4.1 Surface Photometry

We performed surface photometry by fitting ellipses to the galaxy images. This yielded the radial profiles of a number of quantities such as the (local) surface brightness $\mu(r)$, the ellipticity $\varepsilon(r)$, and the deviations from elliptical isophotes parametrized by the Fourier coefficients, e.g. c₄(r). These radial profiles are shown in Appendix  (p. ).

From these radial profiles global parameters can be derived, e.g. the effective radius ${r_{\rm e}}$, the effective mean surface brightness ${{< \hspace{-3pt} \mu \hspace{-3pt}>}_{\rm e}}$, and the mean c₄(r) coefficient ${< \hspace{-4pt} c_4 \hspace{-4pt}>}$. Global here means ``one number per galaxy'', in the sense that an entire radial profile is condensed into a single characteristic number.

The surface photometry is the subject of the present chapter. The determination of global photometric parameters is described in Chapter .

The ellipses fit was done using the GALPHOT program package. GALPHOT was written by Marijn Franx and later developed further by Inger Jørgensen. See Franx et al. (1989b), and JFK92.

It should be noted, that I (BMJ) fitted about 60% of the 227 galaxy observations, including the central field galaxies. The remaining 40% were fitted by Inger Jørgensen.