Kavli Affiliate: Xuebing Wu
| First 5 Authors: Di Wu, Di Wu, , ,
| Summary:
Wide-separation lensed quasars (WSLQs) are a rare subclass of strongly lensed
quasars produced by massive galaxy clusters. They provide valuable probes of
dark-matter halos and quasar host galaxies. However, only about ten WSLQ
systems are currently known, which limits further studies. To enlarge the
sample from wide-area surveys, we developed a catalog-based pipeline and
applied it to the CatNorth database, a catalog of quasar candidates constructed
from Gaia DR3. CatNorth contains 1,545,514 quasar candidates with about 90%
purity and a Gaia G-band limiting magnitude of roughly 21. The pipeline has
three stages. First, we identify groups with separations between 10 and 72
arcsec using a HEALPix grid with 25.6 arcsec spacing and a friends-of-friends
search. We then filter by intra-group color and spectral similarity, reducing
the 1,545,514 sources to 14,244 groups while retaining all known, discoverable
WSLQs. Finally, a visual check, guided by image geometry and the presence of
likely foreground lenses, yields the candidate list with quality labels. We
identify 333 new WSLQ candidates with separations from 10 to 56.8 arcsec. Using
available SDSS DR16 and DESI DR1 spectroscopy, we uncover two new candidate
systems; the remaining 331 candidates lack sufficient spectra and are labeled
as 45 grade A, 98 grade B, and 188 grade C. We also compile 29 confirmed dual
quasars as a by-product. When feasible, we plan follow-up spectroscopy and
deeper imaging to confirm WSLQs among these candidates and enable the related
science.
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