The Evolution of the Inner Regions of Protoplanetary Disks

Abstract

We present a study of the evolution of the inner few au of protoplanetary disks around low-mass stars. We consider nearby stellar groups with ages spanning from 1 to 11 Myr, distributed into four age bins. Combining PANSTARSS photometry with spectral types we derive the reddening consistently for each star, which we use (1) to measure the excess emission above the photosphere with a new indicator of IR excess and (2) to estimate the mass accretion rate (Ṁ ) from the equivalent width of the Hα line. Using the observed decay ofṀ as a constrain to fix the initial conditions and the viscosity parameter of viscous evolutionary models, we use approximate Bayesian modeling to infer the dust properties that produce the observed decrease of the IR excess with age, in the range between 4.5 µm and 24 µm. We calculate an extensive grid of irradiated disk models with a two-layered wall to emulate a curved dust inner edge and obtain the vertical structure consistent with the surface density predicted by viscous evolution. We find that the median dust depletion in the disk upper layers is ǫ ∼ 3 × 10 −3 at 1.5 Myr, consistent with previous studies, and it decreases to ǫ ∼ 3 × 10 −4 by 7.5 Myr. We include photoevaporation in a simple model of the disk evolution and find that a photoevaporative wind mass-loss rate of ∼ 1 − 3 × 10 −9 M ⊙ yr −1 agrees with the decrease of the disk fraction with age reasonably well. The models show the inward evolution of the H 2 O and CO snowlines.

A Census of the Low Accretors. I: The Catalog

“…Still, the level of photoevaporative mass loss rate is unclear. For example, Manzo-Martínez et al (2020) found that the mass loss rate of ∼ 1 − 3 × 10 −9 M yr −1 is consistent with the observed disk fraction in a wide age range. Nevertheless, mass accretion rates much lower than these limits are still observed in many sources (Thanathibodee et al 2018(Thanathibodee et al , 2020Manara et al 2016;Hartmann et al 2016).…”

Gas disk interactions, tides and relativistic effects in the rocky planet formation at the substellar mass limit

“…For low-mass stars, this fraction is 5% (e.g. Damjanov et al 2007;Bayo et al 2012;Riaz et al 2012;Dawson et al 2013;Downes et al 2015;Manzo-Martínez et al 2020). These results suggest that VLMSs and BDs could retain their primordial disks for longer times than more massive stars; the times may be up to several tens of million years.…”

Gas disk interactions, tides and relativistic effects in the rocky planet formation at the substellar mass limit

“…For instance, at ages of " 7Myr, " 30% of the BD still retain their disks in contrast with the 5% for low mass stars (e.g. Damjanov et al 2007;Bayo et al 2012;Riaz et al 2012;Dawson et al 2013;Downes et al 2015;Manzo-Martínez et al 2020). This results suggest that VLMS and BD could retain their primordial disks for longer times than more massive stars up to tens of Myr.…”