Search

New observations of the K i and ultraviolet Na i interstellar lines are presented for some stars embedded in dense clouds and for a few supergiants. The new observations of weak lines, which are essentially unaffected by the adopted velocity distribution for the interstellar material, support the conclusions previously obtained from the interstellar D-lines of Na i and H- and K-lines of Ca ii The new data, when combined with a discussion of the ionization equilibrium, indicate no or moderate depletions at the edges of clouds, but some depletions in the central regions.

A detailed abundance analysis has been performed for three members of M22 and five of ..omega.. Cen. The three giants in M22 are chemically identical with (Fe/H) = -1.78 dex except for a range of Na and, less certainly, Ba larger than the observational and modeling errors. The ..omega.. Cengiants show a range of abundance for all elements, with the light elements and the rare earths (plus Ba) enhanced by a larger factor than the Fe peak nuclei in the more metal-rich ..omega.. Cen stars. The two most metal-rich ..omega.. Cen stars have vastly different Na/Mg and Al/Mg ratios and Sc abundances. Explosive nucleosynthesis fails to predict the Na/Mg observed ratios at large Al/Mg values. The deduced neutron excesses are etaroughly-equal10/sup -2/ and 5 x 10/sup -4/; the former is the largest known for any star. These high values of eta require massive (M> or =12 M/sub sun/) supernova progenitors and may also produce via the s-process the strong enhancement of Ba and the rare earths seen in the metal-rich ..omega.. Cen giants. It is suggested that such massive supernovae were much rarer in the less dense halo field, leading to the observed differences in abundance patterns of globular clustermore » giants versus halo field dwarfs.« less

Observations of the amount of H$alpha$ emission from the disks of 53 galaxies have been made using large entrance apertures so that the maximum possible fraction of the total area of the galaxy is included. These observations reveal a relationship between B--V color and H$alpha$ emission; for a given morphological type the bluer galaxies have more emission at H$alpha$. The effect of the strong emission lines on the colors is not sufficient to produce this trend. Furthermore, the H$alpha$ emission comes from discrete Hii regions ionized by starlight which are limited in the crudest approximation by the number of hot stars rather than the availability of gas. From the range in H$alpha$ emission, the ratio of hot stars to cooler stars corresponding to the observed range in B--V color is obtained. This is compared with a theoretical model by Searle, Sargent, and Bagnuolo which predicts B--V color as a function of the stellar luminosity function in the galaxy. The two separate methods of determining the change in ratio of hot-to-cool stars agree well. Further observational support is thus given to the models of Searle, Sargent, and Bagnuolo. (AIP)

Accurate radial velocities of the optical interstellar features for some of the B stars embedded in the ρ Oph complex are obtained by averaging results of several photographic high-dispersion spectra. In at least one case, there is a real difference between the radial velocity of the atomic features (Na i and Ca ii) and the molecular ones (CH and CN). We show that it is probable that the CH and CN are concentrated either in a separate cloud (i.e., region of space) from the Ca ii and Na i or in a cloud whose outer parts are expanding rather than in a single cloud which is contracting or rotating.

Lower limits for the ratio C^(12)/C^(13) have been determined for eight metal-deficient stars. These limits are inconsistent with the predictions of nearly all of the universal models considered by Wagoner, Fowler, and Hoyle (1967) unless at least one generation of massive, rapidly evolving stars existed before the formation of any of the program stars.