the first galaxies

Luminosity Functions of Galaxies at Different Cosmic Times

Luminosity Functions of Galaxies at Redshifts of 7.4 (700 million years after the Big Bang), 6 (900 million years after the Big Bang), and 3 (2000 million years after the Big Bang). The luminosity function tells us the volume density of galaxies (vertical axis) versus their luminosity (horizontal axis). More negative absolute magnitudes (shown on the horizontal axis as "M_1900") correspond to brighter galaxies. The volume densities on the vertical axis are presented in logarithmic units -- so that a more negative number corresponds to a lower abundance. Galaxies at all epochs are much more abundant at lower luminosities than they are higher luminosities. However, at higher redshifts (earlier times), there are significantly fewer bright galaxies than there are at later times. This is exactly what we expect in hierarchical scenarios where the bright galaxies build up gradually from faint ones. The present diagram includes our luminosity function results through 2008.

Credit:Bouwens

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