Galaxy luminosity profiles show the surface brightness of galaxies as a function of galactocentric radius . They fall into two broad categories: exponential and de Vaucouleurs profiles. The exponential profile is given by
where and are the central surface brightness and scale length of the disk respectively. Disks are best fitted by an exponential profile. The de Vaucouleurs profile (also known as the law) is given by
where and are known as the effective surface brightness and radius respectively. The de Vaucouleurs profile is a purely empirical fit to the profiles of elliptical galaxies and bulges. It is relatively easy to qualitatively determined whether a given galaxy profile is exponential or de Vaucouleurs by plotting log as function of or . In the log plane, an exponential profile will simply look like a straight line whereas a de Vaucouleurs will look ``concave up''. Similarly, in the log plane, a de Vaucouleurs profile will be a straight line whereas the exponential profile will look ``concave down''.
The initial plan was to perform deep SIS imaging on all target galaxies during the August 1994 observing run. However, technical problems and bad weather in July made it necessary to devote most of the August run to spectroscopic observations. Consequently (and unfortunately), the imaging data set is quite heterogeneous: Gunn and MOS images taken by the CNOC cluster surveys for all target galaxies, I band SIS images obtained for 9 galaxies during the July and August runs, and deep V and R images of two galaxies obtained during a third run in September 1994 unrelated to the current project.
Galaxy luminosity profiles were measured using the task ELLIPSE in the STSDAS/ISOPHOTE package. ELLIPSE fits the galaxy luminosity profiles with isophotal ellipses following Jedrzejewski jed87. The fits were made with four degrees of freedom: x and y coordinates of galaxy center, ellipticity and position angle of the semi-major axis. Starting from user-specified values for the semi-major axis, x and y axis center, ellipticity and position angle, ELLIPSE samples the image along a first-guess elliptical path to produce a 1-dimensional intensity distribution as a function of the ellipse eccentric anomaly. The harmonic content of this distribution is analyzed by least-squares fitting, and the changes to the initial parameter values are given by the harmonic amplitudes. Once convergence has been achieved, ELLIPSE proceeds outwards to the next radius until the profile gradient is less than a user-specified fraction of the RMS intensity residuals along the isophotal path. Parameter values are frozen beyond this point to determine the intensity levels of the outwardmost isophotes.
Gunn and luminosity profiles measured from CNOC MOS images are shown in Figures - and Figures - . SIS I band profiles are shown in Figures and . SIS V and R profiles are shown in Figure . The solid lines are exponential profile fits with the scale length shown for each galaxy. The galactocentric radius in kiloparsecs was computed from the apparent size in arcseconds and the galaxy redshift using the angular distance relation for q = 0.5. Discussion of these broad-band galaxy luminosity profiles is deferred to section where they are compared to [OII] morphologies.