Bibcode
Finkelstein, Steven L.; D’Aloisio, Anson; Paardekooper, Jan-Pieter; Ryan, Russell, Jr.; Behroozi, Peter; Finlator, Kristian; Livermore, Rachael; Upton Sanderbeck, Phoebe R.; Dalla Vecchia, Claudio; Khochfar, Sadegh
Referencia bibliográfica
The Astrophysical Journal, Volume 879, Issue 1, article id. 36, 34 pp. (2019).
Fecha de publicación:
7
2019
Revista
Número de citas
280
Número de citas referidas
238
Descripción
We explore scenarios for reionizing the intergalactic medium with low
galaxy ionizing photon escape fractions. We combine simulation-based
halo mass–dependent escape fractions with an extrapolation of the
observed galaxy rest-ultraviolet luminosity functions to solve for the
reionization history from z = 20\to 4. We explore the posterior
distributions for key unknown quantities, including the limiting halo
mass for star formation, the ionizing photon production efficiency, and
a potential contribution from active galactic nuclei (AGNs). We
marginalize over the allowable parameter space using a Markov chain
Monte Carlo method, finding a solution that satisfies the most
model-independent constraints on reionization. Our fiducial model can
match observational constraints with an average escape fraction of
<5% throughout the bulk of the epoch of reionization if (i) galaxies
form stars down to the atomic cooling limit before reionization and a
photosuppression mass of log(M h/M ⊙) ∼ 9
during/after reionization (‑13 < M UV,lim <‑11), (ii) galaxies become more efficient producers of ionizing
photons at higher redshifts and fainter magnitudes, and (iii) there is a
significant but subdominant contribution by AGNs at z ≲ 7. In this
model, the faintest galaxies (M UV >‑15) dominate
the ionizing emissivity, leading to an earlier start to reionization and
a smoother evolution of the ionized volume-filling fraction than models
that assume a single escape fraction at all redshifts and luminosities.
The ionizing emissivity from this model is consistent with observations
at z = 4–5 (and below, when extrapolated), in contrast to some
models that assume a single escape fraction. Our predicted ionized
volume-filling fraction at z = 7 of {Q}{{{H}}II}}
= 78% (±8%) is in modest (∼1σ–2σ) tension
with observations of Lyα emitters at z ∼ 7 and the
damping-wing analyses of the two known z > 7 quasars, which prefer
{Q}{{{H}}II},z=7} ∼ 40%–50%.
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Claudio
Dalla Vecchia