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How black holes accrete

Event Details

Event Dates: 

Friday, March 15, 2013 - 12:00pm

Seminar Location: 

  • CASA Conference Room C324

Speaker Name(s): 

Chris Nixon

Speaker Affiliation(s): 

Seminar Type/Subject

Scientific Seminar Type: 

  • Astrophysics Lunch Seminar

Event Details & Abstract: 

Supermassive black holes (SMBH) reside at the centre of almost all galaxies. There is a vast difference in scale-length between an SMBH and its host galaxy - about 10 orders of magnitude. Galaxies are naturally chaotic places where for example star formation, supernovae and AGN provide random energy and momentum feedback into the surrounding gas. This suggests that accretion on to an SMBH is chaotic, occurring through depositions of gas with random orientations. Therefore retrograde accretion discs are possible, indeed likely. Retrograde accretion is a natural method for keeping the spin of the SMBH low, allowing efficient growth. Accretion discs inclined to the SMBH spin are torn up by the Lense-Thirring effect, significantly enhancing accretion rates from the standard picture of slow viscous accretion. Retrograde accretion can also help to merge an SMBH binary and therefore provide a possible solution to the last parsec problem.