An AGN HR diagram? astro-ph/0201089

[Andrzej Marecki]

> A key to understanding AGN?

No, I don't think it's a "key" to understanding AGNs at all;
unification of AGNs - that's the most important key to understand them.

Just have a look at Fig.1 - I can see *no* correlation between the
star-formation rate and the AGN luminosity for QSOs (open circles) alone,
can you? On the other hand, for Sy galaxies (filled circles), the scatter
in star-formation rate is reeeeally large plus, again, I can see no
correlation. 

So I dare say this pseudo HR diagram is simply an illusion resulting from
putting both these classes of AGNs into one diagram. That alleged
"diagonal strip" is just an effect of large scatter for QSOs combined with
even larger scatter for Seyferts. 

--
Andrzej