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Abstract We present self-consistent radiation hydrodynamic simulations of hydrogen reionization performed with arepo-rt complemented by a state-of-the-art galaxy formation model. We examine how photoheating feedback, due to reionization, shapes the galaxies properties. Our fiducial model completes reionization by z ≈ 6 and matches observations of the Ly α forest, the cosmic microwave background electron scattering optical depth, the high-redshift ultraviolet (UV) luminosity function, and stellar mass function. Contrary to previous works, photoheating suppresses star formation rates by more than $$50{{\ \rm per\ cent}}$$ only in haloes less massive than ∼108.4 M⊙ (∼108.8 M⊙) at z = 6 (z = 5), suggesting inefficient photoheating feedback from photons within galaxies. The use of a uniform UV background that heats up the gas at z ≈ 10.7 generates an earlier onset of suppression of star formation compared to our fiducial model. This discrepancy can be mitigated by adopting a UV background model with a more realistic reionization history. In the absence of stellar feedback, photoheating alone is only able to quench haloes less massive than ∼109 M⊙ at z ≳ 5, implying that photoheating feedback is sub-dominant in regulating star formation. In addition, stellar feedback, implemented as a non-local galactic wind scheme in the simulations, weakens the strength of photoheating feedback by reducing the amount of stellar sources. Most importantly, photoheating does not leave observable imprints in the UV luminosity function, stellar mass function, or the cosmic star formation rate density. The feasibility of using these observables to detect imprints of reionization therefore requires further investigation.
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Chaotic and Clumpy Galaxy Formation in an Extremely Massive Reionization-era Halo
Abstract The SPT 0311–58 system at z = 6.900 is an extremely massive structure within the reionization epoch and offers a chance to understand the formation of galaxies at an extreme peak in the primordial density field. We present 70 mas Atacama Large Millimeter/submillimeter Array observations of the dust continuum and [C ii ] 158 μ m emission in the central pair of galaxies and reach physical resolutions of ∼100–350 pc, among the most detailed views of any reionization-era system to date. The observations resolve the source into at least a dozen kiloparsec-size clumps. The global kinematics and high turbulent velocity dispersion within the galaxies present a striking contrast to recent claims of dynamically cold thin-disk kinematics in some dusty galaxies just 800 Myr later at z ∼ 4. We speculate that both gravitational interactions and fragmentation from massive parent disks have likely played a role in the overall dynamics and formation of clumps in the system. Each clump individually is comparable in mass to other 6 < z < 8 galaxies identified in rest-UV/optical deep field surveys, but with star formation rates elevated by a factor of ~3-5. Internally, the clumps themselves bear close resemblance to greatly scaled-up versions of virialized cloud-scale structures identified in low-redshift galaxies. Our observations are qualitatively similar to the chaotic and clumpy assembly within massive halos seen in simulations of high-redshift galaxies.
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- PAR ID:
- 10323208
- Author(s) / Creator(s):
- ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; more »
- Date Published:
- Journal Name:
- The Astrophysical Journal Letters
- Volume:
- 929
- Issue:
- 1
- ISSN:
- 2041-8205
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.3847/2041-8213/ac61e6
