A strong-lensing elliptical galaxy in the MaNGA survey.

Abstract

I report discovery of a new galaxy-scale gravitational lens system, identified using public data from the MaNGA survey, as part of a systematic search for lensed background line emitters. The lens is SDSS J170124.01+372258.0, a giant elliptical galaxy with velocity dispersion σ = 256 km s−1, at a redshift of zl = 0.122. After modelling and subtracting the target galaxy light, the integral-field data-cube reveals [O II], [O III] and Hβ emission lines corresponding to a source at zs = 0.791, forming an identifiable ring around the galaxy centre. If the ring is formed by a single lensed source, then the Einstein radius is REin ≈ 2.3 arcsec, projecting to ∼5 kpc at the distance of the lens. The total projected lensing mass is MEin = (3.6±0.6)× 1011 M⊙, and the total J-band mass-to-light ratio is 3.0±0.7 solar units. Plausible estimates of the likely dark matter content could reconcile this with a Milky-Way-like initial mass function (for which M/L ≈ 1.5 is expected), but heavier IMFs are by no means excluded with the present data. An alternative interpretation of the system, with a more complex source plane, is also discussed. The discovery of this system bodes well for future lens searches based on MaNGA and other integral-field spectroscopic surveys.