Self-consistent simulations of the high-redshift 21-cm signal with star formation calibrated to hydrodynamic simulations
Year: 2026
Type: article
Abstract: ABSTRACT We present a novel, self-consistent, seminumeric Cosmic Dawn (CD) simulation in which small-scale star formation (SF) is calibrated to the AEOS and Renaissance hydrodynamic simulations. SF proceeds within dark matter (DM) haloes via neural network emulation while considering large-scale fluctuations in density and feedback. We translate the resulting 3D distribution of galaxies into predictions for the 21-cm brightness temperature, $\delta T_{\mathrm{b}}$, and power spectrum, $\Delta ^2(k)$. We simulate several unique realizations to study the impact of varying astrophysics on $\delta T_{\mathrm{b}}$, finding that more efficient Population II (PopII) SF largely yields stronger Lyman-$\alpha$ coupling, resulting in a shallower and wider absorption trough. However, we find that PopII SF dominates $\Delta ^2(k)$ at $z \lesssim 20$ and on smaller scales at intermediate redshifts ($k \gtrsim 0.2\ \mathrm{Mpc^{-1}}$ at $z \simeq 34{\small -}20$) while Population III (PopIII) SF dominates $\Delta ^2(k)$ at $z\gtrsim 34$ and on larger scales at intermediate redshifts. Compared with previous works, we find that the combination of hydrodynamic SF calibration, a critical halo mass for SF considering $\rm {H_{2}}$ self-shielding, and stochastic DM halo merger histories results in both earlier SF and higher SF rates across CD. Further, we find that the delay period separating PopIII and PopII SF ($t_{\rm delay}$) significantly impacts $\delta T_{\mathrm{b}}$, and that one must include DM halo merger histories to properly account for this transition. Finally, we find our fiducial $\delta T_{\mathrm{b}}$ to be detectable at $z\lesssim 25$ with 1080 h of HERA observations under moderate foreground assumptions, and the lack of such a detection at $z \gtrsim 20$ would suggest $t_{\rm delay}$ $\gtrsim$ 30 Myr.
Institutions: Stellenbosch University, University of Toledo
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $3,046
OpenAlex ID: W7221751636