Unveiling a Population of Strong Galaxy-Galaxy Lensed Faint Dusty Star-Forming Galaxies

TL;DR

This paper reports the discovery of a population of faint dusty star-forming galaxies strongly lensed by other galaxies, using deep submillimeter surveys and JWST data, extending the known counts to fainter flux levels and confirming model predictions.

Contribution

It presents the first systematic identification and confirmation of faint galaxy-galaxy lensed dusty galaxies, expanding the understanding of lensing populations at lower flux levels.

Findings

Discovered 13 faint strongly lensed dusty galaxies.

Constructed 450μm number counts down to fainter flux levels.

Lensing fractions align with theoretical model predictions.

Abstract

The measurements of the number density of galaxy-galaxy strong lenses can be used to put statistical constraints on the foreground mass distributions. Dusty galaxies uncovered in submillimeter surveys are particularly useful in this regard because of the large volume probed by these surveys. Previous discoveries of strong galaxy-galaxy lensed dusty galaxies are predominantly the brightest in the sky discovered by Herschel, SPT, and Planck. However, models have also predicted a non-negligible fraction of strong galaxy-galaxy lensed faint dusty galaxies, which were difficult to confirm due to technical difficulties. Utilizing the deepest SCUBA-2 submillimeter survey, STUDIES, in both the COSMOS and the UDS fields, together with a red JWST color selection method, we discover a population of 13 strong galaxy-galaxy lensed faint dusty galaxies. The rich ancillary data allow us to confirm their strongly lensed nature via estimates of redshifts and lens modeling. Our systematic search has allowed us to construct the 450$\mu$m number counts of strongly lensed sources down to the flux levels about an order of magnitude fainter than previous measurements. The measured lensing fractions of $\sim$1% are consistent with predictions from models that also successfully produce the number density of the strong galaxy-galaxy lensed bright dusty galaxies. Future searches from Euclid and Roman are expected to discover orders of magnitude more strongly lensed faint dusty galaxies.