Large Bright Quasar Survey

Large Bright Quasar Survey
Name	Large Bright Quasar Survey
Abbreviation	LBQS
Type	Astronomical survey
Start	1980s
Principal investigators	H. J. Smith; P. S. Osmer
Instruments	Mayall 4m; Palomar 5m; MMT
Area	~1000 deg²
Objects	Quasars

Large Bright Quasar Survey.

The Large Bright Quasar Survey was a wide-field optical quasar search conducted in the 1980s that mapped bright active galactic nuclei across large sky areas using photographic and spectroscopic follow-up from major observatories such as the Kitt Peak National Observatory, Palomar Observatory, and the Multiple Mirror Telescope. It aimed to populate quasar luminosity functions used by contemporaneous programs including the Sloan Digital Sky Survey, the Two Micron All Sky Survey, and the Einstein Observatory source catalogs, informing studies by researchers affiliated with institutions like the Harvard–Smithsonian Center for Astrophysics, Carnegie Institution for Science, and the European Southern Observatory.

Background and Objectives

The survey was initiated amid parallel efforts such as the 3C catalogue, the Veron-Cetty and Veron catalog, and the Palomar-Green survey to characterize bright extragalactic point sources, influenced by theoretical frameworks from researchers at Caltech, Princeton University, and Cambridge University. Principal investigators collaborated with teams from the National Optical Astronomy Observatory, University of Arizona, and the University of California, Berkeley to set objectives: define a statistically robust sample for quasar luminosity functions, probe redshift distributions for comparisons with Hubble Space Telescope deep-field expectations, and provide targets for X-ray follow-up by missions such as ROSAT and ASCA.

Survey Design and Methodology

The LBQS employed objective-prism and color-selection criteria building on techniques used in the Markarian survey and the Sloan Digital Sky Survey early color cuts, utilizing photographic plates from the Palomar Observatory Sky Survey and spectra obtained with instruments at Kitt Peak National Observatory and the Multiple Mirror Telescope. Candidate selection combined photometric cuts, morphological filters, and spectral line identification similar to methods developed at Yale University and Columbia University, followed by slit spectroscopy for confirmation at facilities including the Cerro Tololo Inter-American Observatory and the Mount Hopkins Observatory. Survey area tiling, exposure strategies, and completeness tests referenced statistical approaches from groups at Stanford University and Massachusetts Institute of Technology.

Catalog and Data Products

The published LBQS catalog listed hundreds of quasars with coordinates, magnitudes, redshifts, and spectral classifications that were cross-matched against databases maintained by the NASA/IPAC Extragalactic Database, the SIMBAD astronomical database, and the VizieR service at the Centre de Données astronomiques de Strasbourg. Data products included finder charts, optical spectra, and selection function estimates comparable to releases from the 2dF Galaxy Redshift Survey and the FIRST survey, enabling reuse by teams at the European Space Agency, the Max Planck Institute for Astronomy, and the National Radio Astronomy Observatory for multiwavelength analyses.

Scientific Results and Discoveries

Analyses of the LBQS sample produced measurements of the quasar luminosity function, constraints on quasar evolution, and identification of broad absorption line quasars, results that were compared with X-ray samples from Einstein Observatory and ROSAT and radio properties from the Very Large Array. The catalog contributed to studies of quasar clustering with methods also applied in the 2dF QSO Redshift Survey and informed black hole mass scaling relations explored by researchers at Johns Hopkins University and INAF. LBQS objects served as bright targets for reverberation mapping programs connected to teams at the University of California, Santa Cruz and the Max Planck Institute for Extraterrestrial Physics.

Follow-up Observations and Legacy

LBQS targets were re-observed in optical and infrared bands by instruments on the Hubble Space Telescope, the UK Infrared Telescope, and the Infrared Space Observatory; many were later re-examined in radio surveys such as the NRAO VLA Sky Survey and in X-ray with Chandra X-ray Observatory and XMM-Newton. The survey influenced the design and target selection strategies of later efforts including the Sloan Digital Sky Survey, the 2dF QSO Redshift Survey, and space missions planned by the European Space Agency and NASA, and its legacy persists in archival projects curated by the Mikulski Archive for Space Telescopes and the Canadian Astronomy Data Centre.

Criticisms and Limitations

Contemporaneous critiques compared LBQS selection biases and incompleteness to those of the Palomar-Green survey and cautioned about color-selection effects highlighted in work by teams at University of Cambridge and University of Edinburgh; limitations included photographic plate photometry uncertainties, spectroscopic incompleteness at faint magnitudes, and limited infrared sensitivity relative to later surveys like the Two Micron All Sky Survey and the Wide-field Infrared Survey Explorer. Subsequent re-analyses by groups at University of Chicago and Durham University quantified systematic biases that affected luminosity-function inferences and motivated improved methodologies used by the Sloan Digital Sky Survey and Pan-STARRS.

Category:Astronomical surveys