Investigating the Origin of the Gas in the Debris Disk Around 49 Ceti

Debris disks are signposts of mature planetary systems, analogous to the Kuiper belt in our own solar system. While debris disks tend to have low gas masses, some systems exhibit significant quantities of molecular gas, the origin of which is not yet well understood in some systems. By studying the molecular makeup of this gas, we can determine whether it has primordial origins (meaning it has survived past the dissipation of initial disk dust) or second generation origins (meaning it has been released from the collisions of icy planetesimals). One way to determine the molecular composition and differentiate between primordial and second generation origins is to characterize the vertical structure of the disk by constraining the scale height, h. Gas with primordial origins will have a larger scale height at a given temperature because the molecular composition is dominated by lighter molecules like H₂, while second generation gas will have a smaller scale height because the molecular composition is dominated by heavier molecules made of C and O. We modeled ¹²CO(J=3-2) data (angular resolution 0.13”, linear resolution 8 au) from the Atacama Large Millimeter/submillimeter Array (ALMA) to characterize the gas in the debris disk around the nearby A star 49 Ceti. Using a Markov Chain Monte Carlo (MCMC) algorithm, we constrained the scale height and found a best fit value likely consistent with second generation origins of the gas.