scholarly journals The Jets in 3C 449 Revisited

1982 ◽  
Vol 97 ◽  
pp. 139-140
Author(s):  
T. J. Cornwell ◽  
R. A. Perley
Keyword(s):  
Radio Source ◽  
Radio Sources ◽  
High Luminosity ◽  
Polarization Structure ◽  
Simple Picture

Bridle (this volume) has summarized the overall characteristics of the jets found in numerous low-luminosity and some high-luminosity radio sources. Previous observations made with the partially completed VLA at wavelengths of 6 and 20 cm indicated that 3C449 was an archetypal radio source obeying all the “rules” summarized by Bridle. New observations with the VLA of the polarization structure at 6 and 20 cm have destroyed this simple picture and identify 3C449 as a “rogue” jet source.

scholarly journals VLBA+GBT observations of the COSMOS field and radio source counts at 1.4 GHz

2018 ◽  
Vol 616 ◽  
pp. A128 ◽  
Author(s):  
N. Herrera Ruiz ◽  
E. Middelberg ◽  
A. Deller ◽  
V. Smolčić ◽  
R. P. Norris ◽  
...  
Keyword(s):  
Radio Source ◽  
Flux Density ◽  
Lower Limit ◽  
High Sensitivity ◽  
Host Galaxy ◽  
Radio Sources ◽  
Source Population ◽  
Star Forming ◽  
Brightness Temperatures ◽  
Long Baseline

We present very long baseline interferometry (VLBI) observations of 179 radio sources in the COSMOS field with extremely high sensitivity using the Green Bank Telescope (GBT) together with the Very Long Baseline Array (VLBA) (VLBA+GBT) at 1.4 GHz, to explore the faint radio population in the flux density regime of tens of μJy. Here, the identification of active galactic nuclei (AGN) is based on the VLBI detection of the source, meaning that it is independent of X-ray or infrared properties. The milli-arcsecond resolution provided by the VLBI technique implies that the detected sources must be compact and have large brightness temperatures, and therefore they are most likely AGN (when the host galaxy is located at z ≥ 0.1). On the other hand, this technique only allows us to positively identify when a radio-active AGN is present, in other words, we cannot affirm that there is no AGN when the source is not detected. For this reason, the number of identified AGN using VLBI should be always treated as a lower limit. We present a catalogue containing the 35 radio sources detected with the VLBA+GBT, ten of which were not previously detected using only the VLBA. We have constructed the radio source counts at 1.4 GHz using the samples of the VLBA and VLBA+GBT detected sources of the COSMOS field to determine a lower limit for the AGN contribution to the faint radio source population. We found an AGN contribution of >40−75% at flux density levels between 150 μJy and 1 mJy. This flux density range is characterised by the upturn of the Euclidean-normalised radio source counts, which implies a contribution of a new population. This result supports the idea that the sub-mJy radio population is composed of a significant fraction of radio-emitting AGN, rather than solely by star-forming galaxies, in agreement with previous studies.

scholarly journals High Frequency Peakers

2003 ◽  
Vol 20 (1) ◽  
pp. 79-84 ◽  
Author(s):  
Daniele Dallacasa
Keyword(s):  
Radio Source ◽  
High Frequency ◽  
Peak Frequency ◽  
Source Size ◽  
Host Galaxy ◽  
Radio Sources ◽  
Inner Region

AbstractThere is quite a clear anticorrelation between the intrinsic peak frequency and the overall radio source size in compact steep spectrum (CSS) and gigahertz peaked spectrum (GPS) radio sources. This feature is interpreted in terms of synchrotron self-absorption (although free–free absorption may play a role as well) of the radiation emitted by a small radio source which is growing within the inner region of the host galaxy. This leads to the hypothesis that these objects are young and that the radio source is still developing/expanding within the host galaxy itself.Very young radio sources must have the peak in their radio spectra occurring above a few tens of gigahertz, and for this reason they are termed high frequency peakers (HFPs). These newly born radio sources must be very rare given that they spend very little time in this stage. Ho = 100 km s−1 Mpc−1 and qo = 0.5 are used throughout this paper.

scholarly journals Extended Structure in High-Redshift Radio Sources

1982 ◽  
Vol 97 ◽  
pp. 59-60
Author(s):  
P. J. Duffett-Smith ◽  
A. Purvis
Keyword(s):  
Radio Source ◽  
High Redshift ◽  
Radio Sources ◽  
List Type ◽  
Type Number ◽  
Extended Structure ◽  
Structure Changes ◽  
Lower Luminosity ◽  
Source Structure

We have compared measurements of several hundred 3C and 4C radio sources at large redshifts to investigate how radio-source structure changes over a factor of 5–10 in luminosity. Our results show that for z ≳ 0.6: (i)most sources (both 3C and 4C) have hotspots about 3.5 kpc in size (Ho = 50 km s−1 Mpc−1, Ω = 1);(ii)lower-luminosity sources (bottom of 4C) have less-extended outer lobes.

scholarly journals The Milliarcsecond Core of 3C147 at 6 cm

1984 ◽  
Vol 110 ◽  
pp. 29-30 ◽  
Author(s):  
E. Preuss ◽  
W. Alef ◽  
N. Whyborn ◽  
P.N. Wilkinson ◽  
K.I. Kellermann
Keyword(s):  
Radio Source ◽  
Radio Sources ◽  
Radio Structure ◽  
Extragalactic Radio Sources ◽  
North East ◽  
The North ◽  
Vlbi Observations ◽  
Spectrum Radio ◽  
The One

3C147 is a compact (≲1″), steep spectrum radio source identified with a quasar at z = 0.545 (0″.001 = 7.4 pc; c/Ho = 6000 Mpc and qo = 0.5). The radio structure shown by VLBI observations at 18 cm (Readhead & Wilkinson, 1980; Simon et al., this volume), at 50 cm (Wilkinson et al., 1977), and at 90 cm (Simon et al., 1980 and 1983) shows a bright ‘core’ (60 pc at one end of a ‘jet’ ~0″.2 (1.5 kpc) in length oriented in p.a. ~ −130°. In this sense 3C147 is typical of the one-sided ‘core-jet’ structures commonly found in the centres of other extragalactic radio sources. However, MERLIN observations at 6 cm (Wilkinson, this vol.) and VLA observations at 2 cm (Crane & Kellermann, unpubl.; Readhead et al., 1980) show a larger elongated feature extending ~0″.5 (3.7 kpc) to the North East of the bright core in p.a. ~25° or on the opposite side to the 0″.2 jet.

scholarly journals Kiloparsec Scale Structure in High Luminosity Radio Sources Observed with MTRLI

1982 ◽  
Vol 97 ◽  
pp. 149-156
Author(s):  
Peter N. Wilkinson
Keyword(s):  
Scale Structure ◽  
Radio Link ◽  
Radio Sources ◽  
High Luminosity ◽  
Full Complement

The new Jodrell Bank Multi-Telescope-Radio-Link Interferometer system (MTRLI) began operating in January 1980 with four telescopes and with its full complement of six telescopes in December 19 80. The location of the telescopes and the baseline lengths (in km) thus obtained are shown in Fig. 1. However, before describing some of the exciting new results it has yielded on high luminosity radio sources it is important to outline the capabilities of the instrument since the maps are produced in a rather different way to those from conventional synthesis instruments.

scholarly journals A Comparison of the Structures of 3CR Quasars and Blank Field Radio Sources

1982 ◽  
Vol 97 ◽  
pp. 435-436 ◽  
Author(s):  
F. N. Owen ◽  
J. J. Puschell ◽  
R. A. Laing
Keyword(s):  
Radio Source ◽  
Structural Properties ◽  
Low Frequency ◽  
Radio Sources ◽  
Blank Field ◽  
Sky Survey

The purpose of this communication is to update our knowledge of the radio structural properties of quasars and blank field radio sources (blank field ≡ any radio source without an identification on the Palomar Sky Survey prints). The quasar sample consists of all sources (25) with angular sizes greater than 10 arcsec in the list of Jodrell Bank quasars observed by Owen, Porcas and Neff (1978). The blank fields consist of 16 3CR sources also with structures >10 arcsec based on Cambridge 5 km telescope observations. The sources were selected in low-frequency surveys; their emission at ν < 1 GHz is dominated by extended components with steep spectra. Thus, both samples should be oriented randomly in space except for a slight bias to be in the plane of the sky.

scholarly journals Spectroscopy of faint radio sources: the nature of the sub-mJy radio-source population

1993 ◽  
Vol 263 (1) ◽  
pp. 98-122 ◽  
Author(s):  
C. R. Benn ◽  
M. Rowan-Robinson ◽  
R. G. McMahon ◽  
T. J. Broadhurst ◽  
A. Lawrence
Keyword(s):  
Radio Source ◽  
Radio Sources ◽  
Source Population

scholarly journals High Resolution Imaging of Compact Radio Sources by Gridding with Regularization

1998 ◽  
Vol 164 ◽  
pp. 411-412 ◽  
Author(s):  
S. F. Likhachev ◽  
R. M. Hjellming
Keyword(s):  
High Resolution ◽  
Image Reconstruction ◽  
Radio Source ◽  
Radio Sources ◽  
High Resolution Imaging ◽  
Traditional Methods ◽  
Compact Radio Source ◽  
Ill Posed ◽  
Resolution Imaging

AbstractThe problem of VLBI image reconstruction is a classical example of an ill-posed problem. A new procedure of gridding with regularization has been developed. This procedure was used in traditional methods (CLEAN, Hybrid) to improve the quality of compact radio source images. A few sources (GRO J1655–40, RY Scuti and Cyg X-1), observed with the VLA and VLBA, were processed with this procedure.

scholarly journals The Compact Nonthermal Radio Source at the Galactic Center: an Update

1989 ◽  
Vol 136 ◽  
pp. 527-534
Author(s):  
K. Y. Lo
Keyword(s):  
Radio Source ◽  
Galactic Center ◽  
Central Star ◽  
Radio Sources ◽  
Stellar Objects ◽  
Nonthermal Radio ◽  
Compact Radio Source ◽  
The Galaxy ◽  
Observational Status ◽  
Sgr A

We review the current observational status of Sgr A∗, the compact nonthermal radio source at the galactic center. Sgr A∗ is a unique radio source at a unique location of the Galaxy. It is unlike any compact radio source associated with known stellar objects, but it is similar to extragalactic nuclear compact radio sources. The positional offset between Sgr A∗ and IRS16 places little constraint on the nature of the underlying energy source, since IRS16 need not be the core of the central star cluster. Sgr A∗ is still the best candidate for marking the location of a massive collapsed object.

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