Abstract Details
| Name: Preethi K Affiliation: Christ University Conference ID: ASI2015_499 Title : THREE DIMENSIONAL EXTINCTION MAP AND CATALOG OF ~0.16 MILLION WHITE DWARFS Authors and Co-Authors : K. Preethi 1, S. B. Gudennavar 1, S. G. Bubbly 1, Jayant Murthy 2 and Noah Brosch 3 1 Department of Physics, Christ University, Bangalore-560 029, Karnataka, India 2 Indian Institute of Astrophysics, II Block, Koramangala, Bangalore-560 034, Karnataka, India 3 The Wise Observatory and the School of Physics and Astronomy, the Raymond and Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, Tel Aviv 69978, Israel Abstract Type : Poster Abstract Category : Stars, The Milky Way Galaxy and its neighbours Abstract : We have used photometric data of point sources from Sloan Digital Sky Survey (SDSS) Data Release 8 (DR8) and its cross-matched Galaxy Evolution Explorer (GALEX) General Release 6 (GR6) data from the merged catalog on the CasJbos server. Only unique cross-matches that were classified as stars by the SDSS pipeline were selected, giving us a sample of about 1.8 million stars. Using a model based approach instead of colour-colour diagrams, we were able to classify all point sources by type, which showed nearly 80% to be extragalactic sources such as galaxies and quasars, while rest of them constituted galactic main sequence stars, red giants and white dwarfs. Parameters such as, spectral type of star, galaxy type, distance towards the galactic objects, photometric redshift towards galaxies and quasars, and line of sight extinction towards all sources were determined as a result of the fitting procedure. Of these, about 1.6×10^5 point sources were classified as white dwarfs with distance and extinction towards each of them, and these will be main focus of the paper. The number and spatial distribution of these white dwarfs have been studied and consequently their scale height estimated to be 390 pc. This catalogue of white dwarfs, along with the photometric data and best-fit parameters will be made available as online material. Using these 0.16 million white dwarfs, we have derived a three dimensional extinction map of our Galaxy up to a heliocentric distance of 600 pc in steps of 100 pc and in bins of 1 square degree. We have also derived extinction maps for a smaller subset of white dwarfs with an error-cut in the photometric magnitudes. The extinction map covers an area of 16, 200 square degrees, around 40% of the sky. The variation of extinction with galactic latitude and distance has been examined and results were compared with the integrated extinction map by Schlegel et al. (APJ, 500, 525, 1998), in addition to few other extinction studies. We find our extinctions to be underestimated at low latitudes and overestimated at high latitudes compared to that from Schlegel et al. (APJ, 500, 525, 1998), with a mean difference of about 0.002 mag, in case of the extinction map that includes all about 0.16 million white dwarfs. |