Most globular clusters (GCs) are now known to host multiple stellar populations with different abundances of light elements. Here we use narrow-band photometry and low-resolution spectroscopy for NGC 362 and NGC 6723 to investigate their chemical properties and radial distributions of subpopulations. We confirm that NGC 362 and NGC 6723 are among the GCs with multiple populations showing bimodal CN distribution and CN-CH anticorrelation without a significant spread in calcium abundance. These two GCs show more centrally concentrated CN-weak, earlier generation stars compared to the CN-strong, later generation stars. These trends are reversed with respect to those found in previous studies for many other GCs. Our findings, therefore, seem contradictory to the current scenario for the formation of multiple stellar populations, but mass segregation acting on the two subpopulations might be a possible solution to explain this reversed radial trend.
Bibliographical noteFunding Information:
Support for this work was provided by the National Research Foundation of Korea to the Center for Galaxy Evolution Research, and by KASI under the R and D program (Project No. 2014-1-600-05) supervised by the Ministry of Science, ICT and future Planning. M.P. acknowledges support from Mid-career Researcher Program (No. 2015-008049) through the National Research Foundation (NRF) of Korea.
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All Science Journal Classification (ASJC) codes
- Astronomy and Astrophysics
- Space and Planetary Science