Abstract Details
| Name: Preethi K Affiliation: Christ University Conference ID: ASI2016_443 Title : White Dwarf Catalogue & Extinction Map Authors and Co-Authors : K. Preethi 1, Jayant Murthy 2, S. B. Gudennavar 1, S. G. Bubbly 1, Noah Brosch 3, 1 Department of Physics, Christ University, Bengaluru 560 029, Karnataka, India, 2 Indian Institute of Astrophysics, II Block, Koramangala, Bengaluru 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 : A study of the interstellar medium (ISM) enables us to understand the structure, dynamics and energetics of our Galaxy while also affecting astronomical observations. We now have many observations from space-based and ground-based telescopes. Our goal is to compile and analyse these data, study the ISM on a larger scale and make the database available to the scientific community for further investigations. We have extracted photometric data from Galaxy Evolution Explorer (GALEX) General Release 6 (GR6) and Sloan Digital Sky Survey (SDSS) Data Release 8 (DR8) for over 1.67 million point sources classified as stars by SDSS based on their point spread function. Our preliminary analysis showed 80% of these point sources to be extragalactic and that a colour-cut based method cannot distinguish between stars and galaxies/quasars. We instead adopted a model based approach to classify all sources by type, determine the distance towards the Galactic objects, photometric redshift towards galaxies and quasars, and line of sight extinction. Our model fitting gave us 0.40 million white dwarfs, ~60,000 main-sequence stars, ~20,000 red-giants, 0.34 million quasars and 1.19 million galaxies. Of these, we only included white dwarfs brighter than 22 magnitudes in all bands and with 90% confidence in chi square. We also excluded all sources outside the white dwarf (u−g, g−r) colour space to eliminate any horizontal-branch and blue straggler stars giving us a sample of 35,379 white dwarfs which is the focus of this work. The number and spatial distribution of these white dwarfs were studied and their thin-disk scale height estimated to be 349 pc and 286 pc, above and below the Galactic disk respectively. Based on this catalogue of white dwarfs, we have derived three dimensional extinction maps of our Galaxy in distance steps of 100 pc and in bins of 1 square degree. The map extends to a distance of 800 pc and covers an area of 13,441 square degrees (~32% of the sky). The extinction as a function of Galactic latitude and distance was studied. We have compared our results with the integrated extinction map by Schlegel et al. (1998). We find our extinctions to be underestimated at low latitudes and overestimated at high latitudes as compared to that from Schlegel et al. (1998) and find the median in the difference to be 0.025 mag. |