Clearing the Dust from Globular Clusters

TL;DR

This paper proposes that stellar collisions in globular clusters can rapidly clear dust and gas, explaining the short dust lifetime observed in M15 and linking it to blue straggler formation.

Contribution

It introduces a collision-driven mechanism for dust and gas removal in globular clusters and correlates collision rates with dust lifetime and blue straggler formation.

Findings

Collision rates match dust lifetime estimates in M15.

Stellar collisions can eject gas and destroy dust efficiently.

Blue straggler birthrate aligns with collision-based formation timescales.

Abstract

Recent Spitzer observations of the globular cluster M15 detected dust associated with its intracluster medium. Surprisingly, these observations imply that the dust must be very short-lived compared to the time since the last Galactic plane crossing of the cluster.Here we propose a simple mechanism to explain this short lifetime. We argue that the kinetic energy of the material ejected during a stellar collision may be sufficient to remove the gas and dust entirely from a cluster, or to remove the gas as a wind, in addition to partially destroying the dust. By calculating the rate of stellar collisions using an N-body model for the cluster, we find remarkable agreement between the average time between collisions and the inferred dust lifetime in this cluster, suggesting a possible close relation between the two phenomena. Furthermore, we also obtain the birthrate of blue stragglers formed through collisions in M15. By comparing with the observed number of blue stragglers, we derive an upper limit for their average lifetime which turns out to be consistent with recent model calculations, thereby lending further support to our model.