Constraints on the early Universe star formation efficiency from galaxy clustering and halo modeling of H\(\alpha\) and [O III] emitters

We have developed a theoretical framework that provides observational constraints on the early Universe galaxy-halo connection by combining measurements of the ultraviolet luminosity function (UVLF) and galaxy clustering via the two-point correlation function (2PCF). We implemented this framework in the FRESCO and CONGRESS JWST NIRCam/grism surveys by measuring the 2PCF of spectroscopically selected samples of H\(\alpha\) and [O III] \ emitters at \(3.8<z<9\) in 124 arcmin\(^2\) in GOODS-North and GOODS-South. By fitting the 2PCF and UVLF at \(3.8<z<9\), we inferred that the H\(\alpha\) and [O III] samples at \(\langle z \rangle \sim4.3, 5.4\), and \(7.3\) reside in halos of masses of log\((M_{\rm h}/\)M\(_{\odot}) = 11.5\), \(11.2\), and \(11.0\), respectively, while their galaxy bias increases with redshift with values of \(b_{\rm g} = 4.0\), \(5.0\), and \(7.6\). These halos, however, do not represent extreme overdense environments at these epochs. Our framework constrains the instantaneous star formation efficiency (SFE), defined as the ratio of the star formation rate over the baryonic accretion rate as a function of halo mass. We find that the SFE rises with halo mass, peaks at \(\sim20\%\) at \(M_{\rm h} \sim 3 \times 10^{11}\, {\rm M_{\odot}}\), and declines at higher halo masses. The SFE-\(M_{\rm h}\) shows only a mild evolution with redshift with tentative indications that low-mass halos decrease but the high-mass halos increase in efficiency with redshift. The scatter in the \(M_{\rm UV}-M_{\rm h}\) relation, quantified by \(\sigma_{\rm UV}\), implies modest stochasticity in the UV luminosities of \(\sim 0.7\) magand is relatively constant with redshift. Extrapolating our model to $z>9$ showed that a constant SFE-\(M_{\rm h}\) fixed at \(z=8\) cannot reproduce the observed UVLF, and neither a high maximum SFE nor a high stochasticity alone can explain the high abundances of luminous galaxies seen by JWST. Extending the analysis of the UVLF and 2PCF to \(z>9\) as measured from wider surveys will be crucial to breaking the degeneracies between different physical mechanisms that can explain the high abundance of bright galaxies.

Recommended citation: Shuntov et al. 2025, A&A 699, A231
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