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Microlensing optical depth and event rate in the OGLE-IV Galactic plane fields

Mróz, Przemek and Udalski, Andrzej and Szymanski, Michal K. and Soszyński, Igor and Pietrukowicz, Pawel and Kozlowski, Szymon and Skowron, Jan and Poleski, Radoslaw and Ulaczyk, Krzysztof and Gromadzki, Mariusz and Rybicki, Krzysztof and Iwanek, Patryk and Wrona, Marcin (2020) Microlensing optical depth and event rate in the OGLE-IV Galactic plane fields. Astrophysical Journal Supplement Series, 249 (1). Art. No. 16. ISSN 1538-4365.

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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.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Mróz, Przemek0000-0001-7016-1692
Udalski, Andrzej0000-0001-5207-5619
Szymanski, Michal K.0000-0002-0548-8995
Soszyński, Igor0000-0002-7777-0842
Pietrukowicz, Pawel0000-0002-2339-5899
Kozlowski, Szymon0000-0003-4084-880X
Skowron, Jan0000-0002-2335-1730
Poleski, Radoslaw0000-0002-9245-6368
Ulaczyk, Krzysztof0000-0001-6364-408X
Gromadzki, Mariusz0000-0002-1650-1518
Rybicki, Krzysztof0000-0002-9326-9329
Iwanek, Patryk0000-0002-6212-7221
Wrona, Marcin0000-0002-3051-274X
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.
Funding AgencyGrant Number
National Science Centre (Poland)ETIUDA 2018/28/T/ST9/00096
National Science Centre (Poland)MAESTRO 2014/14/A/ST9/00121
Subject Keywords:Gravitational microlensing ; Microlensing optical depth ; Microlensing event rate ; Milky Way disk ; Milky Way Galaxy
Issue or Number:1
Classification Code:Unified Astronomy Thesaurus concepts: Gravitational microlensing (672); Microlensing optical depth (2145); Microlensing event rate (2146); Milky Way disk (1050); Milky Way Galaxy (1054)
Record Number:CaltechAUTHORS:20200629-133204362
Persistent URL:
Official Citation:Przemek Mróz et al 2020 ApJS 249 16
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:104134
Deposited By: Tony Diaz
Deposited On:29 Jun 2020 21:06
Last Modified:13 Jul 2020 21:58

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