# Radial Wave in the Galactic Disk: New Clues to Discriminate Different Perturbations

**Authors:** Chengye Cao, Zhao-Yu Li, Ralph Schönrich, Teresa Antoja  
**arXiv:** [2403.14953](https://arxiv.org/abs/2403.14953)  
**Date:** 2024-03-22  
**Summary page:** https://www.summarizepaper.com/en/arxiv-id/2403.14953v1/

## Key points

- Study titled "Radial Wave in the Galactic Disk: New Clues to Discriminate Different Perturbations"
- Researchers analyze data to uncover a unique wave pattern in $L_Z-\langle V_R\rangle$ space
- Phase shift $\Delta L_Z$ observed, with peak value of approximately 2300 km/s/kpc
- Three sets of test particle simulations conducted involving satellite galaxy, corotating transient spiral arms, and bar/spirals combination as perturbers
- Satellite impact decreases phase shift amplitude towards higher $L_Z$
- Combining bar and spirals generates distinct $\Delta L_Z$ peak at 2:1 Outer Lindblad Resonance
- $L_Z-\langle V_R\rangle$ wave likely of internal origin within our Galaxy
- Novel method proposed for estimating Galactic Bar's pattern speed based on 2:1 Lindblad resonance peak
- Supports long/slow bar model and provides insights into Milky Way's evolutionary history

## Summary

In their study titled "Radial Wave in the Galactic Disk: New Clues to Discriminate Different Perturbations," authors Chengye Cao, Zhao-Yu Li, Ralph Schönrich, and Teresa Antoja delve into the intricate  that shape the structure of the  By analyzing data from the latest  they uncover a unique  in the $L_Z-\langle V_R\rangle$ space. This discovery is significant for understanding the evolution history of the Milky Way. The researchers observe that this wave pattern systematically shifts towards lower $L_Z$ for stars with higher dynamical hotness. They quantify this phase shift as $\Delta L_Z$, with a peak value of approximately 2300 km/s/kpc. To investigate the origins of this phenomenon, three sets of test particle simulations are conducted. These simulations involve scenarios where a satellite galaxy, corotating transient spiral arms, and a combination of a bar and corotating transient spiral arms act as perturbers. Under the influence of a satellite impact, the researchers find that the phase shift amplitude decreases towards higher $L_Z,$ which they interpret through a model of radial phase mixing. While corotating transient spiral arms do not produce an azimuthally universal phase shift variation pattern, combining both a bar and spirals generates a distinct $\Delta L_Z$ peak at the 2:1 Outer Lindblad Resonance. This observed feature closely resembles the characteristics of the wave pattern identified in their analysis. Based on these findings, it is suggested that the $L_Z-\langle V_R\rangle$ wave is likely of internal origin within our Galaxy. Furthermore, by linking the peak in $\Delta L_Z$ to the 2:1 Lindblad resonance, a novel method for estimating the pattern speed of the Galactic Bar is proposed. This supports the long/slow bar model and provides valuable insights into understanding and reconstructing key aspects of our Milky Way's evolutionary history. The study offers new perspectives on discerning different perturbations shaping our  and highlights avenues for further research in unraveling its complex dynamics.