We study the evolution of the cold gas content of galaxies by splitting the interstellar medium into its atomic and molecular hydrogen components, using the galaxy formation model GAL-FORM in the cold dark matter framework. We calculate the molecular-to-atomic hydrogen mass ratio, H 2 /H I, in each galaxy using two different approaches, the pressure-based empirical relation of Blitz & Rosolowsky and the theoretical model of Krumholz, McKeee & Tumlinson, and apply them to consistently calculate the star formation rates of galaxies. We find that the model based on the Blitz & Rosolowsky law predicts an H I mass function, 12 CO (1-0) luminosity function, correlations between H 2 /H I and stellar and cold gas mass, and infrared-12 CO molecule luminosity relation in good agreement with local and high-redshift observations. The H I mass function evolves weakly with redshift, with the number density of high-mass galaxies decreasing with increasing redshift. In the case of the H 2 mass function, the number density of massive galaxies increases strongly from z = 0 to 2, followed by weak evolution up to z = 4. We also find that H 2 /H I of galaxies is strongly dependent on stellar and cold gas mass, and also on redshift. The slopes of the correlations between H 2 /H I and stellar and cold gas mass hardly evolve, but the normalization increases by up to two orders of magnitude from z = 0 to 8. The strong evolution in the H 2 mass function and H 2 /H I is primarily due to the evolution in the sizes of galaxies and, secondarily, in the gas fractions. The predicted cosmic density evolution of H I agrees with the observed evolution inferred from damped Lyα systems, and is always dominated by the H I content of low-and intermediate-mass haloes. We find that previous theoretical studies have largely overestimated the redshift evolution of the global H 2 /H I due to limited resolution. We predict a maximum of ρ H 2 /ρ H I ≈ 1.2 at z ≈ 3.5.

The Murchison Widefield Array (MWA) has collected hundreds of hours of Epoch of Reionization (EoR) data and now faces the challenge of overcoming foreground and systematic contamination to reduce the data to a cosmological measurement. We introduce several novel analysis techniques, such as cable reflection calibration, hyper-resolution gridding kernels, diffuse foreground model subtraction, and quality control methods. Each change to the analysis pipeline is tested against a two-dimensional power spectrum figure of merit to demonstrate improvement. We incorporate the new techniques into a deep integration of 32 hoursof MWA data. This data set is used to place a systematic-limited upper limit on the cosmological power spectrum of  D2.7 10 2 4 mK 2 at k = 0.27 h Mpc −1 and z = 7.1, consistent with other published limits, and a modest improvement (factor of 1.4) over previous MWA results. From this deep analysis, we have identified a list of improvements to be made to our EoR data analysis strategies. These improvements will be implemented in the future and detailed in upcoming publications.

-Detection of the cosmological neutral hydrogen signal from the Epoch of Reionization, and estimation of its basic physical parameters, is the principal scientific aim of many current lowfrequency radio telescopes. Here we describe the Cosmological HI Power Spectrum Estimator (CHIPS), an algorithm developed and implemented with data from the Murchison Widefield Array (MWA), to compute the two-dimensional and spherically-averaged power spectrum of brightness temperature fluctuations. The principal motivations for CHIPS are the application of realistic instrumental and foreground models to form the optimal estimator, thereby maximising the likelihood of unbiased signal estimation, and allowing a full covariant understanding of the outputs. CHIPS employs an inverse-covariance weighting of the data through the maximum likelihood estimator, thereby allowing use of the full parameter space for signal estimation ("foreground suppression"). We describe the motivation for the algorithm, implementation, application to real and simulated data, and early outputs. Upon application to a set of 3 hours of data, we set a 2σ upper limit on the EoR dimensionless power at k = 0.05 h.Mpc −1 of ∆ 2 k < 7.6×10 4 mK 2 in the redshift range z = [6.2 − 6.6], consistent with previous estimates.