Eruptive Behavior of Magnetically Layered Protoplanetary Disks in Low Metallicity Environments

TL;DR

This study investigates how low metallicity environments influence the structure and eruptive behavior of protoplanetary disks, revealing that metal-poor disks tend to accumulate more mass and exhibit more intense, shorter outbursts during early stages.

Contribution

First numerical study to explore the impact of low metallicity on magnetically layered protoplanetary disk structure and episodic accretion behavior.

Findings

Low metallicity disks accumulate more mass in inner regions.

Outbursts are more powerful and shorter in low metallicity disks.

Outburst occurrence is rarer around low-mass stars at low metallicity.

Abstract

A protoplanetary disk typically forms a dead zone near its midplane at the distance of a few au from the central protostar. Accretion through such a magnetically layered disk can be intrinsically unstable and has been associated with episodic outbursts in young stellar objects. We present the first investigation into the effects of low metallicity environment on the structure of the dead zone as well as the resulting outbursting behavior of the protoplanetary disk. We conducted global numerical hydrodynamic simulations of protoplanetary disk formation and evolution in the thin-disk limit. The consequences of metallicity were considered via its effects on the gas and dust opacity of the disk, the thickness of the magnetically active surface layer, and the temperature of the prestellar cloud core. We show that the metal poor disks accumulate much more mass in the innermost regions, as compared to the solar metallicity counterparts. The duration of the outbursting phase also varies with metallicity - the low metallicity disks showed more powerful luminosity eruptions with a shorter burst phase, which was confined mostly to the early, embedded stages of the disk evolution. The lowest metallicity disks with the higher cloud core temperature showed the most significant differences. The occurrence of outbursts was relatively rare in the disks around low mass stars and this was especially true at lowest metallicities. We conclude that the metal content of the disk environment can have profound effects on both the disk structure and evolution in terms of episodic accretion.