New Estimator for Gravitational Lensing Using Galaxy and Intensity Mapping Surveys.

Area of Science:

• Cosmology
• Astrophysics
• Observational Astronomy

Background:

• Gravitational lensing is a key probe of cosmic structure and dark energy.
• Current methods for measuring lensing potential are limited by cosmic variance and systematic effects.
• Intensity mapping (IM) and galaxy number counts are complementary cosmological probes.

Purpose of the Study:

• Introduce a new tomographic estimator, GIMCO (galaxy intensity mapping cross-correlation estimator), for gravitational lensing potential.
• Improve the signal-to-noise ratio (SNR) for lensing detection, particularly on linear scales and at intermediate redshifts.
• Reduce contamination from density-density correlations and susceptibility to systematic effects.

Main Methods:

• Developed GIMCO by cross-correlating intensity mapping (IM) and galaxy number counts at distinct redshifts (z_f, z_b).
• The estimator is formulated as IM(z_f)×galaxy(z_b) - galaxy(z_f)×IM(z_b).
• Analyzed the impact of cosmic variance, shot noise, and interferometer noise on the SNR.

Main Results:

• GIMCO significantly suppresses cosmic variance, leading to a factor of 30 improvement in SNR for cosmic variance-dominated surveys compared to galaxy counts alone.
• Demonstrated GIMCO's effectiveness with specific survey combinations: Dark Energy Survey (DES) × HIRAX yields SNR ~4, and Euclid × HIRAX yields SNR ~52.
• Showed a factor of 4-5 improvement in SNR for Euclid × HIRAX compared to DES alone, with significant gains below redshift 1.6.

Conclusions:

• GIMCO offers a powerful new tool for detecting gravitational lensing and probing cosmology.
• The estimator is particularly valuable for testing dark energy and modified gravity theories at low and intermediate redshifts.
• GIMCO's reduced susceptibility to systematics and enhanced SNR make it a promising technique for future large-scale surveys.