Gravitational v Relatavistic Red Shift

[Mawech]

We determine the distance of Active Galactic Centers / Quasars by their Hubble (Relativistic) Red Shift; and yet these object are seriously Massive objects which also exert a Gravitational field.
How do we determine which is which, and how much of each is contributing to the total amount of Red Shift?

[TonyE]

There is always a very active debate about how much of a quasar's redshift is due to recession velocity and how much due to gravitational redshift (. Because of this, the distance of quasars is often uncertain unless it is possible to measure the redshift if light from stars/gas in it's galaxy - blanking out light from the central region.

[Cougar]

...how much of each is contributing to the total amount of Red Shift?

I've always heard that, with very distant objects, the cosmological redshift is the major contributor, and the gravitational redshift is practically negligible.

[ngc3314]

There is always a very active debate about how much of a quasar's redshift is due to recession velocity and how much due to gravitational redshift (. Because of this, the distance of quasars is often uncertain unless it is possible to measure the redshift if light from stars/gas in it's galaxy - blanking out light from the central region.

When this has been done, the result is that the optical emission lines from quasars have no more than about a contribution of z=0.02 from gravitational redshift. These emission lines come from regions many Schwarzschild radii out, and the gravitational contribution rises steeply with depth into the potential well. The situation is not so clear for X-ray emission features, which come from very highyl ionized material likely to arise mush closer in, and for which some analyses suggest a gravitational redshift rather larger. In neither case is the gravitational redshift comparable to the total measured values, indicating that the cosmological component dominates by a large factor.

[Mawech]

Thanks folks