Are Globular Clusters the Remnant Nuclei of Progenitor Disk Galaxies?

Böker, Torsten

doi:10.1086/527033

Cited by 50 publications

(47 citation statements)

References 56 publications

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“…In summary, we are unable to draw a firm conclusion about the origin of the newly detected extended component surrounding NGC 5694. It is clear, however, that the evidence presented here, coupled with the results of L06, strongly indicates that this object deserves further investigation, as it may fit into the scenario in which (at least some) GCs are supposed to be the remnants of disrupted dwarf satellites, hence, one of the final end‐states of the building blocks concurring to the hierarchical assembly of the MW (see Bellazzini et al 2008; Böker 2008; Carretta et al 2010, and references therein). Abundance analysis of a significant sample of NGC 5694 giants as well as a photometric survey covering a significantly wider area than that explored here is clearly needed to search for a metallicity spread and determine chemical abundance ratios to shed more light on the nature of this very interesting, and for a long time neglected, GC.…”

Section: Summary and Discussionmentioning

confidence: 60%

A low surface brightness halo surrounding the globular cluster NGC 5694★

Correnti

Bellazzini

Dalessandro

et al. 2011

Monthly Notices of the Royal Astronomical Society

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We report on the discovery of an extended stellar halo surrounding the distant Galactic globular cluster NGC 5694, based on new deep (V≃ 24.5) wide‐field (24 × 20 arcmin2) photometry acquired with the VIMOS at the VLT. Stars with colour and magnitude consistent with the main sequence of the cluster are clearly identified out to r≃ 9 arcmin (≃93 pc) from the cluster centre, much beyond the tidal radius of the King model that best fits the inner profile (rt= 3.15 arcmin). We do not find a clear end of the structure within our field. The overall observed profile cannot be properly fitted with either a King model, an Elson et al. model or a Wilson model; however, it is very smooth and does not show any sign of the break near the tidal radius that is typically observed in stellar systems with tidal tails. The density map we derived does not show evidence of tidal tails, within the considered field. The extra‐tidal component contains ≃ 3.5 per cent of the cluster light (mass) and has a surface density profile falling as ∼r−3.2. The possible origin of the detected structure is discussed, as a clear‐cut conclusion cannot be reached with the available data.

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Section: Summary and Discussionmentioning

confidence: 60%

A low surface brightness halo surrounding the globular cluster NGC 5694★

Correnti

Bellazzini

Dalessandro

et al. 2011

Monthly Notices of the Royal Astronomical Society

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“…We remark that 1) The groups are chosen to have a narrow mass loss spread (0.006 M ), in agreement with past works related to galactic globular clusters , 2008 and extragalactic ones (D'Antona et al 2013). 2) The mass loss needed to simulate the iHB, the bHB and, following the results in , the eHB, has to be increased to reproduce these parts of the HB (see Table 1).…”

Section: Discussionmentioning

confidence: 76%

“…the remnant nucleus of a satellite galaxy which was destroyed when merging with the Milky Way (Norris et al 1997;Lee et al 1999), or a former nuclear star cluster (e.g. Böker 2008;Da Costa 2015). Dating the different populations of this system is indeed a first step to choose among these possibilities, as GCs star formation is generally believed to be contained in a time span of the order of 10 8 yr (D'Ercole et al 2008), while much longer time-scales are possible in the other systems (Georgiev & Böker 2014).…”

Section: Introductionmentioning

confidence: 99%

The mosaic multiple stellar populations in ω Centauri: the horizontal branch and the main sequence

Tailo

Criscienzo

D’Antona

et al. 2016

Mon. Not. R. Astron. Soc.

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We interpret the stellar population of ω Centauri by means of a population synthesis analysis, following the most recent observational guidelines for input metallicities, helium and [(C+N+O)/Fe] contents. We deal at the same time with the main sequences, sub-giant and horizontal branch data. The reproduction of the observed color magnitude features is very satisfying and bears interesting hints concerning the evolutionary history of this peculiar stellar ensemble. Our main results are: 1) no significant spread in age is required to fit the colour-magnitude diagram. Indeed we can use coeval isochrones for the synthetic populations, and we estimate that the ages fall within a ∼ 0.5 Gyr time interval; in particular the most metal rich population can be coeval (in the above meaning) with the others, if its stars are very helium-rich (Y∼0.37) and with the observed CNO enhancement ([(C+N+O)/Fe] = + 0.7); 2) a satisfactory fit of the whole HB is obtained, consistent with the choice of the populations providing a good reproduction of the main sequence and sub giant data. 3) the split in magnitude observed in the red HB is well reproduced assuming the presence of two stellar populations in the two different sequences observed: a metal poor population made of stars evolving from the blue side (luminous branch) and a metal richer one whose stars are in a stage closer to the zero age HB (dimmer branch). This modelization also fits satisfactorily the period and the [Fe/H] distribution of the RR Lyrae stars.

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“…Freeman 1990;Böker 2008;Georgiev et al 2009). Those nuclei or nuclear star clusters of dwarf galaxies that can be studied in close detail (such as M 54 for the Sagittarius galaxy) essentially share the full pattern of properties with GCs (see e.g.…”

Section: Definition Of Globular Clustersmentioning

confidence: 99%

Properties of stellar generations in globular clusters and relations with global parameters

Carretta¹,

Bragaglia²,

Gratton

et al. 2010

A&A

486

712

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We revise the scenario of the formation of Galactic globular clusters (GCs) by adding the observed detailed chemical composition of their different stellar generations to the set of their global parameters. We exploit the unprecedented set of homogeneous abundances of more than 1200 red giants in 19 clusters, as well as additional data from literature, to give a new definition of bona fide GCs, as the stellar aggregates showing the Na-O anticorrelation. We propose a classification of GCs according to their kinematics and location in the Galaxy in three populations: disk/bulge, inner halo, and outer halo. We find that the luminosity function of GCs is fairly independent of their population, suggesting that it is imprinted by the formation mechanism only marginally affected by the ensuing evolution. We show that a large fraction of the primordial population should have been lost by the proto-GCs. The extremely low Al abundances found for the primordial population of massive GCs indicate a very fast enrichment process before the formation of the primordial population. We suggest a scenario for the formation of GCs that includes at least three main phases: i) the formation of a precursor population (likely due to the interaction of cosmological structures similar to those that led to the formation of dwarf spheroidals, but residing at smaller Galactocentric distances, with the early Galaxy or with other structures); ii) the triggering of a long episode of star formation (the primordial population) from the precursor population; and iii) the formation of the current GC, mainly within a cooling flow formed by the slow winds of a fraction of the primordial population. The precursor population is very effective in raising the metal content in massive and/or metal-poor (mainly halo) clusters, while its rôle is minor in small and/or metal-rich (mainly disk) ones. Finally, we use principal component analysis and multivariate relations to study the phase of metal enrichment from first to second generation. We conclude that most of the chemical signatures of GCs may be ascribed to a few parameters, the most important being metallicity, mass, and cluster age. Location within the Galaxy (as described by the kinematics) also plays some rôle, while additional parameters are required to describe their dynamical status.

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Are Globular Clusters the Remnant Nuclei of Progenitor Disk Galaxies?

Cited by 50 publications

References 56 publications

A low surface brightness halo surrounding the globular cluster NGC 5694★

A low surface brightness halo surrounding the globular cluster NGC 5694★

The mosaic multiple stellar populations in ω Centauri: the horizontal branch and the main sequence

Properties of stellar generations in globular clusters and relations with global parameters

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