We tried to match the CMDs of four clusters using our stellar

population synthesis model (Yunnan model). The model uses the SSE and

BSE of Hurley to calculate the evolution of stars. Then the BaSeL

spectra library is used for translating log(g) and log(Teff) to colors

and spectra of populations. All populations adopt the IMF of Salpeter

(alpha=-2.35).

In the work, we matched CMDs by both single stellar populations (SSP)

and binary stellar populations (BSPs). The difference between them is

BSPs take the binary interactions into account.

The results derived from SSP fitting are:

M67 : t= 3.6000 Gyr Z= 0.0200 (m-M)v = 9.5800 E(B-V)= 0.0470

NGC1868: t= 0.9000 Gyr Z= 0.0100 (m-M)v = 18.5100 E(V-I)= 0.0550

NGC1805: t= 0.6000 Gyr Z= 0.0200 (m-M)v = 18.2000 E(V-I)= 0.0280

47Tuc : t= 13.6000 Gyr Z= 0.0040 (m-M)v = 13.2100 E(B-V)= 0.0500

The results derived from BSP fitting are:

M67 : t= 3.2000 Gyr Z= 0.0200 (m-M)v = 9.5800 E(B-V)= 0.0470

NGC1868: t= 1.0000 Gyr Z= 0.0100 (m-M)v = 18.5100 E(V-I)= 0.0550

NGC1805: t= 0.2000 Gyr Z= 0.0200 (m-M)v = 18.2000 E(V-I)= 0.0280

47Tuc : t= 13.6000 Gyr Z= 0.0040 (m-M)v = 13.2100 E(B-V)= 0.0500

The results derived from LF fitting with both SSPs and BSPs are:

NGC1868: t= 0.2000 Gyr

NGC1805: t= 0.2000 Gyr

(the metallicities derived from SSP and BSP fitting are different)

The results derived from spectra fitting with SSPs are:

M67 : t= 14.0000 Gyr Z= 0.004

NGC1868: t= 1.6000 Gyr Z= 0.0003

NGC1805: t= 0.1000 Gyr Z= 0.0300

Models vs. data (generated by S.C. Trager):

47 Tuc

M67

NGC 1805

NGC 1868

In all plots, the upper left panel is the observed data. The upper right panel has the SSP model overlaid in green open points. The lower left panel has the BSP model overlaid in red open points.

47
Tuc SSP model |
47
Tuc BSP model |

M67
SSP model |
M67
BSP model |

NGC
1805 SSP model |
NGC
1805 BSP model |

NGC
1868 SSP model |
NGC
1868 BSP model |