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Star Counts and The Galactic Structure Xu Yan Supervisor: Deng Li Cai.

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Presentation on theme: "Star Counts and The Galactic Structure Xu Yan Supervisor: Deng Li Cai."— Presentation transcript:

1 Star Counts and The Galactic Structure Xu Yan Supervisor: Deng Li Cai

2 Introduction  Sloan digital sky survey  Synthetic star counts model  Future plan

3 Sloan Digital Sky Survey  Five broad band filters,u’,g’,r’,i’,z’ effective wavelengths, 3450Å, 4760Å, 6280Å, 7690Å,9250Å point-source magnitude limit, 22.3, 23.3, 23.1, 22.3, 20.8 (s/n=5)  Pixels subtend 0”.4, PSF width1.4" median in r  Exposure time in each band is 54.1s  ‘run’, six 13’.5 wide strips, ‘rerun’, 12’.5 2 o.5 wide stripe (Chen et. al. 2001)

4 45 survey stripes

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7 DR2 Sky Coverage 3324 sq deg Equatorial http://www.sdss.org/dr2/coverage/index.html

8 DR2 Sky Coverage Galactic http://www.sdss.org/dr2/coverage/index.html

9 Synthetic model  ρ(R,Z), Φ(Mass) → surface number density of some direction of some population  each population → [Fe/H], Mass, Age  From Isochrone → [Fe/H], Teff, g  Color of each star

10 Robin(2003) grou p Age(Gyr)[Fe/H](dex)IMFρ 0 (M Θ PC -3 ) 10 – 0.15 0.01  0.12 dn/dm=m -1.6 (M<1M Θ ) dn/dm=m -3 (M≥1M Θ ) 4*10 -3 20.15 - 1 0.03  0.12 7.9*10 -3 31 - 2 0.03  0.1 6.2*10 -3 42 - 3 0.01  0.11 4*10 -3 53 - 5 -0.07  0.18 5.8*10 -3 65 - 7 -0.14  0.17 4.9*10 -3 77 - 10 -0.37  0.2 6.6*10 -3 811 -0.78  0.3 dn/dm=m -0.5 1.34*10 -3 914 -1.78  0.5 9.32*10 -3

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12 Chen (2001) Bahcall(1980) Robin(2003)

13  PMF ~ IMF  Mass density convert to number density is normalized IMF  Logz=1.03[Fe/H]-1.689 (Carraro et. al. 1994)  z, Age, Mass

14 Pseudo-random in age and metalicity Group1,Mass: 0.1505000D+00 0.1515000D+00 (M ☉ )

15  The tables of bolometric corrections have been applied to Padova database of stellar evolutionary tracks and isochrones. http://pleiadi.pd.astro.it. Interpolate in SDSS Isochrone of Giradi(2004) and Ma(2001) Stellar spectra F λ, spectral library

16 Lupton et al (1999) AB magnitude scale

17 u-g g-r r-I i-z 10 7, 10 8,10 9,10 10 yr (Giradi 2004)

18 12Gyr, z=0.0001,0.0004,0.001,0.004,0.008,0.019,0.03 (Giradi2004)

19  isoc_sloan/isoc_z0.dat.gz Metal-free models from Ma01. isoc_sloan/isoc_z0.dat.gz  isoc_sloan/isoc_z0001.dat.gz isoc_sloan/isoc_z0001.dat.gz  isoc_sloan/isoc_z0004.dat.gz isoc_sloan/isoc_z0004.dat.gz  isoc_sloan/isoc_z001.dat.gz isoc_sloan/isoc_z001.dat.gz  isoc_sloan/isoc_z004.dat.gz isoc_sloan/isoc_z004.dat.gz  isoc_sloan/isoc_z008.dat.gz isoc_sloan/isoc_z008.dat.gz  isoc_sloan/isoc_z019.dat.gz isoc_sloan/isoc_z019.dat.gz  isoc_sloan/isoc_z030.dat.gz isoc_sloan/isoc_z030.dat.gz Basic set obtained by combining Gi00+Gi01 (low- and intermediate-mass stars) with Be94+Gi96 (high masses) isochrones. With overshooting

20 R=50PC z=41.44PC Ra=180 dec=60 skycoverage=1sr L=134.4 b=55.97

21 R=150PC z=124.31PC

22 R=250PC z=207.186PC

23 R=350PC z=290.06PC

24 Mass(M ☉ ) Log(age) group z logT logg u g r u-g g-r 0.200000 9.76540 61 0.0233971 3.62080 2.98324 6.95622 4.73258 3.71290 2.22364 1.01968. 0.200000 9.83367 61 0.0131369 3.61070 3.21589 7.97221 5.66942 4.60236 2.30279 1.06706. R=450PC z=372.94PC

25 Mass(M ☉ ) Log(age) group z logT logg u g r u-g g-r 0.200000 9.19340 31 0.0124033 3.63555 3.41523 7.13436 4.98482 4.02208 2.14954 0.962740 0.200000 9.75101 61 0.0118220 3.63816 3.01763 6.46198 4.38647 3.44567 2.07551 0.940800 0.200000 9.71720 61 0.0124870 3.62821 3.20643 7.34673 5.19215 4.20510 2.15458 0.987050 R=550PC z=455.81PC

26 R=650PC z=538.68

27 R=750PC z=621.56PC

28 R=850PC z=704.43PC

29 R=950PC z=787.37PC

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31 Classify metallicity z>0.019 0.019>z>0.004 z<0.004

32 Classify age Age<12Gyr 5Gyr { "@context": "http://schema.org", "@type": "ImageObject", "contentUrl": "http://images.slideplayer.com/9/2521896/slides/slide_32.jpg", "name": "Classify age Age<12Gyr 5Gyr

33 RA=180 DEC=60 33289 Compare result of model with observation

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37 4422

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39 Future plan  Constrain model with observation  Do further deducing for physical parameter of observational data to obtain distance  Pick up stars that have special meaning to the structure of the Galaxy

40 Thank you!


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