The Star-Forming Properties Of An Ultra-Hard X-ray Selected Sample Of AGN (speaker: Taro Shimizu, University Of Maryland)

Monday October 19, 2015 12:05 pm
Marlar Lounge (37-252)

I present new results on the relationship of star formation to active galactic nuclei (AGN) activity in an ultra-hard X-ray selected sample which show a significant difference in the star-forming properties of AGN hosts both in the star formation rate (SFR) and the location of the star formation. While the observed scaling relations between galaxies and the supermassive black holes (SMBH) they host as well as numerical simulations suggest a star formation AGN connection, popular methods for measuring the SFR of galaxies are routinely contaminated by emission related to the AGN. Further selection methods for constructing samples of AGN are often biased due to obscuration and host galaxy contributions. We selected over 300 AGN in the 14-195 keV energy range to be observed with the Herschel Space Observatory and study their star forming properties in the FIR( 70-500 μm) and allowing us to construct the most complete IR spectral energy distributions (SED) for a large, relatively unbiased sample of AGN. We used SED decomposition techniques to measure the dust temperatures, dust masses, SFR, and IR AGN fractions and compared them to non-AGN star-forming galaxies. The AGN host galaxies lie systematically below the main sequence of star formation primarily due to reduced levels of star formation. This is possibly the first direct indication of large scale AGN feedback affecting galaxies. The FIR morphology of AGN host galaxies are also more compact than normal star-forming galaxies which either suggests a large portion of the FIR originates from the AGN or star-formation primarily occurs near the nucleus. In our analysis a significant fraction of the emission at 70 μm can be associated with the AGN and any estimates of the SFR based on it are overestimated. Finally, I will discuss our measured SFR-AGN correlation and put it in context with the current understanding of galaxy and SMBH growth.

Talk Host:  Michael McDonald

additional information about Taro Shimizu