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The BATC Multicolor Photometric Study of M31 Globular Clusters. Fan Zhou Profs Jun Ma and Xu Zhou BATC Group,NAOC. Size. FOV. Pixel Scale. BQE(~400nm) . RON. New E2V. 4K × 4K. 90’×90’. 12um/pixel 1.3"/pixel. 92.2%. <4e. Old Thick. 2K × 2K. 58’×58’. 15um/pixel 1.7"/pixel. <5%.
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The BATC Multicolor Photometric Study of M31 Globular Clusters Fan Zhou Profs Jun Ma and Xu Zhou BATC Group,NAOC
Size FOV Pixel Scale BQE(~400nm) RON New E2V 4K × 4K 90’×90’ 12um/pixel 1.3"/pixel 92.2% <4e Old Thick 2K × 2K 58’×58’ 15um/pixel 1.7"/pixel <5% >12e 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.
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 1o×1o field in 15 intermediate bands • 1995 Sep.-1999 Dec. • Total EXP:37hr20min
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) JHKs 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=0.0001-0.10) • IMF:Salpeter 1955
The metallicity ~age relationship in M31 • Old metal-poor • Young metal-rich
Future Work • 9o×9o field with >1000 GCs and candidates • Green boxes :Observed already • White boxes: to be observed in the future • 15 intermediate-band