Measurement Of The B-Band Galaxy Luminosity Function With Approximate Bayesian Computation

The galaxy Luminosity Function (LF) is a key observable for galaxy formation, evolution studies and for cosmology. In this work, we propose a novel technique to forward model wide-field broad-band galaxy surveys using the fast image simulator UFig and measure the LF of galaxies in the B-band. We use Approximate Bayesian Computation (ABC) to constrain the galaxy population model parameters of the simulations and match data from the Canada-France-Hawaii Telescope Legacy Survey (CFHTLS). We define a number of distance metrics between the simulated and the survey data. By exploring the parameter space of the galaxy population model through ABC to find the set of parameters that minimize these distance metrics, we obtain constraints on the LFs of blue and red galaxies as a function of redshift. We find that M* fades by Delta M-0.1-1.0,M-b* 0.68 +/- 0.52 and Delta M-0.1-1.0,M-r *= 0.54 +/- 0.48 magnitudes between redshift z = 1 and z = 0.1 for blue and red galaxies, respectively. We also find that phi* for blue galaxies stays roughly constant between redshift z = 0.1 and z = 1, while for red galaxies it decreases of similar to 35%. We compare our results to other measurements, finding good agreement at all redshifts, for both blue and red galaxies. To further test our results, we compare the redshift distributions for survey and simulated data. We use the spectroscopic redshift distribution from the VIMOS Public Extragalactic Redshift Survey (VIPERS) and we apply the same selection in colours and magnitudes on our simulations. We find a good agreement between the survey and the simulated redshift distributions. We provide best-fit values and uncertainties for the parameters of the LF. This work offers excellent prospects for measuring other galaxy population properties as a function of redshift using ABC.