Letters of Intent received in 2019

LoI 2021-2077
Serving Astrophysics and Cosmology with Gravitational Lensing

Topics

Gravitational Lensing: strong, weak, micro - Cosmology - Sky surveys - AGN and quasars - Galaxy evolution - Gravitational waves - Instruments and analysis methods - Visualisation tools and outreach.

Rationale

Gravitational lensing, first seen as mere theoretical curiosity, is now broadly acknowledged as a natural tool to tackle a vast range of astrophysical problems at all spatial and temporal scales, and to constrain cosmological parameters. More than 15 years have passed since the last IAU Symposium directly related to gravitational lensing. Now is the time to review the field and its past and current achievements and to explore new avenues made possible thanks to the emergence of totally new fields such as gravitational waves astronomy. This comes at a time when major surveys will be very close to their start of operations, all with gravitational lensing as the main science driver, e.g. Euclid and LSST, to mention only the most advanced ones. It also comes in a new era where data mining in large - completed - ground based surveys is possible and for which data are now or will soon be in the public domain: DES, PanSTARRS, KiDS, HSC, BOSS, eBOSS, CFIS, Gaia.

The meeting will be hosted by Ecole Polytechnique Fédérale de Lausanne (EPFL) in Switzerland (http://www.epfl.ch). Located on the shore of Geneva Lake, in the French-speaking part of Switzerland, EPFL is one of the top interdisciplinary institutes in Europe. While the core of the week-long meeting will be gravitational lensing, the goal is to gather a broad community of scientists working in theory, observations, instruments and analysis methods to foster interdisciplinary work about this natural phenomenon and to extend its fields of applications in areas where it may have been overlooked.

The meeting itself will include the following areas.

Strong, Micro and Weak Lensing: will include a broad presentation of the 3 lensing regimes, each time confronting theoretical and observational aspects to reflect what’s possible and what’s not practical with gravitational lensing in terms of measurements and realistic astrophysical and cosmological constraints. This section will emphasize the merits, expectations and limitations of gravitational lensing and will draw the best possible picture of where the field stands, now.

Cosmology: will review the expectations we have for weak lensing surveys, confront (and combine) them to spectroscopic surveys and explore lensing in the vicinity of black holes. The impact of time delays in strongly lensed quasars and supernovae on the measurement of H0 will be evaluated as well as ways to reconcile the growing tension between measurements of H0 in the early and later universe.

AGN, Quasars, and Galaxy Formation and Evolution: will emphasize the use of lensing in all 3 regimes to measure dark matter in LSS, clusters, and galaxies or in the form of primordial black holes through microlensing. Focus will be on the evaluation of the level of compatibility of purely lensing-based results with other more traditional approaches.

Gravitational Waves and Black Holes: will include strong and weak lensing of gravitational waves and explore the impact of GW and black hole science. Conversely, it will address how/if GW can be used to constrain cosmology, in particular their use to measure H0.

Instruments and Surveys: will be dedicated to a presentation of the most promising surveys over a broad range of wavelengths, from optical and infrared (Euclid, LSST) to the radio domain (SKA). An overview of synergies with purely optical spectroscopic surveys will be given and of the follow-up facilities that are being put in place (or that are needed) for imaging and spectroscopic data, in particular in the time domain (transient science).

Signal Processing and Analysis Methods: will focus on how to deal with massive surveys at all wavelengths, including the radio domain covered with ALMA and SKA. A part will be devoted to data-mining methods, shape measurements of galaxies, machine learning methods to find, characterize and model strong lensed systems and on how to confront the results achieved solely with lensing to others.

Outreach and Pedagogical Aspects: will emphasize the efforts of the lensing community to advertise the field and to make it understandable to the general public. This will also include presentations in the area of citizen science and virtual reality and will gather the authors of existing pedagogical tools. Eventually it will foster interactions between the different outreach committees of past, ongoing and future surveys.

Note that, depending on the selected invited speakers and participants, the above broad themes will not be addressed sequentially, but mixed, so that gravitational lensing remains perceived as a tool rather than a field in itself.