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Simulating the Impact of X-ray Heating during the Cosmic Dawn | | Hannah E. Ross
; Keri L. Dixon
; Ilian T. Iliev
; Garrelt Mellema
; | | Date: |
21 Jul 2016 | | Abstract: | Upcoming observations of the 21-cm signal from the Epoch of Reionization will
soon provide us with the first direct detection of this era. This signal is
influenced by many astrophysical effects, including long range X-ray heating of
the intergalactic gas. During the preceding Cosmic Dawn era the impact of this
heating on the 21-cm signal is particularly prominent, especially before spin
temperature saturation. We present the largest-volume (244~$h^{-1}$Mpc=349,Mpc
comoving) full numerical radiative transfer simulations to date of this epoch,
including the effects of helium and multi-frequency heating, both with and
without X-ray sources. We show that X-ray sources can contribute significantly
to early heating of the neutral intergalactic medium and, hence, to the
corresponding 21-cm signal. The inclusion of hard, energetic radiation yields
an earlier, extended transition from absorption to emission compared to the
stellar-only case. The presence of X-ray sources decreases the absolute value
of the mean 21-cm differential brightness temperature. These hard sources also
significantly increase the 21-cm fluctuations compared the common assumption of
temperature saturation. The power spectrum is initially boosted on large scales
before decreasing on all scales. Compared to the case of the cold, unheated
intergalactic medium, the signal has lower rms fluctuations and increased
non-Gaussianity, as measured by the skewness and kurtosis of the 21-cm
probability distribution functions. Images of the 21-cm signal with resolutions
around 11~arcmin still show fluctuations well above the expected noise for deep
integrations with the SKA1-Low, indicating that direct imaging of the X-ray
heating epoch could be feasible. | | Source: | arXiv, 1607.6282 | | Services: | Forum | Review | PDF | Favorites | |
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