Fan Zhou Profs Jun Ma and Xu Zhou BATC Group,NAOC The BATC Multicolor Photometric Study of M31...
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Transcript of Fan Zhou Profs Jun Ma and Xu Zhou BATC Group,NAOC The BATC Multicolor Photometric Study of M31...
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 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
2.5log 48.6AB
dF R
md
R
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
9o×9o field with >1000 GCs and candidates
Green boxes:Observed already
White boxes: to be observed in the future
15 intermediate-band
Thanks very much!
http://batc.bao.ac.cn/~fanzhou