Simulating the effect of photoheating feedback during reionization. (arXiv:1903.06167v1 [astro-ph.GA])

Simulating the effect of photoheating feedback during reionization. (arXiv:1903.06167v1 [astro-ph.GA])
<a href="http://arxiv.org/find/astro-ph/1/au:+Wu_X/0/1/0/all/0/1">Xiaohan Wu</a> (Harvard CfA), <a href="http://arxiv.org/find/astro-ph/1/au:+Kannan_R/0/1/0/all/0/1">Rahul Kannan</a> (Harvard CfA), <a href="http://arxiv.org/find/astro-ph/1/au:+Marinacci_F/0/1/0/all/0/1">Federico Marinacci</a> (U Bologna), <a href="http://arxiv.org/find/astro-ph/1/au:+Vogelsberger_M/0/1/0/all/0/1">Mark Vogelsberger</a> (MIT), <a href="http://arxiv.org/find/astro-ph/1/au:+Hernquist_L/0/1/0/all/0/1">Lars Hernquist</a> (Harvard CfA)

We present the first self-consistent radiation hydrodynamic simulation of
hydrogen reionization performed with AREPO-RT complemented by a
state-of-the-art galaxy formation model. We examine how photoheating feedback,
due to the reionization process, shapes the properties of galaxies. Our
fiducial model completes reionization by $zapprox6$ and matches the observed
volume-averaged neutral hydrogen fraction, the electron scattering optical
depth of the cosmic microwave background (CMB) photons, the high-redshift
ultraviolet (UV) continuum luminosity function, and stellar mass function.
Contrary to previous works, photoheating suppresses star formation rates by
larger than $50%$ only in halos less massive than $sim10^{8.4} M_odot$
($sim10^{8.8} M_odot$) at $z=6$ $(z=5)$. By assuming a uniform UV background
instead of self-consistently modelling the patchiness of reionization yields an
earlier onset of suppression of star formation, indicating that such an
approximation acts like an early reionization model. In the absence of stellar
feedback, photoheating alone is only able to quench halos less massive than
$sim10^9 M_odot$ at $zgtrsim5$, implying that photoheating feedback plays a
sub-dominant role in regulating star formation compared to stellar feedback. In
addition, stellar feedback weakens the strength of photoheating feedback by
reducing the amount of stellar sources. Most importantly, photoheating does not
generate any observable flattening in the faint end slope of the UV luminosity
function up to ${rm M_{1500}} = -15$ mag or in the low-mass end of the stellar
mass function down to $10^6 M_odot$. We also do not observe a dip in the
cosmic star formation rate density caused by reionization. The feasibility of
using these observables to detect imprints of reionization therefore requires
further investigation.

We present the first self-consistent radiation hydrodynamic simulation of
hydrogen reionization performed with AREPO-RT complemented by a
state-of-the-art galaxy formation model. We examine how photoheating feedback,
due to the reionization process, shapes the properties of galaxies. Our
fiducial model completes reionization by $zapprox6$ and matches the observed
volume-averaged neutral hydrogen fraction, the electron scattering optical
depth of the cosmic microwave background (CMB) photons, the high-redshift
ultraviolet (UV) continuum luminosity function, and stellar mass function.
Contrary to previous works, photoheating suppresses star formation rates by
larger than $50%$ only in halos less massive than $sim10^{8.4} M_odot$
($sim10^{8.8} M_odot$) at $z=6$ $(z=5)$. By assuming a uniform UV background
instead of self-consistently modelling the patchiness of reionization yields an
earlier onset of suppression of star formation, indicating that such an
approximation acts like an early reionization model. In the absence of stellar
feedback, photoheating alone is only able to quench halos less massive than
$sim10^9 M_odot$ at $zgtrsim5$, implying that photoheating feedback plays a
sub-dominant role in regulating star formation compared to stellar feedback. In
addition, stellar feedback weakens the strength of photoheating feedback by
reducing the amount of stellar sources. Most importantly, photoheating does not
generate any observable flattening in the faint end slope of the UV luminosity
function up to ${rm M_{1500}} = -15$ mag or in the low-mass end of the stellar
mass function down to $10^6 M_odot$. We also do not observe a dip in the
cosmic star formation rate density caused by reionization. The feasibility of
using these observables to detect imprints of reionization therefore requires
further investigation.

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