Colloquium on 15 August 2013
The Equilibrium Model for Galaxy Evolution


Title: The Equilibrium Model for Galaxy Evolution
Speaker: Romeel Davé (SAAO/UWC/AIMS)
Date: Thursday, 15 August 2013
Time: 16:00 - 17:00
Venue: SAAO Auditorium


I will present a new analytic formalism for the evolution of the stellar, gaseous, and metal content of galaxies. It is based on the idea, inspired by state-of-the-art cosmological hydrodynamic simulations, that galaxies live in a slowly-evolving equilibrium between inflows, outflows, and star formation. The critical parameters in this formalism describe ejective feedback (outflows), preventive feedback (retardation of inflows), and wind recycling (return of ejected material). I will illustrate some straightforward predictions of this model, such as the evolution of the specific star formation rates and the second-parameter dependence of the mass-metallicity relation on star formation, that are broadly in agreement with observations. I will highlight areas where the intuition provided by this scenario for the origin of global galaxy properties differs substantially from canonical views. At its core, the equilibrium model intimately connects galaxies and their surrounding gas in a cycle of baryons that is centrally responsible for governing galaxy growth, and hence suggests that improving observations of gas in and around galaxies is the key to understanding galaxy evolution. If time permits I will present early results from a large Hubble program to do so.

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