Studying the Effects of Overlapping Objects in Dark Energy

Observing the clustering of galaxies allows us to calculate the cosmological parameters necessary for understanding dark energy. However, as the density of observed objects increases, multiple galaxies can appear blended and be observed as one galaxy. This affects the galaxy bias (b) and matter-energy density ($\Omega_M$). To see whether incorrectly inferring the galaxy count is significant, we compare the correlation functions in simulated data for “true” and “observed” data sets with 1-to-1 and multiple-to-1 correspondences, respectively. For each data set, we create two correlation functions: one measured directly from the galaxies’ positions and one model derived from their power spectrum. By minimizing the residual between the functions, we compute the ideal values for b and $\Omega_M$ across the possible redshifts that position the galaxies in 3D space. This minimization is done with a Markov chain Monte Carlo (MCMC) estimate that finds one value of $\Omega_M$ and ten values for b corresponding to the ten redshift bins ranging from z = 0.2 to z = 1.2. We find that neither b nor $\Omega_M$ is particularly affected by the inclusion of blended galaxies. The data suggest that the fluctuations found are a result of noise or limitations on the modeling.