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 ) - PowerPoint PPT Presentation

Transcript of Photometric parallax method

  • Gyngyi KerekesEtvs Lrnd University, BudapestMAGPOP 2008, ParisIstvn CsabaiLszl DobosMrton Trencsni

  • Estimate distances of stars create 3D mapsExplore the structure of Milky WayExponencial disks + power-law halo(es)Dwarf galaxies (merging) and streams

    Our goal: reproduce current distributions / find new structuresImprovements in outer regions, giantsGaia (launch around 2011)

  • Polinomial fit to main sequence: Mr=f(r-i)

  • Non-parametric estimatorWe use all magnitudes (colors) from SDSSNearest neighbors of a point in a 5D spaceWeight the estimated parameters with an exponencial distribution

    Can be adopted to other photometric systems

  • MILES libraryINDO-US libraryBright stars from SDSSM67NGC 2420

    Total number of stars: 3392

  • These libraries were targeted to stars with different stellar parametersSynthetic magnitudesCrossmatched with Hipparcos catalogChallenges:wavelength coverage of spectra 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 setAfter 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.

    ExtinctionE(B-V)Distance modulusM670.39.61 (1)NGC24200.412.0 (2)

  • Mrr-i

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

  • Applying Cartesian coordinate system:

  • Stripe 82 in SDSS (~420,000 stars)

  • Apply to all SDSS dataCalculate metallicityCombine with kinematics (USNO, RAVE )GALEX crossmatch