TY - JOUR
T1 - The observable signature of late heating of the Universe during cosmic reionization
AU - Fialkov, Anastasia
AU - Barkana, Rennan
AU - Visbal, Eli
N1 - Funding Information: Acknowledgements We are grateful to S. Naoz for drawing our attention to the work of T. Fragos, who provided us with detailed model spectra of X-ray binaries, which helped motivate this study. This work was supported by Israel Science Foundation grant number 823/09, and bytheLabExENS-ICFP (grant numbers ANR-10-LABX-0010 and ANR-10-IDEX-0001-02 PSL*).
PY - 2014
Y1 - 2014
N2 - Models and simulations of the epoch of reionization predict that spectra of the 21-centimetre transition of atomic hydrogen will show a clear fluctuation peak, at a redshift and scale, respectively, that mark the central stage of reionization and the characteristic size of ionized bubbles. This is based on the assumption that the cosmic gas was heated by stellar remnants-particularly X-ray binaries-to temperatures well above the cosmic microwave background at that time (about 30 kelvin). Here we show instead that the hard spectra (that is, spectra with more high-energy photons than low-energy photons) of X-ray binaries make such heating ineffective, resulting in a delayed and spatially uniform heating that modifies the 21-centimetre signature of reionization. Rather than looking for a simple rise and fall of the large-scale fluctuations (peaking at several millikelvin), we must expect a more complex signal also featuring a distinct minimum (at less than a millikelvin) that marks the rise of the cosmic mean gas temperature above the microwave background. Observing this signal, possibly with radio telescopes in operation today, will demonstrate the presence of a cosmic background of hard X-rays at that early time.
AB - Models and simulations of the epoch of reionization predict that spectra of the 21-centimetre transition of atomic hydrogen will show a clear fluctuation peak, at a redshift and scale, respectively, that mark the central stage of reionization and the characteristic size of ionized bubbles. This is based on the assumption that the cosmic gas was heated by stellar remnants-particularly X-ray binaries-to temperatures well above the cosmic microwave background at that time (about 30 kelvin). Here we show instead that the hard spectra (that is, spectra with more high-energy photons than low-energy photons) of X-ray binaries make such heating ineffective, resulting in a delayed and spatially uniform heating that modifies the 21-centimetre signature of reionization. Rather than looking for a simple rise and fall of the large-scale fluctuations (peaking at several millikelvin), we must expect a more complex signal also featuring a distinct minimum (at less than a millikelvin) that marks the rise of the cosmic mean gas temperature above the microwave background. Observing this signal, possibly with radio telescopes in operation today, will demonstrate the presence of a cosmic background of hard X-rays at that early time.
UR - http://www.scopus.com/inward/record.url?scp=84893930943&partnerID=8YFLogxK
U2 - https://doi.org/10.1038/nature12999
DO - https://doi.org/10.1038/nature12999
M3 - مقالة
SN - 0028-0836
VL - 506
SP - 197
EP - 199
JO - Nature
JF - Nature
IS - 7487
ER -