|Characterizing the Molecular Outflow in Arp 220
|Observations of massive molecular outflows in galaxies can significantly improve our understanding of the connection between AGN-starbursts-feedback and galaxy evolution. It is believed that the energy injection from an AGN or starbursts can quench star formation by expelling the molecular gas out of the galaxy, transforming gas-rich blue galaxies to gas-poor red galaxies. However, the evidence for massive molecular outflows had been missing, until recently, when it was discovered in Mrk231 and NGC1266. We detected a massive molecular outflow in Arp 220 from the FTS spectrum that was observed as a part of the Very Nearby Galaxy Survey GT key project. The signature of a molecular outflow was seen in the P-Cygni profiles of OH+, H2O+ and H2O -- major molecules involved in the ion-neutral chemistry producing water in the ISM. This outflow can be driven by a hidden AGN or starburst activity in Arp 220. Because FTS could not fully resolve this outflow we were only able to provide a lower limit on the mass of the outflow and an upper limit on the velocity. To properly characterize this outflow we propose to use HIFI to fully resolve the P-Cygni line profile so that we can estimate the outflow velocity and mass with higher accuracy. We choose to observe the OH+ 972 GHz P-Cygni line profile, which is about 1000 km-s wide. To completely cover this feature and still have enough continuum to obtain a good baseline subtraction, we propose to observe it over two frequency tunings. In 2.35 hrs per frequency tuning, we will obtain a S-N of about 10 and 5 per 20 km-s resolution bin in the absorption dip and the emission peak, respectively. The total time for the entire observation is 4.7 hrs. Herschel is the only submillimeter facility that is capable of doing this observation.
|Herschel was launched on 14 May 2009! It is the fourth 'cornerstone' mission in the ESA science programme. With a 3.5 m Cassegrain telescope it is the largest space telescope ever launched. It is performing photometry and spectroscopy in approximately the 55-671 µm range, bridging the gap between earlier infrared space missions and groundbased facilities.
|Publisher And Registrant
|European Space Agency
|European Space Agency, 2013, GT2_nrangwal_2, SPG v14.1.0. https://doi.org/10.5270/esa-7ixn257