The Long-term Survival Chances of Young Massive Star Clusters

Abstract

We review the long-term survival chances of young massive star clusters (YMCs), hallmarks of intense starburst episodes often associated with violent galaxy interactions. We address the key question as to whether at least some of these YMCs can be considered protoglobular clusters (GCs), in which case these would be expected to evolve into counterparts of the ubiquitous old GCs believed to be among the oldest galactic building blocks. In the absence of significant external perturbations, the key factor determining a cluster's long-term survival chances is the shape of its stellar initial mass function (IMF). It is, however, not straightforward to assess the IMF shape in unresolved extragalactic YMCs. We discuss in detail the promise of using high-resolution spectroscopy to make progress towards this goal, as well as the numerous pitfalls associated with this approach. We also discuss the latest progress in worldwide efforts to better understand the evolution of entire cluster systems, the disruption processes they are affected by, and whether we can use recently gained insights to determine the nature of at least some of the YMCs observed in extragalactic starbursts as proto-GCs. We conclude that there is an increasing body of evidence that GC formation appears to be continuing until today; their long-term evolution crucially depends on their environmental conditions, however.

Integral-field near-infrared spectroscopy of two blue dwarf galaxies: NGC 5253 and He 2-10

“…de Grijs et al 2003;Elmegreen et al 2005). These clusters could be the progenitors of the old globular clusters observed in most galaxies today (de Grijs & Parmentier 2007), thus providing further evidence for the link between the starburst phenomenon and the formation of galaxies. Moreover, star-forming regions with properties consistent with the more massive HII regions detected locally are observed up to z ∼ 5 (Swinbank et al 2009), and local dwarf galaxies have been identified as scaled down analogs of clumpy starforming galaxies at high redshift (Elmegreen et al 2009).…”

The VMC survey – XVI. Spatial variation of the cluster formation activity in the innermost regions of the Large Magellanic Cloud

“…Those clusters that survive the infant mortality phase will be subject to the processes driving longer-term star cluster dissolution (see for reviews de Grijs & Parmentier 2007;de Grijs 2010). The longer-term dynamical evolution of star clusters is determined by a combination of internal and external timescales.…”

Ultraviolet Spectra of Local Galaxies and their Link with the High-z Population

“…Alternatively, an age effect could be responsible: field stars are older on average because field stars are the relics of dissolved star clusters whose lifetimes of order 10 Myr are longer than O-star lifetimes. Therefore, massive O stars may disappear before cluster dissolution and never contribute to the field population [11].…”