Discovery of a coherent, wave-like velocity pattern for the Radcliffe Wave

TL;DR

This study reveals a wave-like velocity pattern in the Radcliffe Wave using proper motions of Young Stellar Objects, identifying a damped, oscillating structure that may result from galactic perturbations.

Contribution

Introduces a new formalism using Ensemble Empirical Mode Decomposition to analyze the velocity undulation pattern in the Radcliffe Wave, linking it to spatial oscillations and potential galactic interactions.

Findings

Identifies a damped, wave-like velocity pattern in the Radcliffe Wave.

Finds the spatial and velocity undulations share a similar frequency of about 1.5 kpc.

Suggests the undulation may originate from a galactic perturbation such as a dwarf galaxy passage.

Abstract

Recently studies discovered that part of the Gould Belt belongs to a 2.7 kpc-long {coherent, thin} wave consisting of a chain of clouds, where a damped undulation pattern has been identified from the spatial arrangement of the clouds. We use the proper motions of Young Stellar Objects (YSOs) anchored inside the clouds to study the kinematic structure of the Radcliffe Wave in terms of $v_z$, and identify a damped, wave-like pattern from the $v_z$ space, which we call "velocity undulation". We propose a new formalism based on the Ensemble Empirical Mode Decomposition (EEMD) to determine the amplitude, period, and phase of the undulation pattern, and find that the spatial and the velocity undulation share an almost identical spatial frequency of about 1.5 kpc, and both are damped when measured from one side to the other. Measured for the first cycle, they exhibit a phase difference of around $2\pi/3$. The structure is oscillating around the midplane of the Milky Way disk with an amplitude of $\sim\,130\,\pm\,20\,\rm pc$. The vertical extent of the Radcliffe Wave exceeds the thickness of the molecular disk, suggesting that the undulation of the undulation signature might originate from a perturbation, e.g. the passage of a dwarf galaxy.