  We present spectrally and spatially-resolved maps of HNC and HC$_3$N emission
from Titan's atmosphere, obtained using the Atacama Large
Millimeter/submillimeter Array (ALMA) on 2013 November 17. These maps show
anisotropic spatial distributions for both molecules, with resolved emission
peaks in Titan's northern and southern hemispheres. The HC$_3$N maps indicate
enhanced concentrations of this molecule over the poles, consistent with
previous studies of Titan's photochemistry and atmospheric circulation.
Differences between the spectrally-integrated flux distributions of HNC and
HC$_3$N show that these species are not co-spatial. The observed spectral line
shapes are consistent with HNC being concentrated predominantly in the
mesosphere and above (at altitudes $z\gtrsim 400$ km), whereas HC$_3$N is
abundant at a broader range of altitudes ($z\approx70$-600 km). From spatial
variations in the HC$_3$N line profile, the locations of the HC$_3$N emission
peaks are shown to be variable as a function of altitude. The peaks in the
integrated emission from HNC and the line core (upper-atmosphere) component of
HC$_3$N (at $z\gtrsim300$ km) are found to be asymmetric with respect to
Titan's polar axis, indicating that the mesosphere may be more
longitudinally-variable than previously thought. The spatially-integrated HNC
and HC$_3$N spectra are modeled using the NEMESIS planetary atmosphere code and
the resulting best-fitting disk-averaged vertical mixing ratio (VMR) profiles
are found to be in reasonable agreement with previous measurements for these
species. Vertical column densities of the best-fitting gradient models for HNC
and HC$_3$N are $1.9\times10^{13}$ cm$^{-2}$ and $2.3\times10^{14}$ cm$^{-2}$,
respectively.
