Science in the Media
Session 2: A New Discovery

The following is an email excerpt from one NASA astronomer to another:

Date: Thu, 19 Jul 2007 16:07:22
From: Edwin Hubble
To: Arthur Clarke
Subject: Swift and Suzaku discover something new about AGN

Hi Art,

Late last night, the Suzaku and Swift astronomers released some preliminary findings that I think you will find very interesting. I have copied what they sent out. Let me know what you think.

Consensus is emerging that almost all large galaxies have a supermassive black hole at its center, a fraction of which are accreting, making them active galactic nuclei (AGN). AGN are broadly classified into Type I (AGN direct viewed with little absorption) and Type II (heavy line-of-sight absorption, AGN seen predominantly via scattered light). Suzaku observations show that two galaxies detected in the Swift/ BAT (hard X-ray, >keV, survey) to be neither. These are highly absorbed AGN, like traditional Type IIs, but show little sign of scattered light (hence missed by pervious surveys). This discovery may force a re-evaluation of the number of AGN in the local universe. Suzaku follow-up observations of newly discovered (with INTEGRAL or Swift/ BAT) hard X-ray sources are a highly effective method to evaluate the population of such highly absorbed AGN with little scattering.

—Ed





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