  AIMS Our aim is to characterize the size, mass, density and temperature
profiles of the protostellar envelope of HH~46 IRS 1 and its surrounding cloud
material as well as the effect the outflow has on its environment.METHODS The
CHAMP+ and LABOCA arrays on the APEX telescope, combined with lower frequency
line receivers, are used to obtain a large continuum map and smaller heterodyne
maps in various isotopologues of CO and HCO+. The high-J lines of CO (6--5 and
7--6) and its isotopologues together with [C I] 2--1, observed with CHAMP+, are
used to probe the warm molecular gas in the inner few hundred AU and in the
outflowing gas. The data are interpreted with continuum and line radiative
transfer models. RESULTS Broad outflow wings are seen in CO low- and high-J
lines at several positions, constraining the gas temperatures to a constant
value of ~100 K along the red outflow axis and to ~60 K for the blue outflow.
The derived outflow mass is of order 0.4--0.8 M_sol, significantly higher than
previously found. The bulk of the strong high-J CO line emission has a
surprisingly narrow width, however, even at outflow positions. These lines
cannot be fit by a passively heated model of the HH 46 IRS envelope. We propose
that it originates from photon heating of the outflow cavity walls by
ultraviolet photons originating in outflow shocks and the accretion disk
boundary layers. At the position of the bow shock itself, the UV photons are
energetic enough to dissociate CO. The envelope mass of ~5 M_sol is strongly
concentrated towards HH 46 IRS with a density power law of -1.8.
