SAMI (survey)
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| SAMI (survey) | |
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| Name | SAMI |
| Full name | Sydney-AAO Multi-object Integral field spectrograph |
| Type | Astronomical survey |
| Start date | 2013 |
| End date | 2018 |
| Telescopes | Anglo-Australian Telescope |
| Instruments | AAOmega, SAMI instrument |
| Principal investigators | Scott Croom, Joss Bland-Hawthorn |
| Institutions | Australian National University, Australian Astronomical Observatory |
| Data release | Public data releases |
SAMI (survey)
Introduction
The SAMI program was a multi-year optical integral field spectroscopic survey conducted with the Anglo-Australian Telescope, designed to map spatially resolved stellar kinematics, ionized gas, and nebular diagnostics across thousands of nearby galaxies. It combined multi-object integral field capability with the AAOmega spectrograph to obtain spatially sampled spectra, enabling comparisons of internal structure across samples drawn from surveys such as the Sloan Digital Sky Survey, the Galaxy And Mass Assembly project, and the Two Micron All Sky Survey. Key science drivers connected to questions addressed by research groups at the Australian National University, the Australian Astronomical Observatory, and international collaborators focused on mechanisms invoked in studies of the Tully–Fisher relation, the Fundamental Plane (galaxies), and environmental effects seen in clusters like Coma Cluster and groups surveyed in the GAMA fields.
Survey Design and Instrumentation
The instrument design built on concepts from integral field spectroscopy pioneers and used 13 deployable fused-fiber hexabundles developed through collaborations involving University of Sydney groups led by Joss Bland-Hawthorn and Sarah Ellis. SAMI fed the AAOmega dual-beam spectrograph, providing blue and red arms optimized for studies comparable to work from the CALIFA and MaNGA surveys. The multiplexed design enabled simultaneous observations inspired by techniques from the 2dF Galaxy Redshift Survey and informed by projects at the European Southern Observatory and Kitt Peak National Observatory. Instrument commissioning campaigns referenced optical calibration strategies used on instruments such as VIMOS and MUSE and incorporated guiding and field-plate designs analogous to those at the William Herschel Telescope.
Target Selection and Sample
Targets were selected primarily from the GAMA equatorial fields supplemented by bright galaxies from the Sloan Digital Sky Survey (SDSS) and infrared selections from 2MASS. The SAMI sample spanned a broad range in stellar mass, morphology, and environment to probe relationships highlighted in studies of the morphology–density relation, the mass–metallicity relation, and the star formation main sequence. The survey design deliberately included objects in rich environments such as the Virgo Cluster and isolated systems cataloged by the Six-degree-Field Galaxy Survey to compare processes addressed by authors working on ram-pressure stripping and tidal interactions exemplified in literature on galaxies like NGC 4522 and NGC 4254.
Observations and Data Reduction
Observations were carried out with queue scheduling at the Siding Spring Observatory site using the Anglo-Australian Telescope and followed calibration practices used by teams operating the AAOmega instrument. Data reduction pipelines adapted procedures established in projects like GAMA and SDSS-IV MaNGA, employing bias subtraction, flat-fielding, wavelength calibration with arc lamps similar to those used at the European Southern Observatory, and flux calibration using spectrophotometric standards characterized in publications from the Hubble Space Telescope spectrophotometry community. Analysis software incorporated algorithms for spatial reconstruction, covariance tracking, and Voronoi binning methods also used in work on SAURON and ATLAS3D. Quality assessment referenced metrics comparable to those developed for the CALIFA pipeline.
Data Products and Access
Public data releases provided reduced datacubes, ancillary imaging cross-matched to SDSS and VISTA catalogs, value-added catalogs with emission-line measurements and stellar population parameters, and software tools for visualization and analysis following community standards practiced in releases by the MaNGA and CALIFA teams. Data distribution was coordinated through institutional archives at the AAO and mirrored in databases used by the International Virtual Observatory Alliance community, enabling cross-correlation with catalogs from WISE, GALEX, and the Herschel Space Observatory for multiwavelength investigations.
Scientific Results and Key Findings
SAMI produced results elucidating spatially resolved star formation quenching, kinematic signatures of mergers and secular evolution, and radial trends in gas-phase metallicity that informed refinements of the mass–metallicity relation. Key studies demonstrated environmental influences on kinematic morphology consistent with phenomena discussed in work on galaxy harassment and strangulation (astronomy), and identified central ionization sources differentiating between Seyfert and LINER classifications in samples overlapping with catalogs from the Swift and Chandra X-ray Observatory communities. SAMI analyses contributed to understanding angular momentum scaling relations analogous to trends reported in the ATLAS3D and clarified inside-out versus outside-in quenching debated in studies of galaxies such as NGC 1068 and populations analyzed in GAMA.
Legacy and Impact on Galaxy Evolution Studies
The SAMI dataset established benchmarks used by subsequent integral field surveys and instrument projects, influencing designs exemplified by MaNGA and technology developments in fiber-bundle integral field units pursued at institutes including Max Planck Institute for Astronomy and the Leiden Observatory. Its public releases and methodology fostered comparisons with simulations run by groups using codes like IllustrisTNG, EAGLE (project), and semi-analytic models from the Millennium Simulation, strengthening observational constraints on feedback processes invoked in models developed by teams at the Institut d'Astrophysique de Paris and Durham University. SAMI’s combination of multiplex IFU capability and extensive ancillary data continues to inform studies of galaxy kinematics, chemical evolution, and environment-driven transformation across research programs at institutions such as the University of Cambridge and the University of California, Berkeley.
Category:Spectroscopic surveys