The three-dimensional structure of Galactic molecular cloud complexes out to 2.5 kpc

TL;DR

This study reconstructs the three-dimensional structures of 16 Galactic molecular cloud complexes using Gaia data and a novel dust mapping algorithm, revealing diverse shapes and environments that influence star formation.

Contribution

It introduces a new 3D dust mapping method to analyze molecular clouds at high resolution, providing detailed shape, mass, and environmental insights.

Findings

Cloud aspect ratios range from 1 to 11, indicating diverse shapes.

3D boundary definitions are crucial for accurate cloud mass estimates.

Larson's mass-radius relationship holds in 3D analysis.

Abstract

Knowledge of the three-dimensional structure of Galactic molecular clouds is important for understanding how clouds are affected by processes such as turbulence and magnetic fields and how this structure effects star formation within them. Great progress has been made in this field with the arrival of the Gaia mission, which provides accurate distances to $\sim10^{9}$ stars. Combining these distances with extinctions inferred from optical-IR, we recover the three-dimensional structure of 16 Galactic molecular cloud complexes at $\sim1$pc resolution using our novel three-dimensional dust mapping algorithm \texttt{Dustribution}. Using \texttt{astrodendro} we derive a catalogue of physical parameters for each complex. We recover structures with aspect ratios between 1 and 11, i.e.\ everything from near-spherical to very elongated shapes. We find a large variation in cloud environments that is not apparent when studying them in two-dimensions. For example, the nearby California and Orion A clouds look similar on-sky, but we find California to be more sheet-like, and massive, which could explain their different star-formation rates. In Carina, our most distant complex, we observe evidence for dust sputtering, which explains its measured low dust mass. By calculating the total mass of these individual clouds, we demonstrate that it is necessary to define cloud boundaries in three-dimensions in order to obtain an accurate mass; simply integrating the extinction overestimates masses. We find that Larson's relationship on mass vs radius holds true whether you assume a spherical shape for the cloud or take their true extents.