High precision microlensing maps of the Galactic bulge

Abstract

We present detailed maps of the microlensing optical depth and event density over an area of 195 sq. deg towards the Galactic bulge. The maps are computed from synthetic stellar catalogues generated from the Besancon Galaxy Model, which comprises four stellar populations and a three-dimensional extinction map calibrated against the Two-Micron All-Sky Survey. The optical depth maps have a resolution of 15 arcminutes, corresponding to the angular resolution of the extinction map. We compute optical depth and event density maps for all resolved sources above I=19, for unresolved (difference image) sources magnified above this limit, and for bright standard candle sources in the bulge. We show that the resulting optical depth contours are dominated by extinction effects, exhibiting fine structure in stark contrast to previous theoretical optical depth maps. Optical depth comparisons between Galactic models and optical microlensing survey measurements cannot safely ignore extinction or assume it to be smooth. We show how the event distribution for hypothetical J and K-band microlensing surveys, using existing ground-based facilities such as VISTA, UKIRT or CFHT, would be much less affected by extinction, especially in the K band. The near infrared provides a substantial sensitivity increase over current I-band surveys and a more faithful tracer of the underlying stellar distribution, something which upcoming variability surveys such as VVV will be able to exploit. Synthetic population models offer a promising way forward to fully exploit large microlensing datasets for Galactic structure studies.

8 pages, submitted to MNRAS

References in corpus (1)

• Interstellar Extinction and Long-Period Variables in the Galactic Center

Cited by in corpus (30)

• VISTA Variables in the Via Lactea (VVV): The public ESO near-IR variability survey of the Milky Way
• Predictions of the WFIRST Microlensing Survey I: Bound Planet Detection Rates
• Chemical evolution of the Galactic bulge as traced by microlensed dwarf and subgiant stars. IV. Two bulge populations
• Predictions of the Nancy Grace Roman Space Telescope Galactic Exoplanet Survey II: Free-Floating Planet Detection Rates
• ExELS: an exoplanet legacy science proposal for the ESA Euclid mission I. Cold exoplanets
• Astrophysical Applications of Gravitational Microlensing
• Microlensing optical depth and event rate toward the Galactic bulge from 8 yr of OGLE-IV observations
• The Microlensing Event Rate and Optical Depth Toward the Galactic Bulge from MOA-II
• OGLE-III Microlensing Events and the Structure of the Galactic Bulge
• MOA-II Galactic Microlensing Constraints: The Inner Milky Way has a Low Dark Matter Fraction and a Near Maximal Disk
• PopSyCLE: A New Population Synthesis Code for Compact Object Microlensing Events
• Microlensing as a probe of the Galactic structure; 20 years of microlensing optical depth studies
• Prediction on detection and characterization of Galactic disk microlensing events by LSST
• Possible Solution of the long-standing discrepancy in the Microlensing Optical Depth Toward the Galactic Bulge by correcting the stellar number count
• Besançon Galactic model analysis of MOA-II microlensing: evidence for a mass deficit in the inner bulge
• Gaia Data Release 3: Microlensing Events from All Over the Sky
• VVV Survey Microlensing: the Galactic Longitude Dependence
• Empirical microlensing event rates predicted by a phenomenological model
• The OGLE-III planet detection efficiency from six years of microlensing observations (2003 to 2008)
• Predictions for the Detection and Characterization of a Population of Free-Floating Planets with K2 Campaign 9
• Rapidly Rotating Lenses: Repeating features in the lightcurves of short period binary microlenses
• Constraining the Thin Disc Initial Mass Function using Galactic Classical Cepheids
• VVV Survey Microlensing: the Galactic Latitude Dependence
• The microlensing rate and distribution of free-floating planets towards the Galactic bulge
• MaB$\mu$lS-2: high-precision microlensing modelling for the large-scale survey era
• Gravitational Microlensing by Neutron Stars and Radio Pulsars: Event Rates, Timescale Distributions, and Mass Measurements
• A Bayesian algorithm for model selection applied to caustic-crossing binary-lens microlensing events
• A Fast Approximate Approach to Microlensing Survey Analysis
• MOA-2019-BLG-008Lb: a new microlensing detection of an object at the planet/brown dwarf boundary
• VVV survey microlensing: candidate events with source in the far disk