2024/09/24 by Yu-Ching Chen, Chen, Yu-Ching, Arran C. Gross +11
Medicine · Physics and Astronomy · #Astrophysics of Galaxies (astro-ph.GA) #Atomic and Subatomic Physics Research #FOS: Physical sciences #High Energy Astrophysical Phenomena (astro-ph.HE) #Medical Imaging Techniques and Applications
paper · pdf · doi:10.48550/arxiv.2409.16351
openalex publication_date 2024/09/24 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/01
High spatial and spectral resolution observations are essential for identifying sub-arcsecond dual and lensed quasars and confirming their redshifts. We present Gemini/GMOS and HST/STIS optical spectra for 27 dual quasar candidates selected based on their variability-induced astrometric noise or double detections in Gaia (the VODKA project). From this follow-up, we spectroscopically identify 11 star superpositions and 7 dual/lensed quasars. Among the remaining targets, 2 are likely dual/lensed quasars based on additional radio imaging, while the rest are quasars with unknown companions. Without prior photometric or spectroscopic selection, we find the star contamination rate to be 41-67%, while the dual/lensed quasar fraction is \gtrsim 26% in the follow-up VODKA sample. However, when combined with existing unresolved spectra and spatially-resolved two-band color cuts, the dual/lensed quasar fraction can be increased to \gtrsim 67%. Our study highlights the need for high-quality spectral data, including a signal-to-noise ratio of at least 20, spatial resolution that is at least twice finer than the source separation, and a spectral resolution of R \gtrsim 1000, in order to separate close sources, exclude stellar superpositions, and reliably identify dual quasars.