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Optical Identification (optical + identification)
Selected AbstractsHigh frequency GPS sources in the AT20G surveyASTRONOMISCHE NACHRICHTEN, Issue 2-3 2009P.J. Hancock Abstract The Australia Telescope 20 GHz (AT20G) survey was used to select a complete sample of 656 Gigahertz Peaked Spectrum (GPS) sources with spectral turnovers above 5 GHz. The AT20G has near simultaneous observations at 4.8, 8.6 and 20 GHz, which makes it possible to exclude flat spectrum variability as a cause of a source's peaked spectrum. Optical identification of the sample results in 361 QSOs and 104 galaxies and 191 blank fields. Redshifts are known for 104 of the GPS sources. The GPS sources from the AT20G are discussed and compared to previously known samples. The new sample of high frequency peaking GPS sources is found at a lower redshift than previous samples and to also have a lower 5 GHz radio power. Evidence is found to support the idea that the origin of the GPS spectral shape are intrinsically different for galaxies and QSOs. This paper is an elaboration and extension of the talk given at the 4th CSS/GPS conference in Riccione in May this year (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Spin temperatures and covering factors for H i 21-cm absorption in damped Lyman , systemsMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2005S. J. Curran ABSTRACT We investigate the practice of assigning high spin temperatures to damped Lyman , absorption systems (DLAs) not detected in H i 21-cm absorption. In particular, Kanekar & Chengalur have attributed the mix of 21-cm detections and non-detections in low-redshift (zabs, 2.04) DLAs to a mix of spin temperatures, while the non-detections at high redshift were attributed to high spin temperatures. Below zabs= 0.9, where some of the DLA host galaxy morphologies are known, we find that 21-cm absorption is normally detected towards large radio sources when the absorber is known to be associated with a large intermediate (spiral) galaxy. Furthermore, at these redshifts, only one of the six 21-cm non-detections has an optical identification and these DLAs tend to lie along the sight-lines to the largest background radio continuum sources. For these and many of the high-redshift DLAs occulting large radio continua, we therefore expect covering factors of less than the assumed/estimated value of unity. This would have the effect of introducing a range of spin temperatures considerably narrower than the current range of ,Ts, 9000 K, while still supporting the hypothesis that the high-redshift DLA sample comprises a larger proportion of compact galaxies than the low-redshift sample. [source] J06587,5558: a very unusual polarized radio sourceMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2001H. Liang We have found a peculiar radio source, J06587,5558, in the field of one of the hottest known clusters of galaxies, 1E 0657,56. It is slightly extended and highly polarized (54 per cent at 8.8 GHz), and has a very steep spectrum, with at 1.3 GHz, steepening to , at 8.8 GHz . No extragalactic sources are known with such high integrated polarization, and sources with spectra as steep as this are rare. In this Letter, we report the unusual properties of the source J06587,5558 and speculate on its origin and optical identification. [source] A search for the submillimetre counterparts to Lyman break galaxiesMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 1 2000Scott C. Chapman We have carried out targeted submillimetre observations as part of a programme to explore the connection between the rest-frame ultraviolet and far-infrared properties of star-forming galaxies at high redshift, which is currently poorly understood. On the one hand, the Lyman break technique is very effective at selecting galaxies. On the other, ,blank-field' imaging in the submillimetre seems to turn up sources routinely, amongst which some are star-forming galaxies at similar redshifts. Already much work has been done searching for optical identifications of objects detected using the SCUBA instrument. Here we have taken the opposite approach, performing submillimetre photometry for a sample of Lyman break galaxies, the ultraviolet properties of which imply high star formation rates. The total signal from our Lyman break sample is undetected in the submillimetre, at an rms level of ,0.5 mJy, which implies that the population of Lyman break galaxies does not constitute a large part of the recently detected blank-field submillimetre sources. However, our one detection suggests that with reasonable SCUBA integrations we might expect to detect those few Lyman break galaxies that are far-infrared brightest. [source] The source content of low galactic latitude XMM-Newton surveysASTRONOMISCHE NACHRICHTEN, Issue 1-2 2003C. Motch Abstract We present results from a project conducted by the Survey Science Center of the XMM-Newton satellite and aiming at the identification and characterisation of serendipitous EPIC sources at low galactic latitudes. Deep multi-colour optical imaging and spectroscopic observations have been obtained in the framework of several observing campaigns carried out at ING, CFHT and ESO. These observations have lead to a number of optical identifications, mostly with active stars. We describe the identified source content at low galactic latitudes and compare stellar populations properties at low and high galactic latitudes with those expected from stellar X-ray count models. [source] | ||||||||||