  The nearly edge-on galaxy NGC4945 is one of the closest galaxies where an AGN
and starburst coexist, and is one of the brightest sources at 100 keV. Near and
mid-infrared spectroscopy have shown very strong obscuration of its central
region, rivaled only in strength by some of the most deeply obscured ULIRGs. We
aim to determine the spatial distribution of ISM features in the central
426x426 pc^2 of NGC4945. We map the central region of NGC4945 in three
Spitzer-IRS modules (SH, SL and LL). We produce maps of the flux distribution
of the starburst tracers [Ne II], [Ne III], [S III] and [S IV] at 12.81, 15.56,
18.71 and 10.51 mum, respectively, and a map of the AGN narrow-line region
tracer [Ne V] at 14.32 mum. We also mapped the S(1), S(2) and S(3) pure
rotational lines of H2, which trace the distribution of warm molecular
hydrogen. We obtained an extinction map (A_V) based on the apparent strength of
the 9.7 mum silicate absorption feature. Our A_V map traces the contours of the
starburst ring but the highest extinction (A_V(9.85 mum)~60) is found at the
nucleus. Within the uncertainty of the astrometry all emission lines are found
to peak on the nucleus, except for the warm molecular hydrogen emission which
shows a maximum 60-100 pc NW of the nucleus. We favour a scenario in which the
lower H2 0-0 S(1) and S(2) rotational lines originate mainly from an unobscured
extra-nuclear component associated with the super-wind cone observed in the HST
NICMOS map of the H2 1-0 S(1) vibrational line. For the [Ne V] emission we
infer an attenuation of a factor 12-160 (A_V=55-112) based on a comparison of
the ratio of our [Ne V] flux and the absorption-corrected 14-195 keV Swift-BAT
flux to the average [Ne V]/BAT ratio for Seyfert 1 nuclei. The high attenuation
indicates that [Ne V] and [O IV] cannot be used as extinction-free tracers of
AGN power in galaxies with deeply buried nuclei.
