Chemical composition and constraints on mass loss for globular clusters in dwarf galaxies: WLM and IKN

Larsen, S. S.; Brodie, Jean P.; Forbes, Duncan A.; Strader, Jay

doi:10.1051/0004-6361/201322672

Cited by 92 publications

(123 citation statements)

References 115 publications

(204 reference statements)

Supporting

Mentioning

111

Contrasting

Order By: Relevance

“…Lind et al 2009) and the typical percentage of low-sodium stars that are usually classified as 1P stars (∼30%; Prantzos & Charbonnel 2006;Carretta et al 2009b;Carretta 2013). This strongly alleviates the mass budget issue, in better agreement with constraints provided by young massive star clusters (Bastian et al 2014;Hollyhead et al 2015;Krause et al 2016) and star counts in the halo of dwarf galaxies (Larsen et al 2014).…”

Section: Introductionsupporting

confidence: 72%

“…The ubiquitous presence of the Na-O anticorrelation in Galactic and extragalactic GCs (e.g. Carretta et al 2009a;Mucciarelli et al 2009;Lind et al 2011;Larsen et al 2014), together with the C-N and the Mg-Al anticorrelations (see the review by Gratton et al 2012, and references therein), are interpreted as a result of self-enrichment of these systems during their early evolution. On the one hand, GC stars with chemical properties similar to those of Galactic field stars are thought to have formed from original proto-cluster material, and are often referred to as first population (or first generation, hereafter 1P) GC stars.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Evolution of long-lived globular cluster stars

Charbonnel

Chantereau

2016

A&A

View full text Add to dashboard Cite

Context. Long-lived stars in globular clusters exhibit chemical peculiarities with respect to their halo counterparts. In particular, sodium-enriched stars are identified as belonging to a second stellar population born from cluster material contaminated by the hydrogen-burning ashes of a first stellar population. Their presence and numbers in different locations of the colour-magnitude diagram provide important constraints on the self-enrichment scenarios. In particular, the ratio of Na-poor to Na-rich stars on the asymptotic giant branch (AGB) has recently been found to vary strongly from cluster to cluster (NGC 6752, 47 Tuc, and NGC 2808), while it is relatively constant on the red giant branch (RGB). Aims. We investigate the impact of both age and metallicity on the theoretical sodium spread along the AGB within the framework of the fast rotating massive star (FRMS) scenario for globular cluster self-enrichment. Methods. We computed evolution models of low-mass stars for four different metallicities ([Fe/H] = −2.2, −1.75, −1.15, −0.5) assuming the initial helium-sodium abundance correlation for second population stars derived from the FRMS models and using mass loss prescriptions on the RGB with two realistic values of the free parameter in the Reimers formula. Results. Based on this grid of models we derive the theoretical critical initial mass for a star born with a given helium, sodium, and metal content that determines whether that star will climb or not the AGB. This allows us to predict the maximum sodium content expected on the AGB for globular clusters as a function of both their metallicity and age. We find that (1) at a given metallicity, younger clusters are expected to host AGB stars exhibiting a larger sodium spread than older clusters and (2) at a given age, higher sodium dispersion along the AGB is predicted in the most metal-poor globular clusters than in the metal-rich ones. We also confirm the strong impact of the mass loss rate in the earlier evolution phases on the Na cut on the AGB: the higher the mass loss, the stronger the trends with age and metallicity. Conclusions. The theoretical trends we obtain provide, in principle, an elegant qualitative explanation to the different sodium spreads that are observed along the AGB in the Galactic globular clusters of different ages and [Fe/H] values. Although it is real, the slope with both age and metallicity is relatively flat, although it steepens when accounting for mass loss variations. Therefore, additional parameters may play a role in inducing cluster to cluster variations, that are difficult to disentangle from existing data.

show abstract

Section: Introductionsupporting

confidence: 72%

Section: Introductionmentioning

confidence: 99%

Evolution of long-lived globular cluster stars

Charbonnel

Chantereau

2016

A&A

View full text Add to dashboard Cite

show abstract

“…The missing 90%-95% of the G1 stars had to escape, and even more had to escape if G2 stars escaped too, which is likely. These escaping stars presumably comprise the halo of the Milky Way (Prantzos & Charbonnel 2006;Martell, et al 2011), but such large halo amounts are not evident in the Fornax or WLM dwarf galaxies (Larsen et al 2012(Larsen et al , 2014Elmegreen et al 2012).…”

Section: Introductionmentioning

confidence: 99%

Globular Cluster Formation at High Density: A Model for Elemental Enrichment with Fast Recycling of Massive-star Debris

Elmegreen

2017

ApJ

View full text Add to dashboard Cite

The self-enrichment of massive star clusters by p-processed elements is shown to increase significantly with increasing gas density as a result of enhanced star formation rates and stellar scatterings compared to the lifetime of a massive star. Considering the type of cloud core where a globular cluster might have formed, we follow the evolution and enrichment of the gas and the time dependence of stellar mass. A key assumption is that interactions between massive stars are important at high density, including interactions between massive stars and massive star binaries that can shred stellar envelopes. Massive-star interactions should also scatter low-mass stars out of the cluster. Reasonable agreement with the observations is obtained for a cloud core mass of ∼ 4 × 10 6 M ⊙ and a density of ∼ 2 × 10 6 cm −3 . The results depend primarily on a few dimensionless parameters, including, most importantly, the ratio of the gas consumption time to the lifetime of a massive star, which has to be low, ∼ 10%, and the efficiency of scattering low-mass stars per unit dynamical time, which has to be relatively large, such as a few percent. Also for these conditions, the velocity dispersions of embedded globular clusters should be comparable to the high gas dispersions of galaxies at that time, so that stellar ejection by multi-star interactions could cause low-mass stars to leave a dwarf galaxy host altogether. This could solve the problem of missing first-generation stars in the halos of Fornax and WLM.

show abstract

“…In addition, the high fraction of stars in GCs carries important information and implications for questions such as how many stars formed in clusters in a given star A&A 581, A84 (2015) formation epoch and how many clusters remain bound, i.e., implications for star cluster dissolution (e.g. Lada & Lada 2003;Bastian 2008;Goddard et al 2010;Kruijssen 2012;Larsen et al 2014a).…”

Section: Introductionmentioning

confidence: 99%

Optical-near-IR analysis of globular clusters in the IKN dwarf spheroidal: a complex star formation history

Tudorica

Georgiev

Chies-Santos

2015

A&A

View full text Add to dashboard Cite

Context. Age, metallicity, and spatial distribution of globular clusters (GCs) provide a powerful tool for reconstructing major starformation episodes in galaxies. IKN is a faint dwarf spheroidal (dSph) in the M 81 group of galaxies. It contains five old GCs, which makes it the galaxy with the highest known specific frequency (S N = 126). Aims. We estimate the photometric age, metallicity, and spatial distribution of the poorly studied IKN GCs. We search SDSS for GC candidates beyond the HST/ACS field of view, which covers half of IKN. Methods. To break the age-metallicity degeneracy in the V −I colour, we used WHT/LIRIS K S -band photometry and derived photometric ages and metallicities by comparison with SSP models in the V, I, K s colour space. Results. IKN GCs' V IK s colours are consistent with old ages (≥8 Gyr) and a metallicity distribution with a higher mean than is typical for such a dSph ([Fe/H] −1.4 +0.6 −0.2 dex). Their photometric mass range (0.5 < M GC < 4 × 10 5 M ) implies an unusually high mass ratio between GCs and field stars, of 10.6%. Mixture model analysis of the RGB field stars' metallicity suggests that 72% of the stars may have formed together with the GCs. Using the most massive GC−SFR relation, we calculated a star formation rate (SFR) of ∼10 M /yr during its formation epoch. We note that the more massive GCs are closer to the galaxy photometric centre. IKN GCs also appear spatially aligned along a line close to the major axis of the IKN and nearly orthogonal to the plane of spatial distribution of galaxies in the M 81 group. We identify one new IKN GC candidate based on colour and the PSF analysis of the SDSS data. Conclusions. The evidence of i) broad and high metallicity distribution of the field IKN RGB stars and its GCs, ii) high fraction, and iii) spatial alignment of IKN GCs supports a scenario for tidally triggered, complex IKN's star formation history in the context of interactions with galaxies in the M 81 group.

show abstract

Chemical composition and constraints on mass loss for globular clusters in dwarf galaxies: WLM and IKN

Cited by 92 publications

References 115 publications

Evolution of long-lived globular cluster stars

Evolution of long-lived globular cluster stars

Globular Cluster Formation at High Density: A Model for Elemental Enrichment with Fast Recycling of Massive-star Debris

Optical-near-IR analysis of globular clusters in the IKN dwarf spheroidal: a complex star formation history

Contact Info

Product

Resources

About