Context : The M16 nebula is a relatively nearby Hii region , powered by O stars from the open cluster NGC 6611 , which borders to a Giant Molecular Cloud .
Radiation from these hot stars has sculpted columns of dense obscuring material on a few arcmin scales .
The interface between these pillars and the hot ionised medium provides a textbook example of a Photodissociation Region ( PDR ) .

Aims : To constrain the physical conditions of the atomic and molecular material with submillimeter spectroscopic observations .

Methods : We used the APEX submillimeter telescope to map a \sim 3 ^ { \prime } \times 3 ^ { \prime } region in the CO J = 3–2 , 4–3 and 7–6 rotational lines , and a subregion in atomic carbon lines .
We also observed C ^ { 18 } O ( 3–2 ) and CO ( 7–6 ) with longer integrations on five peaks found in the CO ( 3–2 ) map .
The large scale structure of the pillars is derived from the molecular lines ’ emission distribution .
We estimate the magnitude of the velocity gradient at the tips of the pillars and use LVG modelling to constrain their densities and temperatures .
Excitation temperatures and carbon column densities are derived from the atomic carbon lines .

Results : The atomic carbon lines are optically thin and excitation temperatures are of order 60 K to 100 K , well consistent with observations of other Hii region-molecular cloud interfaces .
We derive somewhat lower temperatures from the CO line ratios , of order 40 K. The Ci /CO ratio is around 0.1 at the fingers tips .

Conclusions :