Photometric parallax method

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Gyöngyi Kerekes Eötvös Lóránd University , Budapest. Photometric parallax method. István Csabai László Dobos Márton Trencséni. MAGPOP 2008, Paris. Overview. Estimate distances of stars  create 3 D maps Explore the structure of Milky Way Exponencial disks + power-law halo( es )

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Gyöngyi Kerekes

Eötvös Lóránd University, Budapest

### Photometricparallaxmethod

István Csabai

László Dobos

Márton Trencséni

MAGPOP 2008, Paris

Overview
• 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)
Juricetal, 2008

Polinomial fit to main sequence:

Mr=f(r-i)

Ourestimationmethod
• 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
TrainingSet
• MILES library
• INDO-US library
• Bright stars from SDSS
• M67
• NGC 2420
• Total number of stars: 3392
MILES and INDO-US spectra
• These libraries were targeted to stars with different stellar parameters
• Synthetic magnitudes
• Crossmatchedwith Hipparcos catalog
• Challenges:
• wavelength coverage ofspectra is not enough
• normalization of syntheticmagnitudes

MILES+BaSeL

Brightstarcatalogs
• No bright stars in SDSS!
• Observations with Photometric Telescope (50 cm) to calibrate SDSS stars to USNO stars
• Crossmatch with Hipparcos  117 stars
Openclustersfrom SDSS
• 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.

(1): Anthony-Twarog et al, 2006

(2): An et al, 2007 b.

Preliminaryresults

SDSS Stripe 82 (Image coadd catalog with improved photometry)

~420,000 stars

Mr

Blue: ourestimation

Red: Juric, 2008

g-r

Preliminaryresults

Applying Cartesian coordinate system:

Blue: our estimation

Red: Juric, 2008

Blue: Our estimation

Red: Juric, 2008

Z (pc)

Z (pc)

Preliminaryresults
• Stripe 82 in SDSS (~420,000 stars)
Futureworks
• Apply to all SDSS data
• Calculate metallicity
• Combine with kinematics (USNO, RAVE …)
• GALEX crossmatch