The Microlensing Event Rate and Optical Depth from MOA-II 9 year Survey toward the Galactic Bulge
Abstract
We present measurements of the microlensing optical depth and event rate toward the Galactic bulge using the dataset from the 2006--2014 MOA-II survey, which covers 22 bulge fields spanning ~42 deg^2 between -5 deg < l < 10 deg and -7 deg < b < -1 deg. In the central region with |l|<5 deg, we estimate an optical depth of {\tau} = [1.75+-0.04]*10^-6exp[(0.34+-0.02)(3 deg-|b|)] and an event rate of {\Gamma} = [16.08+-0.28]*10^-6exp[(0.44+-0.02)(3 deg-|b|)] star^-1 year^-1 using a sample consisting of 3525 microlensing events, with Einstein radius crossing times of tE < 760 days and source star magnitude of IsWe confirm our results are consistent with the latest measurements from OGLE-IV 8 year dataset (Mr\'oz et al. 2019). We find our result is inconsistent with a prediction based on Galactic models, especially in the central region with |b|<3 deg. These results can be used to improve the Galactic bulge model, and more central regions can be further elucidated by future microlensing experiments, such as The PRime-focus Infrared Microlensing Experiment (PRIME) and Nancy Grace Roman Space Telescope.
Cite
@article{arxiv.2410.23553,
title = {The Microlensing Event Rate and Optical Depth from MOA-II 9 year Survey toward the Galactic Bulge},
author = {Kansuke Nunota and Takahiro Sumi and Naoki Koshimoto and Nicholas J. Rattenbury and Fumio Abe and Richard Barry and David P. Bennett and Aparna Bhattacharya and Akihiko Fukui and Ryusei Hamada and Shunya Hamada and Naoto Hamasaki and Yuki Hirao and Stela Ishitani Silva and Yoshitaka Itow and Yutaka Matsubara and Shota Miyazaki and Yasushi Muraki and Tsutsumi Nagai and Greg Olmschenk and Clement Ranc and Yuki K. Satoh and Daisuke Suzuki and Paul J. Tristram and Aikaterini Vandorou and Hibiki Yama},
journal= {arXiv preprint arXiv:2410.23553},
year = {2024}
}