Assessing the Predictive Power of Galaxy Formation Models: A Comparison of Predicted and Observed Rest-Frame Optical Luminosity Functions at 2.0<z<3.3

TL;DR

This study evaluates how well current galaxy formation models predict the rest-frame optical luminosity functions of galaxies at redshifts 2.0 to 3.3, revealing successes and notable discrepancies with observations.

Contribution

It compares predictions of semianalytic and hydrodynamic galaxy formation models to observed luminosity functions at high redshift, highlighting areas of agreement and failure.

Findings

Models match observations at some luminosities and redshifts.

All models predict increasing luminosity density over time, contrary to observations.

Discrepancies in galaxy color evolution suggest incomplete modeling of galaxy formation.

Abstract

Recent galaxy formation models successfully reproduce the local luminosity function (LF) of galaxies by invoking mechanisms to suppress star formation in low- and high-mass galaxies. As these models are optimized to fit the LF at low redshift, a crucial question is how well they predict the LF at earlier times. Here we compare recently measured rest-frame V-band LFs of galaxies at redshifts 2.0<z<3.3 to predictions of semianalytic models by De Lucia & Blaizot and Bower et al. and hydrodynamic simulations by Dave et al.. The models succeed for some luminosity and redshift ranges and fail for others. A notable success is that the Bower et al. model provides a good match to the observed LF at z~3. However, all models predict an increase with time of the rest-frame V-band luminosity density, whereas the observations show a decrease. The models also have difficulty matching the observed rest-frame colors of galaxies. In all models the luminosity density of red galaxies increases sharply from z~3 to z~2.2, whereas it is approximately constant in the observations. Conversely, in the models the luminosity density of blue galaxies is approximately constant, whereas it decreases in the observations. These discrepancies cannot be entirely remedied by changing the treatment of dust and suggest that current models do not yet provide a complete description of galaxy formation and evolution since z~3.