The GUAPOS project II. A comprehensive study of peptide-like bond
  molecules
  Peptide-like bond molecules, which can take part to the formation of proteins
in a primitive Earth environment, have been detected up to now only towards a
few sources. We present a study of HNCO, HC(O)NH$_{2}$, CH$_{3}$NCO,
CH$_{3}$C(O)NH$_{2}$, CH$_{3}$NHCHO, CH$_{3}$CH$_{2}$NCO, NH$_{2}$C(O)NH$_{2}$,
NH$_{2}$C(O)CN, and HOCH$_{2}$C(O)NH$_{2}$ towards the hot core G31.41+0.31. We
have used the spectrum obtained from the ALMA 3mm spectral survey GUAPOS, with
an angular resolution of 1.2"$\times$1.2" ($\sim$4500 au), to derive column
densities of all the molecular species, together with other 0.2"$\times$0.2"
($\sim$750 au) ALMA observations to study the morphology of HNCO, HC(O)NH$_{2}$
and CH$_{3}$C(O)NH$_{2}$. We have detected HNCO, HC(O)NH$_{2}$, CH$_{3}$NCO,
CH$_{3}$C(O)NH$_{2}$, and CH$_{3}$NHCHO, for the first time all together
outside the Galactic center. We have obtained molecular fractional abundances
with respect to H$_{2}$ from 10$^{-7}$ down to a few 10$^{-9}$ and with respect
to CH$_{3}$OH from 10$^{-3}$ to $\sim$4$\times$10$^{-2}$. From the comparison
with other sources, we find that regions in an earlier stage of evolution, such
as pre-stellar cores, show abundances at least two orders of magnitude lower
than those in hot cores, hot corinos or shocked regions. Moreover, molecular
abundance ratios towards different sources are found to be consistent between
them within $\sim$1 order of magnitude, regardless of the physical properties
(e.g. different masses and luminosities), or the source position throughout the
Galaxy. New correlations between pairs of molecular abundances have also been
found. These results suggest that all these species are formed on grain
surfaces in early evolutionary stages of molecular clouds, and that they are
subsequently released back to the gas-phase through thermal desorption or
shock-triggered desorption.
