Quasars from a complete spectroscopic survey

Meyer, M. J., Drinkwater, M. J., Phillipps, S. and Couch, W. J. (2001) Quasars from a complete spectroscopic survey. Monthly Notices of The Royal Astronomical Society, 324 2: 343-354. doi:10.1046/j.1365-8711.2001.04265.x

Author Meyer, M. J.
Drinkwater, M. J.
Phillipps, S.
Couch, W. J.
Title Quasars from a complete spectroscopic survey
Journal name Monthly Notices of The Royal Astronomical Society   Check publisher's open access policy
ISSN 0035-8711
Publication date 2001
Sub-type Article (original research)
DOI 10.1046/j.1365-8711.2001.04265.x
Open Access Status DOI
Volume 324
Issue 2
Start page 343
End page 354
Total pages 12
Place of publication Oxford, United Kingdom
Publisher Oxford University Press
Language eng
Abstract With the advent of multi-fibre spectrographs such as the 'Two-Degree Field' (2dF) instrument at the Angle-Australian Telescope, quasar surveys that are free of any preselection of candidates and any biases this implies have become possible for the first time. The first of these is that which is being undertaken as part of the Fornax Spectroscopic Survey, a survey of the area around the Fornax Cluster of galaxies, and aims to obtain the spectra of all objects in the magnitude range 16.5 < b(j) < 19.7. To date, 3679 objects in the central pi -deg(2) area have been successfully identified from their spectral characteristics. Of these, 71 are found to be quasars, 61 with redshifts 0.3 < z < 2.2 and 10 with redshifts z > 2.2. Using this complete quasar sample, a new determination of quasar number counts is made, enabling an independent check of existing quasars surveys. Cumulative counts per square degree at a magnitude limit of b(j) < 19.5 are found to be 11.5 +/- 2.2 for 0.3 < z < 2.2, 2.22 +/- 0.93 for z > 2.2 and 13.7 +/- 3.1 for z > 0.3. Given the likely detection of extra quasars in the Fornax survey, we make a more detailed examination of existing quasar selection techniques. First, looking at the use of a stellar criterion, four of the 71 quasars are 'non-stellar' on the basis of the automated plate measuring facility (APM) b(j) classification, however inspection shows all are consistent with stellar, but misclassified due to image confusion. Examining the ultraviolet excess and multicolour selection techniques, for the selection criteria investigated, ultraviolet excess would find 69 +/- 6 per cent of our 0.3 < z < 2.2 quasars and only 50(-18)(+14), per cent of our z > 2.2 quasars, while the completeness level for multicolour selection is found to be 90(-4)(+3) per cent for 0.3 < z < 2.2 quasars and 80(-12)(+14) per cent for z > 2.2 quasars. The extra quasars detected by our all-object survey thus have unusually red star-like colours, and this appears to be a result of the continuum shape rather than any emission features. An intrinsic dust extinction model may, at least partly, account for the red colours.
Keyword Astronomy & Astrophysics
Qso Redshift Survey
Luminosity Function
Space Distribution
Multicolor Survey
Stellar Objects
Complete Sample
Techniques : Spectroscopic
Quasars : General
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status Unknown

Document type: Journal Article
Sub-type: Article (original research)
Collection: School of Physical Sciences Publications
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Citation counts: TR Web of Science Citation Count  Cited 12 times in Thomson Reuters Web of Science Article | Citations
Scopus Citation Count Cited 11 times in Scopus Article | Citations
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Created: Mon, 13 Aug 2007, 12:23:49 EST