Exploring the Universe with Metal-Poor Stars

Frebel, Anna

doi:10.1007/978-3-642-32362-1_8

Cited by 4 publications

(1 citation statement)

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“…-The CEMPs can also be classified according to the presence or absence of slow (s-) and/or rapid (r-) neutron capture process elements. The peculiar abundances of those showing over-abundances of s-process elements are usually interpreted as being due to accretion from an asymptotic giant branch (AGB) companion (e.g., Masseron et al 2010 (Cayrel et al 2004;Frebel 2011). However, the same stars show a large scatter in C, N, O, and in r-and s-process elements.…”

Section: Galactic Archaeology: the High-redshift Universe Right Here mentioning

confidence: 99%

First stars and reionization: Spinstars

Chiappini

2013

Astron Nachr

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Soon after the Big Bang, the appearance of the first stellar generations (hereafter, first stars) drastically changed the course of the history of the Universe by enriching the primordial gas with elements heavier than helium (referred to as metals) through both stellar winds and supernova explosions. High-resolution hydrodynamical simulations of the formation of the first stars suggest these objects to have formed in dark matter mini-halos, and to have played a key role in the formation of the first galaxies. Today these stars are (most likely) long dead, and even though next generation facilities will push the observational frontier to extremely high redshifts, with the aim of discovering the first galaxies, the first stars will still lie beyond reach. Thus, the only way to constrain our theoretical understanding of the formation of the first stars is to search for their imprints left in the oldest, still surviving, stars in our own backyard: the Milky Way and its satellites. Which imprints are we looking for, and where can we find them? We address these questions in the present review.

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Section: Galactic Archaeology: the High-redshift Universe Right Here mentioning

confidence: 99%

First stars and reionization: Spinstars

Chiappini

2013

Astron Nachr

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Stellar Archaeology in the Galactic Halo With the Ultra-Faint Dwarfs. Vi. Ursa Major Ii

Dall’Ora

Kinemuchi

Ripepi

et al. 2012

ApJ

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We present a B, V color-magnitude diagram (CMD) of the Milky Way dwarf satellite Ursa Major II (UMa II), spanning the magnitude range from V ∼ 15 to V ∼ 23.5 mag and extending over a 18 × 18 arcmin 2 area centered on the galaxy. Our photometry goes down to about 2 magnitudes below the galaxy's 1 Based on data collected at the 1.52 m telescope of the INAF-Osservatorio Astronomico di Bologna, Loiano, Italy, at the 2.3 m telescope of the Wyoming Infrared Observatory (WIRO) at Mt. Jelm, Wyoming, USA, and at the 1.8 m Perkins telescope of the Lowell Observatory, at Anderson Mesa, main sequence turn-off, that we detected at V ∼ 21.5 mag. We have discovered a bona-fide RR Lyrae variable star in UMa II, which we use to estimate a conservative dereddened distance modulus for the galaxy of (m−M) 0 = 17.70±0.04±0.12 mag, where the first error accounts for the uncertainties of the calibrated photometry, and the second reflects our lack of information on the metallicity of the star. The corresponding distance to UMa II is 34.7 +0.6 −0.7 ( +2.0 −1.9 ) kpc. Our photometry shows evidence of a spread in the galaxy subgiant branch, compatible with a spread in metal abundance in the range between Z=0.0001 and Z=0.001. Based on our estimate of the distance, a comparison of the fiducial lines of the Galactic globular clusters (GCs) M68 and M5 ([Fe/H]=−2.27 ± 0.04 dex and −1.33 ± 0.02 dex, respectively), with the position on the CMD of spectroscopically confirmed galaxy members, may suggest the existence of stellar populations of different metal abundance/age in the central region of UMa II.

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Formation of the first stars

2013

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Understanding the formation of the first stars is one of the frontier topics in modern astrophysics and cosmology. Their emergence signalled the end of the cosmic dark ages, a few hundred million years after the Big Bang, leading to a fundamental transformation of the early Universe through the production of ionizing photons and the initial enrichment with heavy chemical elements. We here review the state of our knowledge, separating the well understood elements of our emerging picture from those where more work is required. Primordial star formation is unique in that its initial conditions can be directly inferred from the Λ cold dark matter (ΛCDM) model of cosmological structure formation. Combined with gas cooling that is mediated via molecular hydrogen, one can robustly identify the regions of primordial star formation, the so-called minihalos, having total masses of ~10(6) M⊙ and collapsing at redshifts z ≈ 20-30. Within this framework, a number of studies have defined a preliminary standard model, with the main result that the first stars were predominantly massive. This model has recently been modified to include a ubiquitous mode of fragmentation in the protostellar disks, such that the typical outcome of primordial star formation may be the formation of a binary or small multiple stellar system. We will also discuss extensions to this standard picture due to the presence of dynamically significant magnetic fields, of heating from self-annihalating WIMP dark matter, or cosmic rays. We conclude by discussing possible strategies to empirically test our theoretical models. Foremost among them are predictions for the upcoming James Webb space telescope (JWST), to be launched ~2018, and for 'stellar archaeology', which probes the abundance pattern in the oldest, most-metal poor stars in our cosmic neighborhood, thereby constraining the nucleosynthesis inside the first supernovae.

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Exploring the Universe with Metal-Poor Stars

Cited by 4 publications

References 100 publications

First stars and reionization: Spinstars

First stars and reionization: Spinstars

Stellar Archaeology in the Galactic Halo With the Ultra-Faint Dwarfs. Vi. Ursa Major Ii

Formation of the first stars

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