The Luminosity Function and Clustering of H α Emitting Galaxies at z ≈ 4−6 from a Complete NIRCam Grism Redshift Survey

Abstract We study the luminosity function (LF) and clustering properties of 888 H α emitters (HAEs) at 3.75 < z < 6 in the GOODS-N field. The sample, built from JWST CONGRESS and FRESCO NIRCam grism surveys using a novel redshift assignment algorithm, spans ∼62 arcmin 2 and reaches L H α ∼ 10 41.2 erg s −1 . We identify two prominent filamentary protoclusters at z ≈ 4.41 and z ≈ 5.19, hosting 98 and 144 HAEs, respectively. The observed H α LFs show similar shallow faint-end slopes for both protocluster and field galaxies at 3.75 < z < 5, and for the protocluster at 5 < z < 6 ( α ≈ −1.2 to −1.3). In contrast, the field LF at 5 < z < 6 has a much steeper slope ( α = − 1.8 7 − 0.23 + 0.30 ), suggesting that protocluster galaxies at z > 5 are more evolved, resembling the populations at 3.75 < z < 5. The observed star formation rate density from H α integrated down to 0.45 M ⊙ yr −1 , is 0.05 0 − 0.003 + 0.002 M ⊙ yr − 1 Mpc − 3 at 3.75 < z < 5 and 0.04 6 − 0.004 + 0.006 M ⊙ yr − 1 Mpc − 3 at 5 < z < 6, with protoclusters contributing about 25% and 55%, respectively. This implies a large fraction of star formation at z > 4 occurs in protoclusters. For the first time, we conduct the star formation-rate-limited three-dimensional clustering analysis at z > 4. We find that the filamentary geometry of protoclusters flattens the power-law shape of the HAE autocorrelation functions, with slopes much shallower than the typically assumed value. The autocorrelation function of field HAEs has a correlation length of r 0 = 4.6 1 − 0.68 + 1.00 h − 1 Mpc