Chemical Diversity in Three Massive Young Stellar Objects associated
  with 6.7 GHz CH$_{3}$OH Masers
  We have carried out observations in the 42$-$46 and 82$-$103 GHz bands with
the Nobeyama 45-m radio telescope, and in the 338.2$-$339.2 and 348.45$-$349.45
GHz bands with the ASTE 10-m telescope toward three high-mass star-forming
regions containing massive young stellar objects (MYSOs), G12.89+0.49,
G16.86$-$2.16, and G28.28$-$0.36. We have detected HC$_{3}$N including its
$^{13}$C and D isotopologues, CH$_{3}$OH, CH$_{3}$CCH, and several complex
organic molecules (COMs). Combining our previous results of HC$_{5}$N in these
sources, we compare the $N$(HC$_{5}$N)/$N$(CH$_{3}$OH) ratios in the three
observed sources. The ratio in G28.28$-$0.36 is derived to be
$0.091^{+0.109}_{-0.039}$, which is higher than that in G12.89+0.49 by one
order of magnitude, and that in G16.86$-$2.16 by a factor of $\sim 5$. We
investigate the relationship between the $N$(HC$_{5}$N)/$N$(CH$_{3}$OH) ratio
and the $N$(CH$_{3}$CCH)/$N$(CH$_{3}$OH) ratio. The relationships of the two
column density ratios in G28.28$-$0.36 and G16.86$-$2.16 are similar to each
other, while HC$_{5}$N is less abundant when compared to CH$_{3}$CCH in
G12.89+0.49. These results imply a chemical diversity in the lukewarm ($T \sim
20-30$ K) envelope around MYSOs. Besides, several spectral lines from complex
organic molecules, including very-high-excitation energy lines, have been
detected toward G12.89+0.49, while the line density is significantly low in
G28.28$-$0.36. These results suggest that organic-poor MYSOs are surrounded by
a carbon-chain-rich lukewarm envelope (G28.28$-$0.36), while organic-rich
MYSOs, namely hot cores, are surrounded by a CH$_{3}$OH-rich lukewarm envelope
(G12.89+0.49 and G16.86$-$2.16).
