Late-time growth weakly affects the significance of high-redshift massive galaxies

Recent observations by the James Webb Space Telescope have revealed massive galaxies at very high redshift ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow> <mml:mi>z</mml:mi> <mml:mo>≃</mml:mo> <mml:mn>7</mml:mn> <mml:mo>−</mml:mo> <mml:mn>15</mml:mn> </mml:mrow> </mml:math> ). The question of whether the existence of such galaxies is expected in the corresponding JWST surveys has received a lot of attention, though the answer straddles areas of cosmology and complex astrophysical details of high-redshift galaxy formation. The growth rate of density fluctuations determines the amplitude of overdensities that collapse to form galaxies. Late-time modifications of growth, combined with measurements at both <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow> <mml:mi>z</mml:mi> <mml:mo>∼</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:math> from large-scale structure and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow> <mml:mi>z</mml:mi> <mml:mo>∼</mml:mo> <mml:mn>1000</mml:mn> </mml:mrow> </mml:math> from the cosmic microwave background, affect the predictions for the abundance of first galaxies in the universe. In this paper, we point out that the late-time growth rate of structure affects the statistical significance of high-redshift, high-mass objects very weakly. Consequently, if the existence and abundance of these objects are confirmed to be unexpected, the variations in the late-time growth history are unlikely to explain these anomalies.