2017ApJ...848...17N

To study a molecular-cloud-scale chemical composition, we 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. We conducted our survey through the use of the Nobeyama Radio Observatory 45 m telescope, and observed the area of 16' x 16', which corresponds to 9.0 pc x 9.0 pc. The observed frequency ranges are 87-91, 96-103, and 108-112 GHz. We prepared the spectrum averaged over the observed area, in which eight molecular species (CCH, HCN, HCO⁺, HNC, CS, SO, C¹⁸O, and ¹³CO) 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, H₂CS CH₃CCH, and CH₃CN in addition to the above species. In the spatially averaged spectrum, emission of the species concentrated just around the star-forming core, such as CH₃OH and HC₃N, 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 classified the observed area into five subregions according to the integrated intensity of ¹³CO, and 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 ¹³CO 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.