Preliminary results on galactic dark matter from the complete EROS2 microlensing survey

TL;DR

The EROS-2 survey monitored millions of stars over several years to detect microlensing events, providing new constraints on the presence of massive compact halo objects as dark matter candidates in the Milky Way.

Contribution

This study presents the most sensitive EROS-2 microlensing analysis to date, with improved detection capabilities and new limits on the contribution of machos to galactic dark matter.

Findings

No sufficient microlensing events to explain dark matter

New limits significantly constrain macho contribution

Follow-up on previous candidates shows variability or disqualification

Abstract

The EROS-2 collaboration has conducted a survey of the Magellanic Clouds between July 1996 and February 2003 (6.7 years), in order to search for microlensing phenomena due to putative machos (massive astronomical compact halo objects). About 55 million stars were monitored over 100 deg^2, typically with 400 to 500 measurements per star, simultaneously in two wide passbands. The full EROS-2 Magellanic Cloud data set was processed using the same program chain, and a photometric database was constructed. The lightcurves of the brightest 33 million stars were then searched for the characteristic signature of microlensing phenomena, in the wide timescale range of 1 to 1000 days (corresponding to macho masses ranging from about 0.01 solar mass to a few hundred solar masses). The sensitivity of this new analysis is better by a factor 4. The new EROS-2 microlensing candidates towards the LMC and the corresponding (preliminary) final limits from EROS-2 on the macho content of the halo are presented; they are by far not numerous enough to account for the galactic dark matter. We have also followed, whenever possible, the microlensing candidates that were previously published by the EROS and MACHO collaborations. 1 MACHO and 2 EROS LMC candidates have shown subsequent variability and cannot be considered to be serious candidates.