THE YOUNG CLUSTER IC-348

CCD photometry in BVRI was obtained for about 260 stars in and around IC 348, and multiobject spectroscopy for 80 of these. A somewhat large r region was surveyed for stars having H alpha in emission; over 110 e mission-line stars brighter than about R = 19 were discovered. Because H alpha emission could be detected to a limit near W = 3 Angstrom div ision into weak-line (WTTSs) and classical T Tauri stars (CTTSs) was p ossible on purely spectroscopic grounds. There is a steep rise in the number of emission-line stars below W(H alpha)= 10 Angstrom; the propo rtion of WTTSs to CTTSs in the area surveyed is 58:51. ROSAT detected only about 58% of the spectroscopic WTTSs and about 65% of the CTTSs, although these numbers are sensitive to the survey thresholds. The bul k of the ages of about 100 stars, read off the theoretical tracks of D 'Antona & Mazzitelli, range between about 0.7 and 12 Myr, but the emis sion-line stars, which are most likely to be members of IC 348, have a mean age of 1.3 Myr. Allowance for unresolved binaries would increase this somewhat, but there is a firm upper limit at 2.95 Myr. There is no indication that the ages of the emission-line stars depend upon W(H alpha): the IC 348 WTTSs as a population are not systematically older than the CTTSs, but there is a tendency for the WTTSs to be concentra ted toward the center of IC 348, while the CTTSs are more widely distr ibuted. There is a scattering of emission-H alpha stars over the entir e area surveyed. There are too many to be explained as low-mass member s of an earlier generation of star formation in Per OB2 or as foregrou nd dMe stars. The mass frequency function, based on some 125 stars fit ted to theoretical tracks, rises from 1.5 M. to about 0.2 M., with a s lope very much like that of the Scale initial mass function. The optic al cluster IC 348 radius is about 4.'0, or 0.37 pc. The total mass of optically detectable stars in this volume is 57 M., while the mean spa ce density is about 520 stars pc(-3). The amount of interstellar mater ial remaining within the cluster is small in comparison. Star formatio n in the Per OB2/IC 348 region cannot be characterized by one unique a ge; it appears that stars have been forming in the region now occupied by the association for 10-20 Myr.