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| SAURON project | |
|---|---|
| Name | SAURON project |
| Type | Astronomical integral-field spectroscopic survey |
| Start | 1999 |
| Lead | Marie Bureau |
| Institutions | Centre de Recherche Astrophysique de Lyon; Leiden Observatory; University of Durham; University of Oxford |
| Instruments | SAURON integral-field spectrograph; William Herschel Telescope |
| Wavelength | Optical |
| Targets | Early-type galaxies; spiral bulges |
| Status | Completed (survey phase), ongoing legacy |
SAURON project The SAURON project was an astronomical integral-field spectroscopic survey of nearby galaxys using the SAURON spectrograph on the William Herschel Telescope, conducted by a consortium including teams from the Leiden Observatory, Observatoire de Lyon, University of Oxford, and Durham University. The survey targeted the internal kinematics, stellar populations, and gas properties of early-type galaxies and bulges to study galaxy formation and evolution in the context of hierarchical models like those of Lambda Cold Dark Matter model and observed scaling relations such as the Fundamental Plane (galaxy) and the Faber–Jackson relation. The project produced integral-field maps, catalogs, and analysis tools that informed subsequent efforts including ATLAS3D, CALIFA, and MaNGA.
SAURON was conceived by a core team including Roger Davies, Jesper Andersen, Roland Bacon, Tim de Zeeuw, Eric Emsellem, and Marta Cappellari to exploit the SAURON integral-field unit mounted on the William Herschel Telescope at Observatorio del Roque de los Muchachos for spatially resolved spectroscopy of nearby elliptical galaxy, lenticular galaxy, and spiral bulge systems. The project combined observational campaigns, theoretical interpretation drawing on work from Simon White and Guido W. A. van der Hulst, and comparisons with numerical simulations by groups led by Volker Springel and Naoki Yoshida to address questions posed by the hierarchical formation paradigm and by empirical laws such as the Tully–Fisher relation and the Kormendy relation.
The SAURON spectrograph, developed by teams including Olivier Le Fèvre and Roland Bacon at the Centre de Recherche Astrophysique de Lyon, is an integral-field unit employing lenslet arrays and optimized for the optical wavelength range around Hβ and [O III] emission lines, installed on the 4.2m William Herschel Telescope. Observing runs were scheduled at the Isaac Newton Group of Telescopes and coordinated with instrumentation groups at Observatoire de Paris and European Southern Observatory collaborators to ensure calibration against standard stars from catalogs maintained at European Space Agency. The survey strategy emphasized mosaicking to reach one effective radius for targets, using exposure times calibrated against surface brightness profiles in studies like those of John Kormendy and S. M. Faber.
SAURON targeted a representative sample of 48 nearby early-type galaxies and 24 spiral bulges selected from catalogs compiled by B. J. T. Jones and cross-referenced with the Third Reference Catalogue of Bright Galaxies and redshift lists from the Sloan Digital Sky Survey early releases. Selection criteria included absolute magnitude limits related to the Faber–Jackson relation, morphological classification from the Hubble sequence, environmental classification including membership in clusters such as Virgo Cluster and groups cataloged by Giuseppe Gavazzi, and availability of ancillary data from facilities like the Hubble Space Telescope and the Chandra X-ray Observatory.
Data reduction used bespoke pipelines developed by the team drawing on techniques from integral-field efforts at European Southern Observatory and software libraries influenced by work at Max Planck Institute for Astronomy and Leiden Observatory. Key steps included bias subtraction, flat-fielding, wavelength calibration using arc lamps tied to standards from National Physical Laboratory (United Kingdom), sky subtraction, and construction of datacubes followed by Voronoi tessellation for spatial binning as introduced by Cappellari and Copin. Kinematic extraction employed penalized pixel-fitting methods (pPXF) developed by Marta Cappellari and Eric Emsellem to derive line-of-sight velocity distributions, while stellar-population synthesis comparisons used models from Bruzual & Charlot and Vazdekis to infer ages and metallicities.
SAURON revealed a dichotomy in early-type galaxy kinematics, identifying fast rotators and slow rotators and linking kinematic morphology to formation pathways discussed by Sandage and Toomre & Toomre. The survey mapped kinematically decoupled cores previously noted in studies of NGC 4365 and others, quantified flattening and anisotropy consistent with predictions from simulations by Lia Athanassoula and Victor P. Debattista, and traced ionized-gas misalignments that constrained external accretion scenarios debated by Francoise Combes and Alvio Renzini. SAURON also produced spatially resolved stellar-population gradients that informed chemical evolution models from Christopher McKee-inspired feedback frameworks and constrained supermassive black hole scaling relations pioneered by Geoffrey B. Read and John Kormendy.
SAURON set observational standards for integral-field spectroscopy that influenced large surveys like ATLAS3D, CALIFA, SAMI, and MaNGA, and motivated instrumentation such as MUSE at the Very Large Telescope and proposals for next-generation IFUs on Extremely Large Telescope. The project's public data releases, analysis codes including pPXF, and methodological innovations in binning and kinematic decomposition have been widely adopted by research teams at institutions including Harvard–Smithsonian Center for Astrophysics, Max Planck Institute for Astrophysics, and Carnegie Institution for Science.
The SAURON core consortium collaborated with groups at Institut d'Astrophysique de Paris, California Institute of Technology, University of California, Berkeley, and University of Cambridge and spawned follow-up programs such as ATLAS3D led by Michele Cappellari and multiwavelength campaigns combining data from Spitzer Space Telescope, GALEX, and Chandra X-ray Observatory. Subsequent comparative studies integrated SAURON results with cosmological simulations by teams at Max Planck Institute for Astrophysics and Institute for Computational Cosmology led by Felix Stoehr and informed target selection for surveys with the James Webb Space Telescope and future facilities like Euclid and the Nancy Grace Roman Space Telescope.
Category:Astronomical surveys