New limits from microlensing on Galactic black holes in the mass range 10  M ⊙  <  M  < 1000  M

• Published in: Astronomy and astrophysics (Berlin) 2022-08, Vol.664, p.A106
• Main Authors: Blaineau, T., Moniez, M., Afonso, C., Albert, J.-N., Ansari, R., Aubourg, E., Coutures, C., Glicenstein, J.-F., Goldman, B., Hamadache, C., Lasserre, T., Le Guillou, L., Lesquoy, E., Magneville, C., Marquette, J.-B., Palanque-Delabrouille, N., Perdereau, O., Rich, J., Spiro, M., Tisserand, P.
• Format: Article
• Language: English
• Subjects: ASTRONOMY AND ASTROPHYSICS; Astrophysics; black holes; dark matter; galaxy; gravitational lensing; halo; kinematics and dynamics; Physics; stars; surveys
• ISSN: 0004-6361; 1432-0746; 1432-0756
• DOI: 10.1051/0004-6361/202243430

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  − 10 2   M ⊙ .