Open AccessA population of high‐redshift type 2 quasars – I. Selection criteria and optical spectra
Author(s) -
MartínezSansigre Alejo,
Rawlings Steve,
Lacy Mark,
Fadda Dario,
Jarvis Matt J.,
Marleau Francine R.,
Simpson Chris,
Willott Chris J.
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.1365-2966.2006.10563.x
Subject(s) - physics , quasar , astrophysics , ovv quasar , redshift , supermassive black hole , population , astronomy , luminosity , infrared , galaxy , demography , sociology
We discuss the relative merits of mid‐infrared and X‐ray selection of type 2 quasars. We describe the mid‐infrared, near‐infrared and radio selection criteria used to find a population of redshift z ∼ 2 type 2 quasars which we previously argued suggests that most supermassive black hole growth in the Universe is obscured. We present the optical spectra obtained from the William Herschel Telescope, and we compare the narrow emission‐line luminosity, radio luminosity and maximum size of jets to those of objects from radio‐selected samples. This analysis suggests that these are genuine radio‐quiet type 2 quasars, albeit the radio‐bright end of this population. We also discuss the possibility of two different types of quasar obscuration, which could explain how the ∼2–3:1 ratio of type 2 to type 1 quasars preferred by modelling our population can be reconciled with the ∼1:1 ratio predicted by unified schemes.