are also explored.