FOREVER22: Insights into star formation and clustering properties of protoclusters from simulations and JWST

Abstract

Using cosmological hydrodynamic simulations with radiative transfer, we investigate star formation and overdensity ($\delta$) in Coma-type cluster progenitors from $z=14$ to 6. Our simulations reproduce observed $M_{\mathrm{star}}$-SFR relations and $\delta$ at these redshifts. We find: (1) protocluster (PC) and mean-density field (MF) galaxies show similar $M_{\mathrm{star}}$-SFR relations, with PC galaxies extending to higher $M_{\mathrm{star}}$ and SFR. (2) UV-bright PC galaxies ($M_{\mathrm{UV}}\lesssim -20$~mag) have $>2$ mag higher UV attenuation and shallower UV slopes than MF galaxies. (3) $\delta$ increases with redshift, depending on observational parameters (e.g., $\delta \sim 50$ at $z=14$ to $\delta \sim 3$ at $z=6$ for a search volume of $\sim 3000$~cMpc${}^3$ and a limiting magnitude of $M_{\mathrm{UV}}=-17$~mag). These results indicate that enhanced star formation in PCs is driven by massive galaxy overdensity, not anomalously high specific SFR. While simulated $\delta$ agrees with observed PC candidates (potential Coma progenitors), some MF galaxies show comparable $\delta$. We propose a robust PC identification method using both $\delta$ and $M_{\mathrm{star}}$ of the most massive member. Critical $M_{\mathrm{star}}$ thresholds for Coma progenitors are estimated ($10^{7.1}$ to $10^{10.2}$ M${}_{\odot }$ from $z=14$ to 6). Comparison with JWST observations suggests GS-z14-0 and GS-z14-1, the current highest redshift holders, are likely progenitors of Coma-type clusters.

16 pages, 13 figures, accepted for publication in MNRAS