Quasar Evolution and Fuelling Problem

Quasar evolution and the quasar fuelling problem are interrelated. This thread starts with some back ground to put the theoretical discussions in context and then will, once there is agreement on what is stated in background, provide a link to some of the new papers and observations concerning this subject.

"One Shot" Quasar Theory
There is a theory that every galaxy is active, for a short period, 10 million to 100 million years, when its super massive black hole rapidly grows. The “quasar period” of a galaxy is a 10MM to 100MM year time period when the galaxy in question produces the broad line spectrum of a “quasar”.

10 million to 100 million years is fairly short as compared to the life time of a galaxy and the universe. The "one shot" quasar theory postulates that there is a mechanism(s) that can abruptly end the quasar period of super massive black hole formation and high luminosity.

Quasar Space Density Evolution
There are no observed quasars in the current universe z=0. Moving back in time, the number of observed quasars continues to increase until it reaches a maximum around z=2.5, roughly 11 billion years in the past. The quasar "one shot" theory explains that observation, by postulating that the conditions for turning on the “quasar” period of galaxy formation were optimum 11 billion years ago.

Beyond 11 billion years ago, the number of quasars abruptly drops. The "one shot" quasar theory explains this observation as a reduction in quasar formation favourability, for the time period big bang to 11 billion years ago.

Quasar Luminosity Evolution
Observationally there is a second complication, for any quasar theory. When moving back in time the quasar average luminosity for the quasars’ “on period”, increases exponentially up to around z=2.5 and then increases at even a higher rate to the highest observed redshift quasars z=7.5.

The theories to explain the quasar luminosity evolution and quasar space density evolution are still under development. There is no current theory that can explain the full period of quasar space density evolution and luminosity evolution.

One possible mechanism to explain the increase in average quasar luminosity, as one moves back in time, is that there is an increase in the average super massive black hole mass, for the quasar “on period” as one moves back in time.

Following that hypothesis the super massive black holes for the galaxies that turned on at z=2.5 (11 billion years ago) would be more massive that the super massive black holes that turn on at z=0.5. (5 billion years in the past.) The increase in super black hole mass hypothesis, does not explain the sharp increase in quasar luminosity from z=2.5. Also quantitative analysis has indicated that a postulated increase in super massive black hole mass does not have sufficient mechanism range ability to explain the observed quasar luminosity evolution.

It is therefore necessary to add a mechanism that would enable, when the quasar turns on, to have an increase in the rate of growth of the super massive black hole, for the on time period. A quasar 4 billion years ago would therefore grow slower than a quasar 11 billion years ago. Note there still needs to be a mechanism that would limit the quasar 4 billion years ago’s on period to around 10 MM years, to explain the evolution of quasar space density.


Comment:
Translating redshift “z” to time period was done using Ned Wright's cosmo calculate (Assumed a flat universe.)

http://www.astro.ucla.edu/%7Ewright/CosmoCalc.html