http://arxiv.org/abs/2109.06881
Dual quasars are precursors of binary supermassive black holes, which are important objects for gravitational wave study, galaxy evolution, and cosmology. I report four double quasars, one of which is newly discovered, with separations of 1$-$2 arcsec selected from the DECam Legacy Survey. The Gemini optical spectra confirm that both sources are quasars at the same redshifts. J0118$-$0104 and J0932+0722 are classified as dual quasars, whereas J0037+2058 could be either a dual quasar or a lensed quasar. I estimate the physical properties such as black hole masses and Eddington ratios for the four double quasars. The newly discovered system supplements the incomplete sample of dual quasars at $\sim$10 kpc at $z>0.5$. The results demonstrate that new high-quality imaging surveys with existing spectroscopic data could reveal additional small-scale double quasars. Combined with the dual quasars from the literature, I find a power-law index of 1.45$\pm$0.48 for the distribution of dual quasars as a function of separation between 5$-$20 kpc, steeper than that expected from dynamical friction, though it is likely due to the incomplete sample at $<$15 kpc. I also discuss the implications for future searches with new imaging surveys such as the Dark Energy Survey and the Legacy Survey of Space and Time.
Y. Chen
Thu, 16 Sep 21
15/54
Comments: 9 pages, 6 figures, submitted to MNRAS, comments are welcome