Photometric parallax method

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Photometric parallax method

• Gyöngyi Kerekes
• Eötvös Lóránd University, Budapest

István Csabai László Dobos Márton Trencséni
MAGPOP 2008, Paris
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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)

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Estimating parallax and other physical parameters
from colors
QUERY
TRAINING SET
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Juric et al, 2008

• Polinomial fit to main sequence
• Mrf(r-i)

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Our estimation method

• 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

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Training Set

• MILES library
• INDO-US library
• Bright stars from SDSS
• M67
• NGC 2420
• Total number of stars 3392

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MILES and INDO-US spectra

• These libraries were targeted to stars with
  different stellar parameters
• Synthetic magnitudes
• Crossmatched with Hipparcos catalog
• Challenges
• wavelength coverage ofspectra is not enough
• normalization of syntheticmagnitudes

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Bright star catalogs

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

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Open clusters from 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.

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.
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Training set
Mr
r-i
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Preliminary results

• SDSS Stripe 82 (Image coadd catalog with
  improved photometry)
• 420,000 stars

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Preliminary results

• Applying Cartesian coordinate system

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SDSS Stripe 82 (not coadd)
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Preliminary results

• Stripe 82 in SDSS (420,000 stars)

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Future works

• Apply to all SDSS data
• Calculate metallicity
• Combine with kinematics (USNO, RAVE )
• GALEX crossmatch