Quasar lenses in the south: searches over the DES public footprint

TY - JOUR

T1 - Quasar lenses in the south: searches over the DES public footprint

AU - Agnello, Adriano

AU - Spiniello, Chiara

PY - 2019/10/21

Y1 - 2019/10/21

N2 - We have scanned 5000 deg2 of Southern Sky to search for strongly lensed quasars with five methods, all source oriented, but based on different assumptions and selection criteria. We present a list of high-grade candidates from each method (totalling 98 unique, new candidates), to facilitate follow-up spectroscopic campaigns, including two previously unknown quadruplets, WG 210014.9-445206.4 and WG 021416.37-210535.3. We analyse morphological searches based on Gaia multiplet detection and astrometric offsets, fibre-spectroscopic preselection, and X-ray and radio pre-selection. The performance and complementarity of the methods are evaluated on a common sample of known lenses in the Dark Energy Survey public Data Release 1 (DR1) footprint.We recovered in total 13 known lenses, of which 8 are quadruplets. Morphological and colour selection of objects, from the WISE and Gaia-DR2 surveys, recovers most of those known lenses, but searches in the radio and X-ray cover regimes that are beyond the completeness of Gaia. Given the footprint, pre-selection, and depth limits, the current number of quads indicates that the union of these searches is complete, and the expected purity on high-grade candidates is ≈60 per cent. Ongoing, spectroscopic campaigns confirm this estimate.

AB - We have scanned 5000 deg2 of Southern Sky to search for strongly lensed quasars with five methods, all source oriented, but based on different assumptions and selection criteria. We present a list of high-grade candidates from each method (totalling 98 unique, new candidates), to facilitate follow-up spectroscopic campaigns, including two previously unknown quadruplets, WG 210014.9-445206.4 and WG 021416.37-210535.3. We analyse morphological searches based on Gaia multiplet detection and astrometric offsets, fibre-spectroscopic preselection, and X-ray and radio pre-selection. The performance and complementarity of the methods are evaluated on a common sample of known lenses in the Dark Energy Survey public Data Release 1 (DR1) footprint.We recovered in total 13 known lenses, of which 8 are quadruplets. Morphological and colour selection of objects, from the WISE and Gaia-DR2 surveys, recovers most of those known lenses, but searches in the radio and X-ray cover regimes that are beyond the completeness of Gaia. Given the footprint, pre-selection, and depth limits, the current number of quads indicates that the union of these searches is complete, and the expected purity on high-grade candidates is ≈60 per cent. Ongoing, spectroscopic campaigns confirm this estimate.

KW - catalogues

KW - galaxies: formation

KW - dark matter

U2 - 10.1093/mnras/stz2200

DO - 10.1093/mnras/stz2200

M3 - Journal article

SN - 0035-8711

VL - 489

SP - 2525

EP - 2535

JO - Monthly Notices of the Royal Astronomical Society

JF - Monthly Notices of the Royal Astronomical Society

IS - 2

ER -