[Paper Review] Synergy between the Large Synoptic Survey Telescope and the Square Kilometre Array

David Bacon, Sarah Bridle+19 more|arXiv (Cornell University)|Jan 16, 2015

Radio Astronomy Observations and Technology5 references4 citations

TL;DR

This paper demonstrates that combining data from the Large Synoptic Survey Telescope (LSST) and the Square Kilometre Array (SKA) significantly enhances cosmological and astrophysical science by enabling cross-calibration, systematic error reduction, and complementary constraints. The synergy leverages LSST's high-cadence optical imaging and SKA's deep radio surveys to improve dark energy and gravity parameter constraints, galaxy evolution studies, and transient detection through multi-wavelength, multi-timescale analysis.

ABSTRACT

We provide an overview of the science benefits of combining information from the Square Kilometre Array (SKA) and the Large Synoptic Survey Telescope (LSST). We first summarise the capabilities and timeline of the LSST and overview its science goals. We then discuss the science questions in common between the two projects, and how they can be best addressed by combining the data from both telescopes. We describe how weak gravitational lensing and galaxy clustering studies with LSST and SKA can provide improved constraints on the causes of the cosmological acceleration. We summarise the benefits to galaxy evolution studies of combining deep optical multi-band imaging with radio observations. Finally, we discuss the excellent match between one of the most unique features of the LSST, its temporal cadence in the optical waveband, and the time resolution of the SKA.

Motivation & Objective

• Address the challenge of systematic errors in weak gravitational lensing and galaxy clustering measurements by combining LSST and SKA data.
• Improve constraints on dark energy and modified gravity by integrating LSST's shape and clustering data with SKA's radio continuum and intensity mapping.
• Enable more accurate photometric redshifts and galaxy property calibration by cross-correlating LSST's optical photometry with SKA's spectroscopic redshifts.
• Advance time-domain astrophysics by exploiting LSST's rapid optical cadence and SKA's high time-resolution radio observations to detect and characterize transients.
• Provide a comprehensive picture of galaxy evolution by combining LSST's stellar population and metallicity data with SKA's neutral hydrogen and AGN diagnostics.

Proposed method

• Use LSST's 10-year survey of 18,000 deg² in six optical bands (ugrizy) with 0.2 arcsec² pixels and 3.2 Gigapixel camera to map large-scale structure and detect transients.
• Integrate SKA data from continuum surveys and intensity mapping to measure galaxy clustering and power spectra in the radio band, particularly at high redshift.
• Apply cross-correlation techniques between optical and radio lensing signals to mitigate shape measurement systematics and improve cosmological parameter estimation.
• Combine LSST's nightly image subtraction pipelines with SKA’s commensal transient detection systems to enable rapid follow-up of optical and radio transients.
• Utilize LSST’s Deep Drilling Fields to calibrate SKA’s brightness temperature fluctuation data from the epoch of reionization.
• Leverage LSST’s photometric redshifts and SKA’s spectroscopic redshifts to cross-validate and improve redshift accuracy for galaxy samples.

Experimental results

Research questions

• RQ1 How can the combination of LSST and SKA data improve constraints on dark energy and gravity parameters beyond what either survey can achieve alone?
• RQ2 In what ways do LSST and SKA complement each other in measuring galaxy properties such as neutral hydrogen content, star formation rate, and metallicity?
• RQ3 How does the synergy between LSST’s high-cadence optical observations and SKA’s time-resolved radio data enhance the detection and characterization of astrophysical transients?
• RQ4 To what extent can cross-correlation of optical and radio lensing signals reduce systematic errors in weak gravitational lensing measurements?
• RQ5 How can LSST photometric redshifts be improved using spectroscopic redshifts from SKA continuum surveys, and vice versa?

Key findings

• The combination of LSST and SKA data reduces systematics in weak gravitational lensing by cross-correlating optical and radio shape measurements, which are affected by different systematic effects.
• LSST lensing and clustering data combined with SKA galaxy clustering and spectroscopic redshifts yield tighter constraints on dark energy and gravity parameters than either survey alone.
• Intensity mapping with SKA and continuum surveys combined with LSST’s large-scale structure data improve cosmological parameter estimation, particularly for the equation of state of dark energy.
• Strong lensing studies benefit from the joint capability of LSST and SKA to resolve both lens and source structures in detail, improving mass modeling accuracy.
• LSST’s photometric redshifts for SKA sources are significantly improved through cross-correlation with SKA’s spectroscopic redshifts, reducing photo-z scatter.
• The synergy enables a more complete understanding of galaxy evolution by combining LSST’s stellar population and metallicity data with SKA’s neutral hydrogen and AGN diagnostics, especially in the epoch of reionization.