Tracing the accretion history of supermassive Black Holes through X-ray variability: results from the Chandra Deep Field-South

Understand

We study the X-ray variability properties of distant AGNs in the Chandra Deep Field-South region over 17 years, up to $z\sim 4$, and compare them with those predicted by models based on local samples.

• We use the results of Monte Carlo simulations to account for the biases introduced by the discontinuous sampling and the low-count regime.
• We confirm that variability is an ubiquitous property of AGNs, with no clear dependence on the density of the environment.
• The variability properties of high-z AGNs, over different temporal timescales, are most consistent with a Power Spectral Density (PSD) described by a broken (or bending) power-law, similar to nearby AGNs.