# Modelling the Spatial Distribution and Origin of CO Gas in Debris Disks

## TL;DR

This study uses ALMA observations and thermochemical modeling to analyze CO gas in debris disks, concluding that the gas likely originates from secondary processes like collisions rather than primordial remnants.

## Contribution

The paper introduces a novel combination of high-resolution ALMA data analysis and thermochemical modeling to determine the origin of CO gas in debris disks.

## Key findings

- CO gas masses are around 3×10⁻³ Earth masses.
- Production rates are estimated at approximately 5×10⁻⁷ Earth masses per year.
- Gas likely has a secondary origin from collisions, not primordial.

## Abstract

The detection of gas in debris disks raises the question of whether this gas is a remnant from the primordial protoplanetary phase, or released by the collision of secondary bodies. In this paper we analyze ALMA observations at 1-1.5" resolution of three debris disks where the $^{12}$CO(2-1) rotational line was detected: HD131835, HD138813, and HD156623. We apply the iterative Lucy-Richardson deconvolution technique to the problem of circumstellar disks to derive disk geometries and surface brightness distributions of the gas. The derived disk parameters are used as input for thermochemical models to test both primordial and cometary scenarios for the origin of the gas. We favor a secondary origin for the gas in these disks and find that the CO gas masses ($\sim 3\times10^{-3}$ M$_{\oplus}$) require production rates ($\sim 5\times 10^{-7}$ M$_{\oplus}$~yr$^{-1}$) similar to those estimated for the bona-fide gas rich debris disk $\beta$ Pic.