Chemical Evolution in the Carina Dwarf 1Spheroidal

Koch, Andreas; Grebel, Eva K.; Harbeck, Daniel; Wilkinson, M. I.; Kleyna, Jan; Gilmore, G.; Wyse, Rosemary F. Ġ.; Evans, N. W.

doi:10.1007/978-3-540-34136-9_82

Cited by 2 publications

(2 citation statements)

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“…The stars that were observed were selected from color-magnitude diagrams of each dSph to be giants at the distance of that galaxy, with a bright magnitude limit of V ∼ 17 and faint limit of V < ∼ 20, with a mild trend, following the giant branch, that fainter stars are bluer. The surveys of the Draco dSph and the UMi dSph are described in Wilkinson et al (2004), while that of the Carina dSph is described in Wilkinson et al (2006) and in Koch et al (2006). In general dSph have low velocity dispersions, ∼ 10 km/s, and our membership probabilities were based on iterative Gaussian fitting to the radial velocity distributions.…”

Section: Introductionmentioning

confidence: 99%

Further Evidence of a Merger Origin for the Thick Disk: Galactic Stars along Lines of Sight to Dwarf Spheroidal Galaxies

Wyse

Gilmore

Norris

et al. 2006

ApJ

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The history of the Milky Way Galaxy is written in the properties of its stellar populations. Here we analyse stars observed as part of surveys of local dwarf spheroidal galaxies, but which from their kinematics are highly probable to be non-members. The selection function -designed to target metal-poor giants in the dwarf galaxies, at distances of ∼ 100 kpc -includes F-M dwarfs in the Milky Way, at distances of up to several kpc. The stars whose motions are analysed here lie in the cardinal directions of Galactic longitude ℓ ∼ 270 • and ℓ ∼ 90 • , where the radial velocity is sensitive to the orbital rotational velocity. We demonstrate that the faint F/G stars contain a significant population with V φ ∼ 100 km/s, similar to that found by a targeted, but limited in areal coverage, survey of thickdisk/halo stars by Gilmore, Wyse & Norris (2002). This value of mean orbital rotation does not match either the canonical thick disk or the stellar halo. We argue that this population, detected at both ℓ ∼ 270 • and ℓ ∼ 90 • , has the expected properties of 'satellite debris' in the thick-disk/halo interface, which we interpret as remnants of the merger that heated a pre-existing thin disk to form the thick disk.

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Section: Introductionmentioning

confidence: 99%

Further Evidence of a Merger Origin for the Thick Disk: Galactic Stars along Lines of Sight to Dwarf Spheroidal Galaxies

Wyse

Gilmore

Norris

et al. 2006

ApJ

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“…Consequently, we assume that NGC 121 also is enhanced in α-elements. We note that in this respect NGC 121 differs from the general trend observed in red giant stars in the LMC and in dwarf spheroidal galaxies, where the [α/Fe] ratios at a given [Fe/H] tend to be lower by up to a few tenths of a dex than in the Galactic halo (e.g., Hill et al 2000;Shetrone et al 2001;Fulbright 2002;Johnson et al 2006;Koch et al 2007).…”

Section: Age Of Ngc 121mentioning

confidence: 54%

An Accurate Age Determination for the SMC Star Cluster NGC121 with HST/ACS

Glatt,

Gallagher,

Grebel

et al. 2008

Preprint

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As first Paper of a series devoted to study the old stellar population in clusters and fields in the Small Magellanic Cloud, we present deep observations of NGC 121 in the F555W and F814W filters, obtained with the Advanced Camera for Surveys on the Hubble Space Telescope. The resulting color-magnitude diagram reaches ∼ 3.5 mag below the main-sequence turn-off; deeper than any previous data. We derive the age of NGC 121 using both absolute and relative age-dating methods. Fitting isochrones in the ACS photometric system to the observed ridge line of NGC 121, gives ages of 11.8 ± 0.5 Gyr (Teramo), 11.2 ± 0.5 Gyr (Padova) and 10.5 ± 0.5 Gyr (Dartmouth). The cluster ridge line is best approximated by the α-enhanced Dartmouth isochrones. Placing our relative ages on an absolute age scale, we find ages of 10.9 ± 0.5 Gyr (from the magnitude difference between the main-sequence turn-off and the horizontal branch) and 11.5 ± 0.5 Gyr (from the absolute magnitude of the horizontal branch), respectively. These five different age determinations are all lower by 2 -3 Gyr than the ages of the oldest Galactic globular clusters of comparable metallicity. Therefore we confirm the earlier finding that the oldest globular cluster in the Small Magellanic Cloud, NGC 121, is a few Gyr younger than its oldest counterparts in the Milky Way and in other nearby dwarf galaxies such as the Large Magellanic Cloud, Fornax, and Sagittarius. If it were accreted into the Galactic halo, NGC 121 would resemble the "young halo globulars", although it is not as young as the youngest globular clusters associated with the Sagittarius dwarf. The young age of NGC 121 could result from delayed cluster formation in the Small Magellanic Cloud or result from the random survival of only one example of an initially small number star clusters.

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Chemical Evolution in the Carina Dwarf 1Spheroidal

Cited by 2 publications

References 6 publications

Further Evidence of a Merger Origin for the Thick Disk: Galactic Stars along Lines of Sight to Dwarf Spheroidal Galaxies

Further Evidence of a Merger Origin for the Thick Disk: Galactic Stars along Lines of Sight to Dwarf Spheroidal Galaxies

An Accurate Age Determination for the SMC Star Cluster NGC121 with HST/ACS

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