The Dynamical Implications of Multiple Stellar Formation Events in Galactic Globular Clusters

Downing, J. M. B.; Sills, Alison

doi:10.1086/516744

Cited by 6 publications

(7 citation statements)

References 27 publications

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“…Finally, both D' Ercole et al (2008) and Decressin, Baumgardt, & Kroupa (2008) use N-body dynamical models to study the subsequent evolution of this two-generation cluster and the mixing of the two populations. They concur with the general results of Downing & Sills (2007) that, at the current time, a twogeneration cluster will not be dramatically different from a single-generation cluster in terms of the dynamics and distribution of stars.…”

Section: Possible Explanationssupporting

confidence: 91%

Multiple populations in globular clusters: the possible contributions of stellar collisions

Sills

Glebbeek

2010

Monthly Notices of the Royal Astronomical Society

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Globular clusters were thought to be simple stellar populations, but recent photometric and spectroscopic evidence suggests that the clusters' early formation history was more complicated. In particular, clusters show star‐to‐star abundance variations, and multiple sequences in their colour–magnitude diagrams. These effects seem to be restricted to globular clusters, and are not found in open clusters or the field. In this paper, we combine the two competing models for these multiple populations and include a consideration of the effects of stellar collisions. Collisions are one of the few phenomena which occur solely in dense stellar environments like (proto)globular clusters. We find that runaway collisions between massive stars can produce material which has abundances comparable to the observed second generations, but that very little total mass is produced by this channel. We then add the contributions of rapidly rotating massive stars (under the assumption that massive stars are spun up by collisions and interactions), and the contribution of asymptotic giant branch stars. We find that collisions can help produce the extreme abundances which are seen in some clusters. However, the total amount of material produced in these generations is still too small (by at least a factor of 10) to match the observations. We conclude with a discussion of the additional effects which probably need to be considered to solve this particular problem.

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Section: Possible Explanationssupporting

confidence: 91%

Multiple populations in globular clusters: the possible contributions of stellar collisions

Sills

Glebbeek

2010

Monthly Notices of the Royal Astronomical Society

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“…The second problem is that it has to be recognized that 47 Tuc cannot really be regarded as consisting of a single stellar population any more (Anderson et al 2009). The appropriate paradigm for this situation, let alone its simulation, is full of uncertainties (Downing & Sills 2007; D'Ercole et al 2008; Choi & Yi 2008).…”

Section: Discussion Of the Modelmentioning

confidence: 99%

Monte Carlo simulations of star clusters - VII. The globular cluster 47 Tuc

Giersz

Heggie

2010

Monthly Notices of the Royal Astronomical Society

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We describe Monte Carlo models for the dynamical evolution of the massive globular cluster 47 Tuc (NGC 104). The code includes treatments of two‐body relaxation, most kinds of three‐ and four‐body interactions involving primordial binaries and those formed dynamically, the Galactic tide, and the internal evolution of both single and binary stars. We arrive at a set of initial parameters for the cluster which, after 12 Gyr of evolution, gives a model with a fairly satisfactory match to surface brightness and density profiles, the velocity dispersion profile, the luminosity function in two fields and the acceleration of pulsars. Our models appear to require a relatively steep initial mass function for stars above about turnoff, with an index of about 2.8 (where the Salpeter mass function has an index of 2.35), and a relatively flat initial mass function (index about 0.4) for the lower main sequence. According to the model, the current mass is estimated at 0.9 million solar masses, of which about 34 per cent consists of remnants. We find that primordial binaries are gradually taking over from mass loss by stellar evolution as the main dynamical driver of the core. Despite the high concentration of the cluster, core collapse will take at least another 20 Gyr.

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“…In fact, for a Salpeter (1955) or a Kroupa (2001) IMF, the gas shed by the massive stars during the H-burning phase, or the gas contained in the envelopes of massive AGBs (D' Antona & Caloi 2004;D'Ercole et al 2008;Renzini et al 2015), is in general too scarce to form a large SG population. One can solve this problem by postulating that the GC precursors are more massive (by factors between 5 and 20) than the objects we observe today (e.g., D'Ercole et al 2008;Renzini et al 2015), or alternatively, by invokig a highly nonstandard IMF for the FG, particularly rich in massive stars (D'Antona & Caloi 2004;Downing & Sills 2007). The latter scenario, however, faces some serious difficulties when considering the maximum amount of helium which can be produced by a FG of super massive stars (Renzini et al 2015).…”

Section: Introductionmentioning

confidence: 99%

Paving the way for the JWST: witnessing globular cluster formation at z > 3

Vanzella¹,

Calura²,

Meneghetti³

et al. 2017

Monthly Notices of the Royal Astronomical Society

180

215

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We report on five compact, extremely young (< 10 Myr) and blue (β U V < −2.5, F λ = λ β ) objects observed with VLT/MUSE at redshift 3.1169, 3.235, in addition to three objects at z = 6.145. These sources are magnified by the Hubble Frontier Field galaxy clusters MACS J0416 and AS1063. Their de-lensed half light radii (R e ) are between 16 to 140 pc, the stellar masses are 1 − 20 × 10 6 M , the magnitudes are m U V = 28.8 − 31.4 (−17 < M U V < −15) and specific star formation rates can be as large as ∼ 800 Gyr −1 . Multiple images of these systems are widely separated in the sky (up to 50 ) and individually magnified by factors 3-40. Remarkably, the inferred physical properties of two objects are similar to those expected in some globular cluster formation scenarios, representing the best candidate proto-globular clusters (proto-GC) discovered so far. Rest-frame optical high dispersion spectroscopy of one of them at z = 3.1169 yields a velocity dispersion σ v 20 km s −1 , implying a dynamical mass dominated by the stellar mass. Another object at z = 6.145, with de-lensed31.4), shows a stellar mass and a star-formation rate surface density consistent with the values expected from popular GC formation scenarios. An additional star-forming region at z = 6.145, with de-lensed m U V 32, a stellar mass of 0.5 ×10 6 M and a star formation rate of 0.06 M yr −1 is also identified. These objects currently represent the faintest spectroscopically confirmed star-forming systems at z > 3, elusive even in the deepest blank fields. We discuss how proto-GCs might contribute to the ionization budget of the universe and augment Lyα visibility during reionization. This work underlines the crucial role of JWST in characterizing the restframe optical and near-infrared properties of such low-luminosity high−z objects.

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The Dynamical Implications of Multiple Stellar Formation Events in Galactic Globular Clusters

Cited by 6 publications

References 27 publications

Multiple populations in globular clusters: the possible contributions of stellar collisions

Multiple populations in globular clusters: the possible contributions of stellar collisions

Monte Carlo simulations of star clusters - VII. The globular cluster 47 Tuc

Paving the way for the JWST: witnessing globular cluster formation at z > 3

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