[Paper Review] Cosmology with the Large Synoptic Survey Telescope

Hu Zhan, J. A. Tyson|arXiv (Cornell University)|Jul 21, 2017

Galaxies: Formation, Evolution, PhenomenaPhysics and Astronomy152 references5 citations

TL;DR

The LSST will enable a new era of precision cosmology by conducting a deep, wide, and fast survey of 18,000 square degrees across six optical passbands (ugrizy), reaching a coadded depth of r~27.5 over 10 years, with 800 visits per sky patch. This data will power diverse cosmological probes—large-scale structure, weak lensing, Type Ia supernovae, galaxy clusters, and strong lensing—providing tight constraints on dark energy and the cosmological model when combined with cosmic microwave background data.

ABSTRACT

The Large Synoptic Survey Telescope (LSST) is a high etendue imaging facility that is being constructed atop Cerro Pachon in Northern Chile. It is scheduled to begin science operations in 2022. With an 8.4m (6.5m effective) aperture, a three-mirror design achieving a seeing-limited 9.6deg^2 field of view, and a 3.2 Gigapixel camera, the LSST has the deep-wide-fast imaging capability to carry out an 18,000deg^2 survey in six passbands (ugrizy) to a coadded depth of r~27.5 over 10 years using 90% of its observational time. The remaining 10% will be devoted to deeper and faster time-domain observations and smaller surveys. In total, each patch of the sky in the main survey will receive 800 visits allocated across the six passbands with 30s exposure visits. The huge volume of high-quality LSST data will provide a wide range of science opportunities and open a new era of precision cosmology with unprecedented statistical power and tight control of systematic errors. In this review, we give a brief account of the LSST cosmology program with an emphasis on dark energy investigations. The LSST will address dark energy physics and cosmology in general by exploiting diverse precision probes including large-scale structure, weak lensing, type Ia supernovae, galaxy clusters, and strong lensing. Combined with the cosmic microwave background data, these probes form interlocking tests on the cosmological model and the nature of dark energy. The LSST data products will be made available to the U.S. and Chilean scientific communities and to international partners with no proprietary period. Close collaborations with coeval surveys observing at a variety of wavelengths, resolutions, depths, and timescales will be a vital part of the LSST science program, which will not only enhance specific studies but also allow a more complete understanding of the universe through different windows.

Motivation & Objective

• To establish the LSST as a transformative facility for precision cosmology by leveraging its deep, wide, and fast imaging capabilities.
• To address fundamental questions about dark energy and the nature of cosmic acceleration using diverse observational probes.
• To ensure open, timely access to LSST data for the U.S., Chile, and international scientific communities with no proprietary period.
• To enable synergistic science by integrating LSST data with coeval surveys across wavelengths, resolutions, and timescales.
• To develop a comprehensive cosmology program that interlocks multiple probes to test the standard cosmological model robustly.

Proposed method

• Conduct a 10-year survey of 18,000 square degrees using a 3.2 Gigapixel camera on an 8.4m (6.5m effective) aperture telescope with a 9.6deg² field of view.
• Achieve a coadded depth of r~27.5 in the r-band through 800 visits per sky patch, each with 30-second exposures across six passbands (ugrizy).
• Utilize a three-mirror design to achieve seeing-limited image quality over the wide field of view.
• Employ a dual observing strategy: 90% of time for the main deep-wide survey, 10% for deeper, faster time-domain and smaller-area surveys.
• Integrate LSST data with cosmic microwave background data to form interlocking tests on the cosmological model.
• Foster close collaborations with multi-wavelength, multi-resolution, and multi-timescale surveys to enhance scientific reach and completeness.

Experimental results

Research questions

• RQ1 How can the LSST’s deep, wide, and fast survey capabilities constrain the nature of dark energy through multiple independent cosmological probes?
• RQ2 What is the statistical power and systematic error control achievable in large-scale structure and weak lensing measurements from the LSST dataset?
• RQ3 How do combined constraints from weak lensing, Type Ia supernovae, galaxy clusters, and strong lensing improve tests of the standard cosmological model?
• RQ4 In what ways can open, non-proprietary data access accelerate cosmological discovery and enable cross-survey synergy?
• RQ5 How can multi-wavelength and multi-timescale collaborations enhance the scientific yield of the LSST cosmology program?

Key findings

• The LSST will deliver a coadded depth of r~27.5 across 18,000 square degrees, enabling the detection of faint and distant cosmological sources.
• Each sky patch will receive 800 visits across six passbands, providing exceptional temporal and photometric resolution for time-domain and photometric studies.
• The LSST’s wide-field, high-throughput design allows for unprecedented statistical power in probing large-scale structure and weak gravitational lensing.
• The combination of LSST’s diverse cosmological probes with cosmic microwave background data forms robust, interlocking tests of the cosmological model.
• Open data release with no proprietary period will maximize scientific impact and enable broad community engagement.
• Synergies with coeval surveys across wavelengths, resolutions, and timescales will significantly enhance the completeness and interpretability of cosmological results.