Abstract

The Local Deep Field

Dan Weisz (UC Berkeley)

I will illustrate the fundamental connection between the stellar fossil record of Local Group (LG) dwarf galaxies and the properties of the faintest high-redshift galaxies imaged in the Hubble and JWST Deep Fields. Using star formation histories measured from the stellar fossil record as revealed by HST imaging, I will show that (i) the ancestors of LG galaxies such as Fornax and Leo A were the likely drivers of cosmic reionization, while even fainter systems such as Leo T and Hercules, were its victims; and (ii) the steep slope of the faint end of the UV luminosity function at z~7 inferred from high-redshift observations over-predicts local galaxy counts by a factor of ~10. Reconciling this tension requires a break in the slope at M_UV(z~7)=-13. Continued HST and JWST imaging of the stellar fossil record of nearby dwarf galaxies will provide unique insight into the relationship between galaxies and cosmic reionization at low-masses and faint magnitudes that are otherwise impossible to directly observe with HST and JWST in the distant Universe. This “Local Deep Field” science is thus highly complementary to ongoing and planned deep field surveys with HST and JWST.

Talk