Microlensing optical depth and event rate in the OGLE-IV Galactic plane fields
Abstract
Searches for gravitational microlensing events are traditionally concentrated on the central regions of the Galactic bulge but many microlensing events are expected to occur in the Galactic plane, far from the Galactic Center. Owing to the difficulty in conducting high-cadence observations of the Galactic plane over its vast area, which are necessary for the detection of microlensing events, their global properties were hitherto unknown. Here, we present results of the first comprehensive search for microlensing events in the Galactic plane. We searched an area of almost 3000 square degrees along the Galactic plane (|b| < 7°, 0° < l < 50°, 190° < l < 360°) observed by the Optical Gravitational Lensing Experiment (OGLE) during 2013–2019 and detected 630 events. We demonstrate that the mean Einstein timescales of Galactic plane microlensing events are on average three times longer than those of Galactic bulge events, with little dependence on the Galactic longitude. We also measure the microlensing optical depth and event rate as a function of Galactic longitude and demonstrate that they exponentially decrease with the angular distance from the Galactic Center (with the characteristic angular scale length of 32°). The average optical depth decreases from 0.5 × 10⁻⁶ at l = 10° to 1.5 × 10⁻⁸ in the Galactic anticenter. We also find that the optical depth in the longitude range 240° < l < 330° is asymmetric about the Galactic equator, which we interpret as a signature of the Galactic warp.
Additional Information
© 2020 The American Astronomical Society. Received 2020 April 15; revised 2020 May 12; accepted 2020 May 13; published 2020 July 13. We thank the anonymous referee for his/her comments, which improved the presentation of our results. We thank M. Kubiak, G. Pietrzyński, Ł. Wyrzykowski, and M. Pawlak for their contribution to the collection of the OGLE photometric data analyzed in this paper. P.M. acknowledges support from the National Science Center, Poland (grant ETIUDA 2018/28/T/ST9/00096). The OGLE project has received funding from the National Science Center, Poland, grant MAESTRO 2014/14/A/ST9/00121 to A.U.Attached Files
Published - Mróz_2020_ApJS_249_16.pdf
Submitted - 2004.07289.pdf
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Additional details
- Eprint ID
- 104134
- Resolver ID
- CaltechAUTHORS:20200629-133204362
- ETIUDA 2018/28/T/ST9/00096
- National Science Centre (Poland)
- MAESTRO 2014/14/A/ST9/00121
- National Science Centre (Poland)
- Created
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2020-06-29Created from EPrint's datestamp field
- Updated
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2021-11-16Created from EPrint's last_modified field