Epoch of Reionisation 21cm Forecasting From MCMC-Constrained Semi-Numerical Models

Abstract

The recent low value of Planck (2016) integrated optical depth to Thomson scattering suggests that the reionization occurred fairly suddenly, disfavoring extended reionization scenarios. This will have a significant impact on the 21cm power spectrum. Using a semi-numerical framework, we improve our model from Hassan et al. (2016) to include time-integrated ionisation and recombination effects, and find that this leads to more sudden reionisation. It also yields larger HII bubbles which leads to an order of magnitude more 21cm power on large scales, while suppressing the small scale ionization power. Local fluctuations in the neutral hydrogen density play the dominant role in boosting the 21cm power spectrum on large scales, while recombinations are subdominant. We use a Monte Carlo Markov Chain approach to constrain our model to observations of the star formation rate functions at z = 6,7,8 from Bouwens et al. (2015), the Planck (2016) optical depth measurements, and the Becker & Bolton (2013) ionising emissivity data at z~5. We then use this constrained model to perform 21cm forecasting for LOFAR, HERA, and SKA in order to determine how well such data can characterise the sources driving reionisation. We find that the 21cm power spectrum alone can somewhat constrain the halo mass dependence of ionising sources, the photon escape fraction and ionising amplitude, but combining the 21cm data with other current observations enables us to separately constrain all these parameters. Our framework illustrates how 21cm data can play a key role in understanding the sources and topology of reionisation as observations improve.

20 pages, 16 figues, matches the accepted version for publication in MNRAS

References in corpus (14)

• UV Luminosity Functions at redshifts z~4 to z~10: 10000 Galaxies from HST Legacy Fields
• Observational constraints on Cosmic Reionization
• Efficient Simulations of Early Structure Formation and Reionization
• The morphology of HII regions during reionization
• 21CMMC: an MCMC analysis tool enabling astrophysical parameter studies of the cosmic 21 cm signal
• Simulating Cosmic Reionization at Large Scales II: the 21-cm Emission Features and Statistical Signals
• Inside-out or Outside-in: The topology of reionization in the photon-starved regime suggested by Lyman-alpha forest data
• Cosmic Reionization On Computers I. Design and Calibration of Simulations
• TRAPHIC - Radiative Transfer for Smoothed Particle Hydrodynamics Simulations
• Fast Large-Scale Reionization Simulations
• A New Moment Method for Continuum Radiative Transfer in Cosmological Reionization
• The Reionization of Carbon
• Adding Context to JWST Surveys with Current and Future 21cm Radio Observations
• Models of the Cosmological 21 cm Signal from the Epoch of Reionization Calibrated with Lyman-alpha and CMB Data

Cited by in corpus (7)

• Emulation of reionization simulations for Bayesian inference of astrophysics parameters using neural networks
• Semi-analytic forecasts for JWST -- V. AGN luminosity functions and helium reionization at z = 2-7
• Large scale simulations of H and He reionization and heating driven by stars and more energetic sources
• Constraining the reionization history using deep learning from 21cm tomography with the Square Kilometre Array
• The impact of non-Gaussianity on the Epoch of Reionization parameter forecast using 21-cm power spectrum measurements
• Bayesian Model Selection with Future 21cm Observations of The Epoch of Reionisation
• Analysing the Epoch of Reionization with three-point correlation functions and machine learning techniques