Rapid Evolution of the Innermost Dust Disk of Protoplanetary Disks Surrounding Intermediate-mass Stars

TL;DR

This study investigates the evolution and dissipation timescales of inner dust disks in protoplanetary disks around intermediate-mass stars, revealing a rapid inner disk disappearance likely due to dust growth, impacting planet formation.

Contribution

It provides new estimates of inner dust disk lifetimes at different radii around intermediate-mass stars and highlights the mass-dependent evolution of these disks.

Findings

K-disk lifetime is approximately 3 Myr, decreasing with stellar mass.

MIR disk lifetime is approximately 6.5 Myr, with weak mass dependence.

Inner dust disks disappear faster than outer disks, affecting planet formation around intermediate-mass stars.

Abstract

We derived the intermediate-mass (~=1.5--7 M_sun) disk fraction (IMDF) in the near-infrared JHK photometric bands as well as in the mid-infrared (MIR) bands for young clusters in the age range of 0 to ~10 Myr. From the JHK IMDF, the lifetime of the innermost dust disk (~0.3 AU; hereafter the K disk) is estimated to be ~3 Myr, suggesting a stellar mass (M*) dependence of K-disk lifetime proportional to M*^-0.7. However, from the MIR IMDF, the lifetime of the inner disk (~5 AU; hereafter the MIR disk) is estimated to be ~6.5 Myr, suggesting a very weak stellar mass dependence (proportional to M*^-0.2). The much shorter K-disk lifetime compared to the MIR-disk lifetime for intermediate-mass (IM) stars suggests that IM stars with transition disks, which have only MIR excess emission but no K-band excess emission, are more common than classical Herbig Ae/Be stars, which exhibit both. We suggest that this prominent early disappearance of the K disk for IM stars is due to dust settling/growth in the protoplanetary disk, and it could be one of the major reasons for the paucity of close-in planets around IM stars.