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Session 105 - Galaxies: Counts & Kinematics.
Display session, Saturday, January 10
Exhibit Hall,

[105.07] The UBRI Luminosity Functions for Galaxies in the Coma Cluster

I. Jorgensen, G. J. Hill (U. Texas at Austin)

We have established the luminosity functions for galaxies in the central square degree of the Coma cluster. CCD photometry was obtained in U, B, R and I. The total magnitude of each galaxy is derived as the magnitude within the radius where the ratio of the local surface brightness at that radius and the mean surface brightness within that radius is 0.1. The total magnitudes derived with this method are better estimates of the true total magnitudes than the traditionally used isophotal magnitudes. Isophotal magnitudes are known to deviate systematically from the true total magnitudes depending on the luminosity profile type. The approximate completeness limits for the photometry are as follows: U=20.5 mag, B=21.5 mag, R=21 mag, I=20 mag. We have obtained new measurements of redshifts of galaxies in the sample. Our observations cover 220 galaxies without previous redshift determinations. Together with published data this makes the redshift information complete for galaxies brighter than a total B magnitude of 18.5. A total of 480 members of the cluster have measured redshifts, while 180 foreground and background galaxies have measured redshifts.

The accurate determination of the luminosity functions in U, B, R and I for galaxies in low redshift clusters is important for future investigations of galaxy evolution based on luminosity functions for galaxies in higher redshift clusters.

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