1. Black Holes and Accretion: Observational Frontiers
X-ray Spectra of Active Galactic Nuclei: Inner Disc or an Obscuring Veil?
Black Holes and Accretion: Observational Frontiers
Dom Walton
NASA Postdoctoral Fellow
JPL/Caltech
Hi! Its my pleasure to be here to tell you about my work on the observational side of BH research.
Dom Walton
H51

2. Black Holes and Spin Fully defined by: Mass, M Spin, a
(angular momentum , -1 < a < 1)
Cygnus A
(radio)
Relativistic Jets:
Powered by black hole spin?
Quick fact about black holes, they’re fully defined by mass and spin (angular momentum)
One other cool thing we know some black holes do is launch relativistic jets.
We don’t really know how these are launched, but one popular idea is that they’re powered by BH spin.
Can use the same tools to study both problems!
Host galaxy scale
Walton 4

3. Many minor accretion events
Supermassive Black Hole Growth
Major
accretion events
High
Spin
Supermassive black hole spin is of particular importance, as the SMBH spin distribution carries rare information about their growth history
Major mergers -> spin up, minor mergers -> spin down.
The current sample of 20 SMBH spin measurements is not yet sufficient to probe the intrinsic spin distribution; expanding this sample is one of the main goals I have for this fellowship.
Used to test things like cosmological galaxy formation simulations
Many minor accretion events
Low
Spin

4. Innermost Stable Circular Orbit BH spin
Relativistic Disc Reflection
Fe Kα (= X-rays)
Explain physics of line broadening
Broader the line, the higher the spin!
Innermost Stable Circular Orbit BH spin
Walton 7

5. Relativistic Iron Lines
NGC3783
Occasionally you get supermassive black holes with clean spectra, but more typically you have absorption by intervening material.
NGC1365 is one such example, and changes in this absorption lead to wild changes in the X-ray spectrum at ~2 keV
With broadband X-ray coverage you can accurately model this out, and still robustly measure BH spin
MCG
NGC1365

6. A Partially-Ionised Veil?
Talk about reflection vs absorption degeneracy here

7. A Partially-Ionised Veil?
Talk about reflection vs absorption degeneracy here

8. Relativisic disc reflection? Complex, partially-ionised absorption?
The Essay
Relativisic disc reflection?
Complex, partially-ionised absorption?
The aim for this essay is to consider and compare the observational evidence for each of these interpretations for the broad iron features observed in the X-ray spectra of AGN
Explain physics of line broadening
Broader the line, the higher the spin!