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| PKS B1934-638 | |
|---|---|
| Name | PKS B1934-638 |
| Other names | 1934-638, PKS 1934-638 |
| Type | Radio galaxy |
| Ra | 19h 39m 25.03s |
| Dec | -63° 42′ 45.0″ |
| Epoch | J2000 |
| Redshift | 0.183 |
| Notes | Compact steep-spectrum source; primary Southern flux calibrator |
PKS B1934-638 is a compact, steep-spectrum radio source widely used as a primary flux-density calibrator for radio interferometers in the Southern Hemisphere. It is studied across radio, infrared, optical, ultraviolet, and X-ray observatories and figures in calibration programs for arrays and missions associated with institutions such as Australia Telescope National Facility, Atacama Large Millimeter/submillimeter Array, and Very Large Array. The source's stable flux, well-measured spectrum, and compact morphology make it important for surveys, standards, and multi-facility campaigns involving teams from CSIRO, ESO, and national observatories.
The source was cataloged in the Parkes surveys led by teams at CSIRO and the Parkes Observatory during mid-20th-century radio astronomy programs alongside other Parkes finds like Centaurus A and Pictor A. Early identification relied on interferometric positions from arrays such as the Molonglo Observatory Synthesis Telescope and positional cross-matching with optical plates from facilities like the Anglo-Australian Observatory and photographic catalogs tied to institutions including the Royal Observatory, Edinburgh and the Smithsonian Astrophysical Observatory. Subsequent spectroscopic confirmation used instruments at sites associated with European Southern Observatory and the Australian National University.
At radio wavelengths PKS B1934-638 is characterized by a steep-spectrum continuum measured from surveys by the Parkes Catalogue, the Molonglo Reference Catalogue, and monitoring programs at the Australia Telescope Compact Array. Observations at millimeter bands by ALMA and at centimeter bands by the Very Large Array complement infrared measurements from missions like WISE and optical imaging from telescopes such as the Anglo-Australian Telescope. X-ray limits or detections have been reported from instruments on satellites like ROSAT and follow-up proposals to Chandra X-ray Observatory and XMM-Newton investigate high-energy counterparts. Calibration campaigns involving Herschel Space Observatory and ground facilities at ESO exploit the source’s spectral stability.
The integrated radio spectrum displays a classical steep power-law with a turnover at low frequencies consistent with synchrotron self-absorption or free–free absorption seen in compact sources studied alongside objects like 3C 48 and 3C 286. Flux monitoring programs operated by CSIRO and the NRAO report long-term stability over decades, contrasting with the variability observed in blazars such as 3C 273 and BL Lacertae, making it suitable as a calibrator for experiments by teams at ESO and national observatories. High-frequency spectra from ALMA and centimeter measurements from the ATCA show consistent spectral indices used in models developed in collaboration with researchers at University of Sydney and Monash University.
High-resolution interferometry with arrays like the Long Baseline Array and the Very Long Baseline Array indicates a compact morphology, often unresolved at arcsecond scales and showing sub-arcsecond structure in VLBI maps analogous in compactness to calibrators such as 3C 286 and PKS 1939-63. Radio maps produced by teams at the ATNF and the LBA reveal a symmetric, compact core with no extended lobes at sensitivities typical of survey programs from institutions like CSIRO and ESO. The compactness underpins its use in amplitude and phase calibration for imaging campaigns conducted by consortia including ALMA Partnership and the International VLBI Service.
Optical spectroscopy and imaging associate the source with an early-type galaxy identified in observations performed at the Anglo-Australian Telescope and support facilities at Siding Spring Observatory, with host properties comparable to radio-galaxy hosts cataloged at ESO and the Institute of Astronomy, Cambridge. Environmental studies referencing surveys such as the 2dF Galaxy Redshift Survey and the 6dF Galaxy Survey place the source in a field or poor-group environment rather than a rich cluster like those cataloged by Abell, aligning with multiwavelength assessments from teams at CSIRO and the Australian National University. Stellar population analyses have been informed by comparisons to samples observed with instruments at European Southern Observatory and observatories affiliated with ANU.
Spectroscopic redshift measurements yield z ≈ 0.183, determined with data from spectrographs on telescopes affiliated with European Southern Observatory and the Anglo-Australian Observatory, allowing derivation of luminosity, linear size, and energy density using cosmological parameters adopted in studies by groups at CSIRO and universities such as University of Melbourne. At that redshift the radio luminosity places it among moderately powerful radio galaxies in compilations like the 3CRR and Parkes samples maintained by institutions including the Royal Observatory, Edinburgh and the Smithsonian Astrophysical Observatory. Derived physical parameters inform synchrotron aging and magnetic-field estimates used by researchers collaborating with Monash University and the University of Sydney.
PKS B1934-638 serves as a primary flux-density calibrator for Southern radio telescopes operated by CSIRO, the ATNF, and networks such as the Long Baseline Array and ALMA Partnership. Its stability and well-characterized spectrum underpin calibration schemes analogous to those using 3C 286, 3C 48, and Hydra A, adopted by observatories at ESO and national facilities for precision photometry, imaging, and spectral-line work. The source is integral to pipeline calibration for projects led by consortia including ALMA Partnership, NRAO, and teams at the Australian National University, ensuring consistent flux scales across surveys and epochs.
Category:Radio galaxies Category:Calibration sources