Arecibo Molecular Line Search of Arp 220: The Discovery of Pre-Biotic Molecules E. Momjian, C. Salter, T. Ghosh, B. Catinella, M. Lebron, M. Lerner & R. Minchin (NAIC-Arecibo Observatory) ABSTRACT An on-going Arecibo line search between 1.1 and 10 GHz of the prototypical starburst/megamaser galaxy, Arp 220, has revealed a spectrum rich in molecular transitions. ... 6.7 GHz Methanol Absorption First detection in Arp 220 of the 4-cm excited OH transitions 2 1/2, J=3/2, F=1­1 and 2­2. ...

... 2.3 Data acquisition Spectra generated by the Multibeam correlator contain the usual structure seen in spectra from other H i instruments: a bandpass spectrum which is the sum of the sky , ground and receiver temperatures multiplied by the product of the filters in the receiver chain; superimposed on this is a noise ... Note also that sources extended much beyond ,40 arcmin can be imaged poorly in HIPASS images because of the bandpass sidelobe effect described in Section 3.3. ...