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Predictions of the WFIRST Microlensing Survey. I. Bound Planet Detection Rates

Penny, Matthew T. and Gaudi, B. Scott and Kerins, Eamonn and Rattenbury, Nicholas J. and Mao, Shude and Robin, Annie C. and Calchi Novati, Sebastiano (2019) Predictions of the WFIRST Microlensing Survey. I. Bound Planet Detection Rates. Astrophysical Journal Supplement Series, 241 (1). Art. No. 3. ISSN 1538-4365. doi:10.3847/1538-4365/aafb69.

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The Wide Field InfraRed Survey Telescope (WFIRST) is the next NASA astrophysics flagship mission, to follow the James Webb Space Telescope. The WFIRST mission was chosen as the top-priority large space mission of the 2010 astronomy and astrophysics decadal survey in order to achieve three primary goals: to study dark energy via a wide-field imaging survey, to study exoplanets via a microlensing survey, and to enable a guest observer program. Here we assess the ability of the several WFIRST designs to achieve the goal of the microlensing survey to discover a large sample of cold, low-mass exoplanets with semimajor axes beyond roughly one astronomical unit, which are largely impossible to detect with any other technique. We present the results of a suite of simulations that span the full range of the proposed WFIRST architectures, from the original design envisioned by the decadal survey, to the current design, which utilizes a 2.4 m telescope donated to NASA. By studying such a broad range of architectures, we are able to determine the impact of design trades on the expected yields of detected exoplanets. In estimating the yields we take particular care to ensure that our assumed Galactic model predicts microlensing event rates that match observations, consider the impact that inaccuracies in the Galactic model might have on the yields, and ensure that numerical errors in light-curve computations do not bias the yields for the smallest-mass exoplanets. For the nominal baseline WFIRST design and a fiducial planet mass function, we predict that a total of ~1400 bound exoplanets with mass greater than ~0.1 M⊕ should be detected, including ~200 with mass ≲3 M⊕. WFIRST should have sensitivity to planets with mass down to ~0.02 M⊕, or roughly the mass of Ganymede.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Penny, Matthew T.0000-0001-7506-5640
Gaudi, B. Scott0000-0003-0395-9869
Kerins, Eamonn0000-0002-1743-4468
Rattenbury, Nicholas J.0000-0001-5069-319X
Mao, Shude0000-0001-8317-2788
Calchi Novati, Sebastiano0000-0002-7669-1069
Additional Information:© 2019 The American Astronomical Society. Received 2018 August 6; revised 2018 December 21; accepted 2018 December 31; published 2019 February 25. This paper is dedicated to the memory of Neil Gehrels who, as WFIRST Project Scientist, gracefully shepherded this mission from its formal initiation in 2016, until his untimely death. We miss him and his leadership dearly. We would also like to thank members of the WFIRST Microlensing Science Investigation Team, as well as Jeff Kruk, Dave Content, Kevin Grady, and many others in the WFIRST program office for their support. We would like to thank Chris Hirata and Jay Anderson for their practical help and discussions. We thank the referee for their efforts. Finally, we would like to single out David Bennett, who has been a constant source of input and guidance as we have developed our models and worked on this paper. We recognize that, without his tireless efforts, a microlensing survey on WFIRST would not exist. This work was performed in part under contract with the California Institute of Technology (Caltech)/Jet Propulsion Laboratory (JPL) funded by NASA through the Sagan Fellowship Program executed by the NASA Exoplanet Science Institute. M.T.P. and B.S.G. were supported by NASA grants NNX14AF63G and NNG16PJ32C, as well as the Thomas Jefferson Chair for Discovery and Space Exploration. S.M. was supported by NSFC grants No. 11333003, 11390372, and 11761131004. Facility: Exoplanet Archive. - Software: Matplotlib (Hunter 2007), NumPy (Oliphant 2006), SciPy (Jones et al. 2001), Astropy (The Astropy Collaboration et al. 2013), gnuplot, WebbPSF (Perrin et al. 2012), General Polygon Clipper library (Murta 2015), MATLAB package for astronomy and astrophysics (Ofek 2014).
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Thomas Jefferson Chair for Discovery and Space ExplorationUNSPECIFIED
National Natural Science Foundation of China11333003
National Natural Science Foundation of China11390372
National Natural Science Foundation of China11761131004
Issue or Number:1
Record Number:CaltechAUTHORS:20190225-094628975
Persistent URL:
Official Citation:Matthew T. Penny et al 2019 ApJS 241 3
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:93216
Deposited By: Tony Diaz
Deposited On:25 Feb 2019 17:54
Last Modified:16 Nov 2021 16:56

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