UV Slopes at All Redshifts Are Consistent with H = 1 Stochastic Star Formation Histories

Abstract

Abstract Multiple investigations support describing galaxy growth as a stochastic process with correlations over a range of timescales governed by a parameter, H, empirically and theoretically constrained to be near unity. Here, we show that the distribution of UV-slopes, β, derived from an ensemble of theoretical H = 1 star formation histories is consistent with data at all redshifts z ≤ 16. At z = 0, the median value 〈β H=1〉 = − 2.27 agrees well with the canonical β 0 = −2.23 for local starbursts. At 4 ≲ z ≲ 16, JWST data span the model distribution’s 2nd to 98th percentiles. Values of −2.8 ≤ β ≤ −2.5 should be common in early galaxies without reference to exotic stellar populations—arising solely from a null hypothesis of H = 1 for the underlying diversity of galaxy growth histories. Future data should be interpreted with this fact in mind.