Abstract

The assembly of "normal" galaxies at z~7

Stefano Carniani (University of Cambridge, UK)

In studying the formation and assembly of protogalaxies in the early Universe (z>6) we are still concerned about the galaxies responsible for the end of the Dark Ages, that are expected to be primarily low mass galaxies with modest star formation rates (< 10 Msun/yr). We will present deep ALMA observations targeting the [CII]158um and [OIII]88um line in a spectroscopically confirmed Lyman Break Galaxy at z~7.1 with SFR~7 Msun/yr. We detected [CII] and [OIII] emission fully consistent with Ly-alpha redshift, but spatially offset by 0.7" (~ 4 kpc) from the optical emission and displaced [CII] and [OIII] emission are also visible in recent studies of star-forming galaxies at z>5. These results suggest that the molecular clouds in the central parts of primordial galaxies are rapidaly distrupted by stellar feedback, resulting in [CII] and [OIII] emission mostly arising from more external accreting/satellite clumps of neutral gas. Some of these clumps reveal star-formation in situ that are not visible in the deepest HST near-IR images and only JWST will allow the identification of counterparts for these FIR-line emitters leading to an in-depth study on their properties.

Talk