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Gyöngyi KerekesEötvös Lóránd University, Budapest
MAGPOP 2008, Paris
István CsabaiLászló DobosMárton Trencséni
Estimate distances of stars create 3D maps
Explore the structure of Milky Way Exponencial disks + power-law halo(es) Dwarf galaxies (merging) and streams
Our goal: reproduce current distributions / find new structures
Improvements in outer regions, giants Gaia (launch around 2011)
1510
Mm
d
Polinomial fit to main sequence:
Mr=f(r-i)
Non-parametric estimator We use all magnitudes (colors) from SDSS Nearest neighbors of a point in a 5D space
Weight the estimated parameters with an exponencial distribution
Can be adopted to other photometric systems
MILES library INDO-US libraryBright stars from SDSSM67NGC 2420
Total number of stars: 3392
MILES+BaSeL
These libraries were targeted to stars with different stellar parameters
Synthetic magnitudesCrossmatched with Hipparcos catalogChallenges:
▪ wavelength coverage ofspectra is not enough ▪ normalization of synthetic
magnitudes
No bright stars in SDSS! Observations with Photometric Telescope (50
cm) to calibrate SDSS stars to USNO stars
Crossmatch with Hipparcos 117 stars
First chosen as test objects Turned out at estimation of distances
that giants are overrepresented in the training set
After applying distance modulus from (Harris et al, 1996) we added them to the TS.
Extinction
E(B-V)
Distance modulus
M67 0.3 9.61 (1)
NGC2420 0.4 12.0 (2)(1): Anthony-Twarog et al, 2006(2): An et al, 2007 b.
Mr
r-i
g-r
Mr
Blue: our estimationRed: Juric, 2008
SDSS Stripe 82 (Image coadd catalog with improved photometry)
~420,000 stars
Applying Cartesian coordinate system:
Blue: our estimationRed: Juric, 2008
Z (pc) Z (pc)
Blue: Our estimationRed: Juric, 2008
Stripe 82 in SDSS (~420,000 stars)
Apply to all SDSS dataCalculate metallicityCombine with kinematics (USNO, RAVE
…)GALEX crossmatch