Molecular-Cloud-Scale Chemical Composition II: Mapping Spectral Line
  Survey toward W3(OH) in the 3 mm Band
  In order to study a molecular-cloud-scale chemical composition, we have
conducted a mapping spectral line survey toward the Galactic molecular cloud
W3(OH), which is one of the most active star forming regions in the Perseus
arm, with the NRO 45 m telescope. We have observed the area of 16' $\times$
16', which corresponds to 9.0 pc $\times$ 9.0 pc. The observed frequency ranges
are 87--91, 96--103, and 108--112 GHz. We have prepared the spectrum averaged
over the observed area, in which 8 molecular species CCH, HCN, HCO$^+$, HNC,
CS, SO, C$^{18}$O, and $^{13}$CO are identified. On the other hand, the
spectrum of the W3(OH) hot core observed at a 0.17 pc resolution shows the
lines of various molecules such as OCS, H$_2$CS CH$_3$CCH, and CH$_3$CN, in
addition to the above species. In the spatially averaged spectrum, emission of
the species concentrated just around the star-forming core such as CH$_3$OH and
HC$_3$N is fainter than in the hot core spectrum, whereas emission of the
species widely extended over the cloud such as CCH is relatively brighter. We
have classified the observed area into 5 subregions according to the integrated
intensity of $^{13}$CO, and have evaluated the contribution to the averaged
spectrum from each subregion. The CCH, HCN, HCO$^+$, and CS lines can be seen
even in the spectrum of the subregion with the lowest $^{13}$CO integrated
intensity range ($< 10$ K km s$^{-1}$). Thus, the contributions of the
spatially extended emission is confirmed to be dominant in the spatially
averaged spectrum.
