The protoplanetary disk population in the ρ-Ophiuchi region L1688 and the time evolution of Class II YSOs
Context. Planets form during the first few Myr of the evolution of the star-disk system, possibly before the end of the embedded phase. The properties of very young disks and their subsequent evolution reflect the presence and properties of their planetary content.
Aims: We present a study of the Class II/F disk population in L1688, the densest and youngest region of star formation in Ophiuchus. We also compare it to other well-known nearby regions of different ages, namely Lupus, Chamaeleon I, Corona Australis, Taurus and Upper Scorpius.
Methods: We selected our L1688 sample using a combination of criteria (available ALMA data, Gaia membership, and optical and near-IR spectroscopy) to determine the stellar and disk properties, specifically stellar mass (M⋆), average population age, mass accretion rate (Ṁacc) and disk dust mass (Ṁdust). We applied the same procedure in a consistent manner to the other regions.
Results: In L1688 the relations between Ṁacc and M⋆, Mdust and M⋆, and Ṁacc and Mdust have a roughly linear trend with slopes 1.8-1.9 for the first two relations and ~1 for the third, which is similar to what found in the other regions. When ordered according to the characteristic age of each region, which ranging from ~ 0.5 to ~5 Myr, Ṁacc decreases as t−1, when corrected for the different stellar mass content; Mdust follows roughly the same trend, ranging between 0.5 and 5 Myr, but has an increase of a factor of ~3 at ages of 2-3 Myr. We suggest that this could result from an earlier planet formation, followed by collisional fragmentation that temporarily replenishes the millimeter-size grain population. The dispersion of Ṁacc and Mdust around the best-fitting relation with M⋆, as well as that of Ṁacc versus Mdust are equally large. When adding all the regions together to increase the statistical significance, we find that the dispersions have continuous distributions with a log-normal shape and similar widths (~0.8 dex).
Conclusions: This detailed study of L1688 confirms the general picture of Class II/F disk properties and extends it to a younger age. The amount of dust observed at ~1 Myr is not sufficient to assemble the majority of planetary systems, which suggests an earlier formation process for planetary cores. The dust mass traces to a large extent the disk gas mass evolution, even if the ratio Mdust/Mdisk at the earliest age (0.5-1 Myr) is not known. Two properties are still not understood: the steep dependence of Ṁacc and Mdust on M⋆ and the cause of the large dispersion in the three relations analyzed in this paper, in particular that of the Ṁacc versus Mdust relation.
Astronomy and Astrophysics
- Pub Date:
- July 2022
- protoplanetary disks;
- submillimeter: planetary systems;
- stars: formation;
- Astrophysics - Solar and Stellar Astrophysics;
- Astrophysics - Earth and Planetary Astrophysics