Microlensing Techniques in Quasar Accretion Disks
Summary
Gravitational microlensing of lensed quasars has emerged as a powerful probe of the innermost regions of active galactic nuclei, enabling resolutions down to microarcsecond scales. By monitoring the differential magnification of continuum and emission-line regions as compact objects in a foreground lens galaxy traverse projected caustic networks, researchers can reconstruct the size, temperature profile and kinematics of the accretion disc, as well as the geometry of the broad-line region (BLR). Techniques such as inverse ray-shooting, Bayesian light-curve modelling and high-resolution magnification maps allow the mapping of source structure and motions within relativistic discs. Recent methodological advances include the incorporation of general-relativistic disc models, machine-learning inference of black hole parameters and multi-wavelength campaigns to disentangle intrinsic variability from microlensing signals. These efforts yield constraints on black hole mass, spin and accretion physics, while also informing models of stellar and dark matter distributions in lensing galaxies.
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Microlensing Techniques in Quasar Accretion Disks publication trend
The graph below shows the total number of articles in microlensing techniques in quasar accretion disks across all publications each year (not limited to Nature Index journals).
Technical terms
Gravitational microlensing: Transient magnification of a background quasar by compact masses in a foreground galaxy, causing time-variable amplification of light on microarcsecond scales.
Caustic: A critical curve in the source plane where the microlensing magnification formally diverges, producing sharp changes in observed flux as the source crosses it.
Magnification map: A pixelated representation of the microlensing magnification field across the source plane, generated by ray-shooting simulations through a distribution of microlenses.
Broad-line region (BLR): The region of high-velocity gas close to the quasar nucleus that produces Doppler-broadened emission lines, whose size and geometry can be constrained by microlensing.
Innermost stable circular orbit (ISCO): The smallest radius at which matter can stably orbit a black hole, marking the inner edge of the accretion disc and influencing microlensing light-curve features during caustic crossings.
References
- First Direct Evidence for Keplerian Rotation in Quasar Inner Broad-line Regions. The Astrophysical Journal Letters (2024).
- Microlensing of Strongly Lensed Quasars. Space Science Reviews (2024).
- Resolving the vicinity of supermassive black holes with gravitational microlensing. Monthly Notices of the Royal Astronomical Society (2024).
- An Improved GPU-based Ray-shooting Code for Gravitational Microlensing. The Astrophysical Journal (2022).
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