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Spectrum Radio Sources (spectrum + radio_source)

Distribution by Scientific Domains
Physics and Astronomy100%

Selected Abstracts

The host galaxies of Compact Steep Spectrum and Gigahertz-Peaked Spectrum radio sources

ASTRONOMISCHE NACHRICHTEN, Issue 2-3 2009
J. Holt
Abstract I will review some of the developments in studies of the host galaxy properties of Compact Steep Spectrum (CSS) and Gigahertz-Peaked Spectrum (GPS) radio sources. In contrast to previous reviews structured around observational technique, I will discuss the host galaxy properties in terms of morphology, stellar content and warm gas properties and discuss how compact, young radio-loud AGN are key objects for understanding galaxy evolution (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Deep spectroscopy of 9C J1503+4528: a very young compact steep spectrum radio source at z= 0.521

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2006
K. J. Inskip
ABSTRACT 9C J1503+4528 is a very young compact steep spectrum radio galaxy, with an age of the order of 104 yr. This source is therefore an ideal laboratory for the study of the intrinsic host galaxy/intergalactic medium properties, interactions between the radio source and surrounding interstellar medium, links between star formation and active galactic nucleus (AGN) activity and the radio source triggering mechanism. Here we present the results of a spectroscopic analysis of this source, considering each of these aspects of radio source physics. We find that shock ionization by the young radio source is important in the central regions of the galaxy on scales similar to that of the radio source itself, whilst evidence for an AGN ionization cone is observed at greater distances. Line and continuum features require the presence of a young stellar population (YSP), the best-fitting model for which implies an age of 5 × 106 yr, significantly older than the radio source. Most interestingly, the relative sizes of radio source and extended emission-line region suggest that both AGN and radio source are triggered at approximately the same time. If both the triggering of the radio source activity and the formation of the YSP had the same underlying cause, this source provides a sequence for the events surrounding the triggering process. We propose that the AGN activity in 9C J1503+4528 was caused by a relatively minor interaction, and that a supermassive black hole powering the radio jets must have been in place before the AGN was triggered. [source]

Imaging and spectroscopy of ultrasteep spectrum radio sources,

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2007
Carlos G. Bornancini
ABSTRACT We present a sample of 40 ultrasteep spectrum (USS; ,,, 1.3, S,,,,) radio sources selected from the Westerbork in the Southern Hemisphere (WISH) catalogue. The USS sources have been imaged in K band at the Cerro Tololo Inter-American Observatory (CTIO) and with the Very Large Telescope (VLT) at Cerro Paranal. We also present VLT, Keck and William Herschel Telescope (WHT) optical spectroscopy of 14 targets selection from four different USS samples. For 12 sources, we have been able to determine the redshifts, including four new radio galaxies at z > 3. We find that most of our USS sources have predominantly small (<6 arcsec) radio sizes and faint magnitudes (K, 18). The mean K -band counterpart magnitude is . The expected redshift distribution estimated using the Hubble K,z diagram has a mean of , which is higher than the predicted redshift obtained for the Sydney University Molonglo Sky Survey,NRAO VLA Sky Survey (SUMSS,NVSS) sample and the expected redshift obtained in the 6C** survey. The compact USS sample analysed here may contain a higher fraction of galaxies which are high redshift and/or are heavily obscured by dust. Using the 74, 352 and 1400 MHz flux densities of a subsample, we construct a radio colour,colour diagram. We find that all but one of our USS sources have a strong tendency to flatten below 352 MHz. We also find that the highest redshift source from this paper (at z= 3.84) does not show evidence for spectral flattening down to 151 MHz. This suggests that very low frequency selected USS samples will likely be more efficient to find high redshift galaxies. [source]

Simultaneous, multi-frequency, VLA observations of inverted spectrum radio sources

ASTRONOMISCHE NACHRICHTEN, Issue 2-3 2009
B. PartridgeArticle first published online: 13 FEB 200
Abstract We selected extragalactic sources with inverted spectra at 1.4 to 5 GHz, and observed ,250 of them at the VLA at frequencies from 1.4 to 22 GHz and in some cases 43 GHz. Here we summarize the spectral index distributions, and report on polarization measurements and/or upper limits for a subsample of ,35 sources (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]