Impact of anisotropic photon emission from sources during the epoch of reionisation

Abstract

The reionisation of the intergalactic medium (IGM) was driven by the first stars, galaxies, and accreting black holes. However, the relative importance of these sources and the efficiency by which ionising photons escape into the IGM remain poorly understood. Most reionisation modelling frameworks assume idealised, isotropic emissions. We investigate this assumption by examining a suite of simulations incorporating directed, anisotropic photon emissions. We find that such anisotropic emissions of ionising photons yield a different reionisation geometry compared to the standard, isotropic, case. During the early stages of reionisation (when less than 30 per cent of the Universe is ionised), simulations with narrow photon leakage channels produce smaller ionised bubbles on average. However, these bubbles grow to similar sizes during the middle stages of reionisation. This anisotropy not only produces a distinctive evolution of the size distribution of the ionised regions, but also imprints a feature onto the spherically averaged power spectra of the 21-cm signal throughout reionisation. We observe a suppression in power by about 10-40 per cent at scales corresponding to wavenumbers $k=0.1-1h{\mathrm{Mpc}}^{-1}$, corresponding to the range in which current radio interferometers are most likely to measure the power spectrum. The simulation with the narrowest channel of ionisation emission shows the strongest suppression. However, this anisotropic emission process does not introduce any measurable anisotropy in the 21-cm signal.

References in corpus (38)

• Array Programming with NumPy
• Efficient Simulations of Early Structure Formation and Reionization
• Two Remarkably Luminous Galaxy Candidates at $z\approx 10-12$ Revealed by JWST
• Improved upper limits on the 21-cm signal power spectrum of neutral hydrogen at $\mathbf{z}\approx 9.1$ from LOFAR
• Identification and properties of intense star-forming galaxies at redshifts z>10
• 21CMMC: an MCMC analysis tool enabling astrophysical parameter studies of the cosmic 21 cm signal
• Introducing the THESAN project: radiation-magnetohydrodynamic simulations of the epoch of reionization
• Deep multi-redshift limits on Epoch of Reionisation 21cm Power Spectra from Four Seasons of Murchison Widefield Array Observations
• The brightest galaxies at Cosmic Dawn
• The First Billion Years Project: The escape fraction of ionizing photons in the epoch of reionization
• First Results from HERA Phase I: Upper Limits on the Epoch of Reionization 21 cm Power Spectrum
• Improved Constraints on the 21 cm EoR Power Spectrum and the X-Ray Heating of the IGM with HERA Phase I Observations
• JADES: Probing interstellar medium conditions at $z\sim 5.5-9.5$ with ultra-deep JWST/NIRSpec spectroscopy
• 21cmFAST v3: A Python-integrated C code forgenerating 3D realizations of the cosmic 21cm signal
• Lyman continuum leakage from low-mass galaxies with Mstar < 1.E8 Msun
• The THESAN project: properties of the intergalactic medium and its connection to Reionization-era galaxies
• Constraining the intergalactic medium at $z\approx$ 9.1 using LOFAR Epoch of Reionization observations
• Fast Large-Scale Reionization Simulations
• The THESAN project: Lyman-alpha emission and transmission during the Epoch of Reionization
• LyC escape from SPHINX galaxies in the Epoch of Reionization
• The THESAN project: ionizing escape fractions of reionization-era galaxies
• Bubble size statistics during reionization from 21-cm tomography
• The spectral evolution of the first Galaxies. III. Simulated James Webb Space Telescope spectra of reionization-epoch galaxies with Lyman continuum leakage
• Higher Order Contributions to the 21 cm Power Spectrum
• JADES: Discovery of extremely high equivalent width Lyman-alpha emission from a faint galaxy within an ionized bubble at z=7.3
• Quasar Luminosity Function at z = 7
• Quantifying Distributions of Lyman Continuum Escape Fraction
• The impact of an evolving stellar initial mass function on early galaxies and reionisation
• Measuring the topology of reionization with Betti numbers
• Peering into cosmic reionization: the Ly$\alpha$ visibility evolution from galaxies at $z$ = 4.5-8.5 with JWST
• A halo model approach for the 21-cm power spectrum at cosmic dawn
• Redshift-space distortions in simulations of the 21-cm signal from the cosmic dawn
• Reconstructing the nature of the first cosmic sources from the anisotropic 21-cm signal
• Deeper multi-redshift upper limits on the Epoch of Reionization 21-cm signal power spectrum from LOFAR between z=8.3 and z=10.1
• BEoRN: A fast and flexible framework to simulate the epoch of reionisation and cosmic dawn
• Suppressing variance in 21-cm signal simulations during reionization
• pyC${}^2$Ray: A flexible and GPU-accelerated Radiative Transfer Framework for Simulating the Cosmic Epoch of Reionization
• Constraining cosmic reionization by combining the kinetic Sunyaev-Zel'dovich and the 21 cm power spectra