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

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

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

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)

45 survey stripes

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

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

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

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

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

 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

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

 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

Lupton et al (1999) AB magnitude scale

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

 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

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

R=150PC z=124.31PC

R=250PC z=207.186PC

R=350PC z=290.06PC

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

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

R=650PC z=538.68

R=750PC z=621.56PC

R=850PC z=704.43PC

R=950PC z=787.37PC

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

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

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

4422

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

Thank you!

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