FEEDBACK: a SOFIA Legacy Program to Study Stellar Feedback in Regions of
  Massive Star Formation
  FEEDBACK is a SOFIA legacy program dedicated to study the interaction of
massive stars with their environment. It performs a survey of 11 galactic high
mass star forming regions in the 158 $\mu$m (1.9 THz) line of CII and the 63
$\mu$m (4.7 THz) line of OI. We employ the 14 pixel LFA and 7 pixel HFA upGREAT
instrument to spectrally resolve (0.24 MHz) these FIR structure lines. With an
observing time of 96h, we will cover $\sim$6700 arcmin$^2$ at 14.1$''$ angular
resolution for the CII line and 6.3$''$ for the OI line. The observations
started in spring 2019 (Cycle 7). Our aim is to understand the dynamics in
regions dominated by different feedback processes from massive stars such as
stellar winds, thermal expansion, and radiation pressure, and to quantify the
mechanical energy injection and radiative heating efficiency. The CII line
provides the kinematics of the gas and is one of the dominant cooling lines of
gas for low to moderate densities and UV fields. The OI line traces warm and
high-density gas, excited in photodissociations regions with a strong UV field
or by shocks. The source sample spans a broad range in stellar characteristics
from single OB stars, to small groups of O stars, to rich young stellar
clusters, to ministarburst complexes. It contains well-known targets such as
Aquila, the Cygnus X region, M16, M17, NGC7538, NGC6334, Vela, and W43 as well
as a selection of HII region bubbles, namely RCW49, RCW79, and RCW120. These
CII maps, together with the less explored OI 63 $\mu$m line, provide an
outstanding database for the community. They will be made publically available
and will trigger further studies and follow-up observations.
