Stellar Chemical Signatures and Hierarchical Galaxy Formation

Venn, Kim A.; Irwin, M. J.; Shetrone, Matthew; Tout, Christopher A.; Hill, V.; Tolstoy, Eline

doi:10.1086/422734

Cited by 796 publications

(1,246 citation statements)

References 90 publications

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“…Our results are in agreement with the previous suggestions of Unavane et al (1996) and Venn et al (2004). We cannot rule out, however, the hypothesis that a substantial contribution to the formation of the Galaxy stellar halo was provided by a population of dwarf galaxies which were more massive and more evolved from the point of view of the ISM chemical evolution than the current dSphs and UfDs.…”

Section: O N C L U S I O N Ssupporting

confidence: 89%

“…This result is in agreement with previous works in the literature as the ones of Unavane at al. (1996) and Venn et al (2004). On the other hand, as stated above, if we assume that the Galactic halo formed by accreting enriched gas from dSphs or UfDs, we also need a stellar contribution from dSphs and UfDs to explain the stars at very low [Fe/H] that currently reside in the halo.…”

Section: The Results: the Galactic Halo In The Model 2immentioning

confidence: 98%

“…Major issues are the still relatively small number of discovered Galaxy satellites (the so-called missing satellite problem; e.g. Klypin et al 1999; Moore et al 1999;Bullock 2010) and the different chemical abundance patterns in halo and dSph stars (Shetrone, Côté & Sargent 2001;Venn et al 2004;Vincenzo et al 2014).…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Are ancient dwarf satellites the building blocks of the Galactic halo?

Spitoni¹,

Vincenzo²,

Matteuccí³

et al. 2016

Mon. Not. R. Astron. Soc.

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Section: O N C L U S I O N Ssupporting

confidence: 89%

Section: The Results: the Galactic Halo In The Model 2immentioning

confidence: 98%

See 1 more Smart Citation

Are ancient dwarf satellites the building blocks of the Galactic halo?

Spitoni¹,

Vincenzo²,

Matteuccí³

et al. 2016

Mon. Not. R. Astron. Soc.

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“…One key observable of our Milky Way system is that although its halo population is α-rich (Hawkins et al 2014;Jackson-Jones et al 2014), its (classical) satellites are predominantly α-poor, with an exception for their most metal-poor components (e.g., Shetrone et al 1998Shetrone et al , 2001Shetrone et al , 2003Tolstoy et al 2003;Venn et al 2004;Koch et al 2008;Kirby et al 2010;Starkenburg et al 2013b;Jablonka et al 2015;Frebel & Norris 2015). Several modelling efforts have already pointed out that indeed such a discrepancy could arise in a stellar halo built out of few early-accreted, massive main progenitor galaxies.…”

Section: Relation Between Iron Abundance and Supernovae Type Ia Delaymentioning

confidence: 99%

“…Numerous observational studies (Shetrone et al 1998(Shetrone et al , 2001Tolstoy et al 2003;Venn et al 2004;Koch et al 2008;Tolstoy et al 2009;Kirby et al 2010) reported discrepancies between chemical abundances of satellite galaxies of the Milky Way and field halo stars. These studies show that the present-day satellites are, at least partly, unlike the building blocks of the Milky Way's stellar spheroid.…”

Section: Introductionmentioning

confidence: 99%

Building blocks of the Milky Way's accreted spheroid

Oirschot

Starkenburg

Helmi

et al. 2016

Mon. Not. R. Astron. Soc.

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In the ΛCDM model of structure formation, a stellar spheroid grows by the assembly of smaller galaxies, the so-called building blocks. Combining the Munich-Groningen semi-analytical model of galaxy formation with the high resolution Aquarius simulations of dark matter haloes, we study the assembly history of the stellar spheroids of six Milky Way-mass galaxies, focussing on building block properties such as mass, age and metallicity. These properties are compared to those of the surviving satellites in the same models. We find that the building blocks have higher star formation rates on average, and this is especially the case for the more massive objects. At high redshift these dominate in star formation over the satellites, whose star formation timescales are longer on average. These differences ought to result in a larger α-element enhancement from Type II supernovae in the building blocks (compared to the satellites) by the time Type Ia supernovae would start to enrich them in iron, explaining the observational trends. Interestingly, there are some variations in the star formation timescales of the building blocks amongst the simulated haloes, indicating that [α/Fe] abundances in spheroids of other galaxies might differ from those in our own Milky Way.

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The Second Stars

Herwig

2005

Reviews in Modern Astronomy

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The ejecta of the first probably very massive stars polluted the Big Bang primordial element mix with the first heavier elements. The resulting ultra metal-poor abundance distribution provided the initial conditions for the second stars of a wide range of initial masses reaching down to intermediate and low masses. The importance of these second stars for understanding the origin of the elements in the early universe are manifold. While the massive first stars have long vanished the second stars are still around and currently observed. They are the carriers of the information about the first stars, but they are also capable of nuclear production themselves. For example, in order to use ultra or extremely metal-poor stars as a probe for the r-process in the early universe a reliable model of the s-process in the second stars is needed. Eventually, the second stars may provide us with important clues on questions ranging from structure formation to how the stars actually make the elements, not only in the early but also in the present universe. In particular the C-rich extremely metal-poor stars, most of which show the s-process signature, are thought to be associated with chemical yields from the evolved giant phase of intermediate mass stars. Models of such AGB stars at extremely low metallicity now exist, and comparison with observation show important discrepancies, for example with regard to the synthesis of nitrogen. This may hint at burning and mixing aspects of extremely metal-poor evolved stars that are not yet included in the standard picture of evolution, as for example the hydrogen-ingestion flash. The second stars of intermediate mass may have also played an important role in the formation of heavy elements that form through slow neutron capture reaction chains (s-process). Comparison of models with observations reveal which aspects of the physics input and assumptions need to be improved. The s-process is a particularly useful diagnostic tool for probing the physical processes that are responsible for the creation of elements in stars, like for example rotation. As new observational techniques and strategies continue to penetrate the field, for example the multi-object spectroscopy, or the future spectroscopic surveys, the extremely metalpoor stars will play an increasingly important role to address some of the most fundamental and challenging, current questions of astronomy.

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Stellar Chemical Signatures and Hierarchical Galaxy Formation

Cited by 796 publications

References 90 publications

Are ancient dwarf satellites the building blocks of the Galactic halo?

Are ancient dwarf satellites the building blocks of the Galactic halo?

Building blocks of the Milky Way's accreted spheroid

The Second Stars

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