Precise determination of circumstellar disk lifetimes: Disk evolution in a single star-forming region

TL;DR

This study precisely measures circumstellar disk lifetimes within a single star-forming region, revealing a longer timescale for disk dispersal than previously estimated, which impacts theories of planet formation.

Contribution

It provides a consistent analysis of disk evolution in 33 clusters within one region, reducing uncertainties and refining the disk lifetime estimate to about 5.8 million years.

Findings

Disk lifetime estimated at 5.8 ± 0.3 Myr.

Exponential decay model best fits disk dispersal.

Longer disk lifetimes suggest extended planet formation period.

Abstract

Determining how long circumstellar disks last is key to understanding the timescale of planet formation. Typically, this is done by measuring the fraction of young stars with infrared-excess, a sign of circumstellar material, in stellar clusters of different ages. However, comparing data from different star-forming regions at different distances introduces uncertainties and biases because of the different sample completeness and environment. This study addresses these challenges by analyzing 33 clusters, aged 3 to 21 million years (PARSEC isochrones), within the Scorpius-Centaurus OB association, sampling the stellar IMF from the hydrogen burning limit to about 8 M$_\odot$. By using $\mathit{Gaia}$, 2MASS, and WISE data, we identified stars with infrared-excess through color-color diagrams and spectral energy distributions, ensuring a consistent selection of disk-bearing sources. Our results indicate a disk lifetime of $5.8 \pm 0.3$ Myr, about a factor of two longer than most previous estimates, suggesting that planet formation may have more time than previously thought. We also find that an exponential decay model best describes disk dispersal. These findings emphasize the importance of studying disk evolution in a single star-forming region to reduce uncertainties and refine our understanding of planet formation timelines.