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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

8 DR2 Sky Coverage Galactic

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 –  0.12 dn/dm=m -1.6 (M<1M Θ ) dn/dm=m -3 (M≥1M Θ ) 4*  *  *  *  *  *  *  0.3 dn/dm=m *  *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] (Carraro et. al. 1994)  z, Age, Mass

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

15  The tables of bolometric corrections have been applied to Padova database of stellar evolutionary tracks and isochrones. 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= PC

23 R=350PC z=290.06PC

24 Mass(M ☉ ) Log(age) group z logT logg u g r u-g g-r R=450PC z=372.94PC

25 Mass(M ☉ ) Log(age) group z logT logg u g r u-g g-r 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> >z>0.004 z<0.004

32 Classify age Age<12Gyr 5Gyr

33 RA=180 DEC= 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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