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Barium star formation. II. Monte Carlo analysis
Abstracts
499
seen in the light curve at two large amplitude variations, then this method can accurately identify and determine the long period. The method is effective for data sampled at irregular intervals. (AApS 1998, 18, 260-268) A simulation experiment
on elliptical galaxy formation
LIU Bu-lin Beijing
A&m-
nomical Observatory, CAS, Beijing 100080 Elliptical galaxy formation is simulated using a mode of interacting galaxies in tree code. The structure of the elliptical galaxy is analysed by the method of inertia tensor and curve-fitting. And the relative lengths of the semiaxes of the simulated elliptical galaxy are derived. (AApS 1998, 18, 269-275) Barium star formation. II. Monte Carlo analysis HAN Zhan-wen Centre fOT Astrophysics, University of Sciences & Technology of China, Hefei 280026 Monte Carlo simulations of the model proposed in paper I are carried out and the results are compared with observations in this paper. The results show that most of the strong barium stars are generated from the channels of wind accretion, wind exposure and stable Roche-lobe overflow, while most of the mild ones are from wind accretion and wind exposure. The comprehensive model could be used to explain the numbers of barium stars in the Galaxy, the distribution of orbital periods of barium stars, and the distribution of the mass functions. As shown by the model, the orbital periods and pollution factors are correlated. The model also gives a Galactic birthrate of barium stars of around O.O2yr-‘. The total number of barium stars in the Galaxy brighter than the 10th apparent visual magnitude is estimated to be some 6000, the average mass of strong barium stars is estimated to be about 1.8 Ma, and the average mass of the white dwarf components is about 0.60 Ma. The results also support the views (a) that the thermal pulsation may begin at an earlier phase during the AGB than is usually assumed, (b) that a tidally enhanced stellar wind exists, and (c) that the maximum stellar mass for s-processing is about 2 Ma. (AApS 1998, 18, 276-286) Molecular clouds in different evolutionary stages and star formation chun & SUN Jin Department of Astronomy, Beijing Normal University, Beijing
SUN Yan100875
A systematic comparison between molecular clouds in different evolutionary stages and processes of star formation is made over the range of 8’ to 38’ in Galactic longitude and -lo to $1’ in Galactic latitude by using the Massachusetts-Stony Brook Survey data of 12C0 in the Galactic
plane (HPFW
= 47”) and the IRAS Infrared Sky Survey image data
(1.5’ per pixel). This region is divided into thirty subregions. Then, the space distribution of CO(l-0) emission and the corresponding infrared intensity at 6Opmis obtained for each subregion, and the contours of infrared color temperatures and optical depths of molecular cloud complexes in the corresponding regions are calculated and derived. Moreover, the catalogs of the IRAS infrared point sources and HI1 regions are used. Thus, molecular clouds in different evolutionary stages are identified and divided into four groups ranging from young clouds to evolved clouds, and their main characteristics and relations to the processes of star formation are analysed. The Galatic-longitude distributions of ultracompact HII regions and candidate protostars as well as the ratio between HI1 region-molecular cloud and candidate protostar-molecular cloud associations are analysed statistically. The results
499
seen in the light curve at two large amplitude variations, then this method can accurately identify and determine the long period. The method is effective for data sampled at irregular intervals. (AApS 1998, 18, 260-268) A simulation experiment
on elliptical galaxy formation
LIU Bu-lin Beijing
A&m-
nomical Observatory, CAS, Beijing 100080 Elliptical galaxy formation is simulated using a mode of interacting galaxies in tree code. The structure of the elliptical galaxy is analysed by the method of inertia tensor and curve-fitting. And the relative lengths of the semiaxes of the simulated elliptical galaxy are derived. (AApS 1998, 18, 269-275) Barium star formation. II. Monte Carlo analysis HAN Zhan-wen Centre fOT Astrophysics, University of Sciences & Technology of China, Hefei 280026 Monte Carlo simulations of the model proposed in paper I are carried out and the results are compared with observations in this paper. The results show that most of the strong barium stars are generated from the channels of wind accretion, wind exposure and stable Roche-lobe overflow, while most of the mild ones are from wind accretion and wind exposure. The comprehensive model could be used to explain the numbers of barium stars in the Galaxy, the distribution of orbital periods of barium stars, and the distribution of the mass functions. As shown by the model, the orbital periods and pollution factors are correlated. The model also gives a Galactic birthrate of barium stars of around O.O2yr-‘. The total number of barium stars in the Galaxy brighter than the 10th apparent visual magnitude is estimated to be some 6000, the average mass of strong barium stars is estimated to be about 1.8 Ma, and the average mass of the white dwarf components is about 0.60 Ma. The results also support the views (a) that the thermal pulsation may begin at an earlier phase during the AGB than is usually assumed, (b) that a tidally enhanced stellar wind exists, and (c) that the maximum stellar mass for s-processing is about 2 Ma. (AApS 1998, 18, 276-286) Molecular clouds in different evolutionary stages and star formation chun & SUN Jin Department of Astronomy, Beijing Normal University, Beijing
SUN Yan100875
A systematic comparison between molecular clouds in different evolutionary stages and processes of star formation is made over the range of 8’ to 38’ in Galactic longitude and -lo to $1’ in Galactic latitude by using the Massachusetts-Stony Brook Survey data of 12C0 in the Galactic
plane (HPFW
= 47”) and the IRAS Infrared Sky Survey image data
(1.5’ per pixel). This region is divided into thirty subregions. Then, the space distribution of CO(l-0) emission and the corresponding infrared intensity at 6Opmis obtained for each subregion, and the contours of infrared color temperatures and optical depths of molecular cloud complexes in the corresponding regions are calculated and derived. Moreover, the catalogs of the IRAS infrared point sources and HI1 regions are used. Thus, molecular clouds in different evolutionary stages are identified and divided into four groups ranging from young clouds to evolved clouds, and their main characteristics and relations to the processes of star formation are analysed. The Galatic-longitude distributions of ultracompact HII regions and candidate protostars as well as the ratio between HI1 region-molecular cloud and candidate protostar-molecular cloud associations are analysed statistically. The results