The evolution of galaxies from primeval irregulars to present-day ellipticals

Masao Mori (Senshu University/UCLA) and Masayuki Umemura (University of Tsukuba)
Nature, 640, 440 (2006) (astro-ph/0512424)

Galaxy formation is believed to proceed in a `bottom up' manner, starting with the formation of small clumps of gas and stars that then merge hierarchically into giant systems. The baryonic gas loses thermal energy by radiative cooling and falls towards the centres of the new galaxies, while supernovae blow gas out. Any realistic model therefore requires a proper treatment of these processes, but hitherto this has been far from satisfactory. Here we report a simulation that follows evolution from the earliest stages of galaxy formation through the period of dynamical relaxation, at which point the resulting galaxy is in its final form. The bubble structures of gas revealed in our simulation (for times of less than 3 x 108years) resemble closely high-redshift Lyman-alpha emitters. After 109years, these bodies are dominated by stellar continuum radiation and then resemble the Lyman break galaxies, which are high-redshift star-forming galaxies. At this point, the abundance of elements heavier than helium (`metallicity') appears to be solar. After 1.3 x 1010years, these galaxies resemble present-day ellipticals.
Supplementary Information: Methods (PDF, 207KB) In this Supplementary Information, we describe the initial condition of the present model and our dynamical, chemical, and spectrophotometric scheme to explore the formation and evolution of elliptical galaxies including star formation and supernova feedback.
Supplementary Information: Movie (MPEG, 12.9 MB) This animation visualizes the logarithmic gas density distribution of the simulated galaxy. Simulation box has a physical size of 134 kpc and the number density ranges from 10-4 cm-3 (red) to 1 cm-3 (blue).

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