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Today's Colloquium: Chasing AGN at z>1: a New IR Diagnostic

Submitter: Karina Caputi (Univ. of Groningen)
Description: The observed local correlation between black-hole masses and galaxy bulge masses suggests that nuclear and star formation activity should have been related at some point in the past. Investigating the incidence of AGN among high-redshift galaxies is then crucial to understand whether this idea is actually correct. X-ray data are excellent to reveal the AGN presence, but some highly obscured AGN, or low-luminosity AGN, can be undetected even in typically deep X-ray maps. Searching for a hot-dust component at IR wavelengths offers a powerful alternative to investigate the AGN presence. In this talk I will present a new diagnostic to unveil the presence of AGN in galaxies at z>1, which is especially efficient in the redshift range 1.0 80 microJy, all with secure spectroscopic redshifts zspec>1. I will also show an independent analysis of the AGN presence in these sources performed with a combination of ultra-deep X-ray images, host galaxy morphologies, and modelled dust temperatures. As a conclusion, I will argue that my results indicate that between ~30% and ~50% of IR sources contain an AGN at 1.0
Copyright: Karina Caputi
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