The Astrophysical Journal (Jan 2025)
The Microlensing Event Rate and Optical Depth from MOA-II 9 Yr Survey Toward the Galactic Bulge
- Kansuke Nunota,
- Takahiro Sumi,
- Naoki Koshimoto,
- Nicholas J. Rattenbury,
- Fumio Abe,
- Richard Barry,
- David P. Bennett,
- Aparna Bhattacharya,
- Akihiko Fukui,
- Ryusei Hamada,
- Shunya Hamada,
- Naoto Hamasaki,
- Yuki Hirao,
- Stela Ishitani Silva,
- Yoshitaka Itow,
- Yutaka Matsubara,
- Shota Miyazaki,
- Yasushi Muraki,
- Tsutsumi Nagai,
- Greg Olmschenk,
- Clement Ranc,
- Yuki K. Satoh,
- Daisuke Suzuki,
- Paul. J. Tristram,
- Aikaterini Vandorou,
- Hibiki Yama,
- (MOA collaboration)
Affiliations
- Kansuke Nunota
- ORCiD
- Department of Earth and Space Science, Graduate School of Science, Osaka University , Toyonaka, Osaka 560-0043, Japan
- Takahiro Sumi
- Department of Earth and Space Science, Graduate School of Science, Osaka University , Toyonaka, Osaka 560-0043, Japan
- Naoki Koshimoto
- Department of Earth and Space Science, Graduate School of Science, Osaka University , Toyonaka, Osaka 560-0043, Japan
- Nicholas J. Rattenbury
- Department of Physics, University of Auckland , Private Bag 92019, Auckland, New Zealand
- Fumio Abe
- Institute for Space-Earth Environmental Research, Nagoya University , Nagoya 464-8601, Japan
- Richard Barry
- Code 667, NASA Goddard Space Flight Center , Greenbelt, MD 20771, USA
- David P. Bennett
- Code 667, NASA Goddard Space Flight Center , Greenbelt, MD 20771, USA; Department of Astronomy, University of Maryland , College Park, MD 20742, USA
- Aparna Bhattacharya
- Code 667, NASA Goddard Space Flight Center , Greenbelt, MD 20771, USA; Department of Astronomy, University of Maryland , College Park, MD 20742, USA
- Akihiko Fukui
- Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo , 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan; Instituto de Astrofisica de Canarias , Via Lactea s/n, E-38205 La Laguna, Tenerife, Spain
- Ryusei Hamada
- Department of Earth and Space Science, Graduate School of Science, Osaka University , Toyonaka, Osaka 560-0043, Japan
- Shunya Hamada
- Department of Earth and Space Science, Graduate School of Science, Osaka University , Toyonaka, Osaka 560-0043, Japan
- Naoto Hamasaki
- Department of Earth and Space Science, Graduate School of Science, Osaka University , Toyonaka, Osaka 560-0043, Japan
- Yuki Hirao
- Institute of Astronomy, Graduate School of Science, The University of Tokyo , 2-21-1 Osawa, Mitaka, Tokyo 181-0015, Japan
- Stela Ishitani Silva
- Code 667, NASA Goddard Space Flight Center , Greenbelt, MD 20771, USA; Department of Physics, The Catholic University of America , Washington, DC 20064, USA
- Yoshitaka Itow
- Institute for Space-Earth Environmental Research, Nagoya University , Nagoya 464-8601, Japan
- Yutaka Matsubara
- Institute for Space-Earth Environmental Research, Nagoya University , Nagoya 464-8601, Japan
- Shota Miyazaki
- Institute of Space and Astronautical Science , Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Chuo, Sagamihara, Kanagawa 252-5210, Japan
- Yasushi Muraki
- Institute for Space-Earth Environmental Research, Nagoya University , Nagoya 464-8601, Japan
- Tsutsumi Nagai
- Department of Earth and Space Science, Graduate School of Science, Osaka University , Toyonaka, Osaka 560-0043, Japan
- Greg Olmschenk
- Code 667, NASA Goddard Space Flight Center , Greenbelt, MD 20771, USA
- Clement Ranc
- Sorbonne Université , CNRS, UMR 7095, Institut d’Astrophysique de Paris, 98 bis bd Arago, 75014 Paris, France
- Yuki K. Satoh
- College of Science and Engineering, Kanto Gakuin University , 1-50-1 Mutsuurahigashi, Kanazawa-ku, Yokohama, Kanagawa 236-8501, Japan
- Daisuke Suzuki
- Department of Earth and Space Science, Graduate School of Science, Osaka University , Toyonaka, Osaka 560-0043, Japan
- Paul. J. Tristram
- University of Canterbury Mt. , John Observatory, P.O. Box 56, Lake Tekapo 8770, New Zealand
- Aikaterini Vandorou
- Code 667, NASA Goddard Space Flight Center , Greenbelt, MD 20771, USA; Department of Astronomy, University of Maryland , College Park, MD 20742, USA
- Hibiki Yama
- Department of Earth and Space Science, Graduate School of Science, Osaka University , Toyonaka, Osaka 560-0043, Japan
- (MOA collaboration)
- DOI
- https://doi.org/10.3847/1538-4357/ada352
- Journal volume & issue
-
Vol. 979,
no. 2
p. 123
Abstract
We present measurements of the microlensing optical depth and event rate toward the Galactic bulge using the data set from the 2006 to 2014 MOA-II survey, which covers 22 bulge fields spanning ∼42 deg ^2 between −5° < l < 10° and −7° < b < −1°. In the central region with ∣ l ∣ < 5°, we estimate an optical depth of $\tau =[1.75\pm 0.04]\times 1{0}^{-6}\exp [(0.34\pm 0.02)({3}^{\circ }-| b| )]$ and an event rate of Γ = [16.08 ± 0.28] × 10 ^−6 $\exp [(0.44\pm 0.02)({3}^{\circ }-| b| )]{\mathrm{star}}^{-1}\,{\mathrm{yr}}^{-1}$ using a sample consisting of 3525 microlensing events, with Einstein radius crossing times of t _E < 760 days and a source star magnitude of I _s < 21.4 mag. We confirm our results are consistent with the latest measurements from the OGLE-IV 8 yr data set. We find our result is inconsistent with a prediction based on Galactic models, especially in the central region with ∣ b ∣ < 3°. These results can be used to improve the Galactic bulge model, and more central regions can be further elucidated by upcoming microlensing experiments, such as the PRime-focus Infrared Microlensing Experiment and Nancy Grace Roman Space Telescope.
Keywords
- Galactic center
- Milky Way Galaxy
- Microlensing event rate
- Microlensing optical depth
- Gravitational microlensing
