Further investigations of the CO emission from the North America dust cloud and L1630

This paper reports further observations of the J=1-0 rotational lines of $sup 12$C$sup 16$O and $sup 13$C$sup 16$O in two dust clouds, the North America Nebula dust cloud and L1630. The observations have higher velocity resolution (delta$nu$=0.25 km s$sup -1$) than had been available previously. Unusually bright CO emission is associated with the reflection nebulae NGC 2023 and NGC 2068 in L1630. Bright CO emission from the directions of individual H$alpha$- emission stars in L1630 and the North America cloud is sought, but the CO emission at these places is not enhanced above that of the surrounding material. It is concluded that these stars are too cool to heat the gas appreciably. The shapes of the CO profiles are determined by the large-scale motions of the gas in dust clouds. The possibility that magnetic fields in dust clouds prevent rapid dissipation of turbulent motions in these clouds is discussed. The shapes of the CO profiles observed near NGC 2023 show that the gas motions there are turbulent, rather than systematic radial motions of the gas. From the observations of the North America Nebula dust cloud, it is shown that not more than about 10 percent of the carbon present inmore » the gas is in the form of CO. (AIP)« less