No Luminous Little Red Dots: A Sharp Cutoff in Their Luminosity Function

2025/09/02 by Yilun Ma, Ma, Yilun, Jenny E. Greene +31
Physics and Astronomy · #Galaxies: Formation, Evolution, Phenomena #Astrophysical Phenomena and Observations #Astronomy and Astrophysical Research

paper · pdf · doi:10.48550/arxiv.2509.02662

Abstract

One of the most surprising results of early James Webb Space Telescope (JWST) observations is the discovery of an abundance of red, compact, broad-line objects dubbed "little red dots" (LRDs) at z>4. Their spatial density (∼10^-4-10^-5 \mathrmcMpc^-3) is 100 times more abundant than UV-selected quasars at those redshift if one extrapolates the quasar luminosity function (QLF) down to the LRD regime. However, whether LRDs dominate black hole accretion at quasar-like luminosities (L_bol\gtrsim 10^45-46 \mathrmerg s^-1) remains unanswered, as probing the bright end of the LRD luminosity function requires a much larger area than those able to be surveyed by JWST. In this work, we present our search for the brightest LRDs (K<23.7) at 4.5

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