POINT-AGAPE pixel lensing survey of M31 - Evidence for a MACHO contribution to galactic halos

S.C. Novati, S. Paulin-Henriksson, J. An, P. Baillon, V. Belokurov, B.J. Carr, M. Creze, N.W. Evans, Y. Giraud- Heraud, A. Gould, P. Hewett, P. Jetzer, J. Kaplan, E. Kerins, Stephen Smartt, C.S. Stalin, Y. Tsapras, M.J. Weston

Research output: Contribution to journalArticlepeer-review

80 Citations (Scopus)

Abstract

The POINT-AGAPE collaboration is carrying out a search for gravitational microlensing toward M31 to reveal galactic dark matter in the form of MACHOs (Massive Astrophysical Compact Halo Objects) in the halos of the Milky Way and M31. A high-threshold analysis of 3 years of data yields 6 bright, short- duration microlensing events, which are confronted to a simulation of the observations and the analysis. The observed signal is much larger than expected from self lensing alone and we conclude, at the 95% confidence level, that at least 20% of the halo mass in the direction of M31 must be in the form of MACHOs if their average mass lies in the range 0.5-1 M-circle dot. This lower bound drops to 8% for MACHOs with masses similar to 0.01 M-circle dot. In addition, we discuss a likely binary microlensing candidate with caustic crossing. Its location, some 32' away from the centre of M31, supports our conclusion that we are detecting a MACHO signal in the direction of M31.
Original languageEnglish
Pages (from-to)911-928
Number of pages18
JournalAstronomy and Astrophysics
Volume443
Issue number3
DOIs
Publication statusPublished - Dec 2005

ASJC Scopus subject areas

  • Space and Planetary Science

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