Kinematic Decoupling of Globular Clusters with the Extended Horizontal Branch

Lee, Young-Wook; Gim, Hansung B.; Casetti-Dinescu, Dana I.

doi:10.1086/518653

Cited by 107 publications

(161 citation statements)

References 32 publications

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“…These artificially younger ages may also result from the presence of multiple stellar populations, since Balmer lines are mostly sensitive to the main-sequence turn-off temperature (Worthey 1994). In our Galaxy, the most massive GCs also show indications of unusually hot, extended HBs, multiple stellar populations, and are kinematically distinct from other Galactic GCs (Recio-Blanco et al 2006;Lee et al 2007). Spectroscopic studies have shown that three types of GC populations exist in M 31: old objects with a wide range of metallicities, intermediate age and metallicity GCs, and young GCs with slightly higher metallicity (Perrett et al 2002;Beasley et al 2004Beasley et al , 2005Fusi Pecci et al 2005;Puzia et al 2005a).…”

Section: Agesmentioning

confidence: 65%

Globular cluster content and evolutionary history of NGC 147

Шарина

Davoust

2009

A&A

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Context. Globular clusters are representative of the oldest stellar populations. It is thus essential to have a complete census of these systems in dwarf galaxies, from which more massive galaxies are progressively formed in the hierarchical scenario. Aims. We present the results of spectroscopic observations of eight globular cluster candidates in NGC 147, a satellite dwarf elliptical galaxy of M 31. Our goal is to make a complete inventory of the globular cluster system of this galaxy, determine the properties of their stellar populations, and compare these properties with those of systems of globular clusters in other dwarf galaxies. Methods. The candidates were identified on Canada-France-Hawaii telescope photographic plates. Medium resolution spectra were obtained with the SCORPIO spectrograph at the prime focus of the 6 m telescope of the Russian Academy of Sciences. They were analyzed using predictions of stellar population synthesis models. Results. We were able to confirm the nature of all eight candidates, three of which (GC5, GC7, and GC10) are indeed globular clusters, and to estimate evolutionary parameters for the two brightest ones and for Hodge II. The bright clusters GC5 and GC7 appear to have metallicities ([Z/H] ∼ −1.5 ÷ −1.8) that are lower than the oldest stars in the galaxy. The fainter GC Hodge II has a metallicity [Z/H] = −1.1, similar to that of the oldest stars in the galaxy. The clusters GC5 and GC7 have low alpha-element abundance ratios. The mean age of the globular clusters in NGC 147 is 9 ± 1 Gyr. We also measured the radial velocities of Hodge II and IV, and derived a mass of NGC 147 in good agreement with the value from the literature. The frequency, S n = 6.4, and mass fraction, T = 14 of globular clusters in NGC 147 appear to be higher than those for NGC 185 and 205. Conclusions. Our results indicate that the bright clusters GC5, GC7, and Hodge III formed in the main star-forming period ∼8−10 Gyr ago, while the fainter clusters Hodge I and II formed together with the second generation of field stars.

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Section: Agesmentioning

confidence: 65%

Globular cluster content and evolutionary history of NGC 147

Шарина

Davoust

2009

A&A

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“…About a quarter of all globular clusters exhibit an unusually extended horizontal branch (Lee et al 2007). This "blue hook" morphology probably indicates that such clusters had an unusual evolutionary history.…”

Section: Flattening and Horizontal Branch Morphologymentioning

confidence: 99%

The Flattening of Globular Clusters

Bergh

2008

The Astronomical Journal

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In the three nearest luminous galaxies, the Milky Way System, the Andromeda Galaxy, and NGC 5128, the brightest globular clusters are rounder than the faintest ones. On the other hand (contrary to some previous results) the flattening of individual Large Magellanic Cloud clusters is found to be independent of their luminosities. This suggests the possibility that the relationship between the flattening and luminosity of clusters might depend on host galaxy luminosity. No significant differences are found between the intrinsic flattening distributions of Galactic old halo, Galactic young halo, and Galactic bulge/disk clusters. Such a dependence might perhaps have been expected if tidal forces (which are largest at small Galactocentric distances) removed angular momentum from globular clusters. The preliminary conclusion by Norris that clusters with blue horizontal branches are more flattened than red horizontal-branch (HB) clusters is not confirmed by the larger database that is now available. In other words there is no evidence for the puzzling claimed correlation between the flattening and the horizontal branch morphology of Galactic globular clusters.

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“…Currently available observational data on the phasespace structure of the Galactic stars show signatures of such accretion events of dSphs, as evidenced by the spatial distribution and stellar populations of halo globular clusters (Searle & Zinn 1978;Mackey & Gilmore 2004;Lee et al 2007), streams/overdensities in the spatial distribution of stars (Ibata et al 1994;Newberg et al 2002;Majewski et al 2003;Jurić et al 2008), kinematic substructures (Helmi et al 1999 …”

Section: Introductionmentioning

confidence: 99%

CHEMICAL ABUNDANCES OF THE MILKY WAY THICK DISK AND STELLAR HALO. I. IMPLICATIONS OF [α/Fe] FOR STAR FORMATION HISTORIES IN THEIR PROGENITORS

Ishigaki

Chiba

Aoki

2012

ApJ

107

131

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We present the abundance analysis of 97 nearby metal-poor (−3.3 < [Fe/H] < −0.5) stars having kinematic characteristics of the Milky Way (MW) thick disk and inner and outer stellar halos. The high-resolution, high-signalto-noise optical spectra for the sample stars have been obtained with the High Dispersion Spectrograph mounted on the Subaru Telescope. Abundances of Fe, Mg, Si, Ca, and Ti have been derived using a one-dimensional LTE abundance analysis code with Kurucz NEWODF model atmospheres. By assigning membership of the sample stars to the thick disk, inner halo, or outer halo components based on their orbital parameters, we examine abundance ratios as a function of [Fe/H] and kinematics for the three subsamples in wide metallicity and orbital parameter ranges. We show that, in the metallicity range of −1.

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Kinematic Decoupling of Globular Clusters with the Extended Horizontal Branch

Cited by 107 publications

References 32 publications

Globular cluster content and evolutionary history of NGC 147

Globular cluster content and evolutionary history of NGC 147

The Flattening of Globular Clusters

CHEMICAL ABUNDANCES OF THE MILKY WAY THICK DISK AND STELLAR HALO. I. IMPLICATIONS OF [α/Fe] FOR STAR FORMATION HISTORIES IN THEIR PROGENITORS

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