Gas Flows and Rapid Metal Enrichment in AGN

Grants and Contracts Details


Gas Flows and Rapid Metal Enrichment in AGN. Intellectual Merit. AGN emission lines offer great opportunities for quantitatively understanding accretion processes and fast chemical enrichment related to the formation and evolution of massive black holes. However, the emission lines come from very complex, unresolved structures, so progress has been frustratingly slow. There is now an exciting new round of discovery in this field, driven by the advent of massive spectroscopic surveys such as SDSS. Progress will accelerate as even larger surveys are done. These have revealed new correlations between observable properties, which in principle carry the heretofore-missing information about the detailed nature of the gas flows associated with the AGN process. We are now working our way through the next step, which is to separate physically meaningful correlations from ones that are just mathematical noise. A common approach has been to use Principal Component Analysis (PCA), but this tends to produce eigenvectors that in fact do not carry clear physical meaning. Our team is currently adapting a much more powerful technique, Independent Component Analysis (ICA), to apply to astronomical spectra. The step after that is to connect these spectroscopic measurements back to the physical nature of the emitting gas, and from there back to the overall nature of the AGN. Our first results with ICA, as well as results from older methods, are showing that previous analysis efforts have left out key physical processes, including some that govern the emission from Fe II and other ions with complex energy-level structures. The effect of the beaming of emission lines by optically thick clouds and the role that radiation pressure plays in the cloud stability must be reconsidered. I propose here to carry out key improvements needed in the spectral simulation code Cloudy so that we can properly interpret the ICA results, and then to carry out that analysis. Broader Impacts. The work described in this proposal will have broader impacts upon society in two different ways. First it will support the enhancement of the physics and infrastructure in the spectral simulation code Cloudy. Cloudy is among the more commonly used theory codes in astrophysics. Roughly 200 papers, including many that were parts of graduate student theses, cite the code’s documentation each year. This community use is possible because, by doing ab initio simulations of the atomic and molecular processes leading to the formation of the spectrum, Cloudy can be applied to environments that are macroscopically very different. Both the code and its documentation are freely available on the web. The improvements proposed here will make the code even more valuable to its large body of users. The second impact is in public outreach and STEM education, with an emphasis on making the sciences welcoming to women and minorities. These are driven by our recent construction of a student observatory located on central campus. It is the center of a broad program seeking to promote science education and the physical sciences in the Bluegrass of Kentucky.
Effective start/end date8/15/111/31/16


  • National Science Foundation: $442,361.00


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