A 2MASS All‐Sky View of the Sagittarius Dwarf Galaxy. V. Variation of the Metallicity Distribution Function along the Sagittarius Stream

Chou, Mei-Yin; Majewski, Steven R.; Cunha, Kátia; Smith, Verne V.; Patterson, Richard J.; Martínez–Delgado, David; Law, David R.; Crane, Jeffrey D.; Muñoz, Ricardo R.; López, Ramon Garcia; Geisler, Doug; Skrutskie, Michael F.

doi:10.1086/522483

Cited by 145 publications

(213 citation statements)

References 59 publications

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“…The SF then continues, but at a lower rate, until it is negligible. It has been claimed though that dynamical interactions could remove preferentially the most metal-poor stars of dwarf galaxies (as it has been shown for Sagittarius - Monaco et al 2007;Chou et al 2007), thus modifying the observed present-day SMD. This point, if it were present in the dSph galaxies Leo 1 and Leo2, would imply a higher fraction of metal-poor stars and broader SMDs.…”

Section: Discussionmentioning

confidence: 91%

Chemical evolution models for the dwarf spheroidal galaxies Leo 1 and Leo 2

Lanfranchi

Matteuccí

2010

A&A

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Aims. We investigate the chemical evolutionary history of the dwarf spheroidal galaxies Leo 1 and Leo 2 by means of predictions from a detailed chemical evolution model compared to observations. The model adopts up to date nucleosynthesis and takes into account the role played by supernovae of different types (Ia, II), allowing us to follow in detail the evolution of several chemical elements (H, D, He, C, N, O, Mg, Si, S, Ca, Fe, Ba, and Eu). Methods. Each galaxy model is specified by the prescriptions of the star formation rate and by the galactic wind efficiency chosen to reproduce the main features of these galaxies, in particular the stellar metallicity distributions and several abundance ratios. These parameters are constrained by the star formation histories of the galaxies as inferred by the observed color-magnitude diagrams, indicating extended star formation episodes occurring at early epochs, but also with hints of intermediate stellar populations. Results. The main observed features of the galaxies Leo 1 and Leo 2 can be very well explained by chemical evolution models according to the following scenarios: the star formation occurred in two long episodes at 14 Gyr and 9 Gyr ago that lasted 5 and 7 Gyr, respectively, with a low efficiency (ν = 0.6 Gyr −1 ) in Leo 1, whereas the star formation history in Leo 2 is characterized by one episode at 14 Gyr ago that lasted 7 Gyr, also with a low efficiency (ν = 0.3 Gyr −1 ). In both galaxies an intense wind (nine and eight times the star formation rate -w i = 9 and 8 in Leo 1 and Leo 2, respectively) takes place which defines the pattern of the abundance ratios and the shape of the stellar metallicity distribution at intermediate to high metallicities. Conclusions. The observational constraints can only be reproduced with the assumption of gas removal by galactic winds.

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Section: Discussionmentioning

confidence: 91%

Chemical evolution models for the dwarf spheroidal galaxies Leo 1 and Leo 2

Lanfranchi

Matteuccí

2010

A&A

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“…Stars in the Sgr dSph stream appear to be slightly less metal rich than those in the main body, with metallicity gradients along the stream (Bellazzini et al 2006b;Clewley & Jarvis 2006;Monaco et al 2007;Chou et al 2007). This would not be unexpected if the most metal poor stars were located in the outskirts of Sgr dSph and then subject to the tidal interaction with the MW.…”

Section: Introductionmentioning

confidence: 99%

A wide angle view of the Sagittarius dwarf spheroidal galaxy

Giuffrida

Sbordone

Zaggia

et al. 2010

A&A

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Context. The Sagittarius dwarf Spheroidal Galaxy (Sgr dSph) provides us with a unique possibility of studying a dwarf galaxy merging event while still in progress. Moving along a short-period, quasi-polar orbit in the Milky Way Halo, Sgr dSph is being tidally dispersed along a huge stellar stream. Due to its low distance (25 kpc), the main body of Sgr dSph covers a vast area in the sky (roughly 15 × 7 degrees). Available photometric and spectroscopic studies have concentrated either on the central part of the galaxy or on the stellar stream, but the overwhelming majority of the galaxy body has never been probed. Aims. The aim of the present study is twofold. On the one hand, to produce color magnitude diagrams across the extension of Sgr dSph to study its stellar populations, searching for age and/or composition gradients (or lack thereof). On the other hand, to derive spectroscopic low-resolution radial velocities for a subsample of stars to determine membership to Sgr dSph for the purpose of high resolution spectroscopic follow-up. Methods. We used VIMOS@VLT to produce V and I photometry on 7 fields across the Sgr dSph minor and major axis, plus 3 more centered on the associated globular clusters Terzan 7, Terzan 8 and Arp 2. A last field has been centered on M 54, lying in the center of Sgr dSph. VIMOS high resolution spectroscopic mode has then been used to derive radial velocities for a subsample of the observed stars, concentrating on objects having colors and magnitudes compatible with the Sgr dSph red giant branch. Results. We present photometry for 320 000 stars across the main body of Sgr dSph, one of the richest, and safely the most wide-angle sampling ever produced for this fundamental object. We also provide robust memberships for more than one hundred stars, whose high resolution spectroscopic analysis will be the object of forthcoming papers. Sgr dSph appears remarkably uniform among the observed fields. We confirm the presence of a main Sgr dSph population characterized roughly by the same metallicity of 47 Tuc, but we also found the presence of multiple populations on the peripheral fields of the galaxy, with a metallicity spanning from [Fe/H] = -2.3 to a nearly solar value.

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“…The majority of Sgr stars show peculiar abundance patterns compared to those of nominal Milky Way (MW) stars (left panel, Fig. 1) and, as a group, form a coherent picture of chemical enrichment of the Sgr dwarf spheroidal (dSph) from [Fe/H] = −1.4 to solar abundance (Chou et al 2007(Chou et al , 2009 , Fig. 1); these relative shifts reflect the faster and/or more efficient chemical evolution of Sgr compared to the other satellites.…”

Section: Resultsmentioning

confidence: 99%

Chemical Fingerprinting and Chemical Analysis of Galactic Halo Substructure

et al. 2009

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Abstract. We present high-resolution spectroscopic measurements of the abundances of the α-like element titanium (Ti) and s-process elements yttrium (Y) and lanthanum (La) for M giant candidates of (a) the Sagittarius (Sgr) dwarf spheroidal + tidal tail system, (b) the TriangulumAndromeda (TriAnd) Star Cloud, and (c) the Galactic Anticenter Stellar Structure (GASS, or Monoceros Stream). All three systems show abundance patterns unlike the Milky Way but typical of dwarf galaxies. The Sgr system abundance patterns resemble those of the Large Magellanic Cloud. GASS/Mon chemically resembles Sgr but is distinct from TriAnd, a result that does not support previous suggestions that TriAnd is a piece of the Monoceros Stream.

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A 2MASS All‐Sky View of the Sagittarius Dwarf Galaxy. V. Variation of the Metallicity Distribution Function along the Sagittarius Stream

Cited by 145 publications

References 59 publications

Chemical evolution models for the dwarf spheroidal galaxies Leo 1 and Leo 2

Chemical evolution models for the dwarf spheroidal galaxies Leo 1 and Leo 2

A wide angle view of the Sagittarius dwarf spheroidal galaxy

Chemical Fingerprinting and Chemical Analysis of Galactic Halo Substructure

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