THE LUMINOSITY FUNCTION OF THE YOUNG CLUSTER NGC-2362

We construct the I band luminosity function of the young open cluster NGC 2362 from CCD photometric observations which are complete to a limiting magnitude of 17.6. After empirically correcting for the presence of background field stars, we find the cluster luminosity function to be significantly deficient in low luminosity stars compared to the luminosity function derived from the Salpeter IMF. Although it is impossible to entirely dismiss systematic uncertainties in our correction for field stars, artificial star tests confirm that the deficiency in the cluster luminosity function is not due to observational incompleteness at faint magnitudes. If the observed luminosity function is representative of the luminosity function of the entire cluster, then our observations provide strong evidence that the IMF varies on the scale of individual open clusters. However, our data does not allow us to rule out the existence of an outer halo of low luminosity stars that could account for this deficit. We also find marginal evidence for a dip in the observed luminosity function at magnitudes corresponding to ZAMS spectral types mid-A to mid-F, a characteristic that has been observed in at least one other cluster of similar age.