The faint end of the Z = 5 quasar luminosity function from the cfhtls

Ian D. McGreer, Xiaohui Fan, Linhua Jiang, Zheng Cai

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We presents results from a spectroscopic survey of z ∼ 5 quasars in the CFHT Legacy Survey (CFHTLS). Using both optical color selection and a likelihood method we select 97 candidates over an area of 105 deg2 to a limit of iAB < 23.2, and 7 candidates in the range 23.2 < iAB < 23.7 over an area of 18.5 deg2. Spectroscopic observations for 43 candidates were obtained with Gemini, MMT, and LBT, of which 37 are z > 4 quasars. This sample extends measurements of the quasar luminosity function ∼1.5 mag fainter than our previous work in SDSS Stripe 82. The resulting luminosity function is in good agreement with our previous results, and suggests that the faint end slope is not steep. We perform a detailed examination of our survey completeness, particularly the impact of the Lyα emission assumed in our quasar spectral models, and find hints that the observed Lyα emission from faint z ∼ 5 quasars is weaker than for z ∼ 3 quasars at a similar luminosity. Our results strongly disfavor a significant contribution of faint quasars to the hydrogen-ionizing background at z = 5.

Original languageEnglish (US)
JournalUnknown Journal
StatePublished - Oct 25 2017


  • Quasars: general

ASJC Scopus subject areas

  • General

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