Deep Extragalactic Visible Legacy Survey: Data Release 1 blended spectra search for candidate strong gravitational lenses

Here, we present a catalogue of blended spectra in Data Release 1 of the Deep Extragalactic Visible Legacy Survey (DEVILS) on the Anglo-Australian Telescope. Of the 23 197 spectra, 181 showed signs of a blend of redshifts and spectral templates. We examine these blends in detail for signs of either a candidate strong lensing galaxy or a useful overlapping galaxy pair. One of the three DEVILS target fields, COSMOS (D10), is close to complete and it is fully imaged with Hubble Space Telescope Advanced Camera for Surveys, and we visually examine the 57 blended spectra in this field in the F814W postage stamps. Nine are classical strong lensing candidates with an elliptical as the lens, out to higher redshifts than any previous search with spectroscopic surveys such as Sloan Digital Sky Survey (SUSS) or Galaxy And Mass Assembly. The gravitational lens candidate success rate is similar to earlier such searches (0.1 per cent). Strong gravitational lenses identified with blended spectroscopy have typically shown a high success rate (>70 per cent), which make these interesting targets for future higher resolution lensing studies, monitoring for supernova cosmography, or searches for magnified atomic hydrogen signal.

Automated summary

In this study, we present a catalogue of blended spectra in the DEVILS data release. Out of 23,197 spectra, 181 showed signs of a blend of redshifts and spectral templates. We examined these blends, and identified nine strong gravitational lensing candidates. By visually examining the Hubble Space Telescope images, we found useful overlapping galaxy pairs.