EÖTVÖS UNIVERSITY BUDAPEST Department of Physics of Complex Systems Photometric parallax estimation using the MILES catalog and BaSeL models István Csabai László Dobos Márton Trencsényi Norbert Purger Géza Herczeg István Csabai László Dobos Márton Trencsényi Norbert Purger Géza Herczeg G YÖNGYI K EREKES MAGPOP M EETING, M ALTA 19 November 2015 G YÖNGYI K EREKES MAGPOP M EETING, M ALTA 19 November 2015

PHOTOMETRIC PARALLAX Based on different distance measurements for stars: o Trigonometric parallax (nearest stars) o Main sequence fitting (open clusters) o Cepheid variable stars (globular clusters), etc. Calculation of absolute magnitudes Color-magnitude diagram Main sequence fitting with a function If we know the color index of a star, we can estimate the distance.

PHOTOMETRIC PARALLAX Problems: We can only estimate for main sequence stars Color indices are metallicity-dependent (especially B, V) We need continuous parameters Hawley, 2002 (spectroscopic parallax)

PHOTOMETRIC PARALLAX ESTIMATIONS Juric et al, 2005 THE MILKY WAY TOMOGRAPHY WITH SDSS

OUR CONCEPTION Compile a set of spectra from MILES for a wide wavelength range. Obtain distances to these stars. Calculate Sloan synthetic magnitudes and get a semi-empirical training set. Based on 4 color indices and we can search nearest neighbours the Sloan stars and estimate distances to them.

MILES DATABASE 985 stars Wavelength range: 3525 – 7500 Å at 2.3 Å spectral resolution Atmospheric data estimated using CEN01b (T eff, log g, [Fe/H])

MILES DATABASE T eff vs log g Large range of atmospheric parameters: from metal-rich, cool stars to hot, metal-poor stars. Cenarro et al, 2006

HIPPARCOS Trigonometric parallax About stars Error: mas for stars brighter than 9 mag

MILES – HIPPARCOS CROSSMATCH Based on coordinates (40 arcsec)  614 stars HRD [V>10]

MILES – HIPPARCOS CROSSMATCH CMD

B A S E L MODEL Used for fitting: spectra Method: least χ 2 Spectra fitted: χ 2 =0.344 χ 2 =3.578 χ 2 =11.886

S PECTRA FITTING Cut at χ 2 = 3 Result: 562 stars

S PECTRA FITTING

SYNTHETIC MAGNITUDES u’, g’, r’, i’, z’ (Sloan filters) [Fukugita et al, 1996]

SYNTHETIC MAGNITUDES Jester et al filter transformation equations:  g=V+0.64(B-V)-0.13  r=V-0.46(B-V)+0.11

COLOR-COLOR DIAGRAMS g – r vs r – i for Sloan stars (red dots) and for MILES stars (green crosses) r – i g – r SDSS stars selection: Relative error in magnitudes < 0.04% Magnitudes in range [14;17] Upper CCD from Michael Richmond

COLOR-COLOR DIAGRAMS u-g vs g-r for Sloan stars (red dots) and for MILES stars (green crosses)

OUR ESTIMATION We have code for nonparametric estimation (multidimensional indexing integrated with databases) It was created for photometric redshift calculation and estimation of physical parameters of galaxies This code can be adapted for photometric parallax estimation: 5-D (4 CI & M) spaces  nearest neighbour searching  absolute manitude & parallax estimation

FUTURE TASKS Improve calibration of spectra in order to get accurate synthetic magnitudes Find better models  better fits of spectraMake some tests for known open clusters, globular clustersCreate a 3D map of Milky Way Improve models of thin and thick disk, galaxy formation…