Stellar Mass Dependent Disk Dispersal

TL;DR

This study investigates how the dispersal of circumstellar disks depends on stellar mass, finding evidence that higher-mass stars lose their disks faster, likely due to photoevaporation, with implications for planet formation and orbital characteristics.

Contribution

It provides observational evidence for stellar mass dependent disk dispersal and supports photoevaporation as the primary mechanism, enhancing understanding of disk evolution and planet formation.

Findings

Higher-mass stars show faster disk dispersal than lower-mass stars.

Photoevaporation is the likely dominant mechanism for disk dispersal.

Potential impact on the orbital distribution of exoplanets around different stellar masses.

Abstract

We use published optical spectral and IR excess data from nine young clusters and associations to study the stellar mass dependent dispersal of circumstellar disks. All clusters older than ~3 Myr show a decrease in disk fraction with increasing stellar mass for Solar to higher mass stars. This result is significant at about the 1 $\sigma$ level in each cluster. For the complete set of clusters we reject the null hypothesis--that Solar and intermediate-mass stars lose their disks at the same rate--with 95-99.9% confidence. To interpret this behaviour, we investigate the impact of grain growth, binary companions, and photoevaporation on the evolution of disk signatures. Changes in grain growth timescales at fixed disk temperature may explain why early-type stars with IR excesses appear to evolve faster than their later-type counterparts. Little evidence that binary companions affect disk evolution suggests that photoevaporation is the more likely mechanism for disk dispersal. A simple photoevaporation model provides a good fit to the observed disk fractions for Solar and intermediate-mass stars. Although the current mass-dependent disk dispersal signal is not strong, larger and more complete samples of clusters with ages of 3-5 Myr can improve the significance and provide better tests of theoretical models. In addition, the orbits of extra-Solar planets can constrain models of disk dispersal and migration. We suggest that the signature of stellar mass dependent disk dispersal due to photoevaporation may be present in the orbits of observed extra Solar planets. Planets orbiting hosts more massive than ~1.6 Msun may have larger orbits because the disks in which they formed were dispersed before they could migrate.