Fan Zhou Profs Jun Ma and Xu Zhou BATC Group,NAOC The BATC Multicolor Photometric Study of M31 Globular Clusters

The BATC Multicolor Photometry System  The Bejing-Arizona-Taiwan-Connecticut (BATC) group was created by Academician Chen J.-S. 15 years ago.  60/90 cm f/3 Schmidt Telescope at Xionglong. >12e <4e RON <5%15um/pixel 1.7"/pixel 58’×58’2K × 2KOld Thick 92.2%12um/pixel 1.3"/pixel 90’×90’4K × 4KNew E2V BQE(~400nm)‏Pixel ScaleFOVSize

The BATC intermediate band filters The BATC multicolor photometric system includes 15 intermediate band filters, covering the total optical wavelength range from ~3000 to ~10000Å. The filters are designed to avoid the brightest and most variable night sky emission lines.

The BATC multicolor photometry of M31 The central 1 o ×1 o field in 15 intermediate bands 1995 Sep Dec. Total EXP:37hr20mi n

The ages of M31 GCs Jiang & Ma (2003) use the Battistini et al. (1987) to obtain BATC SEDs of 172 GCs Using the BC96 SSP model to derive the ages and metallicities Nearly all the GCs are older than 1 Gyr Metal-poor ->old Metal-rich->young

Break the degeneracy! One big problem in the SSP model: age~metallcity degeneracy! Reddening also affects it! Idea: use the known metallicty and reddening to derive the age.

Our data for our sample GCs BATC(13) + Broadband(5) + 2MASS(3) JHK s photometry (Galleti et al. 2004). Spectroscopic [Fe/H] obtained: Perrett et al. (2002) and Barmby et al. (2000) The reddening data: Barmby priv. comm.

BC03 SSP model Age: 0.1Myr ~ 20 Gyr Wavelength: 91 Å-160 μm Track: Padova 1994 (Z= )‏ IMF:Salpeter 1955

The SED fitting with BC03 model

The age distribution of our sample GCs in M31

The metallicity ~age relationship in M31 Old  metal-poor Young  metal-rich

Future Work  9 o ×9 o field with >1000 GCs and candidates  Green boxes :Observed already  White boxes: to be observed in the future  15 intermediate- band

Thanks very much!