A DETAILED STUDY OF AN EXTREMELY QUIESCENT CORE - L-1498

We have mapped the dense quiescent core L 1498 in (CO)-O-18(1-0), (CO) -O-18(2-1), CS(2-1), and CS(3-2) with angular resolutions between 12 a nd 25 are seconds. We have also obtained spectra of (CS)-S-34(2-1) and (3-2) as well as of CS(5-4) at one position. Our (CO)-O-18 maps show a ring-shaped structure in good agreement with a recent study by Zhou et al. (1994). From our (CO)-O-18 map, we find a mass of 0.9 solar mas ses for the core. Comparison with a recent millimeter continuum observ ation suggests that CO may be underabundant by a factor of 3 relative to average molecular cloud material but the uncertainties in this numb er are large. We find several small scale structures in our maps with a diameter of approximately 0.02 parsec and a mass of approximately 0. 01 solar masses. These are not gravitationally bound whereas the large r scale core seems to be. An intriguing feature of our results is that the CS profiles are double-peaked with the blue peak generally strong er than the red. If one decomposes the double-peaked profiles, one fin ds that the individual CS velocity component linewidths are extremely narrow (0.11-0.18 kms(-1)) and only marginally wider than the width ex pected for pure thermal broadening (0.10 kms(-1)). We conclude that we are observing a structure which is to a good approximation static. Th e double-peaked nature of the CS profiles could either be due to absor ption by a foreground low density cloud or because we are observing tw o layers of gas adjacent to one another and with slightly different li ne-of-sight velocities.