Question

1- Do you think measuring surface brightnesses of galaxies as a function of redshift is a practical method for testing cosmological models? Explain the problems that might arise.

2- Ignoring relativity and cosmology, how does the surface brightness (flux per square arcsecond) depend on distance?

Answer 1

1. Surface brightness is independed of redshift. Surface brightness of a galaxy also depend on the size and shape of galaxy. Hence it is not good choice to use surface brightness of galaxies as a function of redshift.

2. Brightness

Here L is lumniosity (intrinsic rate of emmiting energy), D is distance from source. Hence brightness is inversly proportional to distance square.

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