Population Gradients in Local Group Dwarf Spheroidal Galaxies

Harbeck, Daniel; Grebel, Eva K.; Holtzman, Jon A.; Guhathakurta, Puragra; Brandner, W.; Geisler, Doug; Sarajedini, Ata; Dolphin, Andrew E.; Hurley-Keller, Denise; Mateo, Mario

doi:10.1086/324232

Cited by 239 publications

(340 citation statements)

References 47 publications

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“…In Sextans, the spatial scale of the velocity feature matches closely the scale on which the nature of the stellar populations changes, as indicated by the radial variation of the horizontal branch ratio (see e.g. Lee et al 2003;Harbeck et al 2001). Recently, Tolstoy et al (2004) have found that in the Sculptor dSph, differences in the spatial distribution of the stellar populations are mirrored by variations in the velocity dispersions of the populations.…”

Section: Observations Of Kinematic Substructure In Local Group Dsphsmentioning

confidence: 73%

“…In the core of Carina, the velocity distribution of the more metal-rich population is noticeably narrower than that of the metal-poor population. This may indicate that at small radii the stellar distribution (and hence the observed kinematics) is dominated by a more concentrated population with smaller velocity dispersion, possibly corresponding to the red clump population identified by Harbeck et al (2001). Thus, kinematic substructure appears to be a common feature in dSphs.…”

Section: Observations Of Kinematic Substructure In Local Group Dsphsmentioning

confidence: 90%

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Substructure in dwarf spheroidals – a star cluster connection?

Wilkinson

Kleyna²,

Evans

et al. 2005

Proc. IAU

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Abstract. The observational evidence for kinematic substructure in Local Group dSphs is reviewed. The properties of these substructures are consistent with their being disrupted star clusters. The persistence of cold substructure argues strongly against the presence of dark matter cusps in the haloes of dSphs. A formation scenario for dSphs is described involving the merger of star clusters in the potential well of a low-mass dark matter halo.

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Section: Observations Of Kinematic Substructure In Local Group Dsphsmentioning

confidence: 73%

Section: Observations Of Kinematic Substructure In Local Group Dsphsmentioning

confidence: 90%

Substructure in dwarf spheroidals – a star cluster connection?

Wilkinson

Kleyna²,

Evans

et al. 2005

Proc. IAU

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“…Often their stellar populations are purely old, but mixtures of old and intermediate-age populations are found as well. In dSphs where several populations can be distinguished the younger and/or more metal-rich populations are more centrally concentrated, indicating extended star formation episodes in the centers of the shallow potential wells of their parent galaxies (Harbeck et al 2001). The gas deficiency of dSphs remains an unsolved puzzle -dSphs typically contain even less gas than expected from red giant mass loss over time scales of several Gyr.…”

Section: Local Group Dwarf Spheroidalsmentioning

confidence: 99%

“…Only one dSph with clearly episodic star formation is known (Carina, Smecker-Hane et al 1994 andMonelli et al 2003). DSphs with several populations typically show population gradients in the sense that more metal-rich and/or younger populations are more centrally concentrated (Harbeck et al 2001). Substructure of this kind is not necessarily symmetrically distributed (e.g., Stetson et al 1998).…”

Section: Dwarf Spheroidal Star Formation Histories and Abundancesmentioning

confidence: 99%

Near-field cosmology with Local Group dwarf spheroidals

Grebel¹

2005

Proc. IAU

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Abstract. The Local Group offers an excellent laboratory for near-field cosmology by permitting us to use the resolved stellar content of its constituent galaxies as probes of galaxy formation and evolution, which in turn is an important means for testing cosmological models of hierarchical structure formation. In this review, we discuss the the least massive, yet most numerous type of galaxy in the Local Group, the dwarf spheroidal galaxies, and compare their properties to cosmological predictions. In particular, we point out problems found with a simple building block scenario and with effects expected from reionization. We show that the star formation histories of dSphs are inconsistent with the predicted cessation of star formation after reionization; instead, extended star formation episodes are observed. The Galactic dSphs contain in part prominent intermediate-age populations, whereas the Galactic halo does not. Conversely, the M31 dSphs are almost entirely old, while the M31 halo contains a substantial intermediate-age population. These differences in the population structure as well as the differences in the modes of star formation inferred from [α/Fe] ratios make dSphs unlikely major contributors to the build-up of the Galactic and M31 halo unless most of the accretion occurred at early epochs. On the other hand, there is clear evidence for ongoing harassment and accretion of a number of dSphs.

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“…Group dSphs have shown us that, in spite of their current quiescent appearance, most of the systems have had surprisingly complicated evolutionary histories (Harbeck et al 2002). It would be interesting to compare the chemical and star formation histories for DSphs in the Local group and in the other nearby groups.…”

Section: New Deep C-m Diagrams and Spectroscopy Of Individual Red Giamentioning

confidence: 99%

Age and Metallicity of a Globular Cluster in the Dwarf Spheroidal Galaxy DDO 78

Шарина¹,

Сильченко²,

Burenkov³

Eso Astrophysics Symposia

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Abstract. We present the results of moderate resolution spectroscopy for a globular cluster in the M81 group dwarf spheroidal galaxy DDO 78. The DDO 78 globular cluster, 4 Milky Way globular clusters, spectroscopic and radial velocity standards were observed with the Long-slit spectrograph of the 6-m telescope (SAO RAS, Russia). Lick spectrophotometric indices were determined in the bandpasses adopted by Burstein et al. (1984). We have derived the mean metallicity of the globular cluster in DDO78 to be [Fe/H] = −1.6 ± 0.1 dex by taking the weighted mean of metallicities obtained from the strength of several absorption features. We have estimated an age for the globular cluster of 9-12 Gyr similar to that found for the Galactic globular cluster NGC 362, which resembles our cluster by chemical abundance and integrated spectrophotometric properties.

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Population Gradients in Local Group Dwarf Spheroidal Galaxies

Cited by 239 publications

References 47 publications

Substructure in dwarf spheroidals – a star cluster connection?

Substructure in dwarf spheroidals – a star cluster connection?

Near-field cosmology with Local Group dwarf spheroidals

Age and Metallicity of a Globular Cluster in the Dwarf Spheroidal Galaxy DDO 78

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