Environment and Protostellar Evolution
  Even today in our Galaxy, stars form from gas cores in a variety of
environments, which may affect the properties of resulting star and planetary
systems. Here we study the role of pressure, parameterized via ambient clump
mass surface density, on protostellar evolution and appearance, focussing on
low-mass, Sun-like stars and considering a range of conditions from relatively
low pressure filaments in Taurus, to intermediate pressures of cluster-forming
clumps like the Orion Nebula Cluster (ONC), to very high pressures that may be
found in the densest Infrared Dark Clouds (IRDCs) or in the Galactic Center
(GC). We present unified analytic and numerical models for collapse of
prestellar cores, accretion disks, protostellar evolution and bipolar outflows,
coupled to radiative transfer (RT) calculations and a simple astrochemical
model to predict CO gas phase abundances. Prestellar cores in high pressure
environments are smaller and denser and thus collapse with higher accretion
rates and efficiencies, resulting in higher luminosity protostars with more
powerful outflows. The protostellar envelope is heated to warmer temperatures,
affecting infrared morphologies (and thus classification) and astrochemical
processes like CO depletion to dust grain ice mantles (and thus CO
morphologies). These results have general implications for star and planet
formation, especially via their effect on astrochemical and dust grain
evolution during infall to and through protostellar accretion disks.
