0 Assigned ID: 329 ----- Attempting Submission 1 (Fri Apr 11 02:13:20 GMT 2014) ----- HST Phase I Proposal 329 (sfh_dwarfs.apt) successfully submitted. ----- Attempting Submission 2 (Fri Apr 11 21:26:25 GMT 2014) ----- We propose to perform a suite of hydrodynamical simulations in order to understand the connection between dwarf galaxy star formation histories, stellar content, and central dark matter densities. This will leverage one of HST's unique and enduring scientific contributions, deep and uniform photometry of nearby dwarf galaxies that enables reconstructions of their ancient (z~6-10) star formation histories, to shed light on some of the main problems in galaxy formation and cosmology. Analysis of HST observations has definitively shown that dwarfs exhibit a surprising variety of star formation histories: some dwarfs host nearly purely ancient populations, while others have formed 90% of their stars after redshift 1. This diversity is unexpected in current theoretical models, which predict primarily old stellar populations in low-mass objects. The topic of star formation histories of dwarfs has also received significant attention recently in the context of possible small-scale problems of the LCDM model: if episodic bursts of star formation inject energy into dwarfs' dark matter halos, it may provide a natural explanation of the observed low densities of dwarf galaxies within LCDM. Our simulations will adopt physically-motivated, explicit feedback prescriptions that are fixed by our knowledge of stellar evolution. We will choose halos having diverse mass assembly histories within a narrow range of mass and compare their star formation histories to HST observations of nearby isolated dwarf galaxies, thereby testing fundamental aspects of galaxy formation modeling and dark matter astrophysics. Data from our simulations will be publicly released via a dedicated website. RESOLVED STELLAR POPULATIONS Default Medium false false false false true SUPPORTED