2dF QSO Redshift Survey

2dF QSO Redshift Survey
Name	2dF QSO Redshift Survey
Acronym	2QZ
Operators	Anglo-Australian Observatory; Lawrence Berkeley National Laboratory; University of Cambridge
Telescope	Anglo-Australian Telescope
Instrument	Two-degree Field spectrograph
Started	1997
Completed	2002
Objects	quasars
Redshift range	0.3–2.9
Area	7400 square degrees

2dF QSO Redshift Survey was a large spectroscopic campaign that measured redshifts for over 25,000 quasars using the Anglo-Australian Telescope and the Two-degree Field spectrograph. It provided one of the first wide-area, homogeneously selected quasar samples for statistical studies of large-scale structure, quasar luminosity evolution, and the intergalactic medium. The project involved teams from institutions including the Anglo-Australian Observatory, University of Cambridge, University of Oxford, and University of Edinburgh and produced public catalogues that remain widely cited by researchers working with data from the Sloan Digital Sky Survey, 2dF Galaxy Redshift Survey, and other large surveys.

Overview

The survey targeted optically selected active galactic nuclei traditionally classified as quasars and sought to map their three-dimensional distribution across a broad redshift interval where proximate clustering and cosmic evolution are most informative. It built on precursor efforts by groups at the Royal Greenwich Observatory and the European Southern Observatory and complemented contemporaneous projects like the Sloan Digital Sky Survey and the FIRST Survey. The resulting dataset enabled cross-comparisons with radio catalogues such as NVSS and X‑ray samples from ROSAT and facilitated joint analyses with cosmic microwave background measurements from WMAP.

Survey Design and Instrumentation

Survey design centered on using the Two-degree Field spectrograph on the Anglo-Australian Telescope to exploit its 400-fibre multiplexing capability over a two-degree field. Instrument development drew on experience from instruments at the W. M. Keck Observatory and the European Southern Observatory instrumentation groups. The tiling strategy and plate design were optimized using techniques familiar from the 2dF Galaxy Redshift Survey and informed by scheduling constraints driven by facilities at the Siding Spring Observatory. Data acquisition benefited from coordination with computing groups at Lawrence Berkeley National Laboratory and the Institute of Astronomy, Cambridge.

Target Selection and Observations

Targets were selected from photometric catalogues assembled from the United Kingdom Schmidt Telescope photographic plates and modern CCD surveys, applying colour selection criteria that were calibrated against spectroscopic samples from Palomar Observatory and Cerro Tololo Inter-American Observatory. The selection algorithm incorporated colour cuts to separate quasars from stars such as those catalogued by Henry Draper Catalog and matched candidates to astrometric references anchored to the International Celestial Reference Frame. Observations were conducted in survey campaigns scheduled with coordination among principal investigators from University of Durham, University of Leicester, and University of New South Wales.

Data Reduction and Catalogues

Raw spectra were processed with pipelines developed by teams at the Anglo-Australian Observatory and the Cambridge Astronomical Survey Unit, employing sky subtraction, wavelength calibration against arc lamps tied to standards used at National Optical Astronomy Observatory, and automated redshift estimation methods validated with template libraries from the Sloan Digital Sky Survey collaboration. The survey released public catalogues that listed coordinates, redshifts, magnitudes, and quality flags; these catalogues were integrated into archival systems used by the Centre de Données astronomiques de Strasbourg and the NASA/IPAC Extragalactic Database and have been used in meta-analyses alongside datasets from 2MASS and GALEX.

Scientific Results and Impact

Key scientific outcomes included measurements of quasar clustering over comoving scales that constrained bias evolution models developed in the context of work by researchers at Institute for Advanced Study and Max Planck Institute for Astrophysics. The survey provided empirical determinations of the quasar luminosity function that influenced models of supermassive black hole growth studied by groups at Harvard–Smithsonian Center for Astrophysics and Black Hole Initiative. Cross-correlation studies with galaxy samples from the 2dF Galaxy Redshift Survey and the Sloan Digital Sky Survey refined understanding of large-scale structure and baryon acoustic oscillation signatures compared with theoretical predictions from Planck (spacecraft) cosmological parameters. The 2QZ data underpinned investigations into quasar environment, feedback, and the ionizing background, informing follow‑up programmes at Very Large Telescope and Keck Observatory.

Limitations and Systematic Errors

The survey faced limitations inherent to optical colour selection, including incompleteness for reddened or dust-obscured quasars known from studies at Spitzer Space Telescope and Chandra X-ray Observatory. Fiber allocation constraints introduced angular selection effects analogous to those quantified in the 2dF Galaxy Redshift Survey, and photometric calibration tied to photographic plate zero points produced systematic magnitude errors addressed in later comparisons with CCD-based surveys such as Sloan Digital Sky Survey. Redshift measurement failures and misclassifications required quality-flagging that influenced some clustering analyses and prompted methodological developments by teams at University College London and Australian National University.

Category:Astronomical surveys