Probing the formation of the first low‐mass stars with stellar archaeology

By A. Frebel, Jarrett L. Johnson, Volker Bromm. 2007

168 citations recorded by the source corpus.

ABSTRACT We investigate the conditions under which the ﬁrst low-mass stars formed in theUniverse by confronting theoretical predictions governing the transition from massivePopulationIII to low-mass PopulationII stars with recent observational C and/or Oabundance data of metal-poor Galactic stars. We introduce a new “observer-friendly”function, the transition discriminant D trans , which provides empirical constraints aswell as a powerful comparison between the currently available data of metal-poor halostars and theoretical predictions of the formation of the ﬁrst low-mass stars (. 1M ⊙ ).Speciﬁcally, we comparethe empirical stellarresults with the theorythat ﬁne-structurelines of C and O dominate the transition from PopIII to PopII in the early Universe.We ﬁnd the currently-available data for halo stars as well as for dSph galaxies andglobularclusters to be consistent with this theory. An explanationfor the observedlackof metal-poor stars in dSph galaxies and globular clusters is also suggested. Finally, wepredict that any star to be found with [Fe/H] . −4 should have enhanced C and/orO abundances. The high C and O abundances of the two most iron-poor stars are inline with our prediction.Key words: cosmology: early Universe — stars: abundances — stars: Population II— Galaxy: halo — Galaxy: stellar content — techniques: spectroscopic

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/2a8f70ffccbca214afdde155c839fa9ec82cb7c7

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Citations in the corpus

The First Billion Years project: the escape fraction of ionizing photons in the epoch of reionization (2015, methodology): “We choose a critical metallicity of Zcrit = 10−4 Z , with Z = 0.02, a value roughly consistent with both theory and the inferred metallicities of metal-poor stars (Frebel et al. 2007; Caffau et al. 2011). c© 2014 RAS, MNRAS 000, 1–21”
HIGH-RESOLUTION SPECTROSCOPY OF EXTREMELY METAL-POOR STARS IN THE LEAST EVOLVED GALAXIES: URSA MAJOR II and COMA BERENICES (2009, background): “Overall, C excesses in the most metalpoor stars point toward the important role of C in the early universe and as a potential cooling agent of the primordial ISM (Beers & Christlieb 2005; Aoki et al. 2007a; Frebel et al. 2007a).”
The First Billion Years project: the impact of stellar radiation on the co-evolution of Populations II and III (2012, background): “…place is unknown, we have chosen a value of the metallicity above which Pop II stars form and below which Pop III stars form2 that is roughly consistent with the prevailing theory as well as with the inferred metallicities of the most metal-poor stars (e.g. Frebel et al. 2007; Caffau et al. 2011).”
The first galaxies : assembly, cooling and the onset of turbulence (2008, background): “They may have been the key drivers of early IGM enrichment (Madau et al. 2001), and the host systems for the formation of the first low-mass stars that can be probed in the present-day Milky Way via stellar archaeology (Frebel et al. 2007; Karlsson et al. 2007).”
CARBON-ENHANCED METAL-POOR STAR FREQUENCIES IN THE GALAXY: CORRECTIONS FOR THE EFFECT OF EVOLUTIONARY STATUS ON CARBON ABUNDANCES (2014, background): “These two populations are thought to be formed by gas clouds that were influenced by at least two different primary cooling channels (Frebel et al. 2007; Schneider et al. 2012; Ji et al. 2014).”
The first stars: formation of binaries and small multiple systems (2009, background): “…binary nature of Pop III stars, provided that they would not grow to become very massive, may also yield a direct primordial formation pathway to carbon-enhanced metal-poor (CEMP) stars, those metal-poor halo stars with unusually high carbon abundance (e.g. Frebel et al. 2007; Tumlinson 2007).”
Can Supermassive Black Holes Form in Metal-enriched High-Redshift Protogalaxies? (2008, background): “This level of metallicity is approximately the same as the value at which the metal cooling rate exceeds the H2 cooling rate in clouds that are already collapsing by molecular cooling (Bromm & Loeb 2003b; Santoro & Shull 2006; Frebel et al. 2007).”
Ubiquitous seeding of supermassive black holes by direct collapse (2012, background): “The critical metallicity at which the transition occurs from Pop III to Pop II ranges from10−4 to 10−6 Z⊙ (e.g. Frebel et al. 2007).”
THE MOST METAL-POOR STARS. IV. THE TWO POPULATIONS WITH [Fe/H] ≲ −3.0 (2012, background): “Two cooling channels Following Bromm & Loeb (2003) and Frebel et al. (2007a), we assume that during the subsequent star formation within the second generation, the material with large enhancements of carbon and oxygen fragmented to form low-mass, long-lived stars that are still observed today.”
Near-Field Cosmology with Extremely Metal-Poor Stars (2015, background): “…supported by the age dating of the rare group of r-process enhanced stars which have ages of 13 – 14Gyr and [Fe/H] ∼ −3.0 (e.g., Hill et al. 2002, Frebel et al. 2007a, Sneden, Cowan & Gallino 2008), it is of critical importance to verify this, by investigating high-redshift early gaseous…”