21-cm fluctuations from inhomogeneous X-ray heating before reionization

By J. Pritchard, S. Furlanetto. 2006

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Many models of early structure formation predict a period of heating immediately preceding reionization, when X-rays raise the gas temperature above that of the cosmic microwave background. These X-rays are often assumed to heat the intergalactic medium (IGM) uniformly, but in reality will heat the gas more strongly closer to the sources. We develop a framework for calculating fluctuations in the 21-cm brightness temperature that originate from this spatial variation in the heating rate. High-redshift sources are highly clustered, leading to significant gas temperature fluctuations (with fractional variations ∼40 per cent, peaking on k∼0.1 Mpc^−1 scales). This induces a distinctive peak-trough structure in the angle-averaged 21-cm power spectrum, which may be accessible to the proposed Square Kilometre Array. This signal reaches the ∼10 mK level, and is stronger than that induced by Lyα flux fluctuations. As well as probing the thermal evolution of the IGM before reionization, this 21-cm signal contains information about the spectra of the first X-ray sources. Finally, we consider disentangling temperature, density and Lyα flux fluctuations as functions of redshift.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/ead295765668afee7044bc6a5261844a7690f558

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Citations in the corpus

Hydrogen Epoch of Reionization Array (HERA) (2016, background): “The IGM is then expected to be heated by first generation X–ray binaries (Furlanetto 2006; Pritchard & Furlanetto 2007; Mesinger et al. 2013) or by the hot interstellar medium produced by the first supernovae (Pacucci et al. 2014), although the heating timing and magnitude is still very much…”
Radiation Backgrounds at Cosmic Dawn: X-Rays from Compact Binaries (2016, background): “…Lyα background photons to mix the hyperfine levels and of a pre-heating mechanism, such as X-ray radiation from the first galaxies or AGNs (e.g., Field 1958; Madau et al. 1997; Ciardi & Madau 2003; Chen & Miralda-Escudé 2004; Kuhlen et al. 2006; Furlanetto 2006; Pritchard & Furlanetto 2007).”
Signatures of X-rays in the early Universe (2012, methodology): “This run differs from the fiducial only in having an X-ray efficiency which is a factor of ≈5 higher, making it more in line with several previous works (e.g. Furlanetto 2006; Pritchard & Furlanetto 2007; Santos et al. 2008; Warszawski et al. 2009; Mack & Wyithe 2011; Valdés et al. 2012).”
21 cm cosmology in the 21st century (2011, background): “The details of the signal depend primarily on the total Lyα emissivity and not on the shape of the spectrum (but see [72, 53] for details of how precision measurements of the 21 cm fluctuations might say something about the source spectrum).”
Fast large volume simulations of the 21-cm signal from the reionization and pre-reionization epochs (2009, methodology): “The analytical models have also been useful to understand the possible contributions to the 21 cm signal at high redshifts (Barkana & Loeb 2005; Pritchard & Furlanetto 2007), although it is at low redshifts (z .”
INTENSITY MAPPING WITH CARBON MONOXIDE EMISSION LINES AND THE REDSHIFTED 21 cm LINE (2011, methodology): “For simplicity, we assume that the spin temperature of the 21 cm transition is much larger than the CMB temperature globally, which is likely a good approximation during most of the EoR (Ciardi & Madau 2003, Pritchard & Furlanetto 2007).”
Stellar black holes at the dawn of the universe (2011, methodology): “A boosted X-ray emissivity of star forming also affects the fluctuations in the 21 cm background (Pritchard & Furlanetto 2007; Pritchard & Loeb 2008).”
Inferring the astrophysics of reionization and cosmic dawn from galaxy luminosity functions and the 21-cm signal (2018, background): “By heating the IGM prior to the bulk of reionization, Xrays are expected to play a dominant role during the CD (e.g. Pritchard & Furlanetto 2007; McQuinn & O’Leary 2012; Mesinger et al. 2013).”
Upper Limits on the 21 cm Epoch of Reionization Power Spectrum from One Night with LOFAR (2017, background): “…al. 2014; Watkinson & Pritchard 2014) and its power spectrum as a function of redshift (e.g Morales & Hewitt 2004; Bharadwaj & Ali 2005; Barkana & Loeb 2005; McQuinn et al. 2006; Bowman et al. 2006; Pritchard & Furlanetto 2007; Jelić et al. 2008; Harker et al. 2009, 2010; Pritchard & Loeb 2008).”
Reionization and the Cosmic Dawn with the Square Kilometre Array (2012, background): “The models suggest that it is dominated by the clustering of the radiation sources on large scales and by their radiation profile on intermedate scales (Barkana & Loeb 2005b; Chuzhoy et al. 2006; Pritchard & Furlanetto 2007).”
Fundamental physics with the Square Kilometre Array (2018, background): “…interferometers — LOFAR, PAPER, MWA, HERA — are targeting the spatial fluctuations of the 21 cm signal, due to the ionised bubbles during cosmic reionisation as well as Lyman-α fluctuations (Barkana & Loeb, 2005b) and X-ray heating fluctuations (Pritchard & Furlanetto, 2007) during cosmic dawn.”
21cmfast: a fast, seminumerical simulation of the high‐redshift 21‐cm signal (2010, methodology): “When normalized to the same epoch, our power-spectrum evolution agrees fairly well with the analytical model of Pritchard & Furlanetto (2007), as well as its application to a numerical (Santos et al. 2008) and a seminumerical (MF07) simulation (Santos et al. 2009, cf. their fig.”
Reionization and Cosmology with 21-cm Fluctuations (2009, background): “The fluctuations and evolution of the kinetic and spin temperatures of HI are frontier issues in theoretical studies of the EoR (e.g. Pritchard & Furlanetto 2007, Pritchard & Loeb 2008).”