A high-resolution VLT/FLAMES study of individual stars in the centre of the Fornax dwarf spheroidal galaxy

Letarte, B.; Hill, V.; Tolstoy, Eline; Jablonka, P.; Shetrone, Matthew; Venn, Kim A.; Spite, M.; Irwin, M. J.; Battaglia, G.; Helmi, Amina; Primas, F.; François, P.; Kaufer, A.; Szeifert, T.; Arimoto, N.; Sadakane, Kozo

doi:10.1051/0004-6361/200913413

Cited by 217 publications

(400 citation statements)

References 91 publications

Supporting

Mentioning

353

Contrasting

Unclassified

Order By: Relevance

“…However, errors in the determination of T eff could also shift the ionization equilibrium in the same way. This is the same discrepancy already reported by Letarte et al (2010), for the Fornax dSph, observed with the same FLAMES setup. Letarte et al (2010) warns us that CaI could also be affected by NLTE effects in the same way as TiI, without any possibility to check since we cannot measure CaII lines in these stars.…”

Section: Magnesiumsupporting

confidence: 87%

See 1 more Smart Citation

VLT/FLAMES spectroscopy of red giant branch stars in the Carina dwarf spheroidal galaxy

Lemasle

Hill

Tolstoy

et al. 2012

A&A

Self Cite

191

View full text Add to dashboard Cite

Context. The ages of individual Red Giant Branch stars can range from 1 Gyr old to the age of the Universe, and it is believed that the abundances of most chemical elements in their photospheres remain unchanged with time (those that are not affected by the first dredge-up). This means that they trace the interstellar medium in the galaxy at the time the star formed, and hence the chemical enrichment history of the galaxy. Aims. Colour-Magnitude Diagram analysis has shown the Carina dwarf spheroidal to have had an unusually episodic star formation history and this is expected to be reflected in the abundances of different chemical elements. Methods. We use the VLT-FLAMES multi-fibre spectrograph in high-resolution mode (R≈20000) to measure the abundances of several chemical elements, including Fe, Mg, Ca and Ba, in a sample of 35 individual Red Giant Branch stars in the Carina dwarf spheroidal galaxy. We also combine these abundances with photometry to derive age estimates for these stars. This allows us to determine which of two distinct star formation episodes the stars in our sample belong to, and thus to define the relationship between star formation and chemical enrichment during these two episodes.

show abstract

Section: Magnesiumsupporting

confidence: 87%

“…Following Letarte et al (2010), we applied a line-by-line HFS correction to La and Eu lines in the few cases where we managed to detect these elements. This correction only depends Table 5.…”

Section: Determination Of Stellar Parameters and Abundancesmentioning

confidence: 99%

VLT/FLAMES spectroscopy of red giant branch stars in the Carina dwarf spheroidal galaxy

Lemasle

Hill

Tolstoy

et al. 2012

A&A

Self Cite

191

View full text Add to dashboard Cite

show abstract

“…We compare our results with high-resolution spectroscopic analyses of RGBs with [Fe/H] ≤ −2.5 in the Milky Way halo (Cayrel et al 2004;Cohen et al 2008;Aoki et al 2005Aoki et al , 2007Cohen et al 2006;Lai et al 2008;Honda et al 2004) and in faint (Ursa MajorII and Coma Berenices, Boötes I, Leo IV) and classical (Sextans, Draco, Fornax, Carina, Sculptor) dSphs (Letarte et al 2010;Shetrone et al 2001;Fulbright et al 2004;Koch et al 2008a;Cohen & Huang 2009;Aoki et al 2009;Norris et al 2010;Simon et al 2010;Frebel et al 2010b,a). We distinguish between unmixed and mixed RGBs in order to be able to draw a reliable comparison sample for the elements that are sensitive to mixing.…”

Section: Comparison Samplesmentioning

confidence: 90%

“…The program calrai is used to analyze all DART datasets and in particular the VLT/giraffe spectroscopy of Fornax, Sculptor, and Sextans dSphs (Hill et al in prep. ;Letarte et al, 2010;Tafelmeyer et al, in prep.). The results of these works are partly summarized in Tolstoy et al (2009).…”

Section: Observations and Data Reductionmentioning

confidence: 99%

Extremely metal-poor stars in classical dwarf spheroidal galaxies: Fornax, Sculptor, and Sextans

Tafelmeyer

Jablonka

Hill

et al. 2010

A&A

Self Cite

152

287

View full text Add to dashboard Cite

We present the results of a dedicated search for extremely metal-poor stars in the Fornax, Sculptor, and Sextans dSphs. Five stars were selected from two earlier VLT/Giraffe and HET/HRS surveys and subsequently followed up at high spectroscopic resolution with VLT/UVES. All of them turned out to have [Fe/H] < ∼ −3 and three stars are below [Fe/H] ∼ −3.5. This constitutes the first evidence that the classical dSphs Fornax and Sextans join Sculptor in containing extremely metal-poor stars and suggests that all of the classical dSphs contain extremely metal-poor stars. One giant in Sculptor at [Fe/H] = −3.96 ± 0.06 is the most metal-poor star ever observed in an external galaxy. We carried out a detailed analysis of the chemical abundances of the α, iron peak, and the heavy elements, and we performed a comparison with the Milky Way halo and the ultra faint dwarf stellar populations. Carbon, barium, and strontium show distinct features characterized by the early stages of galaxy formation and can constrain the origin of their nucleosynthesis.

show abstract

“…Data for the observed stars to compare our simulation results with are taken from the SAGA (Stellar Abundances for Galactic Archaeology) database (e.g., Suda et al 2008, Suda et al 2011, Yamada et al 2013in particular [Eu/Fe] abundance observations are mainly from e.g., Francois et al 2007, Simmerer et al 2004, Barklem et al 2005, Ren et al 2012, Roederer et al 2010, Roederer et al 2014a, Roederer et al 2014b, Roederer et al 2014c, Shetrone, Côté, Stetson 2001, Shetrone et al 2003, Geisler et al 2005, Cohen & Huang 2009, Letarte et al 2010, Starkenburg et al 2013, McWilliam et al 2003. From the raw data, we excluded carbon enriched metal poor stars ("CEMPs") and stars with binary nature, since the surface abundances of such objects are expected to be affected by internal pollution from deeper layers or pollution from the binary companion.…”

Section: Observed Stellar Abundancesmentioning

confidence: 99%

Galactic evolution of rapid neutron capture process abundances: the inhomogeneous approach

Wehmeyer¹,

Pignatari²,

Thielemann³

2015

Mon. Not. R. Astron. Soc.

177

203

View full text Add to dashboard Cite

For the origin of heavy r-process elements, different sources have been proposed, e.g., core-collapse supernovae or neutron star mergers. Old metal-poor stars carry the signature of the astrophysical source(s). Among the elements dominantly made by the r-process, europium (Eu) is relatively easy to observe. In this work we simulate the evolution of europium in our galaxy with the inhomogeneous chemical evolution model 'ICE', and compare our results with spectroscopic observations. We test the most important parameters affecting the chemical evolution of Eu: (a) for neutron star mergers the coalescence time scale of the merger (t coal ) and the probability to experience a neutron star merger event after two supernova explosions occurred and formed a double neutron star system (P NSM ) and (b) for the sub-class of magneto-rotationally driven supernovae ("Jet-SNe"), their occurrence rate compared to standard supernovae (P Jet−SN ). We find that the observed [Eu/Fe] pattern in the galaxy can be reproduced by a combination of neutron star mergers and magneto-rotationally driven supernovae as r-process sources. While neutron star mergers alone seem to set in at too high metallicities, Jet-SNe provide a cure for this deficiency at low metallicities. Furthermore, we confirm that local inhomogeneities can explain the observed large spread in the europium abundances at low metallicities. We also predict the evolution of [O/Fe] to test whether the spread in α-elements for inhomogeneous models agrees with observations and whether this provides constraints on supernova explosion models and their nucleosynthesis.

show abstract

A high-resolution VLT/FLAMES study of individual stars in the centre of the Fornax dwarf spheroidal galaxy

Cited by 217 publications

References 91 publications

VLT/FLAMES spectroscopy of red giant branch stars in the Carina dwarf spheroidal galaxy

VLT/FLAMES spectroscopy of red giant branch stars in the Carina dwarf spheroidal galaxy

Extremely metal-poor stars in classical dwarf spheroidal galaxies: Fornax, Sculptor, and Sextans

Galactic evolution of rapid neutron capture process abundances: the inhomogeneous approach

Contact Info

Product

Resources

About