218 articles – 619 Notices  [english version]
 HAL : hal-00001338, version 2
 arXiv : astro-ph/0403543
 Astronomy and Astrophysics 426 (2004) 65-73
 Versions disponibles : v1 (23-03-2004) v2 (02-06-2004)
 Dark halo baryons not in ancient halo white dwarfs
 M. Crézé1, 2, V. Mohan3, A.C. Robin4, C. Reylé4, H. J. Mc Cracken5, J.-C. Cuillandre6, O. Le Fèvre7, Y. Mellier5, 8
 (2004)
 Having ruled out the possibility that stellar objects are the main contributor of the dark matter embedding galaxies, microlensing experiments cannot exclude the hypothesis that a significant fraction of the Milky Way dark halo might be made of MACHOs with masses in the range $0.5-0.8 \msun$. Ancient white dwarfs are generally considered the most plausible candidates for such MACHOs. We report the results of a search for such white dwarfs in a proper motion survey covering a 0.16 sqd field at three epochs at high galactic latitude, and 0.938 sqd at two epochs at intermediate galactic latitude (VIRMOS survey), using the CFH telescope. Both surveys are complete to I = 23, with detection efficiency fading to 0 at I = 24.2. Proper motion data are suitable to separate unambiguously halo white dwarfs identified by belonging to a non rotating system. No candidates were found within the colour-magnitude-proper motion volume where such objects can be safely discriminated from any standard population as well as from possible artefacts. In the same volume, we estimate the maximum white dwarf halo fraction compatible with this observation at different significance levels if the halo is at least 14 gigayears old and under different ad hoc initial mass functions. Our data alone rules out a halo fraction greater than 14% at 95% confidence level. Combined with two previous investigations exploring comparable volumes pushes the limit below 4 % (95% confidence level) or below 1.3% ( 64% confidence), this implies that if baryonic dark matter is present in galaxy halos, it is not, or it is only marginally in the form of faint hydrogen white dwarfs.
 Domaine : Physique/Astrophysique/Cosmologie et astrophysique extra-galactiquePlanète et Univers/Astrophysique
 Mots Clés : dark matter – galaxy halo – white dwarf
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 hal-00001338, version 2 http://hal.archives-ouvertes.fr/hal-00001338 oai:hal.archives-ouvertes.fr:hal-00001338 Contributeur : Michel Crézé <> Soumis le : Mercredi 2 Juin 2004, 13:54:30 Dernière modification le : Mercredi 13 Septembre 2006, 13:47:22