Using the Daeduk Radio Telescope, we have observed J = 1 → 0 transitions of 1 12 C O , 13 C O a n d C 18 O toward OMC-l. The column densities of 1 \~ 5 × 10 17 c m − 2 a n d 1 \~ 3 × 10 16 c m − 2 have been derived, for 13 C O and C 18 O , respectively, in the 11 ′ × 11 ′ region centered at Orion - KL. The double isotope ratio [ 13 C O ] / [ C 18 O ] was found to be larger than the cosmic abundance ratio by factors of 2 \~ 10 which may result from the chemical fractionation effect.

The observed radial UBV colour variations (both B-V and U-B) of some globular clusters are examined for correlations with radial variations in the integrated spectra. The results show that the presence of a radial colour gradient is correlated with the presence of a gradient of the CN (and possibly the G-band) line strength, in the sense that the CN (and possibly the G-band) is stronger in the centre (where the cluster is redder) and becomes weaker in the outer region of the cluster (where the cluster is bluer). This may suggest that a primordial abundance, possibly nitrogen and carbon gradient was set up in the early stage of cluster formation.

Surface density distributions for globular clusters were obtained from photoelectric surface photometry (using centered aperture photometry). These surface brightness profiles were then compared with the theoretical surface density distribution of King's model. From the comparison of the theoretical and observed surface density distributions, we determine he structural parameters of the clusters (the core radius r c , the tidal cut off r t , and the concentration factor C).

Four stars in the central region of 47 Tuc were observed spectroscopically using IPCS. The observed result showed that two asymptotic giant branch stars have the excess of nitrogen compared with the red giant branch stars, which indicates that the radial colour gradient in a globular clursters, at least for 47 Tuc, comes from the abundance gradient among the giant stars.