Spectroscopy of Giants in the Sextans Dwarf Spheroidal Galaxy

Suntzeff, Nicholas B.; Mateo, Mario; Terndrup, D. M.; Olszewski, Edward W.; Geisler, Doug; Weller, W.

doi:10.1086/173383

Cited by 89 publications

(121 citation statements)

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“…the Sextans dSph (Suntzeff et al 1993). Another well studied galaxy is Draco, where Shetrone et al (1998) found −3.0 < [Fe/H]< −1.5 confirming earlier findings of a substantial metallicity spread (Lehnert et al 1992).…”

Section: Chemical Abundances Of Local Group De/dsph Galaxiessupporting

confidence: 75%

The most metal-poor galaxies

Kunth

Östlin

2000

Astronomy and Astrophysics Review

381

428

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Metallicity is a key parameter that controls many aspects in the formation and evolution of stars and galaxies. In this review we focus on the metal deficient galaxies, in particular the most metal-poor ones, because they play a crucial rôle in the cosmic scenery. We first set the stage by discussing the difficult problem of defining a global metallicity and how this quantity can be measured for a given galaxy. The mechanisms that control the metallicity in a galaxy are reviewed in detail and involve many aspects of modern astrophysics: galaxy formation and evolution, massive star formation, stellar winds, chemical yields, outflows and inflows etc. Because metallicity roughly scales as the galactic mass, it is among the dwarfs that the most metalpoor galaxies are found. The core of our paper reviews the considerable progress made in our understanding of the properties and the physical processes that are at work in these objects. The question on how they are related and may evolve from one class of objects to another is discussed. While discussing metal-poor galaxies in general, we present a more detailed discussion of a few very metal-poor blue compact dwarf galaxies like IZw18. Although most of what is known relates to our local universe, we show that it pertains to our quest for primeval galaxies and is connected to the question of the origin of structure in the universe. We discuss what QSO absorption lines and known distant galaxies tell us already? We illustrate the importance of star-forming metal-poor galaxies for the determination of the primordial helium abundance, their use as distance indicator and discuss the possibility to detect nearly metal-free galaxies at high redshift from Lyα emission.

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Section: Chemical Abundances Of Local Group De/dsph Galaxiessupporting

confidence: 75%

The most metal-poor galaxies

Kunth

Östlin

2000

Astronomy and Astrophysics Review

381

428

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“…- (1) (12) Mateo et al 1993; (13) Mateo et al 1998a; (14) Mateo et al 1998b; (15) Odenkirchen et al 2001; (16) Suntzeff et al 1993;(17) van der Marel et al 1994; (18) Vogt et al 1995;(19) Walker et al 2006;(20) Westfall et al 2006. only modestly disturbed by its interaction with M31 (a similar conclusion is reached through other arguments by Choi et al 2002).…”

mentioning

confidence: 67%

Local Group Dwarf Galaxies and the Fundamental Manifold of Spheroids

Zaritsky

Gonzalez

Zabludoff

2006

ApJ

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The fundamental manifold (FM), an extension of the fundamental plane formalism, incorporates all spheroiddominated stellar systems from dwarf ellipticals up to the intracluster stellar populations of galaxy clusters by accounting for the continuous variation of the mass-to-light ratio within the effective radius with scale.Here r e we find that Local Group dwarf spheroidal and dwarf elliptical galaxies, which probe the FM relationship roughly one decade lower in than previous work, lie on the extrapolation of the FM. When combined with the earlier r e data, these Local Group dwarfs demonstrate the validity of the empirical manifold over nearly 4 orders of magnitude in . The continuity of the galaxy locus on the manifold and, more specifically, the overlap on the r e FM of dwarf ellipticals like M32 and dwarf spheroidals like Leo II, imply that dwarf spheroidals belong to the same family of spheroids as their more massive counterparts. The only significant outliers are Ursa Minor and Draco. We explore whether the deviation of these two galaxies from the manifold reflects a breakdown in the coherence of the empirical relationship at low luminosities or rather the individual dynamical peculiarities of these two objects. We discuss some implications of our results for how the lowest mass galaxies form.

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“…In all cases, the selected CaT index uses a linear combination of the EW of two or three individual Ca ii lines to form the line strength index ΣW . For example, Suntzeff et al (1993) and Cole et al (2000) used a linear combination of the two strongest lines (8542 Å and 8662 Å), while in other cases all three lines were used, but each line was assigned a different weight in deriving the sum (e.g., Rutledge et al 1997a). Since our spectra are of high enough quality that all three CaT lines are well measured, we adopted for ΣW the same definition as C04, in which all three lines are used with equal weight, namely,…”

Section: Metallicitiesmentioning

confidence: 99%

Ca II TRIPLET SPECTROSCOPY OF SMALL MAGELLANIC CLOUD RED GIANTS. I. ABUNDANCES AND VELOCITIES FOR A SAMPLE OF CLUSTERS

Parisi

Grocholski

Geisler

et al. 2009

The Astronomical Journal

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We have obtained near-infrared spectra covering the Ca II triplet lines for a large number of stars associated with 16 Small Magellanic Cloud (SMC) clusters using the VLT + FORS2. These data compose the largest available sample of SMC clusters with spectroscopically derived abundances and velocities. Our clusters span a wide range of ages and provide good areal coverage of the galaxy. Cluster members are selected using a combination of their positions relative to the cluster center as well as their location in the color-magnitude diagram, abundances, and radial velocities (RVs). We determine mean cluster velocities to typically 2.7 km s −1 and metallicities to 0.05 dex (random errors), from an average of 6.4 members per cluster. By combining our clusters with previously published results, we compile a sample of 25 clusters on a homogeneous metallicity scale and with relatively small metallicity errors, and thereby investigate the metallicity distribution, metallicity gradient, and age-metallicity relation (AMR) of the SMC cluster system. For all 25 clusters in our expanded sample, the mean metallicity [Fe/H] = −0.96 with σ = 0.19. The metallicity distribution may possibly be bimodal, with peaks at ∼−0.9 dex and −1.15 dex. Similar to the Large Magellanic Cloud (LMC), the SMC cluster system gives no indication of a radial metallicity gradient. However, intermediate age SMC clusters are both significantly more metal-poor and have a larger metallicity spread than their LMC counterparts. Our AMR shows evidence for three phases: a very early (> 11 Gyr) phase in which the metallicity reached ∼−1.2 dex, a long intermediate phase from ∼10 to 3 Gyr in which the metallicity only slightly increased, and a final phase from 3 to 1 Gyr ago in which the rate of enrichment was substantially faster. We find good overall agreement with the model of Pagel & Tautvaišiene, which assumes a burst of star formation at 4 Gyr. Finally, we find that the mean RV of the cluster system is 148 km s −1 , with a velocity dispersion of 23.6 km s −1 and no obvious signs of rotation amongst the clusters. Our result is similar to what has been found from a wide variety of kinematic tracers in the SMC, and shows that the SMC is best represented as a pressure supported system.

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Spectroscopy of Giants in the Sextans Dwarf Spheroidal Galaxy

Cited by 89 publications

References 0 publications

The most metal-poor galaxies

The most metal-poor galaxies

Local Group Dwarf Galaxies and the Fundamental Manifold of Spheroids

Ca II TRIPLET SPECTROSCOPY OF SMALL MAGELLANIC CLOUD RED GIANTS. I. ABUNDANCES AND VELOCITIES FOR A SAMPLE OF CLUSTERS

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