PopSyCLE: A New Population Synthesis Code for Compact Object Microlensing Events

Lam, Casey; Lu, Jessica R.; Hosek, Matthew W.; Dawson, William A.; Golovich, Nathan

doi:10.3847/1538-4357/ab5fd3

Cited by 47 publications

(119 citation statements)

References 112 publications

(141 reference statements)

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“…Mróz et al (2020a) conducted the largest Galactic plane search for microlensing events prior to this work, discovering 630 events in the OGLE survey observing 3000 square degrees of the Galactic plane between 2013 and 2019. ZTF Lam et al (2020) found that black holes could be identified by placing microlensing events in the t E -π E space and looking for the events with the largest t E and the shortest π E . In Figure 14 we place our events in this space, alongside all observable events from within our PopSyCLE simulations.…”

Section: Discussionmentioning

confidence: 99%

“…Only a few can be rigorously follow up astrometrically and the astrometric signal of events found toward the bulge is at the edge of current observational capabilities. Simulations indicate that black hole candidates can be ideally selected from a list of microlensing events by searching for those with larger Einstein crossing time and smaller microlensing parallaxes (Lam et al 2020). Furthermore simulations indicate that events in the Galactic plane have larger microlensing parallaxes and astrometric shifts overall that can make finding black hole candidates amongst these surveys easier than surveys pointed toward the Galactic bulge (Medford et al 2020).…”

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confidence: 96%

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60 Microlensing Events from the Three Years of Zwicky Transient Facility Phase One

Medford¹,

Lu²,

Nugent³

et al. 2022

Preprint

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Microlensing events have historically been discovered throughout the Galactic bulge and plane by surveys designed solely for that purpose. We conduct the first multi-year search for microlensing events on the Zwicky Transient Facility (ZTF), an all-sky optical synoptic survey that observes the entire visible Northern sky every few nights. We discover 128 high quality microlensing events in the three years of ZTF-I using the bulk lightcurves in the ZTF Public Data Release 5. We find an excess of longduration Galactic plane events when comparing our results to both previous surveys and simulations. 35 of our events are found outside of the Galactic plane (|b| ≥ 15 • ), nearly tripling the number of previously discovered events in the stellar halo from surveys pointed toward the Magellanic Clouds and the Andromeda Galaxy. We also record 1690 ongoing candidate events as potential microlensing that can continue to be observed by ZTF-II for identification. The scalable and computationally efficient methods developed in this work can be applied to future synoptic surveys such as the Rubin Observatory's Legacy Survey of Space and Time and the Nancy Grace Roman Space Telescope as they attempt to find microlensing events in even larger and deeper datasets.

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Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 96%

60 Microlensing Events from the Three Years of Zwicky Transient Facility Phase One

Medford¹,

Lu²,

Nugent³

et al. 2022

Preprint

Self Cite

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show abstract

“…For initial-final mass relationships of remnants, we apply the model used by Lam et al (2020), where a linear relation of Kalirai et al (2008), M WD = 0.109M ini + 0.394M , is used for white dwarfs and a modified probabilistic relation based on Raithel et al (2018) is used for neutron stars and black holes. See Appendix C of Lam et al (2020) and references therein for more details.…”

Section: Stellar Mass Functionmentioning

confidence: 99%

A Parametric Galactic Model toward the Galactic Bulge Based on Gaia and Microlensing Data

Koshimoto,

Baba,

Bennett

2021

Preprint

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We developed a parametric Galactic model toward the Galactic bulge by fitting to spatial distributions of the Gaia DR2 disk velocity, VVV proper motion, BRAVA radial velocity, OGLE-III red clump star count, and OGLE-IV star count and microlens rate, optimized for use in microlensing studies. We include the asymmetric drift of Galactic disk stars and the dependence of velocity dispersion on Galactic location in kinematic model, which has been ignored in most previous models used for microlensing studies. We show that our model predicts a microlensing parameter distribution that is significantly different from the one with a typically used model in the previous studies. Through our modeling, we estimate various fundamental model parameters for our Galaxy, including the initial mass function (IMF) in the inner Galaxy. Combined constraints from star counts and the microlensing event timescale distribution from the OGLE-IV survey, in addition to a prior on the bulge stellar mass, enable us to successfully measure IMF slopes using a broken power law form over a broad mass range, α bd = 0.22 +0.20 −0.55 for M < 0.08 M , α ms = 1.16 +0.08 −0.15 for 0.08 M ≤ M < M br , and α hm = 2.32 +0.14 −0.10 for M ≥ M br , as well as a break mass at M br = 0.90 +0.05 −0.14 M . This is significantly different from the Kroupa IMF for local stars, but similar to the Zoccali IMF measured from a bulge luminosity function. We also estimate the dark matter mass fraction in the bulge region of 28 ± 7% which could be larger than a previous estimate. Because our model is purely parametric, it can be universally applied using the parameters provided in this paper.

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“…This method has also been used to make detailed predictions for exoplanet microlensing yields for forthcoming space missions such as Euclid (Penny et al 2013) and NGRST (Penny et al 2019) using a more recent version of the BGM (variant BGM1106). Recently, a population synthesis based microlensing model has been developed to study microlensing due to black holes (Lam et al 2020). Penny et al (2019) noted that the BGM1106 model does not provide a close match to the HST stellar kinematics study of Clarkson et al (2008).…”

Section: The Besançon Galactic Modelmentioning

confidence: 99%

MaBμlS-2: high-precision microlensing modelling for the large-scale survey era

Specht

Kerins

Awiphan

et al. 2020

Monthly Notices of the Royal Astronomical Society

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Galactic microlensing datasets now comprise in excess of 104 events and, with the advent of next-generation microlensing surveys that may be undertaken with facilities such as the Rubin Observatory (formerly LSST) and Roman Space Telescope (formerly WFIRST), this number will increase significantly. So too will the fraction of events with measurable higher order information, such as finite-source effects and lens–source relative proper motion. Analysing such data requires a more sophisticated Galactic microlens modelling approach. We present a new second-generation Manchester–Besançon Microlensing Simulator (MaBμlS-2), which uses a version of the Besançon population synthesis Galactic model that provides good agreement with stellar kinematics observed by the Hubble Space Telescope (HST) towards the bulge. MaBμlS-2 provides high-fidelity signal-to-noise limited maps of the microlensing optical depth, rate and average time-scale towards a 400 deg2 region of the Galactic bulge in several optical to near-infrared pass-bands. The maps take full account of the unresolved stellar background, as well as limb-darkened source profiles. Comparing MaBμlS-2 with the efficiency-corrected OGLE-IV 8000 event sample shows a much improved agreement over the previous version of MaBμlS and succeeds in matching even small-scale structural features in the OGLE-IV event rate map. However, evidence remains for a small underprediction of the event rate per source and overprediction of the time-scale. MaBμlS-2 is available online (www.mabuls.net, Specht & Kerins) to provide on-the-fly maps for user-supplied cuts in survey magnitude, event time-scale and relative proper motion.

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PopSyCLE: A New Population Synthesis Code for Compact Object Microlensing Events

Cited by 47 publications

References 112 publications

60 Microlensing Events from the Three Years of Zwicky Transient Facility Phase One

60 Microlensing Events from the Three Years of Zwicky Transient Facility Phase One

A Parametric Galactic Model toward the Galactic Bulge Based on Gaia and Microlensing Data

MaBμlS-2: high-precision microlensing modelling for the large-scale survey era

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