Large 21-cm signals from AGN-dominated reionization

作者：Kulkarni Girish; Choudhury Tirthankar Roy; Puchwein Ewald; Haehnelt Martin G

来源：Monthly Notices of the Royal Astronomical Society, 2017, 469(4): 4283-4291.

DOI：10.1093/mnras/stx1167

• galaxies: active
• galaxies: high-redshift
• intergalactic medium
• quasars: general
• dark ages, reionization, first stars

We present predictions for the spatial distribution of 21-cm brightness temperature fluctuations from high-dynamic-range simulations for active galactic nucleus (AGN)-dominated reionization histories that have been tested against available Ly alpha and cosmic microwave background (CMB) data. We model AGNs by extrapolating the observedM(bh) - sigma relation to high redshifts and assign them ionizing emissivities consistent with recent UV luminosity function measurements. We assess the observability of the predicted spatial 21-cm fluctuations in the late stages of reionization in the limit in which the hydrogen 21-cm spin temperature is significantly larger than the CMB temperature. Our AGN-dominated reionization histories increase the variance of the 21-cm emission by a factor of up to 10 compared to similar reionization histories dominated by faint galaxies, to values close to 100 mK(2) at scales accessible to experiments (k less than or similar to 1 cMpc(-1) h). This is lower than the sensitivity reached by ongoing experiments only by a factor of about 2 or less. When reionization is dominated by AGNs, the 21-cm power spectrum is enhanced on all scales due to the enhanced bias of the clustering of the more massive haloes and the peak in the large scale 21-cm power is strongly enhanced and moved to larger scales due to bigger characteristic bubble sizes. AGN-dominated reionization should be easily detectable by Low Frequency Array (and later Hydrogen Epoch of Reionization Array and Phase 1 of the Square Kilometre Array) at their design sensitivity, assuming successful foreground subtraction and instrument calibration. Conversely, these could become the first non-trivial reionization scenarios to be ruled out by 21-cm experiments, thereby constraining the contribution of AGNs to reionization.

• 出版日期2017-8