SUMSS

SUMSS
Name	SUMSS
Full name	Sydney University Molonglo Sky Survey
Caption	Molonglo Observatory Synthesis Telescope
Area	Southern Sky (decl. < -30°)
Frequency	843 MHz
Resolution	45 arcsec × 45 arcsec cosec
Epochs	1997–2007
Observatory	Molonglo Observatory Synthesis Telescope
Operator	University of Sydney

SUMSS

SUMSS is a centimetre‑wave radio imaging programme carried out with the Molonglo Observatory Synthesis Telescope at the Molonglo University of Sydney facility near Canberra. It produced a wide‑area mosaic and source catalogue covering the southern celestial hemisphere comparable in sky coverage and sensitivity to northern surveys such as the NRAO VLA Sky Survey and complements observations from instruments including the Parkes Observatory, Australia Telescope Compact Array, Very Large Array, Giant Metrewave Radio Telescope, and space missions like IRAS and ROSAT. The project involved collaborations among researchers at the University of Sydney, the Australian National University, and international partners, yielding data widely used by teams studying active galactic nuclei, supernova remnants, galaxy clusters, and galactic structure.

Overview

SUMSS was conceived to provide a uniform radio map of the southern sky at 843 MHz using the east–west baseline of the Molonglo Molonglo Observatory Synthesis Telescope and to produce a large, well‑characterised catalogue of discrete radio sources. The survey strategy paralleled goals of the NRAO VLA Sky Survey and sought to enable cross‑matching with optical catalogues such as the Sloan Digital Sky Survey, infrared surveys like the Two Micron All Sky Survey, ultraviolet datasets from GALEX, and X‑ray catalogues from ROSAT and Chandra. SUMSS supported multiwavelength studies involving teams at the University of Sydney, the CSIRO, and the Australian Astronomical Observatory.

Survey Design and Observations

Observations used the east–west arm of the Molonglo telescope, originally developed as the Molonglo Cross and reconfigured as a synthesis instrument similar in concept to the Cambridge One‑Mile Telescope and influenced by arrays like the Westerbork Synthesis Radio Telescope. The survey footprint targeted declinations south of −30°, overlapping at higher declinations with the Sydney‑University Molonglo Sky Survey commissioning fields and matching regions examined by the Parkes Radio Telescope and the Fornax Cluster programmes. Pointing centres, integration times, and snapshot strategies were planned with reference to calibration sources such as 3C 273, Hydra A, PKS B1934‑638, and standards used at the Australia Telescope Compact Array. Observing campaigns were scheduled to avoid interference from terrestrial transmitters and coordinated with monitoring efforts by the Australian Communications and Media Authority where necessary.

Data Processing and Catalogues

Raw visibilities were reduced using pipelines developed at the University of Sydney and tested against methods from the Common Astronomy Software Applications suite and legacy packages employed by the NRAO and ATNF. Processing steps included flagging for radio‑frequency interference identified by comparisons with data from the Parkes Observatory and the Molonglo Observatory, calibration using primary standards such as PKS B1934‑638 and secondary calibrators, deconvolution with CLEAN algorithms inspired by work at the National Radio Astronomy Observatory, and mosaicking across overlapping fields similar to techniques used in the FIRST survey. Catalogues were released providing positions, peak and integrated flux densities, angular sizes and fit uncertainties, and were cross‑referenced with optical catalogues including SuperCOSMOS Sky Survey, the Two Micron All Sky Survey, and radio compilations like the PMN survey and the MRC catalogue.

Scientific Results and Applications

SUMSS data have been used to identify and classify thousands of radio galaxys, to study morphology of Fanaroff–Riley sources, and to compile samples for follow‑up with the Australia Telescope Compact Array and the Very Large Array. Results include identification of new supernova remnants in the Galactic plane, measurements of diffuse radio emission in galaxy clusters such as the Centaurus Cluster and the Fornax Cluster, and statistical analyses of source counts used to constrain models of cosmic evolution tested against surveys like the NVSS and FIRST. SUMSS enabled multiwavelength studies of Seyfert galaxys, BL Lacertae objects, and quasar samples cross‑matched with optical data from the Anglo‑Australian Telescope and spectroscopic catalogues from the Two Degree Field Galaxy Redshift Survey and the 6dF Galaxy Survey.

Comparison with Other Radio Surveys

SUMSS is directly comparable to the NRAO VLA Sky Survey in scope for continuum imaging at metre to centimetre wavelengths but differs in frequency, angular resolution, and declination coverage. Unlike the NVSS which used the Very Large Array, SUMSS used the Molonglo synthesis telescope with an elongated synthesized beam that produced beam ellipticity varying with declination, a characteristic also encountered in surveys such as the PMN southern survey carried out with the Parkes Radio Telescope. SUMSS complements higher‑resolution studies from the FIRST survey and lower‑frequency work from the GMRT and the Low Frequency Array by filling a niche at 843 MHz in the southern sky, providing essential cross‑identifications for programmes at the Atacama Large Millimeter/submillimeter Array and next‑generation facilities like the Square Kilometre Array pathfinders.

Data Access and Usage

SUMSS catalogues and mosaicked images were made available through the data archives hosted by the University of Sydney and mirrored at national facilities including the Astronomical Data Centre and the CSIRO Data Access Portal. Users routinely cross‑match SUMSS entries with optical and infrared resources such as the SuperCOSMOS Sky Survey, 2MASS, and spectroscopic datasets from the Anglo‑Australian Telescope for identification and redshift determination. Data products have licensing and citation recommendations set by the originating teams at the University of Sydney and partner institutions, and continue to serve as reference datasets for proposals to observatories including the ATCA, VLA, GMRT, and forthcoming SKA science programmes.

Category:Radio astronomy surveys