DEEP INFRARED ARRAY PHOTOMETRY OF GLOBULAR-CLUSTERS .1. M4

We have obtained deep J, H, and K images of four fields in and around the globular cluster M4, and these data are used to investigate the photometric properties of giant branch and main-sequence stars in this object. The giant branch derived from our data is offset from the aperture measurements tabulated by Frogel, Persson, & Cohen by roughly 0.1 mag in J - K, in the sense that our photometry has smaller J - K values. Evidence is presented which suggests that it is the previously published aperture measurements which are in error, and, based on our array photometry, M4 no longer occupies a discrepant location on the (J - K)0 GB - [Fe/H] diagram of Frogel, Cohen, & Persson. Selected isochrones from Bergbusch & VandenBerg have been transformed onto the near-infrared observational plane for comparison with our observations. The models reproduce the general morphologies of the giant branch and main sequence, although only after large (approximately 0.2 mag) offsets are applied to the model colors and brightnesses. Finally, the data are used to investigate the mass function of main-sequence stars down to approximately 0.2 M.. Although the slope of the mass function depends on the morphology of the lower main sequence in the color-magnitude diagram, it appears that the mass function is flat or decreasing.