  The importance of the physical environment in the evolution of newly formed
low-mass stars remains an open question. In particular, radiation from nearby
more massive stars may affect both the physical and chemical structure of these
kinds of young stars. Aims: To constrain the physical characteristics of a
group of embedded low-mass protostars in Corona Australis in the vicinity of
the young luminous Herbig Be star R CrA. Methods: Millimetre wavelength maps of
molecular line and continuum emission towards the low-mass star forming region
IRS7 near R CrA from the SMA and APEX are presented. The maps show the
distribution of 18 lines from 7 species (H2CO, CH3OH, HC3N, c-C3H2, HCN, CN and
SiO) on scales from 3" to 60" (400-8000 AU). Using a set of H2CO lines, we
estimate the temperatures and column densities in the region using LTE and
non-LTE methods. The results are compared with 1-D radiative transfer modelling
of the protostellar cores. These models constrain which properties of the
central source, envelope, and environment can give rise to the observed line
and continuum emission. Results: Most of the H2CO emission from the regions
emerges from two elongated narrow ridges dominating the emission picked up in
both interferometric and single-dish measurements. The temperatures inferred
from the H2CO lines are no less than ~30 K and more likely 50-60 K, and the
line emission peaks are offset by ~2500 AU from the location of the embedded
protostars. The temperatures can not be explained by the heating from the young
stellar objects themselves. Irradiation by the nearby Herbig Be star R CrA
could, however, explain the high temperatures. The elevated temperatures can in
turn impact the physical and chemical characteristics of protostars and lead to
enhanced abundances of typical tracers of photon dominated regions seen in
single-dish line surveys of embedded protostars in the region.
