The FUor Mass Distribution Matches the Solar Neighborhood IMF: Evidence for a Universal Eruptive Phase

TL;DR

This study uses high-resolution spectra of FUor objects to infer their mass distribution, finding it consistent with the Solar neighborhood initial mass function, supporting the idea of a universal eruptive phase in star formation.

Contribution

It provides the first direct observational evidence linking FUor mass distribution to the universal initial mass function, implying a common eruptive phase in young stars.

Findings

FUor disks exhibit Keplerian rotation.

Mass distribution of FUors matches the Solar neighborhood IMF.

Supports universal eruptive phase in star formation.

Abstract

Eruptive accretion events are expected to play an important role in the mass buildup stage of individual star formation. FU Ori objects (FUors) experience the most extreme eruptive outbursts, which raise the accretion rate of the disk from $10^{-9}-10^{-8} \ M_\odot \ \mathrm{yr}^{-1}$ to $10^{-5}-10^{-4} \ M_\odot \ \mathrm{yr}^{-1}$ and last for decades. During an outburst, the disk is approximately 100 times brighter than the star, making direct study of the central star impossible. However, the disk is expected to be in Keplerian rotation around the star, enabling indirect constraints on properties of the central source via observations of the disk. Using $1-2.4 \ \mu$m high resolution spectra of several tens of FUors, we demonstrate the expected Keplerian rotation in their inner disks. We then adopt a Keplerian rotational broadening profile to model the line profiles of spectral lines, and focussing on the H-band region, we infer the mass distribution of FUors. We finally show that this mass distribution is consistent with inferred Solar neighborhood initial mass functions, suggesting all young stars undergo a period of FUor outbursts in their pre main-sequence evolution.