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Radiation Backgrounds at Cosmic Dawn: X-Rays from Compact Binaries

17 Pith papers cite this work. Polarity classification is still indexing.

17 Pith papers citing it
abstract

We compute the expected X-ray diffuse background and radiative feedback on the intergalactic medium (IGM) from X-ray binaries prior and during the epoch of reionization. The cosmic evolution of compact binaries is followed using a population synthesis technique that treats separately neutron stars and black hole binaries in different spectral states and is calibrated to reproduce the observed X-ray properties of galaxies at z<4. Together with an updated empirical determination of the cosmic history of star formation, recent modeling of the stellar mass-metallicity relation, and a scheme for absorption by the IGM that accounts for the presence of ionized HII bubbles during the epoch of reionization, our detailed calculations provide refined predictions of the X-ray volume emissivity and filtered radiation background from "normal" galaxies at z>6. Radiative transfer effects modulate the background spectrum, which shows a characteristic peak between 1 and 2 keV. While the filtering of X-ray radiation through the IGM slightly increases the mean excess energy per photoionization, it also weakens the radiation intensity below 1 keV, lowering the mean photoionization and heating rates. Numerical integration of the rate and energy equations shows that the contribution of X-ray binaries to the ionization of the bulk IGM is negligible, with the electron fraction never exceeding 1%. Direct HeI photoionizations are the main source of IGM heating, and the temperature of the largely neutral medium in between HII cavities increases above the temperature of the cosmic microwave background (CMB) only at z<10, when the volume filling factor of HII bubbles is already >0.1. Therefore, in this scenario, it is only at relatively late epochs that the bulk of neutral intergalactic hydrogen may be observable in 21-cm emission against the CMB.

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2026 14 2025 3

representative citing papers

21cmEMUv3: a hybrid diffusion-LSTM emulator of 21cmFAST summary observables

astro-ph.CO · 2026-05-29 · unverdicted · novelty 6.0

21cmEMUv3 emulates the cylindrical 21cm power spectrum via score-based diffusion and six other 21cmFAST observables via LSTM networks at sub-percent accuracy, then uses the emulator to infer a lower limit on soft-band X-ray luminosity from HERA data.

The Lumina Project: Intergalactic Clumping and Recombination Sinks

astro-ph.GA · 2026-06-16 · unverdicted · novelty 4.0

Simulations show recombination-weighted clumping is systematically lower than density-based measures, density-only prescriptions overpredict rates by 1.29-1.84 depending on redshift, and a new phase-space clumping factor isolates thermal and ionization effects at fixed density.

The Lumina Project: CMB Optical Depth Fluctuations from Patchy Reionization

astro-ph.CO · 2026-05-18 · unverdicted · novelty 4.0

The Lumina simulation shows that explicit light-cone integrations produce a CMB optical depth 7% higher than volume-weighted ionization histories, with the excess accumulating near redshift 8 and mass-weighted estimates capturing most of the difference.

Can current models predict the local black hole merger rate?

astro-ph.HE · 2026-06-01 · unverdicted · novelty 3.0

Theoretical predictions for local BBH merger rates exceed observations by a factor >10 under conservative SFRD and metallicity assumptions, indicating need for revisions in stellar evolution.

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