An X-ray and radio study of the cluster A 2717

We present an X-ray, radio and optical study of the cluster A 2717. The central D galaxy is associated with aWide- Angled-Tailed (WAT) radio source. A Rosat PSPC observation of the cluster shows that the cluster has a well constrained temperature of 1.9+0.3 −0.2 × 107 K. The pressure of the intracluster medium was found to be comparable to the mininum pressure of the radio source suggesting that the tails may in fact be in equipartition with the surrounding hot gas

An X-ray and Radio study of the Cluster A2717

We present an X-ray, radio and optical study of the cluster A2717. The central D galaxy is associated with a Wide-Angled-Tailed (WAT) radio source. A Rosat PSPC observation of the cluster shows that the cluster has a well constrained temperature of 2x10^7 K. The pressure of the intracluster medium was found to be comparable to the mininum pressure of the radio source suggesting that the tails may in fact be in equipartition with the surrounding hot gas.Comment: 7 pages, 6 Postscript figures, to appear in Astronomy and Astrophysics 199

A Quantitative Evaluation of the Galaxy Component of COSMOS and APM Catalogs

We have carried out an independent quantitative evaluation of the galaxy component of the "COSMOS/UKST Southern Sky Object Catalogue" (SSC) and the "APM/UKST J Catalogue" (APM). Using CCD observations our results corroborate the accuracy of the photometry of both catalogs, which have an overall dispersion of about 0.2 mag in the range 17 <= b_J <= 21.5. The SSC presents externally calibrated galaxy magnitudes that follow a linear relation, while the APM instrumental magnitudes of galaxies, only internally calibrated by the use of stellar profiles, require second-order corrections. The completeness of both catalogs in a general field falls rapidly fainter than b_J = 20.0, being slightly better for APM. The 90% completeness level of the SSC is reached between b_J = 19.5 and 20.0, while for APM this happens between b_J = 20.5 and 21.0. Both SSC and APM are found to be less complete in a galaxy cluster field. Galaxies misclassified as stars in the SSC receive an incorrect magnitude because the stellar ones take saturation into account besides using a different calibration curve. In both cases, the misclassified galaxies show a large diversity of colors that range from typical colors of early-types to those of blue star-forming galaxies. A possible explanation for this effect is that it results from the combination of low sampling resolutions with properties of the image classifier for objects with characteristic sizes close to the instrumental resolution. We find that the overall contamination by stars misclassified as galaxies is < 5% to b_J = 20.5, as originally estimated for both catalogs. Although our results come from small areas of the sky, they are extracted from two different plates and are based on the comparison with two independent datasets.Comment: 14 pages of text and tables, 8 figures; to be published in the Astronomical Journal; for a single postscript version file see ftp://danw.on.br/outgoing/caretta/caretta.p

SUMSS: A Wide-Field Radio Imaging Survey of the Southern Sky. I. Science goals, survey design and instrumentation

The Molonglo Observatory Synthesis Telescope, operating at 843 MHz with a 5 square degree field of view, is carrying out a radio imaging survey of the sky south of declination -30 deg. This survey (the Sydney University Molonglo Sky Survey, or SUMSS) produces images with a resolution of 43" x 43" cosec(Dec.) and an rms noise level of about 1 mJy/beam. SUMSS is therefore similar in sensitivity and resolution to the northern NRAO VLA Sky Survey (NVSS; Condon et al. 1998). The survey is progressing at a rate of about 1000 square degrees per year, yielding individual and statistical data for many thousands of weak radio sources. This paper describes the main characteristics of the survey, and presents sample images from the first year of observation.Comment: 27 pages, 12 figures (figures 2, 8, 10 in jpg format); AJ, in pres

An unbiased sample of bright southern Compact Steep Spectrum and Gigahertz Peaked Spectrum Sources

Compact Steep Spectrum (CSS) and Gigahertz Peaked Spectrum (GPS) sources are classes of compact, powerful, extragalactic objects. These sources are thought to be the earliest stages in the evolution of radio galaxies, capturing the ignition (or, in some cases, re-ignition) of the AGN. As well as serving as probes of the early stages of large-scale radio sources, these sources are good, stable, amplitude calibrators for radio telescopes. We present an unbiased flux density limited (>1.5 Jy at 2.7 GHz) catalogue of these objects in the Southern Hemisphere, including tabulated data, radio spectra, and where available, optical images and measurements. The catalogue contains 26 sources, consisting of 2 new candidate and 15 known CSS sources, and 9 known GPS sources. We present new Australia Telescope Compact Array (ATCA) data on ten of these 26 sources, and data on a further 42 sources which were excluded from our final sample. This bright sample will serve as a reference sample for comparison with subsequent faint (mJy level) samples of CSS and GPS candidates currently being compiled.Comment: Accepted by MNRAS. 13 figures and 10 tables. The full version of Table 8 will be available online after publication by MNRAS. Boldface commands remove

The Molonglo Southern 4 Jy sample (MS4). II. ATCA imaging and optical identification

Of the 228 sources in the Molonglo Southern 4 Jy Sample (MS4), the 133 with angular sizes < 35 arcsec have been imaged at 5 GHz at 2-4 arcsec resolution with the Australia Telescope Compact Array. More than 90% of the sample has been reliably optically identified, either on the plates of the UK Schmidt Southern Sky Survey or on R-band CCD images made with the Anglo-Australian Telescope. A subsample of 137 sources, the SMS4, defined to be a close southern equivalent of the northern 3CRR sample, was found to have global properties mostly consistent with the northern sample. Linear sizes of MS4 galaxies and quasars were found to be consistent with galaxy-quasar unification models of orientation and evolution.Comment: 102 pages; 6 figures in 21 Postscript files. To appear in Astronomical Journal. For higher-resolution versions of some figures, see http://www.physics.usyd.edu.au/astrop/rwh/ms4

Observations of travelling ionospheric disturbance over Adelaide, Australia

A Travelling Ionospheric Disturbance (TID) passing over Adelaide, Australia was observed simultaneously in 630.0 nm airglow images and high time resolution 2 – 22 MHz ionospheric sounder data by the Defence Science and Technology Group (DST group) on the 27th of January 2014 from approximately 10 UT to 20 UT. A comparison between the two observations shows a strong inverse correlation between the night-time ionospheric virtual height measurement, h'F, and airglow intensity in both large and small scale features. This event was unusual in two ways: a) it occurred at solar maximum and b) part of the TID split into a smaller TID before reforming. TID wavelength, velocity and period parameters calculated from both airglow and high-frequency (HF) radio measurements and are found to be in agreement.Anne. M. Unewisse, Manuel. A. Cervera, Trevor. J. Harris and Andrew. D. Coo

Airglow observations from ELOISE

In August and September 2015, the Defence Science and Technology Group (DST Group) undertook the Elevation-scanned Oblique Incidence Sounder Experiment (ELOISE): a unique campaign to observe and characterise mid-latitude ionospheric disturbances across Australia using a large number of measurement systems located at 18 sites spanning the Australian mainland. As part of this experiment, two airglow imagers were deployed in the Alice Springs region co-located with a dense Quasi-Vertical Incidence Sounder (QVIS) subnetwork. Airglow images taken over Alice Springs at 630.0 nm and 557.7 nm are discussed and compared to High Frequency soundings from one baseline of the QVIS network. When strong travelling ionospheric disturbances (TIDs) are present, an inverse relationship is seen between airglow intensity and measurements of virtual height at 2.4 MHz and a correlation is seen between the two airglow measurements. The time lag between the two airglow observations and QVIS virtual height time series over a range of HF frequencies is used to derive characteristics of travelling ionospheric disturbances.Anne M. Unewisse, Manuel A. Cervera, Lenard H. Pederick, Trevor J. Harris and Andrew D. Coo