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

By P. Madau, Tassos Fragos. 2016

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We compute the expected X-ray diffuse background and radiative feedback on the intergalactic medium (IGM) from X-ray binaries prior to 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 H ii 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. Because of the energy dependence of photoabsorption, soft X-ray photons are produced by local sources, while more energetic radiation arrives unattenuated from larger cosmological volumes. 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 He i photoionizations are the main source of IGM heating, and the temperature of the largely neutral medium in between H ii cavities increases above the temperature of the cosmic microwave background (CMB) only at z ≲ 10, when the volume filling factor of H ii bubbles is already ≳0.1. Therefore, in this scenario, it is only at relatively late epochs that neutral intergalactic hydrogen may be observable in 21 cm emission against the CMB.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/0ec5d18ab40e947fc3b08c85cf5d9dff5a7384f9

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Citations in the corpus

The effect of the metallicity-specific star formation history on double compact object mergers (2019, methodology): “…490, 3740–3759 (2019) D ow nloaded from https://academ ic.oup.com /m nras/article-abstract/490/3/3740/5588621 by U niversity Library, U niversity of Am sterdam user on 17 February 2020 model favours an SFR similar to Madau & Fragos (2017), which includes the contribution from stars in binaries.”
Inferring the astrophysics of reionization and cosmic dawn from galaxy luminosity functions and the 21-cm signal (2018, unknown): “The heating and ionization rates per baryon inside the mostly neutral IGM are calculated with (see also, e.g. Baek & Ferrara 2013; Madau & Fragos 2017; Eide et al. 2018) QX(x, z) = ∫ ∞ Max[ν0,ντ=1] dν 4πJ hν ∑ i (hν − E thi ) fheat fi xiσi (19) and Γion,X(x, z) = ∫ ∞ Max[ν0,ντ=1] dν 4πJ hν ∑ i fi…”
Two populations of LIGO-Virgo black holes (2020, unknown): “be estimated as [112] SFR(z) ∝ (1 + z) 2.”
The origin of spin in binary black holes (2019, methodology): “…follow a truncated log-normal distributed, N(log10(Z) | µ(z), σ) ≡ dP d log10(Z) (z) = 1 σ √ 2π exp − (log10(Z) − µ(z))22σ2 (B.2) with standard deviation σ = 0.5 and mean µ = log10 ( Z̄(z) ) − ln(10)2 σ2 where the mean metallicity is (Madau & Fragos 2017) Z̄(z) = Z × 100.153−0.074·z 1.34 .”
Feedback-regulated star formation and escape of LyC photons from mini-haloes during reionization (2016, background): “…is likely to be massive stars in dwarf galaxies (Haehnelt et al. 2001; ? e-mail: tkimm@ast.cam.ac.uk Cowie et al. 2009; Fontanot et al. 2014; Madau & Fragos 2016, c.f., Madau & Haardt 2015); however, the timescale over which reionisation occurred and the mass range of haloes which provided…”
Consistent modelling of the meta-galactic UV background and the thermal/ionization history of the intergalactic medium (2018, methodology): “(11) We use a modified version of the best-fitting comoving star formation rate density (SFRD) proposed by Madau & Fragos (2017).”
One Channel to Rule Them All? Constraining the Origins of Binary Black Holes Using Multiple Formation Pathways (2020, methodology): “At a given redshift, metallicities are distributed following a truncated log-normal metallicity distribution around the empirical median metallicity from Madau & Fragos (2017) assuming a standard deviation of 0.5 dex (Bavera et al. 2020a, Section 2.2): log10 〈Z/Z 〉 = 0.153− 0.074z1.”
Evolutionary roads leading to low effective spins, high black hole masses, and O1/O2 rates for LIGO/Virgo binary black holes (2017, methodology): “(4)), SFRD and average metallicity evolution from Madau & Fragos (2017) (Eqs.”