TY - JOUR

T1 - Revisiting the Lensed Fraction of High-redshift Quasars

AU - Yue, Minghao

AU - Fan, Xiaohui

AU - Yang, Jinyi

AU - Wang, Feige

N1 - Funding Information:
We appreciate the valuable comments from Dr. Fabio Pacucci, Prof. Stuart Wyithe, and the anonymous referee. M.Y., X.F., and J.Y. acknowledge supports by NSF grants AST 19-08284. F.W. is thankful for the support provided by NASA through the NASA Hubble Fellowship grant #HST-HF2-51448.001-A awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Incorporated, under NASA contract NAS5-26555.
Publisher Copyright:
© 2022. The Author(s). Published by the American Astronomical Society.

PY - 2022/2/1

Y1 - 2022/2/1

N2 - The observed lensed fraction of high-redshift quasars (∼0.2%) is significantly lower than previous theoretical predictions (≳4%). We revisit the lensed fraction of high-redshift quasars predicted by theoretical models, where we adopt recent measurements of galaxy velocity dispersion functions (VDFs) and explore a wide range of quasar luminosity function (QLF) parameters. We use both analytical methods and mock catalogs, which give consistent results. For ordinary QLF parameters and the depth of current high-redshift quasar surveys (m z ≲ 22), our model suggests a multiply imaged fraction of F multi ∼0.4%-0.8%. The predicted lensed fraction is ∼1%-6% for the brightest z s ∼6 quasars (m z ≲ 19), depending on the QLF. The systematic uncertainties of the predicted lensed fraction in previous models can be as large as 2-4 times and are dominated by the VDF. Applying VDFs from recent measurements decreases the predicted lensed fraction and relieves the tension between observations and theoretical models. Given the depth of current imaging surveys, there are ∼15 lensed quasars at z s > 5.5 detectable over the sky. Upcoming sky surveys like the Legacy Survey of Space and Time survey and the Euclid survey will find several tens of lensed quasars at this redshift range.

AB - The observed lensed fraction of high-redshift quasars (∼0.2%) is significantly lower than previous theoretical predictions (≳4%). We revisit the lensed fraction of high-redshift quasars predicted by theoretical models, where we adopt recent measurements of galaxy velocity dispersion functions (VDFs) and explore a wide range of quasar luminosity function (QLF) parameters. We use both analytical methods and mock catalogs, which give consistent results. For ordinary QLF parameters and the depth of current high-redshift quasar surveys (m z ≲ 22), our model suggests a multiply imaged fraction of F multi ∼0.4%-0.8%. The predicted lensed fraction is ∼1%-6% for the brightest z s ∼6 quasars (m z ≲ 19), depending on the QLF. The systematic uncertainties of the predicted lensed fraction in previous models can be as large as 2-4 times and are dominated by the VDF. Applying VDFs from recent measurements decreases the predicted lensed fraction and relieves the tension between observations and theoretical models. Given the depth of current imaging surveys, there are ∼15 lensed quasars at z s > 5.5 detectable over the sky. Upcoming sky surveys like the Legacy Survey of Space and Time survey and the Euclid survey will find several tens of lensed quasars at this redshift range.

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U2 - 10.3847/1538-4357/ac409b

DO - 10.3847/1538-4357/ac409b

M3 - Article

AN - SCOPUS:85125724493

SN - 0004-637X

VL - 925

JO - Astrophysical Journal

JF - Astrophysical Journal

IS - 2

M1 - 169

ER -