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 Giant Radio Sources: Evolution and GMRT Observations

2002 ◽  
Vol 199 ◽  
pp. 199-202
Author(s):  
C.H. Ishwara-Chandra ◽  
D.J. Saikia
Keyword(s):  
Background Radiation ◽  
Radio Galaxies ◽  
Radio Sources ◽  
Microwave Background ◽  
Radiation Losses ◽  
Inverse Compton ◽  
Microwave Background Radiation

We study the evolution of giant radio sources and show that they are less luminous than the smaller-sized sources, and are roughly consistent with the evolutionary scenarios where the smaller-sized sources evolve to giants undergoing radiative and expansion losses. Inverse-Compton radiation losses due to the microwave background radiation dominates over the synchrotron losses for giant sources, while for the smaller sources, the latter dominates. We show that giant radio galaxies and quasars are consistent with the unified scheme, and their large sizes are not due to stronger cores. We also present preliminary GMRT images of three giant sources.

scholarly journals The Microwave Background Radiation

1990 ◽  
Vol 139 ◽  
pp. 333-343 ◽  
Author(s):  
G. De Zotti ◽  
L. Danese ◽  
L. Toffolatti ◽  
A. Franceschini
Keyword(s):  
Large Scale ◽  
Background Radiation ◽  
High Redshift ◽  
Dust Emission ◽  
Radio Sources ◽  
Microwave Background ◽  
Satisfactory Explanation ◽  
X Ray ◽  
Microwave Background Radiation ◽  
X Ray Background

We review the data on the spectrum and isotropy of the microwave background radiation and the astrophysical processes that may produce spectral distortions and anisotropies. As yet no fully satisfactory explanation has been found for the submillimeter excess observed by Matsumoto et al. (1988). The most precise data at λ > 1 mm disagree with nonrelativistic comptonization models which match the excess. Distortions produced by a very hot intergalactic medium yielding the X-ray background do not fit the submillimeter data. Very special requirements must be met for the interpretation in terms of high-redshift dust emission to work.Reported anisotropies on scales of several degrees and of tens of arcsec may be produced, at least in part, by discrete sources. Because the best experiments at cm wavelengths are close to the confusion limit, they provide interesting information on the large-scale distribution of radio sources.

scholarly journals Ghost Images in a Universe with Inhomogeneous Mass Distribution

1972 ◽  
Vol 44 ◽  
pp. 478-491 ◽  
Author(s):  
J. M. Barnothy ◽  
M. F. Barnothy
Keyword(s):  
Mass Distribution ◽  
Background Radiation ◽  
Positive Curvature ◽  
Radio Sources ◽  
Microwave Background ◽  
Microwave Background Radiation ◽  
Discrete Radio Sources ◽  
Ghost Images

An attempt is made to explain Morgan cD supergiant galaxies, the microwave background radiation and extended discrete radio sources as ghost images in a universe of strong positive curvature and inhomogeneous mass distribution.

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 On the X-Ray Emission from the Powerful Radio galaxies

1996 ◽  
Vol 175 ◽  
pp. 407-408
Author(s):  
G. Brunetti ◽  
G. Setti ◽  
A. Comastri
Keyword(s):  
Radiation Flux ◽  
Background Radiation ◽  
Radio Galaxies ◽  
X Rays ◽  
Microwave Background ◽  
X Ray ◽  
Near Ir ◽  
Inverse Compton ◽  
Microwave Background Radiation ◽  
Low Sensitivity

There is a growing evidence that radio loud quasars and powerful FR II radio galaxies belong to the same population. While X-ray observations of low redshift radio galaxies generally support the unified scheme relating the FR II radio galaxies to the radio quasars, nevertheless detailed studies of the X-ray properties of distant radio galaxies are made difficult due to both the low sensitivity of X-ray-satellites and to the emission of the hot intracluster gas in which they are normally embedded. We point out that significant fluxes of X-rays are produced in the strong radio galaxies by the Inverse Compton (IC) process. In the framework of the unified scheme the radio galaxies are pervaded both by an intense radiation flux from the misdirected hidden quasar and the cosmic microwave background radiation flux (CMB). From the standpoint of IC computation the far and near-IR emissions of the hidden quasar are of particular importance.

scholarly journals The Microwave Background Radiation: An Alternative View

1992 ◽  
Vol 9 ◽  
pp. 287-289
Author(s):  
Jayant V. Narlikar
Keyword(s):  
Background Radiation ◽  
Big Bang ◽  
Alternative View ◽  
List Type ◽  
Recent Past ◽  
Microwave Background ◽  
Microwave Background Radiation ◽  
Big Bang Model ◽  
The One ◽  
The Universe

Why do we need to think about any alternatives when the primordial interpretation of the microwave background radiation (MBR) has been accepted by so many for so long? The answer is that the primordial interpretation, in spite of its successes has manifest shortcomings in spite of attempts to remove them by so many for so long. To mention a few: a)Why is the MBR temperature 2.7 K? The value is taken as a parameter in all early universe calculations; it is not predicted by the hot big bang theory with or without inflation.b)There are other astrophysical processes of comparable energy density and other radiation backgrounds that have no primordial origin; why should MBR alone stand out as the odd one out just at this epoch?c)Why are there no signatures of structure formation on the MBR; why is it so smooth?d)The hot big bang model relates to the universe in the first three minutes while the MBR is observed in the more recent past; are we not making too long a jump across from the one to the other?

scholarly journals The Microwave Background Radiation: Recent Advances and New Problems

1989 ◽  
Vol 8 ◽  
pp. 681-688 ◽  
Author(s):  
G. de Zotti ◽  
L. Toffolatti
Keyword(s):  
Large Scale ◽  
Background Radiation ◽  
Dust Emission ◽  
Radio Sources ◽  
Microwave Background ◽  
Precise Data ◽  
Intensity Measurements ◽  
Planck Spectrum ◽  
Microwave Background Radiation ◽  
Source Confusion

AbstractThe substantially improved intensity measurements at wavelengths longward of the intensity peak of the microwave background are fully consistent with a Planck spectrum. The most precise data disagree with non-relativistic comptonization models for the large submillimeter excess observed by the Nagoya-Berkeley collaboration. The interpretation of such excess as dust emission at high redshifts also faces severe difficulties. Reported anisotropies on scales of several degrees and of tens of arcsec may be contributed, at least in part, by discrete sources. Just because the best experiments at cm wavelengths nave already got close to the source confusion limit, they also provide interesting information on the large scale distribution of radio sources. Polarimetry may be decisive in clarifying the origin of observed fluctuations.

scholarly journals Background Radiation: Probes and Future Tests

1996 ◽  
Vol 168 ◽  
pp. 389-398
Author(s):  
Martin J. Rees
Keyword(s):  
Background Radiation ◽  
Light Element ◽  
Mass Range ◽  
Black Body ◽  
Big Bang ◽  
List Type ◽  
Microwave Background ◽  
Background Spectrum ◽  
Element Abundances ◽  
Microwave Background Radiation

The clearest evidence for the ‘hot big bang’ is of course the microwave background radiation. Its spectrum is now known, from the FIRAS experiment on COBE, to be a very precise black body – indeed, the deviations due to high-z activity, hot intergalactic gas, etc are smaller than many people might have expected. Also the light element abundances have remained concordant with the predictions of big bang nucleosynthesis, thereby giving us confidence in extrapolating back to when the universe was a few seconds old (see Copi, Schramm and Turner 1994 for a recent review). These developments give us grounds for greater confidence in this model than would have been warranted ten years ago. Several things could have happened which would have refuted the picture, but they haven't happened. For instance:(i)Objects could have been found where the helium abundance was far below 23 per cent.(ii)The background spectrum at millimetre wavelengths could have been weaker than a black body with temperature chosen to fit the Rayleigh-Jeans part of the spectrum.(iii)A stable neutrino might have been discovered in the mass range 100eV-1MeV.

scholarly journals RAiSE X: searching for radio galaxies in X-ray surveys

2020 ◽  
Vol 493 (4) ◽  
pp. 5181-5194 ◽  
Author(s):  
Ross J Turner ◽  
Stanislav S Shabala
Keyword(s):  
Cosmic Microwave Background ◽  
Surface Brightness ◽  
Background Radiation ◽  
Ambient Medium ◽  
High Redshift ◽  
Radio Galaxies ◽  
Microwave Background ◽  
X Ray ◽  
Inverse Compton ◽  
Microwave Background Radiation

ABSTRACT We model the X-ray surface brightness distribution of emission associated with Fanaroff & Riley type-II radio galaxies. Our approach builds on the RAiSE dynamical model which describes broad-band radio frequency synchrotron evolution of jet-inflated lobes in a wide range of environments. The X-ray version of the model presented here includes: (1) inverse-Compton upscattering of cosmic microwave background radiation; (2) the dynamics of the shocked gas shell and associated bremsstrahlung radiation; and (3) emission from the surrounding ambient medium. We construct X-ray surface brightness maps for a mock catalogue of extended FR-IIs based on the technical characteristics of the eRosita telescope. The integrated X-ray luminosity function at low redshifts (z ≤ 1) is found to strongly correlate with the density of the ambient medium in all but the most energetic sources, whilst at high-redshift (z > 1) the majority of objects are dominated by inverse-Compton lobe emission due to the stronger cosmic microwave background radiation. By inspecting our mock spatial brightness distributions, we conclude that any extended X-ray detection can be attributed to AGN activity at redshifts z ≥ 1. We compare the expected detection rates of active and remnant high-redshift radio AGNs for eRosita and LOFAR, and future more sensitive surveys. We find that a factor of ten more remnants can be detected using X-ray wavelengths over radio frequencies at z > 2.2, increasing to a factor of 100 for redshifts z > 3.1.

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