Formation of ω Centauri from an ancient nucleated dwarf galaxy in the young Galactic disc

Bekki, Kenji; Freeman, K. C.

doi:10.1046/j.1365-2966.2003.07275.x

Cited by 343 publications

(394 citation statements)

References 27 publications

Supporting

Mentioning

366

Contrasting

Unclassified

Order By: Relevance

“…In the popular scenario of the formation of ω Cen as a disrupted dwarf galaxy (see, e.g., Bekki & Freeman 2003, and references therein), it can be speculated that, if any of the subpopulations of ω Cen is free from (anti)-correlations, that population is a likely candidate for its putative parent galaxy field population. This was discussed for the case of the VMP (very metal-poor) population defined in Paper I, and was also discussed by Pancino (2003) and Carretta et al (2010).…”

Section: Discussionmentioning

confidence: 99%

The subgiant branch ofω Centauri seen through high-resolution spectroscopy

Pancino

Mucciarelli

Bonifacio

et al. 2011

A&A

View full text Add to dashboard Cite

We analyze spectra of 18 stars belonging to the faintest subgiant branch in ω Centauri (the SGB-a), obtained with GIRAFFE@VLT at a resolution of R 17 000 and a S /N ratio between 25 and 50. We measure abundances of Al, Ba, Ca, Fe, Ni, Si, and Ti and we find that these stars have [Fe/H] = −0.73 ± 0.14 dex, similarly to the corresponding red giant branch population (the RGB-a). We also measure [α/Fe] = +0.40 ± 0.16 dex, and [Ba/Fe] = +0.87 ± 0.23 dex, in general agreement with past studies. It is very interesting to note that we found a uniform Al abundance, [Al/Fe] = +0.32 ± 0.14 dex, for all the 18 SGB-a stars analysed here, thus supporting past evidence that the usual (anti-)correlations are not present in this population, and suggesting a non globular cluster-like origin of this particular population. In the dwarf galaxy hypothesis for the formation of ω Cen, this population might be the best candidate for the field population of its putative parent galaxy, although some of its properties appear contradictory. It has also been suggested that the most metal-rich population in ω Cen is significantly enriched in helium. If this is true, the traditional abundance analysis techniques, based on model atmospheres with normal helium content, might lead to errors. We have computed helium enhanced atmospheres for three stars in our sample and verified that the abundance errors due to the use of non-enhanced atmospheres are negligible. Additional, indirect support to the enhanced helium content of the SGB-a population comes from our Li upper limits.

show abstract

Section: Discussionmentioning

confidence: 99%

The subgiant branch ofω Centauri seen through high-resolution spectroscopy

Pancino

Mucciarelli

Bonifacio

et al. 2011

A&A

View full text Add to dashboard Cite

show abstract

“…• thick disks come from early partly-formed thin disks, heated by accretion events such as the accretion event which is believed to have brought omega Centauri into the Galaxy (Bekki & Freeman, 2003). In this picture, thin disk formation began early, at z = 2 to 3.…”

Section: The Formation Of the Thick Diskmentioning

confidence: 99%

Structure and Evolution of the Milky Way

Freeman

2011

Astrophysics and Space Science Proceedings

View full text Add to dashboard Cite

This review discusses the structure and evolution of the Milky Way, in the context of opportunities provided by asteroseismology of red giants. The review is structured according to the main Galactic components: the thin disk, thick disk, stellar halo, and the Galactic bar/bulge. The review concludes with an overview of Galactic archaeology and chemical tagging, and a brief account of the upcoming HERMES survey with the AAT. The Thin Disk: Formation and EvolutionHere are some of the issues related to the formation and evolution of the Galactic thin disk:• Building the thin disk: its exponential radial structure, and the role of mergers.• The star formation history: chemical evolution and continued gas accretion.• Evolutionary processes in the disk: disk heating, radial mixing.• The outer disk: chemical properties and chemical gradients.Many of the basic observational constraints on the properties of the Galactic disk are still uncertain. At this time, we do not have reliable information about the star formation history of the disk. We do not know how the metallicity distribution and the stellar velocity dispersions in the disk have evolved with time. One might have expected that these observational questions were well understood by now, but this is not yet so. The basic observational problem is the difficulty of measuring ages for individual stars.The younger stars of the Galactic disk show a clear abundance gradient of about 0.07 dex kpc −1 , outlined nicely by the cepheids (Luck et al., 2006). In the outer disk, for the older stars, the abundance gradient appears to be even stronger: the

show abstract

“…In order to investigate the accretion processes of AGB ejecta and cold ISM, we use our original simulation code (Bekki 2013;Bekki 2015b, c) that can be run on GPU clusters. The code enables us to investigate chemical evolution, dust formation and evolution (Bekki 2013), formation of molecular hydrogen on dust grains (Bekki 2015b), photo-electric heating of gas by dust and star formation in galaxies (Bekki 2015c). Since the details of the code are already given in our previous papers, we just briefly explain the code in the present study.…”

Section: The Modelmentioning

confidence: 99%

“…Although GC formation processes based on the VMSC scenario have been extensively investigated by several authors (e.g., D08; Bekki 2011, B11), recent observations have suggested potentially serious problems of the VMSC scenario (e.g., Larsen et al 2012). Although some massive GCs such as ω Cen could have been formed from nucleated dwarf galaxies (e.g., Freeman 1993;Bekki & Freeman 2003), it is not clear whether typical GCs can be formed in the SGN scenario. The top-heavy IMF scenario has not clearly explained why the IMFs of FG stars can be top-heavy in GC formation.…”

Section: Introductionmentioning

confidence: 99%

Globular cluster formation with multiple stellar populations from hierarchical star cluster complexes

Bekki¹

2017

Mon. Not. R. Astron. Soc.

View full text Add to dashboard Cite

Most old globular clusters (GCs) in the Galaxy are observed to have internal chemical abundance spreads in light elements. We discuss a new GC formation scenario based on hierarchical star formation within fractal molecular clouds. In the new scenario, a cluster of bound and unbound star clusters ('star cluster complex', SCC) that have a power-law cluster mass function with a slope (β) of 2 is first formed from a massive gas clump developed in a dwarf galaxy. Such cluster complexes and β = 2 are observed and expected from hierarchical star formation. The most massive star cluster ('main cluster'), which is the progenitor of a GC, can accrete gas ejected from asymptotic giant branch (AGB) stars initially in the cluster and other low-mass clusters before the clusters are tidally stripped or destroyed to become field stars in the dwarf. The SCC is initially embedded in a giant gas hole created by numerous supernovae of the SCC so that cold gas outside the hole can be accreted onto the main cluster later. New stars formed from the accreted gas have chemical abundances that are different from those of the original SCC. Using hydrodynamical simulations of GC formation based on this scenario, we show that the main cluster with the initial mass as large as [2 − 5] × 10 5 M ⊙ can accrete more than 10 5 M ⊙ gas from AGB stars of the SCC. We suggest that merging of hierarchical star cluster complexes can play key roles in stellar halo formation around GCs and self-enrichment processes in the early phase of GC formation.

show abstract

Formation of ω Centauri from an ancient nucleated dwarf galaxy in the young Galactic disc

Cited by 343 publications

References 27 publications

The subgiant branch ofω Centauri seen through high-resolution spectroscopy

The subgiant branch ofω Centauri seen through high-resolution spectroscopy

Structure and Evolution of the Milky Way

Globular cluster formation with multiple stellar populations from hierarchical star cluster complexes

Contact Info

Product

Resources

About