Probing protoplanetary disk evolution in the Chamaeleon II region

M Villenave,F Ménard,Á Ribas,J P Williams,C Pinte,M R Schreiber,D A Principe,C Caceres,L Cieza,A Hales,M Benisty,M Ansdell,I Kamp,H Canovas,G Van Der Plas,W R F Dent

doi:10.1051/0004-6361/202140496

Abstract

Context. Characterizing the evolution of protoplanetary disks is necessary to improve our understanding of planet formation. Constraints on both dust and gas are needed to determine the dominant disk dissipation mechanisms. Aims. We aim to compare the disk dust masses in the Chamaeleon II (Cha II) star-forming region with other regions with ages between 1 and 10 Myr. Methods. We use ALMA band 6 observations (1.3 mm) to survey 29 protoplanetary disks in Cha II. Dust mass estimates are derived from the continuum data. Results. Out of our initial sample of 29 disks, we detect 22 sources in the continuum, 10 in 12CO, 3 in 13CO, and none in C18O (J = 2−1). Additionally, we detect two companion candidates in the continuum and 12CO emission. Most disk dust masses are lower than 10 M⊕, assuming thermal emission from optically thin dust. Including non-detections, we derive a median dust mass of 4.5 ± 1.5 M⊕ from survival analysis. We compare consistent estimations of the distributions of the disk dust mass and the disk-to-stellar mass ratios in Cha II with six other low mass and isolated star-forming regions in the age range of 1–10 Myr: Upper Sco, CrA, IC 348, Cha I, Lupus, and Taurus. When comparing the dust-to-stellar mass ratio, we find that the masses of disks in Cha II are statistically different from those in Upper Sco and Taurus, and we confirm that disks in Upper Sco, the oldest region of the sample, are statistically less massive than in all other regions. Performing a second statistical test of the dust mass distributions from similar mass bins, we find no statistical differences between these regions and Cha II. Conclusions. We interpret these trends, most simply, as a sign of decline in the disk dust masses with time or dust evolution. Different global initial conditions in star-forming regions may also play a role, but their impact on the properties of a disk population is difficult to isolate in star-forming regions lacking nearby massive stars.

Highlights

Planets are thought to form in gas- and dust-rich protoplanetary disks that orbit young stars
We find that most distributions, including that of Chamaeleon II (Cha II), have similar medians and shapes, but Upper Sco, CrA, and IC 348 show a noticeable difference compared with the others, with median dust masses up to one order of magnitude smaller than in other regions for Upper Sco and CrA
We note that when performing a parametric estimate of the dust mass distribution (e.g., Williams et al 2019), we find similar results with the distributions of Upper Sco and CrA shifted to lower mass compared to the other regions

Summary

Introduction

Planets are thought to form in gas- and dust-rich protoplanetary disks that orbit young stars. Characterizing the physical properties and evolutionary mechanisms of protoplanetary disks is essential for the understanding of planet formation. Various infrared studies have shown that the typical dissipation timescale of protoplanetary disks is about 3 Myr (e.g., Mamajek 2009; Ribas et al 2014), the oldest disks typically being up to 10 Myr old. These observations trace either small, warm dust particles (in the continuum) or accretion signatures (Fedele et al 2010), which are not sensitive to the dissipation of the bulk gas and dust mass, more relevant for planet formation.

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Conclusion