Other
Scientific paper
Jan 2011
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011aas...21723303a&link_type=abstract
American Astronomical Society, AAS Meeting #217, #233.03; Bulletin of the American Astronomical Society, Vol. 43, 2011
Other
Scientific paper
The observed phenomena of star formation (SF) and active galactic nuclei (AGN) have long been thought to be intimately linked, but to date the details of their connection have remained elusive. In recent years the Sloan Digital Sky Survey (SDSS) has provided very large samples of high quality galaxy spectra, allowing progress to be made in statistical analyses of the AGN/SF link. However, such analyses currently rely on measurements of particular emission line ratios and the Baldwin, Phillips & Terlevich (BPT) diagrams to classify objects as SF-dominated, AGN-dominated, or "composite". Such classifications do not produce complete samples of objects with SF or AGN, and are not sensitive to the low-level activity that may shed important light on the relationship between the different sources.
I will present a new technique, based on mean field independent component analysis, which allows the fractional contribution of AGN and SF to each object to be quantified. In doing so, we can classify objects based on direct measurements of their compositions, rather than the indirect BPT-based methods. We are able to disentangle the AGN and SF contributions to the "composite" region, that encompasses a large number of the objects observed by the SDSS. Additionally, low-level SF can be identified in AGN-dominated galaxies, and low-level AGN in SF-dominated galaxies. The technique can be applied to all galaxy spectra in the SDSS with the required spectral coverage, and readily extended to encompass other spectroscopic surveys. Together, these developments allow a new level of precision in the study of the link between AGN and SF.
JTA acknowledges the support of an STFC PhD studentship.
Allen James T.
Baldwin John
Ferland Gary
Hewett Paul C.
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