Work

LIMFAST. V. Probing Reionization with the Synergy Between 21 cm and Photometric Galaxy Surveys

Year: 2026

Type: preprint

Abstract: Cross-correlating the 21\,cm signal from intergalactic neutral hydrogen with the galaxy distribution is a powerful probe of the Epoch of Reionization and the physical mechanisms driving it. While upcoming surveys with the SKA-Low radio telescope and the Roman Space Telescope offer ideal synergies for this measurement, foreground mitigation of 21\,cm data requires exquisite redshift precision of galaxies, effectively excluding the rich photometrically selected samples of Lyman-break galaxies (LBGs) with typical redshift uncertainties $σ_z \gtrsim 0.1$. We overcome this challenge using a squared statistic of the foreground-cleaned 21\,cm signal. Squaring the filtered 21\,cm signal couples surviving high $k_\parallel$ modes into low $k_\parallel$ fluctuations accessible to photometric LBG surveys. This higher-order cross-correlation statistic remains measurable even when direct cross-correlations are strongly suppressed. Applying Fisher matrix analysis to this LBG--21\,cm$^2$ cross-correlation signal simulated by the \texttt{LIMFAST} code over $6 \lesssim z \lesssim 10$, we investigate the prospects for constraining EoR physics combining SKA-Low 21\,cm measurements and Roman photometric galaxy samples. For an overlapping survey area covering 10\,deg$^2$, we find that the LBG--21\,cm$^2$ cross-correlation is detectable at high significance across much of the EoR through 1000\,hours of SKA-Low integration with 15\,MHz bandwidth and a Roman photometric galaxy sample from the High-Latitude Wide-Area Survey (HLWAS) reaching $m_\mathrm{AB,lim}=27$ and photo-$z$ uncertainties of $σ_z \sim 0.1$--0.3. The characteristic sign evolution of the large-scale cross-power spectrum---driven primarily, though not exclusively, by the evolving neutral fraction---provides strong constraints on the physical parameters governing the ionization and thermal history of the IGM.

Source: arXiv (Cornell University)

DOI: 10.48550/arxiv.2609.35957

Authors: Sun, Guochao, Lidz, Adam, Chang, Tzu-Ching, Faucher-Giguère, Claude-André, Furlanetto, Steven R., Kundu, Aritra, Mirocha, Jordan

Institutions: Northwestern University, University of Pennsylvania, California Institute of Technology, Jet Propulsion Laboratory, University of California, Los Angeles

Language: English

Topic: Radio Astronomy Observations and Technology

Subfield: Astronomy and Astrophysics

Field: Physics and Astronomy

Domain: Physical Sciences

Open Access status: green

Funders: National Science Foundation, National Aeronautics and Space Administration, California Institute of Technology, Aspen Center for Physics, Space Telescope Science Institute, Jet Propulsion Laboratory

Awards: G1274589133, G1883672585, Collaborative Research: CDS&E: Constraining the uncertain physics of galaxy formation: cosmic rays, black holes, and beyond, G2595738051, G2676722403, G2769906720, G3516546945, G4799347951, G517611944, G6107654830, Star Formation, ISM, and Winds in Bursty vs. Steady Galaxies, Unlocking the Early History of Galaxy Formation, Programs on Critical Problems in Physics, Astrophysics and Biophysics at the Aspen Center for Physics, G830101876, Cold, Hot, and Feedback: Fundamental Physics of the Circumgalactic Medium

OpenAlex ID: W7214990914

Cites: 12

Cited by:

Related to: 10