Rationale

Recent measurements of the Hubble constant and (to a lesser extent) of the density and clustering strength of matter, hint at the possibility that cosmological parameters estimated at high- and low-redshift are inconsistent. Such a finding could be a sign that the highly successful Lambda CDM standard model of cosmology does not fully describe the true nature of our Universe, or could simply be a reflection of unrecognised systematics within one or more of these analyses. As a result, recent studies of low redshift probes utilising, in particular, the gravitational lensing of large scale structures (i.e. cosmic shear) have been particularly focused on the exploration and mitigation of systematic effects. At the sensitivity of current surveys, the community’s understanding of cosmic shear systematics is largely acceptable. However with the immense statistical power of next generation cosmic shear surveys, it will soon become paramount for the community to understand these systematics with unprecedented accuracy, particularly before proposing extensions to the standard LCDM paradigm: i.e. via dark energy, modified gravity, massive neutrinos, etc. Moreover, with the start of Rubin’s science operation and the launch of Euclid both in 2023, the IAU General Assembly 2022 is an extremely timely opportunity to address these questions. The aim of this focus meeting is therefore to bring together experts from the ongoing and future lensing surveys, thereby fostering collaboration between traditionally competitive teams, in order to build a consensus regarding cosmic shear methodologies, and identify the key systematics and cosmological models that will need to be tested in the 2020’s

SOC

  • Nicolas Martinet (LAM, France; co-chair)
  • Angus Wright (Ruhr University Bochum, Germany; co-chair)
  • Chris Blake (Swinburne University, Australia)
  • Zuhui Fan (Yunnan University, China)
  • Catherine Heymans (ROE, UK)
  • Elisabeth Krause (Steward Observatory, USA)
  • Clotilde Laigle (IAP, France)
  • Rachel Mandelbaum (Carnegie Mellon University, USA)
  • Peter Schneider (AIfA, Bonn, Germany)
  • Masahiro Takada (IPMU Tokyo, Japan)

Invited Speakers

  • Alexandra Amon (Cambridge, UK)
  • Marika Asgari (Hull, UK)
  • Matteo Cataneo (Bonn, Germany)
  • Hendrik Hildebrandt (Bochum, Germany)
  • Chris Hirata (Ohio State Univ., USA)
  • Renee Hlozek (Dunlap Institute, Canada)
  • Francois Lanusse (CEA, France)
  • Jia Liu (Kavli IPMU, Japan)
  • Hironao Miyatake (KMI, Japan)
  • Sherry Suyu (MPA/TUM, Germany)
  • Jun Zhang (Shanghai Jiao Tong Univ., China)

Programme

Code of conduct

The organisers are committed to ensuring that the focus meeting is supportive and inclusive of all members of the astronomical community, regardless of their expression of identity, their nationality, or their academic seniority. All participants must read and respect the IAU Code of Conduct on Ethics and Anti-Harassment in order to participate in this meeting.

Key Topics

  • Calibration of the redshift distribution
  • Current weak lensing surveys
  • Weak-lensing systematics
  • Non-standard lensing probes
  • Tensions in cosmology
  • Modelling extensions to LCDM
  • Future weak-lensing analyses

Session Outline and Summary

The meeting will be divided into 6 sessions of 1.5 hours each. We plan to group blocks of 2 sessions into 3 primary topics of interest (thereby allowing each topic to be covered in a full 3 hours). These topics are:

  1. Current weak-lensing surveys;
  2. Understanding tensions in cosmology; and
  3. Future weak-lensing analyses.

Generally each topic will be covered by 1 review talk, 6 regular talks, and one discussion session. The aim of this discussion time will be to summarize the topic, and identify interesting issues that will require further dedicated study in the 2020s. Contributed posters will be displayed during coffee breaks and advertised at the relevant discussion sessions.

Session 1: Current weak lensing surveys (1/2)

Presentation of the state-of-the-art of cosmic shear two-point statistics analyses (e.g., Dark Energy Survey, Kilo Degree Survey, Hyper Suprime Cam survey). Focus on weak-lensing systematics (e.g., photometric redshift calibration, galaxy shape measurement, intrinsic alignments of galaxies, baryon feedback)

Invited Speakers

  • Alexandra Amon
  • Marika Asgari
  • Hironao Miyatake

Session 2: Current weak lensing surveys (2/2)

Focus on non-standard lensing probes (e.g., bispectrum, peak statistics, minkowski functionals, mass map machine learning)

Invited Speakers

  • Jia Liu

Session 3: Tensions in cosmology (1/2)


Focus on non weak-lensing systematics (e.g., CMB systematics, H0 measurements)

Invited Speakers

  • Sherry Suyu (review)
  • Renee Hlozek

Session 4: Tensions in cosmology (2/2)


Focus on modelling extensions to LCDM (e.g., neutrinos, time-dependent dark energy, exotic models)

Invited Speakers

  • Matteo Cataneo

Session 5: Future weak-lensing analyses (1/2)


Presentation of future Stage IV weak-lensing surveys (e.g., Euclid, Rubin LSST, China Space Station Telescope, Roman)

Invited Speakers

  • Hendrik Hildebrandt
  • Jun Zhang
  • Francois Lanusse
  • Chris Hirata

Session 6: Future weak-lensing analyses (2/2)


Continuation of session 5, focussing on discussion of key points to retain for the future of cosmic shear.

Registration

Registration and abstract submission open on the 1st of January 2022 via the IAU General Assembly website:

https://www.iauga2021.org/

Practical information

Important dates

  • Meeting dates: August 10th – 11th 2022
  • Opening of registration: January 1st 2022
  • Abstract submission deadline: March 31st 2022
  • Poster submission deadline: May 31st 2022

Venue

BEXCO, Busan, South Korea
Room location to be announced later

Contact

For any information regarding the General Assembly, please contact the National Organizing Committee: sec@iauga2021.org

For information related to this Focus Meeting, please contact Nicolas Martinet (nicolas.martinet@lam.fr) and Angus Wright (awright@astro.ruhr-uni-bochum.de)