A view of Large Magellanic Cloud HII regions N159, N132, and N166
  through the 345 GHz window
  We present results obtained towards the HII regions N159, N166, and N132 from
the emission of several molecular lines in the 345 GHz window. Using ASTE we
mapped a 2.4' $\times$ 2.4' region towards the molecular cloud N159-W in the
$^{13}$CO J=3-2 line and observed several molecular lines at an IR peak very
close to a massive young stellar object. $^{12}$CO and $^{13}$CO J=3-2 were
observed towards two positions in N166 and one position in N132. The $^{13}$CO
J=3-2 map of the N159-W cloud shows that the molecular peak is shifted
southwest compared to the peak of the IR emission. Towards the IR peak we
detected emission from HCN, HNC, HCO$^{+}$, C$_{2}$H J=4-3, CS J=7-6, and
tentatively C$^{18}$O J=3-2. This is the first reported detection of these
molecular lines in N159-W. The analysis of the C$_{2}$H line yields more
evidence supporting that the chemistry involving this molecular species in
compact and/or UCHII regions in the LMC should be similar to that in Galactic
ones. A non-LTE study of the CO emission suggests the presence of both cool and
warm gas in the analysed region. The same analysis for the CS, HCO$^{+}$, HCN,
and HNC shows that it is very likely that their emissions arise mainly from
warm gas with a density between $5 \times 10^5$ to some $10^6$ cm$^{-3}$. The
obtained HCN/HNC abundance ratio greater than 1 is compatible with warm gas and
with an star-forming scenario. From the analysis of the molecular lines
observed towards N132 and N166 we propose that both regions should have similar
physical conditions, with densities of about 10$^3$ cm$^{-3}$.
