  Compact Obscured Nuclei (CONs) account for a significant fraction of the
population of luminous and ultraluminous infrared galaxies (LIRGs and ULIRGs).
These galaxy nuclei are compact, with radii of 10-100~pc, with large optical
depths at submm and far-infrared wavelengths, and characterized by
vibrationally excited HCN emission. It is not known what powers the large
luminosities of the CON host galaxies because of the extreme optical depths
towards their nuclei. CONs represent an extreme phase of nuclear growth, hiding
either a rapidly accreting supermassive black hole or an abnormal mode of star
formation. Here we apply principal component analysis (PCA) tomography to
high-resolution (0.06$^{\prime\prime}$) ALMA observations at frequencies 245 to
265~GHz of the nearby CON (59~Mpc) IC~860. PCA is a technique to unveil
correlation in the data parameter space, and we apply it to explore the
morphological and chemical properties of species in our dataset. The leading
principal components reveal morphological features in molecular emission that
suggest a rotating, infalling disk or envelope, and an outflow analogous to
those seen in Galactic protostars. One particular molecule of astrochemical
interest is methanimine (CH$_2$NH), a precursor to glycine, three transitions
of which have been detected towards IC 860. We estimate the average CH$_2$NH
column density towards the nucleus of IC~860 to be $\sim10^{17}$cm$^{-2}$, with
an abundance exceeding $10^{-8}$ relative to molecular hydrogen, using the
rotation diagram method and non-LTE radiative transfer models. This CH$_2$NH
abundance is consistent with those found in hot cores of molecular clouds in
the Milky Way. Our analysis suggests that CONs are an important stage of
chemical evolution in galaxies, that are chemically and morphologically similar
to Milky Way hot cores.
