ALMA Measurement of 10 kpc-scale Lensing Power Spectra towards the Lensed Quasar MG J0414+0534

Understand

The lensing power spectra for gravitational potential, astrometric shift, and convergence perturbations are powerful probes to investigate dark matter structures on small scales.

• We report the first lower and upper bounds of these lensing power spectra on angular scale $\sim 1$arcsec towards the anomalous quadruply lensed quasar MG$\,$J0414+0534 at a redshift $z=2.639$.
• To obtain the spectra, we conducted observations of MG$\,$J0414+0534 using the Atacama Large Millimeter/submillimeter Array (ALMA) with high angular resolution (0.02 arcsec to 0.05 arcsec).
• We developed a new partially non-parametric method in which Fourier coefficients of potential perturbation are adjusted to minimize the difference between linear combinations of weighted mean de-lensed images.