We interpret the fact that we saw more AGNs in the past than we do today to indicate that:
A) there were fewer galaxy-galaxy interactions in the past
B) there were more galaxy-galaxy interactions in the past
C) supermassive black holes were larger in the past
D) today's AGNs are primarily hidden by large amounts of cold gas and dust
E) AGNs had bigger central black holes in the past

Question

Quizplus · Accepted Answer

AGNs are powered by accretion of material onto supermassive black holes at the center of galaxies. Galaxy-galaxy interactions can trigger the inflow of gas towards the center and increase the accretion rate onto the central black hole. Therefore, more galaxy-galaxy interactions in the past could have led to a higher incidence of AGNs.

We Interpret the Fact That We Saw More AGNs in the Past