I've had a quick look at a few lecture pdfs and papers as supplementals to my own given lecture notes, but I can't seem to get a proper explanation for what cosmic downsizing is.

The closest explanation I have is that it is the lower population/size of large AGN or quasars in the current Universe when compared to high redshifted galactic observations.

How far off base am I?

  • 1
    $\begingroup$ Yes, basically it refers to the different evolution of faint and bright AGN with time. Have a look at Fanidakis+ 12. $\endgroup$
    – pela
    May 22, 2018 at 12:52

1 Answer 1


That is the exact definition. Galaxies in the universe today are smaller than they were in the past. There is no good explanation as to why this is the case.

The first hit in the Google search you linked too seems pretty clear on this definition.

  • $\begingroup$ Apologies if the question seemed redundant. Sometimes you get caught up in long paragraphs of mathematics and indecipherable theory and it is nice for people to talk to you about theorems in plain language. I did not mean to annoy you with the simplicity of the question. $\endgroup$ May 22, 2018 at 23:05

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