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Proper motion surveys and the Galactic dark matter

Proper motion surveys and the Galactic dark matter. Bertrand Goldman N.M.S.U. – N.A.S.A./Ames. Summary. White dwarfs contribution to the Galactic halo Constraints from proper motion surveys (EROS 2 proper motion survey) Some positive results SNAP surveys Halo white dwarfs Brown dwarfs.

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Proper motion surveys and the Galactic dark matter

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  1. Proper motion surveysand theGalactic dark matter Bertrand Goldman N.M.S.U. – N.A.S.A./Ames

  2. Summary • White dwarfs contribution to the Galactic halo • Constraints from proper motion surveys (EROS 2 proper motion survey) • Some positive results • SNAP surveys • Halo white dwarfs • Brown dwarfs

  3. Why white dwarfs? • Microlensing results towards the Magellanic Clouds • MACHO positive signal: 20%, ≈0.5 Mo • EROS 20% upper limits • Various indirect constraints • C and N pollution (Brook et al. 2003) • D and He pollution (Fields et al. 2000) • TeV rays surviving the progenitors’ redshifted light(Graff et al. 2000) Alcock et al, 2001

  4. Why not white dwarfs? • No strong direct constraints: • HWD LF depends on cooling function, WD mass and progenitors’ IMF(bias toward high masses makes WD cooler) • Liebert et al, 1998 disk WD LF vtan >250km/sWD LF Chabrier, 1999

  5. EROS 2 proper motion survey • Uses the EROS 2two-broad band,wide-field imager1º2, 2x32Mpix • 250º 2 over five years,mid and high Galactic latitudes • Data shared with the nearby SNe search program

  6. EROS 2 proper motion surveyresults • no candidate 95% CL limits • Color-dependent when combining both bands • 7% for MV =17 to30% for MV =18 • if 5+% DA WDs,  age > 14 Gyr Goldman et al, 2002

  7. Other proper motion surveys • Several other failed to detect halo WDs • Knox et al, 1999 (stacked plates) • Crézé et al, 2004 (CFHT 12k) • Other reported halo white dwarf discoveries: • Ibata et al, 2001: ≈10%(2 confirmed fast, cool WDs in survey plates) • Oppenheimer et al. 2001 (and Salim et al. 2003): 1–2% of the halouncertainties on the nature of those objects:young (Hansen, 2001); thick disk dynamics and contamination (Reylé et al, Reid et al, Flynn et al, 2001)

  8. SNAP contribution • Detection of 14 Gyr white dwarfs, in most bands, high above the Galactic plan:1,500 pc with proper motion (deep fields)3,000 pc by color, flattening measurementthousands of WDs if halo is made of 1% WDs • WD LF of the thick disk to the end with height distribution • LSST will also solve these questions Using the Chabrier et al, 1999 cooling functions

  9. Brown dwarfs • 8 detection in two or more bands ofTeff = 300K BDs (9MJ@5Gyr, or 4MJ@1Gyr)375pc3 with proper motion and parallaxes 6,000pc3 with the deep field surveys12,500 pc3 with a 500º2 wide field survey • Detection of Teff = 220K planets (5MJ@5Gyr, or 2MJ@1Gyr) in the deep surveys up to 15pc (5pc3) Using the Baraffe et al, 2003 models • WISE would do better

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