We aim to retrieve ghost streams under the assumption that all the globular clusters in our Galaxy were formed in very early merge events. Our results are based on two speculations： that the specific energy and angul...We aim to retrieve ghost streams under the assumption that all the globular clusters in our Galaxy were formed in very early merge events. Our results are based on two speculations： that the specific energy and angular momentum of the globular clusters after merge are not changed in the course of evolution and that the globular clusters with a common origin would stay in the same orbit plane as the parent galaxy. After taking into account the apogalacticum distance of the orbits, we suggest with some Confidence five possible streams. The number of streams is consistent with the previous results. Three of the four well established members of the Sagittadus stream were found to be in one of our streams. Several other globular clusters in our result were also thought to come from accretion by previous researchers. The orbital parameters of the streams are derived, which provide a way to test whether these streams are true with the help of more accurate measurement of proper motions of the globular clusters.展开更多
A Viable scenario for globula r cluster formation is suggested in CDM model.In this scenario the smaller scale fluctuations superpo sed on proto-galaxy will form proto-dwarf-galaxies. In their multi-phase ISM the warm...A Viable scenario for globula r cluster formation is suggested in CDM model.In this scenario the smaller scale fluctuations superpo sed on proto-galaxy will form proto-dwarf-galaxies. In their multi-phase ISM the warm clouds,which are thermally stable and gravitationally marginally stable with appropriate masses and metallicities, might be the proper progenitors of GCs.In the virialization of a proto-galaxy,these dwarf galaxies will acquire kinetic energy and collide with each other. As strong external disturbances. these collisions will cause a short timescale thermal instability,and further stimulate gravitational instability which is necessary for the transformation of progenitors into GCs.展开更多
We re-examine the properties of the star cluster population in the circumnuclear starburst ring in the face-on spiral galaxy NGC 7742, whose young cluster mass function has been reported to exhibit significant deviati...We re-examine the properties of the star cluster population in the circumnuclear starburst ring in the face-on spiral galaxy NGC 7742, whose young cluster mass function has been reported to exhibit significant deviations from the canonical power law. We base our reassessment on the clusters＇ luminosi- ties （an observational quantity） rather than their masses （a derived quantity）, and confirm conclusively that the galaxy＇s starburst-ring clusters--and particularly the youngest subsample, log（t yr-1） ≤7.2- show evidence of a turnover in the cluster luminosity function well above the 90% completeness limit adopted to ensure the reliability of our results. This confirmation emphasizes the unique conundrum posed by this unusual cluster population.展开更多
基金Supported by the National Natural Science Foundation of China.
文摘We aim to retrieve ghost streams under the assumption that all the globular clusters in our Galaxy were formed in very early merge events. Our results are based on two speculations： that the specific energy and angular momentum of the globular clusters after merge are not changed in the course of evolution and that the globular clusters with a common origin would stay in the same orbit plane as the parent galaxy. After taking into account the apogalacticum distance of the orbits, we suggest with some Confidence five possible streams. The number of streams is consistent with the previous results. Three of the four well established members of the Sagittadus stream were found to be in one of our streams. Several other globular clusters in our result were also thought to come from accretion by previous researchers. The orbital parameters of the streams are derived, which provide a way to test whether these streams are true with the help of more accurate measurement of proper motions of the globular clusters.
基金Project supported by the National Natural Science Foundation of China
文摘A Viable scenario for globula r cluster formation is suggested in CDM model.In this scenario the smaller scale fluctuations superpo sed on proto-galaxy will form proto-dwarf-galaxies. In their multi-phase ISM the warm clouds,which are thermally stable and gravitationally marginally stable with appropriate masses and metallicities, might be the proper progenitors of GCs.In the virialization of a proto-galaxy,these dwarf galaxies will acquire kinetic energy and collide with each other. As strong external disturbances. these collisions will cause a short timescale thermal instability,and further stimulate gravitational instability which is necessary for the transformation of progenitors into GCs.
基金supported by the National Key Research and Development Program of China(Grant 2017YFA0402702)the National Natural Science Foundation of China(Grant Nos.U1631102,11373010and 11633005)
文摘We re-examine the properties of the star cluster population in the circumnuclear starburst ring in the face-on spiral galaxy NGC 7742, whose young cluster mass function has been reported to exhibit significant deviations from the canonical power law. We base our reassessment on the clusters＇ luminosi- ties （an observational quantity） rather than their masses （a derived quantity）, and confirm conclusively that the galaxy＇s starburst-ring clusters--and particularly the youngest subsample, log（t yr-1） ≤7.2- show evidence of a turnover in the cluster luminosity function well above the 90% completeness limit adopted to ensure the reliability of our results. This confirmation emphasizes the unique conundrum posed by this unusual cluster population.
