Methanol and its relation to the water snowline in the disk around the young outbursting star V883 Ori

TL;DR

This study reports the detection of methanol in the disk around the young outbursting star V883 Ori, revealing insights into the disk's chemical composition and the location of the water snowline, using ALMA observations.

Contribution

First detection of methanol in V883 Ori's disk, showing thermal desorption and implications for the water snowline's location in outbursting young stars.

Findings

Methanol emission follows Keplerian rotation in the disk.

The methanol emission suggests a larger water snowline than previously thought.

Outbursting young stars are effective for studying ice composition in planet formation regions.

Abstract

We report the detection of methanol in the disk around the young outbursting star V883 Ori with the Atacama Large Millimeter/submillimeter Array (ALMA). Four transitions are observed with upper level energies ranging between 115 and 459 K. The emission is spatially resolved with the 0.14" beam and follows the Keplerian rotation previously observed for C$^{18}$O. Using a rotational diagram analysis, we find a disk-averaged column density of $\sim10^{17}$ cm$^{-2}$ and a rotational temperature of $\sim90-100$ K, suggesting that the methanol has thermally desorbed from the dust grains. We derive outer radii between 120 and 140 AU for the different transitions, compared to the 360 AU outer radius for C$^{18}$O. Depending on the exact physical structure of the disk, the methanol emission could originate in the surface layers beyond the water snowline. Alternatively, the bulk of the methanol emission originates inside the water snowline, which can then be as far out as ~100 AU, instead of 42 AU as was previously inferred from the continuum opacity. In addition, these results show that outbursting young stars like V883 Ori are good sources to study the ice composition of planet forming material through thermally desorbed complex molecules, which have proven to be hard to observe in more evolved protoplanetary disks.