Multiple collisions in N59 bubble: Sequential cloud-cloud collisions

TL;DR

This study reveals multiple sequential cloud-cloud collisions in the N59 bubble, linking these events to star formation, with detailed velocity component analysis and identification of young stellar objects at collision interfaces.

Contribution

It provides the first detailed analysis of sequential multiple cloud-cloud collisions in N59 and their role in triggering star formation.

Findings

Four distinct velocity components identified in N59 gas.

514 YSO candidates clustered at collision interfaces.

Sequential collisions occurred over the past 2 million years.

Abstract

We report that the gas components in the N59 bubble suffered from sequential multiple cloud-cloud collision (CCC) processes. The molecular gas in the N59 bubble can be decomposed into four velocity components, namely Cloud A [95, 108] km s$^{-1}$, Cloud B [86, 95] km s$^{-1}$, Cloud C [79, 86] km s$^{-1}$ and Cloud D [65, 79] km s$^{-1}$. Four CCC processes occurred among these four velocity components, i.e., Cloud A vs. Cloud B, Cloud A vs. Cloud C, Cloud C vs. Cloud D, and Cloud A vs. Cloud D. Using Spitzer MIR and UKIDSS NIR photometric point source catalogs, we identified 514 YSO candidates clustered in 13 YSO groups, and most of them (~60$\%$) were located at the colliding interfaces, indicating that they were mainly triggered by these four CCC processes. We also found that these four collisions occurred in a time sequential order: the earliest and most violent collision occurred between Cloud A and Cloud D about 2 Myr ago, then Cloud B collided with Cloud A about 1 Myr ago, and finally, Cloud C collided with Clouds A and D simultaneously about 0.4 Myr ago.