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

Lanfranchi, Gustavo A.; Matteuccí, F.

doi:10.1051/0004-6361/200913045

Cited by 32 publications

(46 citation statements)

References 63 publications

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“…They found [Fe/H] = -1.95±0.15, which corresponds to Zspec =(2.38 ± 0.79)×10 −4 . Similarly for Cetus, the Z * (0-2Gyr)=(3.30±1.00) ×10 −4 is in agreement to the Fe abundance obtained by Lewis et al (2007). They estimated [Fe/H] ∼ -1.90, which is equivalent to Zspec ∼ 2.52 × 10 −4 .…”

Section: T Ucanasupporting

confidence: 84%

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Chemical history of isolated dwarf galaxies of the Local Group – I. dSphs: Cetus and Tucana

Avila-Vergara

Carigi

Hidalgo

et al. 2016

Mon. Not. R. Astron. Soc.

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For the first time, we obtain chemical evolution models (CEMs) for Tucana and Cetus, two isolated dwarf spheroidal galaxies (dSphs) of the Local Group. The CEMs have been built from the star formation histories (SFHs) and the metallicity histories, both obtained independently by the LCID project from deep color-magnitude diagrams. Based on our models, we find that the chemical histories were complex and can be divided into different epochs and scenarios. In particular, during 75% of the SFH, the galaxies behaved as closed boxes and, during the remaining 25%, either received a lot of primordial gas by accretion or they lost metals through metal-rich winds. In order to discriminate between these two scenarios, abundances ratios in old stars are needed. At t∼4.5 Gyr, the galaxies lost most of their gas due to a shortstrong, well-mixed wind. We obtain very similar CEMs for both galaxies, although Cetus is twice as massive as Tucana. We conclude that the star formation in both galaxies began with only 1.5% of the baryonic mass fraction predicted by ΛCDM.

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Section: T Ucanasupporting

confidence: 84%

“…Some models inferred the SFH when reproducing the present-time properties and metal distribution functions (e.g. Lanfranchi & Matteucci 2010, Romano & Starkenburg 2013, Ross et al 2015, for example). Other SFHs from CMDs and different CEMs for dSphs are mentioned in the excellent review article by Tolstoy, Hill, & Tosi (2009).…”

Section: Introductionmentioning

confidence: 99%

Chemical history of isolated dwarf galaxies of the Local Group – I. dSphs: Cetus and Tucana

Avila-Vergara

Carigi

Hidalgo

et al. 2016

Mon. Not. R. Astron. Soc.

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“…Thus, one needs to choose a constant [α/Fe] value for the whole metallicity range used in the isochrones. We note that the present day high-resolution spectroscopic measurements of metallicities of the dSphs studied here permit the determination of the location of the knee in conjuction with detailed chemical evolution models in the cases of Sculptor and Carina (Geisler et al 2007;Koch et al 2008a;Lanfranchi et al 2006), while in the remaining dSphs only limits on the position of the knee can be placed (e.g., Koch 2009;Tolstoy et al 2009;Lanfranchi & Matteucci 2010, and references therein).…”

Section: General Error Sources For Photometric Metallicitiesmentioning

confidence: 93%

Spectroscopic versus photometric metallicities: Milky Way dwarf spheroidal companions as a test case

Lianou

Grebel

Koch

2011

A&A

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Aims. The method of deriving photometric metallicities using red giant branch stars is applied to resolved stellar populations under the common assumption that they mainly consist of single-age old stellar populations. We explore the effect of the presence of mixed-age stellar populations on deriving photometric metallicities. Methods. We use photometric data sets for the five Galactic dwarf spheroidals Sculptor, Sextans, Carina, Fornax, and Leo II in order to derive their photometric metallicity distribution functions from their resolved red giant branches using isochrones of the Dartmouth Stellar Evolutionary Database. We compare the photometric metallicities with published spectroscopic metallicities based on the analysis of the near-infrared Ca triplet (Ca T), both on the metallicity scale of Carretta & Gratton and on the scale defined by the Dartmouth isochrones. In addition, we compare the photometric metallicities with published spectroscopic metallicities based on spectral synthesis and medium-resolution spectroscopy, and on high resolution spectra where available. Results. The mean properties of the spectroscopic and photometric metallicity samples are comparable within the intrinsic scatter of each method although the mean metallicities of dSphs with pronounced intermediate-age population fractions may be underestimated by the photometric method by up to a few tenths of dex in [Fe/H]. The star-by-star differences of the spectroscopic minus the photometric metallicities show a wide range of values along the fiducial spectroscopic metallicity range, with the tendency to have systematically lower photometric metallicities for those dwarf spheroidals with a higher fraction of intermediate-age populations. Such discrepancies persist even in the case of the purely old Sculptor dSph, where one would naïvely expect a very good match when comparing with medium or low resolution metallicity measurements. Overall, the agreement between Ca T metallicities and photometric metallicities is very good in the metallicity range from ∼−2 dex to ∼−1.5 dex. We find that the photometric method is reliable in galaxies that contain small (less than 15%) intermediate-age stellar fractions. Therefore, in the presence of mixed-age stellar populations, one needs to quantify the fraction of the intermediate-age stars in order to assess their effect on determining metallicities from photometry alone. Finally, we note that the comparison of spectroscopic metallicities of the same stars obtained with different methods reveals similarly large discrepancies as the comparison with photometric metallicities.

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“…On the other hand, outflows remove metals from galaxies and tend to slow down the growth of their metal content at later time. These ingredients are usually included in the simulation of dwarf galaxies, but with different levels of complexity and different numerical methods, including one-zone models (e.g., Carigi et al 2002;Lanfranchi & Matteucci 2003, 2004Fenner et al 2006;Gibson 2007;Lanfranchi & Matteucci 2010;Lanfranchi et al 2006;Vincenzo et al 2014;Homma et al 2015;Kobayashi et al 2015;Ural et al 2015a), semi-analytical models (e.g., Romano & Starkenburg 2013;Romano et al 2015), and hydrodynamical simulations (e.g., Kawata et al 2006;Marcolini et al 2008;Revaz et al 2009;Pilkington et al 2012;Revaz & Jablonka 2012;Hirai et al 2015;Revaz et al 2016).…”

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confidence: 99%

The Impact of Modeling Assumptions in Galactic Chemical Evolution Models

Côté

O’Shea

Ritter

et al. 2017

ApJ

101

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We use the OMEGA galactic chemical evolution code to investigate how the assumptions used for the treatment of galactic inflows and outflows impact numerical predictions. The goal is to determine how our capacity to reproduce the chemical evolution trends of a galaxy is affected by the choice of implementation used to include those physical processes. In pursuit of this goal, we experiment with three different prescriptions for galactic inflows and outflows and use OMEGA within a Markov Chain Monte Carlo code to recover the set of input parameters that best reproduces the chemical evolution of nine elements in the dwarf spheroidal galaxy Sculptor. This provides a consistent framework for comparing the best-fit solutions generated by our different models. Despite their different degrees of intended physical realism, we found that all three prescriptions can reproduce in an almost identical way the stellar abundance trends observed in Sculptor. This result supports the similar conclusions originally claimed by Romano & Starkenburg (2013) for Sculptor. While the three models have the same capacity to fit the data, the best values recovered for the parameters controlling the number of Type Ia supernovae and the strength of galactic outflows, are substantially different and in fact mutually exclusive from one model to another. For the purpose of understanding how a galaxy evolves, we conclude that only reproducing the evolution of a limited number of elements is insufficient and can lead to misleading conclusions. More elements or additional constraints such as the galaxy's star formation efficiency and the gas fraction are needed in order to break the degeneracy between the different modeling assumptions. Our results show that the successes and failures of chemical evolution models are predominantly driven by the input stellar yields, rather than by the complexity of the galaxy model itself. Simple models such as OMEGA are therefore sufficient to test and validate stellar yields. OMEGA is part of the NuGrid chemical evolution package and is publicly available online at http://nugrid.github.io/NuPyCEE.

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

Cited by 32 publications

References 63 publications

Chemical history of isolated dwarf galaxies of the Local Group – I. dSphs: Cetus and Tucana

Chemical history of isolated dwarf galaxies of the Local Group – I. dSphs: Cetus and Tucana

Spectroscopic versus photometric metallicities: Milky Way dwarf spheroidal companions as a test case

The Impact of Modeling Assumptions in Galactic Chemical Evolution Models

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