Chemical Evolution in Hierarchical Models of Cosmic Structure. I. Constraints on the Early Stellar Initial Mass Function

By Jason Tumlinson. 2005

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I present a new Galactic chemical evolution model motivated by and grounded in the hierarchical theory of galaxy formation, as expressed by a halo merger history of the Galaxy. This model accurately reproduces the "metallicity distribution function" (MDF) for Population II stars residing today in the Galactic halo. Model MDFs are calculated for a fiducial Galaxy formation scenario and a range of assumptions about the astrophysics of star formation and chemical enrichment at early times. The observed MDF and the apparent absence of true Population III stars from the halo strongly imply that there is some critical metallicity, Zcr ≲ 10-4 Z☉, below which low-mass star formation is inhibited and perhaps impossible. The observed constraints from the halo MDF, relative metal abundances from extremely metal-poor Galactic halo stars, and the ionizing photon budget needed to reionize the IGM together imply a stellar IMF below Zcr that is peaked in the range of massive stars that experience core-collapse supernovae, with mean mass ⟨M⟩ = 8-42 M☉. This mass range is similar to the masses predicted by models of primordial star formation that account for formation feedback. A set of five plausible IMF cases is presented, ranging from broadly peaked with mean mass ~15 M☉ to narrowly peaked at mean mass ~70 M☉. These IMF cases cannot be distinguished formally by the available constraints, but the models with lower characteristic mass produce overall better fits to the available data. The model also implies that metal-poor halo stars below [Fe/H] ≲ -3 had only 1-10 metal-free stars as their supernova precursors, such that the relative abundances in these halo stars exhibit IMF-weighted averages over the intrinsic yields of the first supernovae. This paper is the first part of a long-term project to connect the high-redshift in situ indicators of early star formation with the low-z, old remnants of the first stars.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/18ac15171317e102156c03ec1ca719eb985d8b2a

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Citations in the corpus

A Universal Stellar Initial Mass Function? A critical look at variations in extreme environments (2010, background): “The lack of many extremely metal poor stars, [Fe/H] −4, indicates that extremely low metallicity stars had lifetimes shorter than the current age of the Universe, implying that no low mass ( 1M⊙) primordial stars were formed (e.g. Tumlinson 2006).”
Nucleosynthesis in Stars and the Chemical Enrichment of Galaxies (2013, background): “Hierarchical (semianalytic) models (Tumlinson 2006) include cosmological mass accretion.”
The Formation of the First Stars. II. Radiative Feedback Processes and Implications for the Initial Mass Function (2007, background): “…observations such as these, Daigne et al. (2004) argue that the stars responsible for reionizing the universe mostly likely had masses P100 M , and Tumlinson (2006) concludes that stars above 140 M could have contributed at most 10% of the iron observed in extremely metal-poor stars (those with…”
Supernova Nucleosynthesis in Population III 13-50 M☉ Stars and Abundance Patterns of Extremely Metal-poor Stars (2007, methodology): “…models; Argast et al. (2000) has suggested that a halo ISM is unmixed and inhomogeneous at ½Fe/H < 3:0, intermediate between unmixed and well mixed at 3:0 < ½Fe/H < 2:0, and well mixed at ½Fe/H > 2:0; Tumlinson (2006) has suggested that the mean number of reflected SNe is 10 at ½Fe/H 2:8.”
The First Stellar Cluster (2007, background): “The fact that no population III star has ever been observed in the Milky Way provides some observational support for this prediction (Tumlinson 2006).”
Resolving the Formation of Protogalaxies. III. Feedback from the First Stars (2007, result): “We must take care when comparing our results to observations since we made the simplification that every Pop III star produces a PISN (for a detailed semi-analytic model of metal enrichment, see Tumlinson 2006).”
Fragmentation of star-forming clouds enriched with the first dust (2006, background): “The interpretation of shape and low-metallicity tail of the metallicity distribution function should provide important insights on the origin of the first low-mass stars that have formed in the Universe (Schneider et al. 2003; Tumlinson 2006; Salvadori, Schneider & Ferrara (in preparation).”
Population III stars: hidden or disappeared? (2007, background): “…stars, this common wisdom has to face the fact that no metal-free stars have yet been found by surveys of metal-poor stars of the Milky Way halo (Cayrel et al. 2004; Beers & Christlieb 2005; Tumlinson, Venkatesan, Shull 2004; Tumlinson 2006; Daigne et al. 2006; Salvadori, Schneider & Ferrara 2007).”
FORMATION RATES OF POPULATION III STARS AND CHEMICAL ENRICHMENT OF HALOS DURING THE REIONIZATION ERA (2009, background): “…2003; Yoshida et al. 2006; Gao et al. 2007), but there is some tension with the abundance patterns observed in the most metal-poor Milky Way stars, which are better explained under the assumption that their progenitor Population III stars were only moderately massive—8 M M 42 M —(Tumlinson 2006).”
Two populations of metal-free stars in the early Universe (2006, background): “…generation of metal-free stars by means of formation environment provides a possible physical explanation to the empirically derived argument that early star formation might have been dominated by a less top-heavy IMF (e.g. Umeda & Nomoto 2002, 2003; Tumlinson et al. 2004; Tumlinson 2006a,b).”
The Complete CEERS Early Universe Galaxy Sample: A Surprisingly Slow Evolution of the Space Density of Bright Galaxies at z ∼ 8.5–14.5 (2023, background): “…by F23 and Harikane et al. ( 2023a ) , a change in the characteristic stellar mass from ∼ 1 to ∼ 10 M e is expected when the cosmic microwave background temperature is higher and the gas metallicities are lower ( e.g., Larson 1998; Bromm et al. 2002; Tumlinson 2006; Steinhardt et al. 2023 ) .”
Resolving the Formation of Protogalaxies. I. Virialization (2007, background): “…Kitayama et al. 2004; Alvarez et al. 2006; Yoshida et al. 2006a; Abel et al. 2007), metal enrichment from primordial stars (Heger & Woosley 2002; Tumlinson 2006), AGN feedback (Springel et al. 2005; Kuhlen & Madau 2005), and “normal” metal-enriched star formation (see Larson 2003, for a review).”
The First Stars: Mass Growth Under Protostellar Feedback (2011, background): “…nearby dwarf galaxies may preserve the nucleosynthetic pattern of the first SNe, so this may help to explain the lack of PISNe chemical signatures found in these nearby stars (e.g. Christlieb et al. 2002; Beers & Christlieb 2005; Frebel et al. 2005; Tumlinson 2006; but see Karlsson et al. 2008).”
CHEMICAL EVOLUTION IN HIERARCHICAL MODELS OF COSMIC STRUCTURE. II. THE FORMATION OF THE MILKY WAY STELLAR HALO AND THE DISTRIBUTION OF THE OLDEST STARS (2009, methodology): “Paper I in this series (Tumlinson 2006) made an attempt at such a model in the form of a new stochastic, hierarchical model of Galactic chemical evolution, based purely on the “Extended Press-Schecter” mergertree formalism (Somerville & Kolatt 1999).”
Predicted UV properties of very metal-poor starburst galaxies (2010, methodology): “The cases computed here correspond to the cases A, B, and E in the chemical evolution study of Tumlinson (2006).”