Open AccessSimulating wide‐field quasar surveys from the optical to near‐infrared
Author(s) -
Maddox Natasha,
Hewett Paul C.
Publication year - 2006
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1111/j.1365-2966.2005.09984.x
Subject(s) - quasar , physics , astrophysics , galaxy , redshift , astronomy , luminosity , spectral energy distribution , sky , population , active galactic nucleus , ovv quasar , photometry (optics) , luminous infrared galaxy , stars , demography , sociology
A number of deep, wide‐field, near‐infrared (NIR) surveys employing new infrared cameras on 4‐m class telescopes are about to commence. These surveys have the potential to determine the fraction of luminous dust‐obscured quasars that may have eluded surveys undertaken at optical wavelengths. In order to understand the new observations it is essential to make accurate predictions of surface densities and number–redshift relations for unobscured quasars in the NIR based on information from surveys at shorter wavelengths. The accuracy of the predictions depends critically on a number of key components. The commonly used single power‐law representation for quasar spectral energy distributions (SEDs) is inadequate and the use of an SED incorporating the upturn in continuum flux at λ∼ 12 000 Å is essential. The presence of quasar host galaxies is particularly important over the rest‐frame wavelength interval 8000 < λ < 16 000 Å and we provide an empirical determination of the magnitude distribution of host galaxies using a low‐redshift sample of quasars from the Sloan Digital Sky Survey Data Release 3 quasar catalogue. A range of models for the dependence of host galaxy luminosity on quasar luminosity is investigated, along with the implications for the NIR surveys. Even adopting a conservative model for the behaviour of host galaxy luminosity the number counts for shallow surveys in the K band increase by a factor of 2. The degree of morphological selection applied to define candidate quasar samples in the NIR is found to be an important factor in determining the fraction of the quasar population included in such samples.