Predictions for the CO Emission of Galaxies from a Coupled Simulation of Galaxy Formation and Photon Dominated Regions

Abstract

AbstractIn this Chapter, I present a hybrid model which combines the galaxy formation model GALFORM with the Photon Dominated Region code UCL \(_{-}\) PDR to study the emission from the rotational transitions of \(^{12}\mathrm{CO}\) (CO) in galaxies from \(z=0\) to \(z=6\). From the predicted H\(_2\) mass and the conditions in the interstellar medium, the CO emission in the rotational transitions 1-0 to 10-9 is estimated by applying the UCL \(_{-}\) PDR model to each galaxy. Deviations from the Milky-Way CO-H\(_2\) conversion factor come mainly from variations in metallicity, and in the average gas and star formation rate surface densities. In the local universe, the model predicts a CO\((\mathrm{{1}-{0}})\) luminosity function, CO-to-total infrared (IR) luminosity ratios for multiple CO lines and a CO spectral line energy distribution (SLED) which are in good agreement with observations of luminous and ultra-luminous IR galaxies. At high redshifts, the predicted CO SLED of the brightest IR galaxies reproduces the shape and normalisation of the observed CO SLED. The model predicts little evolution in the CO-to-IR luminosity ratio for different CO transitions, in good agreement with observations up to \(z\approx 5\). This new hybrid model is used to explore the potential of using colour selected samples of high-redshift star-forming galaxies to characterise the evolution of the cold gas mass in galaxies through observations with the Atacama Large Millimeter Array.KeywordsNormal Star-forming GalaxiesLyman-break Galaxies (LBGs)Ultra-luminous IR Galaxies (ULIRGs)Submillimeter Galaxies (SMGs)High Redshift GalaxiesThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.