The Milky Way Project and ATLASGAL: The distribution and physical properties of cold clumps near infrared bubbles

TL;DR

This study analyzes the distribution and physical properties of cold dense material around infrared bubbles in the Galactic Plane, revealing how bubble expansion influences interstellar medium structure and star formation potential.

Contribution

It provides the first statistical analysis linking cold clump distribution and properties to infrared bubbles, highlighting their impact on interstellar medium reordering and star formation.

Findings

Nearly half of cold clumps are near bubbles, with a quarter on their rims.

Clumps along bubble rims are denser and more turbulent.

Clumps inside bubbles tend to be denser and hotter, indicating star formation activity.

Abstract

We present a statistical study of the distribution and physical properties of cold dense material in and around the inner Galactic Plane near infrared bubbles as catalogued by the Milky Way Project citizen scientists. Using data from the ATLASGAL 870 um survey, we show that 48 +/- 2% of all cold clumps in the studied survey region (|l| <= 65 degrees, |b| <= 1 degree) are found in close proximity to a bubble, and 25 +/- 2% appear directly projected towards a bubble rim. A two-point correlation analysis confirms the strong correlation of massive cold clumps with expanding bubbles. It shows an overdensity of clumps along bubble rims that grows with increasing bubble size, which shows how interstellar medium material is reordered on large scales by bubble expansion around regions of massive star formation. The highest column density clumps appear resistent to the expansion, remaining overdense towards the bubbles' interior rather than being swept up by the expanding edge. Spectroscopic observations in ammonia show that cold dust clumps near bubbles appear to be denser, hotter and more turbulent than those in the field, offering circumstantial evidence that bubble-associated clumps are more likely to be forming stars. These observed differences in physical conditions persist for beyond the region of the bubble rims.