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| Southern H-Alpha Sky Survey Atlas | |
|---|---|
| Name | Southern H-Alpha Sky Survey Atlas |
| Abbreviation | SHASSA |
| Type | Astronomical survey |
| Established | 1997–2000 |
| Principal investigator | Gaustad et al. |
| Institutions | Cerro Tololo Inter-American Observatory, University of Chicago, Space Telescope Science Institute |
| Wavelength | H-alpha (656.3 nm) |
| Sky coverage | Southern celestial hemisphere |
| Products | Calibrated images, mosaics, emission maps |
Southern H-Alpha Sky Survey Atlas is a wide-field astronomical imaging survey that mapped diffuse hydrogen-alpha emission across the southern celestial hemisphere. Conducted in the late 1990s by a collaboration of observatories and universities, the atlas produced calibrated narrowband images that have been widely used by researchers studying the interstellar medium, star formation, and Galactic structure. The project interfaces with many observatories, space missions, and catalogues for multiwavelength studies.
The survey was led by collaborators including the Cerro Tololo Inter-American Observatory, the University of Chicago, and the Space Telescope Science Institute, and it complements northern surveys such as the Virginia Tech Spectral-Line Survey and the Wisconsin H-Alpha Mapper. It targeted the H-alpha emission line at 656.3 nm to trace ionized hydrogen in objects like H II regions, planetary nebulae, supernova remnants, and the warm ionized medium associated with the Milky Way. The survey is referenced alongside work from the Anglo-Australian Observatory, the Harvard-Smithsonian Center for Astrophysics, and initiatives associated with the European Southern Observatory.
Observations were made using wide-field CCD imagers mounted at sites such as the Cerro Tololo Inter-American Observatory and other southern facilities linked to the National Optical Astronomy Observatory. The instrumental setup included narrowband H-alpha filters and continuum filters, a CCD detector array, and a telescope optical train comparable to systems used in projects at Kitt Peak National Observatory and Palomar Observatory. Exposure strategies and pointing patterns were coordinated with catalogs and positional standards from the United States Naval Observatory and astrometric references tied to the Two Micron All Sky Survey and the Hipparcos mission. Data acquisition incorporated calibration sequences similar to those practiced at the European Southern Observatory and the Australian Astronomical Observatory.
Raw CCD frames were processed with pipelines informed by procedures developed at the Space Telescope Science Institute and the Smithsonian Astrophysical Observatory, including bias subtraction, flat-field correction, and cosmic-ray removal. Continuum subtraction employed off-band images to isolate line emission, following methodologies comparable to those used in surveys by the Max Planck Institute for Astronomy and the California Institute of Technology. Photometric and astrometric calibration referenced catalogues such as the Guide Star Catalog, the Tycho-2 Catalogue, and flux standards from the International Astronomical Union, ensuring compatibility with databases maintained by the Centre de Données astronomiques de Strasbourg and the National Aeronautics and Space Administration archives.
The atlas covers the southern celestial hemisphere with overlapping fields assembled into mosaics and emission maps, producing products including calibrated FITS images, smoothed intensity maps, and continuum-subtracted frames. Products were designed for interoperability with data sets from the Infrared Astronomical Satellite, the Wilkinson Microwave Anisotropy Probe, the Planck mission, and radio surveys like the Parkes Observatory catalogs and the Australia Telescope Compact Array. Ancillary products reference object lists intersecting catalogs such as SIMBAD, the NASA/IPAC Extragalactic Database, and the Sloan Digital Sky Survey where overlap exists near the celestial equator.
The atlas has supported studies of Galactic structure, H II region morphology, and diffuse ionized gas, informing analyses by teams associated with the Max Planck Institute for Radio Astronomy, the Laboratoire d'Astrophysique de Marseille, and the Harvard-Smithsonian Center for Astrophysics. It has been used to identify and characterize planetary nebulae alongside catalogs from the Anglo-Australian Observatory and discoveries tied to surveys like the INT Photometric H-Alpha Survey and the Digitized Sky Survey. Cross-comparison with observations from the Hubble Space Telescope, the Chandra X-ray Observatory, and the Spitzer Space Telescope enabled multiwavelength studies of supernova remnants and star-forming complexes referenced in works from Princeton University, the University of Cambridge, and the Massachusetts Institute of Technology.
Comparative assessments place the atlas alongside the Virginia Tech Spectral-Line Survey, the Wisconsin H-Alpha Mapper, and the INT Photometric H-Alpha Survey in terms of spatial resolution, sensitivity, and sky coverage. Differences in instrumentation link it to facilities like Kitt Peak National Observatory, Palomar Observatory, and the Anglo-Australian Telescope, while calibration philosophies echo standards used by the European Southern Observatory and the Space Telescope Science Institute. The atlas is frequently cross-referenced with catalogs and data releases from the Two Micron All Sky Survey, the Sloan Digital Sky Survey, and the Planck Collaboration to exploit complementary wavelength coverage and resolution.
Calibrated images and mosaics have been distributed to the astronomical community via institutional archives managed by the Space Telescope Science Institute, the National Optical Astronomy Observatory, and data services like the Centre de Données astronomiques de Strasbourg and NASA/IPAC. Usage typically involves software developed at the Smithsonian Astrophysical Observatory, the European Space Agency, and community tools that support FITS standards promulgated by the International Astronomical Union. The data are cited in publications from institutions including the University of Chicago, Harvard University, Princeton University, and the Max Planck Society for research on Galactic emission, extragalactic foregrounds, and comparisons with missions such as Planck and WMAP.
Category:Astronomical surveys