On the properties of massive Population III stars and metal-free stellar populations

By Daniel Schaerer. 2001

695 citations recorded by the source corpus.

We present realistic models for massive Population III stars and stellar populations based on non-LTE model atmospheres, recent stellar evolution tracks and up-to-date evolutionary synthesis models, to study their spectral properties, including their dependence on age, star formation history, and IMF. (..) The main results regarding integrated stellar populations are: * For young bursts and the case of a constant SFR, nebular continuous emission - neglected in previous studies - dominates the spectrum redward of Lyman-alpha (...). Therefore predicted emission line equivalent widths are considerably smaller than found in earlier studies, whereas the detection of the continuum is eased. Nebular line and continuous emission strongly affect the broad band photometric properties of Pop III objects. * Due to stellar evolution, the hardness of the ionising spectrum decreases rapidly, leading to the disappearance of the characteristic HeII 1640 recombination lines after ~ 3 Myr in instantaneous bursts. * The relative efficiency of ionising photon energy to heavy element rest mass production, eta, of metal-poor and metal-free populations is increased by factors of ~ 4 to 18 with respect to solar metallicity and for ``standard'' IMFs. * The lowest values of eta ~ 1.6 - 2.2 % are obtained for IMFs exclusively populated with high mass stars (M_low >~ 50 Msun). If correct, the yields dominated by pair creation SNae then predict large overabundances of O/C and Si/C compared to solar abundance ratios. Detailed results are given in tabular form and as fit formulae for implementation in other calculations. (abridged abstract)

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/f6158c5d473cd52b5137473b442a6aaa8882b048

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Astronomy and Astrophysics

In Instrumentation

Citations in the corpus

Chemical Evolution in Hierarchical Models of Cosmic Structure. I. Constraints on the Early Stellar Initial Mass Function (2005, background): “…to be the high Lyα equivalent width (which may have been detected already at z ∼ 5; Malhotra & Rhoads 2002) and strong He II λ1640 nebular emission (Tumlinson, Giroux, & Shull 2001); these sensitive indicators of stellar IMF from 10 − 500 M⊙ are also unique to Z = 10−4Z⊙ 3 (Schaerer 2002; TSV03).”
The transition from Population III to normal galaxies: Lyα and He II emission and the ionising properties of high redshift starburst galaxies (2002, methodology): “…for searches of primordial galaxies, it is of interest to explore how far extreme properties such as strong He ii emission predicted for Pop III starbursts (Tumlinson & Shull 2000, Tumlinson et al. 2001, 2002; Oh et al. 2001, Bromm et al. 2001b, Schaerer 2002) are truly limited to zero metallicity.”
Resolving the Formation of Protogalaxies. I. Virialization (2007, background): “They are believed to have stellar masses ∼100 M⊙ (Abel et al. 2002; Omukai & Palla 2003; Tan & McKee 2004; Yoshida et al. 2006b) and produce ∼1050 photons s−1 that can ionize hydrogen and dissociate H2 (Schaerer 2002).”
Building up the Population III initial mass function from cosmological initial conditions (2016, methodology): “We apply our slope of αMF = 1.13 to such a cluster, assuming an IMF ranging from 0.1 to 200 M⊙, and we use Lzams and Teff values taken from Schaerer (2002).”
The First Billion Years project: the escape fraction of ionizing photons in the epoch of reionization (2015, background): “In low-metallicity gas, the stars that form are generally hotter (Schaerer 2002) and follow a more top-heavy initial mass function (IMF) (Bromm & Larson 2004).”
A critical analysis of the ultraviolet continuum slopes (β) of high-redshift galaxies: no evidence (yet) for extreme stellar populations at z > 6 (2011, background): “As discussed by several authors, while the bluest galaxies observed atz ≃ 3− 4 haveβ ≃ −2, values as low (i.e. blue) asβ = −3 can in principle be produced by a young, low-metallicity stellar population (e.g. Bouwens et al. 2010b; Schaerer 2002).”
The birth of a galaxy – II. The role of radiation pressure (2012, methodology): “We use mass-dependent hydrogen ionising and LW photon luminosities and lifetimes of the Pop III stars from Schaerer (2002).”
Suppression of H2 Cooling in the Ultraviolet Background (2007, background): “Nearby star formation can boost the LWradiation over its background value, but these bursts are short-lived as Population III lifetimes are only 3Myr (Schaerer 2002).”
FORMATION RATES OF POPULATION III STARS AND CHEMICAL ENRICHMENT OF HALOS DURING THE REIONIZATION ERA (2009, background): “…an enhanced efficiency compared to Population II stars due to the high effective temperatures of massive metalfree stars (Tumlinson & Shull 2000; Schaerer 2002), and these sources could be responsible for a significant fraction of the Thompson optical depth to reionization deriving from z > 7…”
The physics of gamma-ray bursts & relativistic jets (2014, background): “…until the redshift of ∼ 15–20, when the first stars were born, and the strong UV radiation from them contributed to the reionization of the universe, and bringing to an end the cosmic dark age (e.g. Tumlinson and Shull, 2000; Schaerer, 2002; Venkatesan and Truran, 2003; Bromm and Larson, 2004).”
EVIDENCE FOR PopIII-LIKE STELLAR POPULATIONS IN THE MOST LUMINOUS Lyα EMITTERS AT THE EPOCH OF REIONIZATION: SPECTROSCOPIC CONFIRMATION (2015, methodology): “Given these observations, Lyα searches should also be able to find metalfree, PopIII stellar populations (since galaxies dominated by PopIII emit large amounts of Lyα photons, e.g. Schaerer 2002, 2003).”
STAR FORMATION RATES AND STELLAR MASSES OF z = 7–8 GALAXIES FROM IRAC OBSERVATIONS OF THE WFC3/IR EARLY RELEASE SCIENCE AND THE HUDF FIELDS (2009, background): “A second possible effect is nebular continuum emission (NEC), which would cause a reddening of both β and H160 − [3.6] (shown are the models of Schaerer 2002 with Z = 1/50 Z⊙, t = 300 Myr CSF, and 0% escape fraction).”
Self-regulated reionization (2006, background): “Massive stars are more efficient producers of ionizing photons, emitting up toNi ∼ 105 ionizing photons per stellar atom (Bromm et al. 2001; Schaerer 2002; Venkatesan & Truran 2003).”
The birth of a galaxy – III. Propelling reionization with the faintest galaxies (2014, background): “In particular, Lyα emission from the H II region will be strong in these galaxies, perhaps having an intrinsic equivalent width (EW) as high as 1500 Å (Schaerer 2002; Johnson et al. 2009; Dijkstra & Wyithe 2010).”
Two populations of metal-free stars in the early Universe (2006, methodology): “Schaerer (2002) has provided time-integrated spectral properties of metal-free stars over a wide range of masses, and our calculations of ηLW are based on this work.”
Predicted UV properties of very metal-poor starburst galaxies (2010, methodology): “Building on the earlier calculations of Schaerer (2002, 2003), we have computed evolutionary synthesis models for a wide range of metallicities from Pop III (zero metallicity) to solar metallicity covering a wider range of IMFs – including power laws and log-normal IMFs with different…”
The Formation of the First Stars. II. Radiative Feedback Processes and Implications for the Initial Mass Function (2007, background): “The hardness of the radiation field is also sensitive to the mass (e.g., Tumlinson & Shull 2000; Schaerer 2002), so that He reionization can be affected.”