Exploiting synergies between <i>JWST</i> and cosmic 21-cm observations to uncover star formation in the early Universe

ABSTRACT In the current era of James Webb Space Telescope (JWST), we continue to uncover a wealth of information about the Universe deep into the Epoch of Reionization. In this work, we use a suite of simulations with 21cmspace to explore the astrophysical properties of early galaxies and their imprint on high-redshift observables. Our analysis incorporates a range of multiwavelength data sets including ultraviolet luminosity functions (UVLFs) from Hubble Space Telescope and JWST spanning $z=6\,$–$\, 14.5$, the 21-cm global signal and power spectrum limits from SARAS 3 (Shaped Antenna measurement of the background RAdio Spectrum) and HERA (Hydrogen Epoch of Reionization Array), respectively, as well as present-day diffuse X-ray and radio backgrounds. We constrain a flexible halo-mass and redshift dependent model of star formation efficiency (SFE), defined as the fraction of gas converted into stars, and find that it is best described by minimal redshift evolution at $z\approx 6\,$–$\, 10$, followed by rapid evolution at $z\approx 10\,$–$\, 15$. Using Bayesian inference, we derive functional posteriors of the SFE, inferring that haloes of mass $M_h=10^{10}\, \mathrm{M}_{\odot }$ have efficiencies of $\approx 1 \,$–$\, 2{{\ \rm per\ cent}}$ at $z\lesssim 10$, $\approx 8{{\ \rm per\ cent}}$ at $z=12$, and $\approx 21{{\ \rm per\ cent}}$ at $z=15$. We also highlight the synergy between UVLFs and global 21-cm signal from SARAS 3 in constraining the minimum virial conditions required for star formation in haloes. In parallel, we find the X-ray and radio efficiencies of early galaxies to be $f_X = 0.8^{+9.7}_{-0.4}$ and $f_r \lesssim 16.9$, respectively, improving upon previous works that exclude UVLF data. Our results underscore the critical role of UVLFs in constraining early galaxy properties, and their synergy with 21-cm and other mutliwavelength observations.