No evolution was found in the ratio FeII/MgII; however, since the FeII bump is a strong BLR coolant, its strength depends on several other parameters and may not depend primarily on the iron abundance.
Indeed, according to many models, during the early phases, when the host galaxy is still metal poor, the accreting black hole is embedded within the dusty ISM, and therefore difficult to detect in optical surveys. Only during the late evolutionary phases, when the galaxy is already metal rich, the quasar develops winds powerful enough to expel large quantities of gas and dust, so that the quasar becomes visible to optical observations.
Also, sometimes I wish research papers were threaded like a giant forum so I could see which papers are rebuttals or confirmations of which other papers. I'd like to know how people end up addressing the "carbon problem" :)
It certainly would be nice to have the kind of system that you asked, even if one can find the relevant papers relatively easily. It would make things easy. But hey, isn't there a nice and useful subject for a website...
Powered by mwForum 2.15.0 © 1999-2008 Markus Wichitill