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Star Counts and The Galactic Structure

Star Counts and The Galactic Structure

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Star Counts and The Galactic Structure

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  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 2o.5 wide stripe (Chen et. al. 2001)

  4. 45 survey stripes

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

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

  7. 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

  8. Robin(2003)

  9. Chen (2001) Bahcall(1980) Robin(2003)

  10. 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

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

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

  13. AB magnitude scale Lupton et al (1999)

  14. u-g g-r r-I i-z (Giradi 2004) 107 , 10 8,109,1010 yr

  15. 12Gyr, z=0.0001,0.0004,0.001,0.004,0.008,0.019,0.03 (Giradi2004)

  16. isoc_sloan/isoc_z0.dat.gzMetal-free models from Ma01. • isoc_sloan/isoc_z0001.dat.gz • isoc_sloan/isoc_z0004.dat.gz • isoc_sloan/isoc_z001.dat.gz • isoc_sloan/isoc_z004.dat.gz • isoc_sloan/isoc_z008.dat.gz • isoc_sloan/isoc_z019.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

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

  18. R=150PC z=124.31PC

  19. R=250PC z=207.186PC

  20. R=350PC z=290.06PC

  21. 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

  22. 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

  23. R=650PC z=538.68

  24. R=750PC z=621.56PC

  25. R=850PC z=704.43PC

  26. R=950PC z=787.37PC

  27. Classify metallicity z>0.019 0.019>z>0.004 z<0.004

  28. Classify age Age<12Gyr 5Gyr<Age<12Gyr Age<5Gyr

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

  30. 4422

  31. 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

  32. Thank you!