How are black holes created?
What is their spin distribution?
What is the shape and location of the hot X-ray corona? We know it is compact (<10Rg, from microlensing) and parallel to the disc (from polarimetry). But how is it powered? In practical terms: what sets the LUV-LX relation? The relation can be reproduced with AGNSED models, but this requires the corona to change with the accretion rate. What is causing this? Why is the dependence with luminosity and not Eddington ratio, which is different to all other dependencies?
What is the shape and location of the “soft excess”? Is it the Comptonized disc? Why does the Comptonization radius depend on Eddington ratio but not luminosity?
How much central engine diversity is there, or do fundamental parameters (MBH, lam_edd) set the geometry? Broad line variability studies suggest there is geometric diversity.
What sets the LMIR-LX relation? Why do the X-rays become relatively X-ary weak at high luminosities? Why is there a tight relation to 6µm and 12µm instead of vast scatter? Is it because whenever the AGN is on, there is likely dust nearby?
Are all bolometric corrections Eddington-ratio dependent? Does the LUV-LX relation bend over at high luminosities? The LMIR-LX does, so it would make sense if the LUV-LX does as well. How does the fundamental plane of black hole activity (LX-Lrad-MBH) play along here?
What causes the covering factor to change with Eddington ratio, and why does this happen at different redshifts at different Eddington ratios? If the Eddington limit, modified to account for dust instead of just electron scattering, shapes the nuclear region (how exactly is it regulated? what is its shape? what is its distance?), then it is puzzling why this nuclear process should be limited differently at different redshifts. I suspect that instead, the regulation of the Eddington limit is due to the availability of gas, setting both covering factor and luminosity distribution. Like a small gas tank on a car with exponential hunger over time, the gas is unlikely to be full when power is at the maximum.
To think a bit more systematically, here are the eleven components:
- Black hole – MBH, lam_edd
- Hot corona
- Warm corona
- Accretion disc
- BLR
- Hot dust
- Cold torus
- Outflows (UFO, atomic, ionised, molecular)
- Nuclear attenuation
- Host stellar potential
- Galaxy attenuation
- Host star formation
1 is related to everything <8 by the Eddington ratio being important.
4 is related to everything as a power source.
are 2&3 related? lags perhaps suggest so.
5 may be influenced by 2&3 through over-ionisation.
6&7 is related to?
4 -> 8 -> 10 -> 12 is a key process, potentially with involvement of 3 and 9.
No funding agency cares about obscuration and the torus. Framing via fundamental black hole physics is essential.
Transients probe accretion processes in a unique way, but the fueling is different and may not be the same because of the magnetic field structure. How to stand out in 30 years of AGN research?
To test the empty fuel hypothesis, need SPHEREx + Euclid + eROSITA + SDSS-V.
To test geometry of corona, need eROSITA + SDSS-V.
To test co-evolution, need {eROSITA, NewAthena} + LS10 + Euclid + {SDSS-V,4MOST}.
Leave a Reply