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 Interpretation of Cosmological Information on Radio Sources

1977 ◽  
Vol 74 ◽  
pp. 247-257
Author(s):  
G. Burbidge
Keyword(s):  
Radio Astronomy ◽  
Background Radiation ◽  
Radio Galaxies ◽  
Radio Sources ◽  
List Type ◽  
Type Number ◽  
Radio Flux ◽  
Powerful Radio ◽  
Microwave Background ◽  
Microwave Background Radiation

The topic that I have to introduce today is concerned with the question as to whether or not we can obtain any cosmological information from radio astronomy. Alternatively, we may ask “Where does radio astronomy have an impact on cosmology?” There are several areas that must be discussed. They are: 1)The discovery and interpretation of the microwave background radiation.2)The identification of powerful radio sources and the discovery that many of them have large redshifts. If we can prove that the large redshifts mean that the objects are at great distances, then we can use these radio sources as follows:(a)We can attempt to obtain a Hubble relation for the optical objects which are identified with radio galaxies;(b)We can look for a relation between the angular diameters of the radio sources and the redshifts of the optically identified objects and we can also look at relations between the angular diameter and the radio flux;(c)We can construct log N - log S curves and we can carry out luminosity volume tests.

scholarly journals Radio Source Environments at Redshifts > 0.5

1996 ◽  
Vol 175 ◽  
pp. 321-322
Author(s):  
M. Lacy ◽  
S. Rawlings ◽  
M. Wold ◽  
A. Bunker ◽  
K.M. Blundell ◽  
...  
Keyword(s):  
Radio Source ◽  
High Redshift ◽  
Elliptical Galaxies ◽  
Radio Sources ◽  
Powerful Radio ◽  
Host Galaxies ◽  
Local Universe ◽  
Wide Range ◽  
Age Of The Universe ◽  
The Universe

The most powerful radio sources in the local Universe are found in giant elliptical galaxies. Looking back to a redshift of 0.5 (≈ half the age of the Universe for ω = 1), we see that these host galaxies are increasingly found in moderately rich clusters. This fact gives us hope that radio sources can be used as tracers of high density environments at high redshift. By exploiting radio source samples selected over a wide range in luminosity (Blundell et al., these proceedings), we will also be able to test whether the luminosities of radio sources are correlated with their environments.

scholarly journals Dust-Embedded AGN in Unusually Warm IRAS Galaxies

1989 ◽  
Vol 134 ◽  
pp. 406-407
Author(s):  
J. P. Vader ◽  
J. A. Frogel ◽  
F. C. Gillett ◽  
M. H. K. de Grijp
Keyword(s):  
Radio Galaxies ◽  
Radio Sources ◽  
List Type ◽  
Broad Line ◽  
Type Number ◽  
Early Type ◽  
Energy Distributions ◽  
Near Ir ◽  
Line Region ◽  
The One

The IRAS Point Source Catalog contains only 61 sources identified as galaxies whose energy distribution peaks at 60 mμ. The scarcity of such galaxies has prompted a search for possible common properties. This sample of ‘60 mμ peakers’, 21 of which are previously identified galaxies, partially overlaps with that of warm IRAS galaxies studied by de Grijp et al. (1987) and contains similar percentages of Seyfert (65%) and starburst galaxies on the one hand, and of strong and weak radio sources on the other hand. A remarkable characteristic is, however, that about half of the 60 mμ peakers seem to be early-type galaxies. The fact that such galaxies are rarely IRAS sources and, if so, have FIR energy distributions peaking at 100 mμ similar to those of spirals, implies that we are sampling active or nuclear starburst early-type galaxies with a very large success rate. The observational data accumulated so far further show that: (i)objects with smaller FIR to near-IR flux ratios have redder J-K colors and warmer 60 to 25 mμ colors, i.e., an infared spectrum dominated by warmer dust and/or a nonthermal source (Figs. 1a,b);(ii)out of 32 objects with radio data, the 5 compact radio sources with luminosities intermediate between those af radio-quiet and radio-loud AGN have among the warmest 60 to 25 mμ colors (Fig. 2). Such warm FIR colors are not a common characteristic of radio galaxies and quasars (Golombek et al. 1987, Neugebauer et al. 1986).(iii)the 60 mμ luminosities range from 109 to 1012 L0, and are largest for Mkn 231, 2306+0505 (Hill et al. 1987) and 2046+1925 (Frogel et al. 1988). The latter 2 objects, along with 0052-7054 (Frogel and Elias 1987) which also belongs to our sample, are Seyfert 2 galaxies with evidence for the presence of a dust-obsured broad line region.

scholarly journals Shock Models of Time Variability and Superluminal Motion in Compact Extragalactic Radio Sources

1988 ◽  
Vol 129 ◽  
pp. 81-82
Author(s):  
Philip A. Hughes ◽  
Hugh D. Aller ◽  
Margo F. Aller
Keyword(s):  
Mode Conversion ◽  
Lorentz Factor ◽  
Time Variability ◽  
Radio Sources ◽  
List Type ◽  
Random Component ◽  
Type Number ◽  
Flow Energy ◽  
Bl Lacertae ◽  
Superluminal Motion

Following the success of a simple shock model for outbursts in BL Lacertae and 3C 279 (see Aller, Aller & Hughes, this meeting) we have constructed computer codes to study in detail the radiation from shocked, relativistic jets. These codes compute the transfer of synchrotron radiation, accounting for polarized emission and absorption, rotation, and mode conversion for a turbulent collimated flow with one or more shocks propagating parallel to the jet axis. We present results for a flow that evolves adiabatically, with the turbulence represented by a random component to the magnetic field within each computational cell, and with the shocks prescribed analytically following Königl (Phys. Fluids, 23, 1083, 1980). From the evolution of the total and polarized fluxes as a function of frequency, and from the corresponding projection of the source structure on the plane of the sky, we see that this type of model a.is capable o f explaining the variability of compact radio sources - see Aller, Aller & Hughes, this meeting,b.highlights the care needed when interpreting VLBI maps, in that i)the component separations are frequency dependent (see Fig. 1)ii)the ‘core’ is not always the brightest component (see Fig. 1)iii)the Doppler boosting factor of the shocked flow is not directly related to the Lorentz factor derived from the apparent superluminal motion of a componentiv)a multiplicity of components can give rise to both apparent contractions and accelerations,c.clearly shows the link between time variability of compact sources and evolving VLBI structure, and suggests that both may be understood in terms of weak shocks that tap a small fraction of a jet's flow energy,d.enables us to probe the physical conditions of the flow and the ambient material.

scholarly journals Radio-optical Identification of Very-Steep Spectrum Radio Sources from the UTR-2 Catalogue

2002 ◽  
Vol 199 ◽  
pp. 217-218 ◽  
Author(s):  
H. Andernach ◽  
O.V. Verkhodanov ◽  
N.V. Verkhodanova
Keyword(s):  
Radio Source ◽  
High Redshift ◽  
Radio Galaxies ◽  
Image Databases ◽  
Radio Continuum ◽  
Radio Sources ◽  
Optical Identification ◽  
X Ray ◽  
Spectrum Radio

We used radio source catalogues accessible from the CATS database to establish radio continuum spectra for decametric radio sources in the UTR-2 catalogue. In an attempt to find further candidates for high-redshift radio galaxies, we searched the FIRST and NVSS surveys for counterparts of a sample of UTR sources with ultra-steep radio spectra (USS, α ≤ −1.2, S ∼ vα). We derived accurate positions and sizes for 23 of these USS sources. The search for optical counterparts from the APM (object) and DSS (image) databases, as well as infrared and X—ray identifications of these UTR sources are in progress.

scholarly journals Polarization Variability of Some Compact Radio Sources

1982 ◽  
Vol 97 ◽  
pp. 331-333
Author(s):  
M. M. Komesaroff ◽  
D. K. Milne ◽  
P. T. Rayner ◽  
J. A. Roberts ◽  
D. J. Cooke
Keyword(s):  
Circular Polarization ◽  
Linear Polarization ◽  
Position Angle ◽  
Linear Increase ◽  
Monitoring Programme ◽  
Radio Sources ◽  
List Type ◽  
Type Number ◽  
5 Ghz ◽  
Superluminal Expansion

Figure 1 shows observations for four sample sources from the Parkes 5 GHz polarization monitoring programme. Interesting features illustrated include •Sudden changes of the position angle of the linear polarization by ≳ 70° in PKS 0537-441 and 1253-055 (3C279).•A linear increase in the position angle of the polarization of PKS 2134+004 through 70° over 3/12; years.•Distinct bursts of circular polarization in PKS 0430+052, 0537-441 and 1253-055. In PKS 0430+052 (3C120) such a burst coincides with the possible superluminal expansion (Walker et al., 1981). In PKS 1253-055 (3C279) a burst of circular polarization is currently occurring at a time of very low linear polarization.

Polarization of extragalactic radio sources: CMB foregrounds and telescope calibration issues

2016 ◽  
Vol 25 (11) ◽  
pp. 1640009 ◽  
Author(s):  
Marcella Massardi ◽  
Vincenzo Galluzzi ◽  
Rosita Paladino ◽  
Carlo Burigana
Keyword(s):  
Cosmic Microwave Background ◽  
Radio Source ◽  
High Redshift ◽  
The Other ◽  
Radio Sources ◽  
Polarization Rotation ◽  
Microwave Background ◽  
Extragalactic Radio Sources ◽  
Systematic Effects ◽  
The One

Radio source observations play important roles in polarimetric cosmological studies. On the one hand, they constitute the main foregrounds for cosmic microwave background (CMB) radiation on scales smaller than 30 arcmin up to 100 GHz, on the other they can be used as targets for validation of products of polarimetric experiments dedicated to cosmology. Furthermore, extragalactic high-redshift sources have been used for cosmic polarization rotation (CPR) investigation. In this paper, we will discuss the support to cosmological studies from ground-based polarimetric observations in the radio and millimetric wavelength bands. Most of the limits to accuracy improvements arise from systematic effects and low calibration quality. We will discuss some details of interferometric calibration procedures and show some of the perspectives that the Atacama large millimeter array (ALMA) could offer for CPR studies.

scholarly journals A VLBA 15 GHz Small Separation Gravitational Lens Survey

1996 ◽  
Vol 173 ◽  
pp. 405-406
Author(s):  
A.R. Patnaik ◽  
M.A. Garrett ◽  
A. Polatidis ◽  
D. Bagri
Keyword(s):  
High Frequency ◽  
Gravitational Lens ◽  
Radio Sources ◽  
List Type ◽  
Type Number ◽  
Morphological Classification ◽  
Small Separation

We have embarked on a 15 GHz VLBA survey of 1000 flat spectrum sources. We present the results from a 24 hour pilot observing run in which 72 sources were mapped. The primary aims of this project are: –to search for small separation (1-150 mas) gravitational lens systems–to identify targets for current mm and anticipated Space VLBI programs–a morphological classification of compact radio sources at relatively high frequency with sub-mas resolution.

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