New limits from microlensing on Galactic black holes in the mass range 10 M⊙ < M < 1000 M⊙
Perdereau, O.; Aubourg, E.; Goldman, B.; Le Guillou, L.; Palanque-Delabrouille, N.; Hamadache, C.; Tisserand, P.; Rich, J.; Magneville, C.; Marquette, J. -B.; Moniez, M.; Ansari, R.; Coutures, C.; Glicenstein, J. -F.; Afonso, C.; Albert, J. -N.; Spiro, M.; Blaineau, T.; Lasserre, T.; Lesquoy, E.
France, Germany, United States
Abstract
We searched for long-duration microlensing events originating from intermediate-mass black holes (BH) in the halo of the Milky Way, using archival data from the EROS-2 and MACHO photometric surveys towards the Large Magellanic Cloud (LMC). We combined data from these two surveys to create a common database of light curves for 14.1 million objects in the LMC, covering a total duration of 10.6 years, with flux series measured in four wide passbands. We carried out a microlensing search on these light curves, complemented by the light curves of 22.7 million objects, observed only by EROS-2 or only by MACHO, over about 7 years, with flux series measured in only two passbands. A likelihood analysis, taking into account the LMC self-lensing and Milky Way disk contributions, allows us to conclude that compact objects with masses in the range 10 − 100 M⊙ cannot make up more than ∼15% of a standard halo total mass (at a 95% confidence level). Our analysis sensitivity weakens for heavier objects, although we still rule out the possibility of ∼50% of the halo being made of ∼1000 M⊙ BHs. Combined with previous EROS results, an upper limit of ∼15% of the total halo mass can be obtained for the contribution of compact halo objects in the mass range 10−6 − 102 M⊙.