Multicolor CCD Photometry of the SMC Cluster Kron 3

Alcaino, G.; Liller, W.; Alvarado, F.; Kravtsov, V. V.; Ipatov, A. P.; Samus, N. N.; Smirnov, O.

doi:10.1086/118158

Cited by 15 publications

(24 citation statements)

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“…Taking a central value of the HB index as representative of an entire cluster is contingent upon the fact that the HB index does not vary radially within the cluster – while this is still somewhat of an open matter (see, e.g. Alcaino et al 1996a), we observed no evidence for systematic radial HB dependence in the clusters with no field contamination (e.g. NGC 1466).…”

Section: New Measurements Of Horizontal Branch Morphology In Externmentioning

confidence: 73%

Comparing the properties of local globular cluster systems: implications for the formation of the Galactic halo

Mackey

Gilmore

2004

Monthly Notices of the Royal Astronomical Society

207

285

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We investigate the hypothesis that some fraction of the globular clusters presently observed in the Galactic halo formed in external dwarf galaxies. This is done by means of a detailed comparison between the 'old halo', 'young halo' and 'bulge/disc' subsystems defined by Zinn and the globular clusters in the Large Magellanic Cloud, Small Magellanic Cloud, and Fornax and Sagittarius dwarf spheroidal galaxies. We first use high-quality photometry from Hubble Space Telescope images to derive a complete set of uniform measurements of horizontal branch (HB) morphology in the external clusters. We also compile structural and metallicity measurements for these objects and update the data base of such measurements for the Galactic globular clusters, including new calculations of HB morphology for 11 objects. Using these data together with recent measurements of globular cluster kinematics and ages we examine the characteristics of the three Galactic cluster subsystems. Each is quite distinct in terms of their spatial and age distributions, age-metallicity relationships, and typical orbital parameters, although we observe some old halo clusters with ages and orbits more similar to those of young halo objects. In addition, almost all of the Galactic globular clusters with large core radii fall into the young halo subsystem, while the old halo and bulge/disc ensembles are characterized by compact clusters. We demonstrate that the majority of the external globular clusters are essentially indistinguishable from the Galactic young halo objects in terms of HB morphology, but ∼20-30 per cent of external clusters have HB morphologies most similar to the Galactic old halo clusters. We further show that the external clusters have a distribution of core radii which very closely matches that for the young halo objects. The old halo distribution of core radii can be very well represented by a composite distribution formed from ∼83-85 per cent of objects with structures typical of bulge/disc clusters, and ∼15-17 per cent of objects with structures typical of external clusters. Taken together our results fully support the accretion hypothesis. We conclude that all 30 young halo clusters and 15-17 per cent of the old halo clusters (10-12 objects) are of external origin. Based on cluster number counts, we estimate that the Galaxy may have experienced approximately seven merger events with cluster-bearing dwarf-spheroidal-type galaxies during its lifetime, building up ∼45-50 per cent of the mass of the Galactic stellar halo. Finally, we identify a number of old halo objects which have properties characteristic of accreted clusters. Several of the clusters associated with the recently proposed dwarf galaxy in Canis Major fall into this category.

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Section: New Measurements Of Horizontal Branch Morphology In Externmentioning

confidence: 73%

Comparing the properties of local globular cluster systems: implications for the formation of the Galactic halo

Mackey

Gilmore

2004

Monthly Notices of the Royal Astronomical Society

207

285

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“…The merging scenario had been proposed because of the broad RGB from ground-based BVRI photometry (Alcaino et al 1999) and because of the preliminary evidence of a metallicity dispersion from high-resolution spectroscopy of two RGB stars ( Hill et al 2000) (½Fe/H $ 0:2 Y0:3 dex). However, the tiny RGB sequence presented in this work, as well as the recent iron abundance estimate from high-resolution spectra of 11 RGB stars presented by Ferraro et al (2006), definitely exclude any significant metallicity spread within the cluster.…”

Section: Discussionmentioning

confidence: 99%

“…In this paper we present the results for one of the most massive and luminous globular clusters in the LMC, namely NGC 1978. This cluster for years has been considered a peculiar object (1) because of its high ellipticity ( ¼ 0:3; Fischer et al 1992), significantly larger than those typically measured in stellar clusters (Goodwin 1997), and (2) because it has been suspected to harbor a chemically inhomogeneous stellar population (Alcaino et al 1999;Hill et al 2000). However, Ferraro et al (2006) have recently presented high-resolution spectra for 11 giants in this cluster, obtaining ½Fe/H ¼ À0:38 dex, with a very low dispersion ( ¼ 0:07 dex), firmly excluding the presence of a significant metallicity spread in this cluster.…”

Section: Introductionmentioning

confidence: 99%

The Globular Cluster NGC 1978 in the Large Magellanic Cloud

et al. 2007

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We have used deep, high-resolution Hubble Space Telescope ACS observations to image the cluster NGC 1978 in the Large Magellanic Cloud. This high-quality photometric data set allowed us to confirm the high ellipticity ( $ 0:30 AE 0:02) of this stellar system. The derived color-magnitude diagram allowed a detailed study of the main evolutionary sequences; in particular, we have detected the so-called bump along the red giant branch (at V 555 ¼ 19:10 AE 0:10). This is the first detection of this feature in an intermediate-age cluster. Moreover, the morphology of the evolutionary sequence and the population ratios have been compared with the expectations of different theoretical models (namely, BaSTI, Pisa Evolutionary Library [PEL], and Padua) in order to quantify the effect of convective overshooting. The best agreement (in terms of both morphology and star counts) has been found within the PEL isochrone, with Z ¼ 0:008 (consistent with the most recent determination of the cluster metallicity, ½M/H ¼ À0:37 dex) and a mild overshooting efficiency (Ã os ¼ 0:1). By adopting this theoretical set an age of ¼ 1:9 AE 0:1 Gyr has been obtained.

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“…By fitting isochrones to the cluster CMD, Rich et al (1984) proposed a range in age from 5 to 8 Gyr for Kron 3. Comparing theoretical isochrones (Vandenberg & Bell 1985) to the cluster CMDs, Alcaino et al (1996) proposed an even older age range (8-10 Gyr) than previously claimed for Kron 3. Using archival HST/WFPC2 data, Mighell et al (1998) proposed that the cluster is 4.7(±0.6) Gyr old.…”

Section: Introductionmentioning

confidence: 59%

“…Using the optical spectra obtained from Anglo-Australian Telescope (AAT), Gascoigne (1980) estimated the metallicity to be [Fe/H] = −0.6 dex. Studies by Hodge (1982); Rich et al (1984); Alcaino et al (1996); Glatt et al (2008) reported that the cluster metallicity (Z) is 0.001 ([Fe/H] = −1.3 dex), whereas Dias et al (2010) estimated the metallicity as Z = 0.0002. Therefore, large ranges in age and metallicity have been suggested for this cluster.…”

Section: Introductionmentioning

confidence: 99%

Detection of extended Red Clump in the SMC cluster Kron 3

Nayak

Subramaniam²,

Subramanian³

et al. 2019

Proc. IAU

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For the first time, we report the identification of NUV bright red clump (RC) stars and the extension of RC stars over two magnitudes both in color and magnitude axis in NUV vs (NUV – optical) color magnitude diagram. We find that the extension of RC is not due to photometric uncertainties. We suggest that the extension could be an effect of field star contamination. We also suggest that if it is an intrinsic property of the cluster then age and/or metallicity spread within the cluster could be the possible reasons for extended RC.

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Multicolor CCD Photometry of the SMC Cluster Kron 3

Cited by 15 publications

References 0 publications

Comparing the properties of local globular cluster systems: implications for the formation of the Galactic halo

Comparing the properties of local globular cluster systems: implications for the formation of the Galactic halo

The Globular Cluster NGC 1978 in the Large Magellanic Cloud

Detection of extended Red Clump in the SMC cluster Kron 3

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