5.1 Unified Model Flashcards
Describe the side view of an AGN
Two large kidney shaped toruses of dust/molecular gas feeding horizontally into narrow accretion disks onto a SMBH
SMBH has collimated jets shooting vertically
Also surrounded by a broad line region
What is a broad line region
Rapidly rotating very ionised gas around the SMBH
High rotational velocities = broad emission lines
What is a narrow line region
A region of ionised gas with slower rotation
Low rotation velocities = narrow emission lines
Describe what jets are, and what is a requirement for them to occur?
Outflows of material ejected at relativistic speeds, collimated by strong magnetic fields
- Require a high accretion rate
How does the accretion disk power an AGN?
The infalling material loses angular momentum due to collisions and energy dissipation
- Spirals towards the BH
Describe the torus of dust/gas surrounding the SMBH
It is optically thick
- Dust and molecular gas orbiting far away from the SMBH on the accretion disk plane
What is the type I / II dichotomy?
The presence of optical spectra with either broader or narrow emission lines
Describe how the unified model of AGN explains the type I /II dichotomy
Type I: Looking at SMBH above the torus of gas
- Unobstructed view of centre (broad region + BH)
Type II: Torus blocks view of centre
- Only narrow line regions are observed
Type I/II dichotomy is a consequence of viewing angle
How does the unified AGN model explain Blazers?
Blazers are AGN with strong x-ray emission and variability
- Looking directly at the relativistic beam emission of the SMBH
- Subject to shocks due to the outflow of material
How does the unified AGN model explain the radio quiet/radio loud AGN
It depends on the absence or presence of jets
- Which in turn depends on the level of accretion onto a BH
Explain a piece of evidence for confirmation of the AGN model
Observational data shifted from a broad emission type I spectrum to a narrow emission type II over 10 years
- Torus has blocked our view
Describe how polarised and unpolarised light confirmed the evidence for the AGN model
Unpolarised - Type II narrow emission
Polarised - Type I broad emission as this spectrum was reflected by the far side of the torus
