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I have several questions regarding “Surface Brightness Dimming” in the “Quantities Derived from Redshift” section of the Nasa/ipac Extragalactic Database.

As an example, please use quasar IRAS F08279+5255 with the redshift z=3.9122

For Surface Brightness Dimming NED lists Flux Density per Unit Area=0.00172, and Magnitude per Unit Area=6.913 mag.

1) Am I correct in understanding that 99.828% of the flux from this quasar is attenuated, and that any absolute magnitude calculated by the distance modulus equation has to be corrected by -6.913?

2) Please let me know the physical cause of this dimming. Is it light absorption / scatter by the intergalactic medium, or some phenomenon related to the expansion of the unverse?

3) To which photometric band would the specified value apply?

4) If possible, please give me the equation relating redshift, z, to flux or magnitude dimming. I can find absolutely nothing on the web. NED specifies that this dimming is derived from the redshift alone.

Thank you.

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