|Can AGN keep the gas in their host galaxies from becoming gravitationally bound and forming stars?
|The discovery of molecular outflows from AGN and starburst galaxies has been a major success of the Herschel Space Observatory and moved AGN feedback into the focus of Herschel science. However, feedback is more than winds, and observations of winds alone will only provide a limited picture of how AGN regulate star formation in galaxies. Recent observations suggest that gas-rich AGN host galaxies can have very low star-formation rates, up to 60 times less than expected for their gas surface densities. Why are these galaxies not forming stars? One possibility is that the injection of mechanical energy through the AGN is making the gas too turbulent to become gravitationally bound, to collapse and to form stars. Thus, star formation in AGN host galaxies may be regulated by fundamentally similar mechanisms as star formation in molecular clouds in the Milky Way and other .ordinary. galaxies. Here we propose to measure [CII]158 with PACS in 6 nearby galaxies with radio nuclei to test this hypothesis. We focus on galaxies with radio nuclei without strong star formation or quasar emission, because we wish to study the consequences of the rapid injection of mechanical energy through the AGN into the ISM. Radio-dominated AGN provide the cleanest environment for such a study because their UV radiation is faint, and we expect the shock contribution to dominate over that of UV heated star forming gas. However, many of our results can be cautiously extended to all types of mechanical interactions between AGN and gas. We will compare the [CII] line fluxes with those of warm H2 in the Spitzer archive. For highly turbulent gas that is not gravitationally bound, we expect the gas not to be well shielded, resulting in high [CII]-H2 ratios of 1-5. For the same reason, [CII] could also be an interesting tracer of low surface-brightness emission from winds. NIR imaging spectroscopy will serve as a benchmark to separate systemic line emi...ssion from putative wind components and to measure turbulent velocities in the CNM.
|Neon and [C II] 158 μm Emission Line Profiles in Dusty Starbursts and Active Galactic Nuclei . Samsonyan Anahit et al. . The Astrophysical Journal Supplement Series, Volume 226, Issue 1, article id. 11, 18 pp. (2016). . 226 . 10.3847/0067-0049/226/1/11 . 2016ApJS..226...11S ,
|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, OT2_nnesvadb_3, SPG v14.2.0. https://doi.org/10.5270/esa-0e7rjbo