  We are presenting here a follow-up study of the molecular gas and dust in the
environs of the star forming region NGC 3503. This study aims at dealing with
the interaction of NGC 3503 with its parental molecular cloud, and also with
the star formation in the region. To analyze the molecular gas we use CO(2-1),
13CO(2-1), C18O(2-1), and HCN(3-2) line data obtained with the APEX telescope.
To study the distribution of the dust, we make use of images at 870 microns
from the ATLASGAL survey and IRAC-GLIMPSE archival images. We use public 2MASS
and WISE data to search for candidate YSOs in the region. The new APEX
observations allowed the substructure of the molecular gas in the velocity
range from -28 to -23 km/s to be imaged in detail. The morphology of the
molecular gas close to the nebula, the location of the PDR, and the shape of
radio continuum emission suggest that the ionized gas is expanding against its
parental cloud, and confirm the "champagne flow" scenario. We have identified
several molecular clumps and determined some of their physical and dynamical
properties. We have compared the physical properties of the clumps to
investigate how the molecular gas has been affected by the HII region. Clumps
adjacent to the ionization fronts of NGC 3503 and/or the bright rimmed cloud
SFO62 have been heated and compressed by the ionized gas, but their line width
is not different to those that are too distant to the ionization fronts. We
identified several candidate YSOs in the region. Their spatial distribution
suggests that stellar formation might have been boosted by the expansion of the
nebula. We discard the "collect and collapse" scenario and propose alternative
mechanisms such as radiatively driven implosion on pre-existing molecular
clumps or small-scale Jeans gravitational instabilities.
