The hierarchy of structure in the early Universe and its role in the formation, growth and suppression of galaxies as traced with KMOS

• Applicant: Dr. David Wilman
• Subject Area: Astrophysics and Astronomy
• Term: from 2012 to 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 209829205

In the dense cores of gravitationally collapsed halos, gas cools, stars form, and galaxies are born. Most stars appear to form in disks,conserving the angular momentum of the accreting gas. Just a few Gigayears after the big bang, the formation of stars and galaxies was at its peak, with most stars forming in turbulent disks, conserving the angular momentum of the accreting gas. The growth of each galaxy and its disk (in mass and size) must relate to the rate of gas accretion and its angular momentum, and thus to the source of the gas: the galaxy's environment. Our DFG previous project and associated 75 night VLT-KMOS program KMOS3D project provides mapping of the Halpha+[NII] emission line complex (tracing newly formed stars) in ~600-800 mass-selected galaxies at the epoch of peak galaxy formation (z=0.7-2.8). The time invested in the project combined with the unique efficiency of KMOS, simultaneously targeting 24 galaxies for spectral mapping in the near-infrared, mean that we are uniquely able to map star formation even in galaxies with low star formation rates. Combined with HST images of our targets, we have thence derived radial profiles in Halpha (tracing star formation) and continuum (tracing older stars), the former with unprecedented depth.We have accurately derived and calibrated measures of our galaxies' environments, never before achieved at these high redshifts and taking full advantage of the impressive coverage in our target fields especially of the underlying 3dHST survey from which KMOS3D targets are selected. This provides the necessary tools to examine how galaxy growth is affected by the conditions of its environment.This will allow us to fully exploit the complete dataset and all the methods and dataproducts developed by us and our collaborators. Moreover, we are in an unrivaled position to accurately quantify size and morphology (1D and 2D) for both KMOS3D galaxies and our extensive local comparison samples HAGGIS and Ha3. The dominant mode of recent galaxy evolution has been the quenching of star formation, mostly affecting massive galaxies and the satellites of massive halos. A detailed comparison with the local Universe means we can trace both growth and quenching of star formation in galaxies and their disks over 85% of cosmic time and a wide range of environments. We will also capitalize on the analysis of KMOS3D galaxy dynamics to spatially resolve the formation of rotationally supported disks, and to constrain the joint influences of AGN-driven outflows and environmental effects on the quenching of star formation. Finally we will put our results in a physical context by comparing with semi-analytical and hydrodynamical models of galaxy formation.

• DFG Programme: Research Grants