Demographics of Protoplanetary Disks: A Simulated Population of Edge-on Systems

TL;DR

This study uses radiative transfer simulations to model protoplanetary disks, predicting their occurrence rate and biases in detection, revealing many edge-on disks are likely undiscovered in nearby star-forming regions.

Contribution

The paper introduces a quantitative, observation-driven method to identify edge-on protoplanetary disks and assesses biases in current detection techniques using simulated populations.

Findings

Predicted 6.2% occurrence rate of edge-on disks.

Edge-on disks are under-represented in existing samples.

Several dozen edge-on disks likely remain undiscovered.

Abstract

The structure of protoplanetary disks plays an essential role in planet formation. Disks that are highly inclined, or ''edge-on'', are of particular interest since their geometry provides a unique opportunity to study the disk's vertical structure and radial extent. Candidate edge-on protoplanetary disks are typically identified via their unique spectral energy distribution and subsequently confirmed through high-resolution imaging. However, this selection process is likely biased toward the largest, most massive disks, and the resulting sample may not accurately represent the underlying disk population. To investigate this, we generated a grid of protoplanetary disk models using radiative transfer simulations and determined which sets of disk parameters produce edge-on systems that could be recovered by aforementioned detection techniques--i.e., identified by their spectral energy distribution and confirmed through follow-up imaging with HST. In doing so, we adopt a quantitative working definition of "edge-on disks" that is observation-driven and agnostic about the disk inclination or other properties. Folding in empirical disk demographics, we predict an occurrence rate of 6.2% for edge-on disks and quantify biases towards highly inclined, massive disks. We also find that edge-on disks are under-represented in samples of Spitzer-studied young stellar objects, particularly for disks with M $\lesssim$ 0.5 $M_\odot$. Overall, our analysis suggests that several dozen edge-on disks remain undiscovered in nearby star-forming regions, and provides a universal selection process to identify edge-on disks for consistent, population-level demographic studies.