Kavli Affiliate: George Efstathiou
| First 5 Authors: Peter H. Sims, Harry T. J. Bevins, Anastasia Fialkov, Dominic Anstey, Will J. Handley
| Summary:
Observations of the Epoch of Reionization (EoR) have the potential to answer
long-standing questions of astrophysical interest regarding the nature of the
first luminous sources and their effects on the intergalactic medium (IGM). We
present astrophysical constraints from a Neural Density Estimation-Accelerated
Bayesian joint analysis of constraints deriving from Cosmic Microwave
Background power spectrum measurements from Planck and SPT, IGM neutral
fraction measurements from Lyman-line-based data sets and 21-cm power spectrum
upper limits from HERA, LOFAR and the MWA. In the context of the model
employed, the data is found to be consistent with galaxies forming from
predominantly atomic-cooled hydrogen gas in dark matter halos, with masses
$M_mathrm{min} gtrsim 2.6 times 10^{9}~M_{odot} ((1+z)/10)^{frac{1}{2}}$
at 95% credibility ($V_mathrm{c} gtrsim 50~mathrm{km~s^{-1}}$) being the
dominant galactic population driving reionization. These galaxies reionize the
neutral hydrogen in the IGM over a narrow redshift interval ($Delta
z_mathrm{re} < 1.8$ at 95% credibility), with the midpoint of reionization
(when the sky-averaged IGM neutral fraction is 50%) constrained to $z_{50} =
7.16^{+0.15}_{-0.12}$. Given the parameter posteriors from our joint analysis,
we find that the posterior predictive distribution of the global 21-cm signal
is reduced in amplitude and shifted to lower redshifts relative to the model
prior. We caution, however, that our inferences are model-dependent. Future
work incorporating updated, mass-dependent star formation efficiencies in
atomic cooling halos, informed by the latest UV luminosity function constraints
from the James Webb Space Telescope, promises to refine these inferences
further and enhance our understanding of cosmic reionization.
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