scholarly journals 9.10. The cause of the spectral turnover in the GPS source 0108+388: free-free absorption or SSA?

1998 ◽  
Vol 184 ◽  
pp. 401-402
Author(s):  
J. M. Marr ◽  
F. Crawford ◽  
G. B. Taylor
Keyword(s):  
Magnetic Fields ◽  
Radio Source ◽  
High Frequency ◽  
Radio Sources ◽  
Host Galaxies ◽  
Ionized Gas ◽  
High Frequencies ◽  
Extragalactic Radio Sources ◽  
Competing Models ◽  
Frequency Radiation

The radio source 0108 + 388 is a canonical example of a class of extragalactic radio sources, referred to as Gigahertz-Peaked Spectrum (GPS) sources, whose spectra peak at high frequencies. There are two competing models for the cause of the high frequency turnover: free-free absorption (f-f) of the lower frequency radiation by ionized gas in the host galaxies (e.g. van Breugel 1984), or synchrotron self-absorption (SSA) due to exceptionally large magnetic fields, (e.g. Hodges, Mutel, & Phillips 1984).

scholarly journals Equipartition: Fact or Fiction?

1990 ◽  
Vol 140 ◽  
pp. 235-236
Author(s):  
Nebojsa Duric
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Total Energy ◽  
Radio Source ◽  
Spiral Galaxies ◽  
Source Parameters ◽  
Minimum Energy ◽  
Energy Criterion ◽  
Radio Sources ◽  
Extragalactic Radio Sources

The use of equipartition calculations in estimating magnetic field strengths and energetics of extragalactic radio sources is widespread and well known. Since it is one of the few ways in which to calculate radio source parameters, it is important to determine how reasonable the approach generally is. Since this assumption is approximately a minimum energy criterion one expects that deviations from equipartition are limited at some level by independently determined constraints on the total energy. In this regard we have analyzed radio images of nearby spiral galaxies in order to determine equipartition magnetic fields and relativistic gas energies and to explore their possible nonequipartition configurations.

scholarly journals Searching for signs of jet-driven negative feedback in the nearby radio galaxy UGC 05771

2019 ◽  
Vol 489 (4) ◽  
pp. 4944-4961 ◽  
Author(s):  
Henry R M Zovaro ◽  
Nicole P H Nesvadba ◽  
Robert Sharp ◽  
Geoffrey V Bicknell ◽  
Brent Groves ◽  
...  
Keyword(s):  
Star Formation ◽  
Radio Source ◽  
Large Fraction ◽  
Host Galaxy ◽  
Radio Sources ◽  
Host Galaxies ◽  
Ionized Gas ◽  
Spectrum Radio ◽  
Hydrodynamical Simulations ◽  
Jet Plasma

ABSTRACT Hydrodynamical simulations predict that the jets of young radio sources can inhibit star formation in their host galaxies by injecting heat and turbulence into the interstellar medium (ISM). To investigate jet–ISM interactions in a galaxy with a young radio source, we have carried out a multiwavelength study of the z = 0.025 Compact Steep Spectrum radio source hosted by the early-type galaxy UGC 05771. Using Keck/OSIRIS observations, we detected H2 1–0 S(1) and [Fe ii] emission at radii of 100s of parsecs, which traces shocked molecular and ionized gas being accelerated outwards by the jets to low velocities, creating a ‘stalling wind’. At kpc radii, we detected shocked ionized gas using observations from the CALIFA survey, covering an area much larger than the pc-scale radio source. We found that existing interferometric radio observations fail to recover a large fraction of the source’s total flux, indicating the likely existence of jet plasma on kpc scales, which is consistent with the extent of shocked gas in the host galaxy. To investigate the star formation efficiency in UGC 05771, we obtained IRAM CO observations to analyse the molecular gas properties. We found that UGC 05771 sits below the Kennicutt–Schmidt relation, although we were unable to definitively conclude if direct interactions from the jets are inhibiting star formation. This result shows that jets may be important in regulating star formation in the host galaxies of compact radio sources.

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 Magnetic Fields & Ionized Gas in Elliptical Galaxy Halos

1990 ◽  
Vol 140 ◽  
pp. 459-462
Author(s):  
Richard G. Strom
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Elliptical Galaxy ◽  
Radio Sources ◽  
Early Type ◽  
Ionized Gas ◽  
X Ray ◽  
Galaxy Halos ◽  
Field Strengths

Faraday depolarization estimates of thermal densities within the components of double radio sources agree well with estimates from X-ray observations of hot halos around early-type galaxies, provided magnetic field strengths are close to their equipartition values. Internal Faraday dispersion is the main cause of the depolarization observed.

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 Connection Between Optical and High Frequency Radio Variability in AGN

1994 ◽  
Vol 159 ◽  
pp. 411-411
Author(s):  
M. Tornikoski ◽  
E. Valtaoja ◽  
A.G. Smith ◽  
A.D. Nair
Keyword(s):  
High Frequency ◽  
Optical Data ◽  
Research Station ◽  
Radio Sources ◽  
Data Sets ◽  
Temporal Data ◽  
Extragalactic Radio Sources ◽  
Radio Data

We have been searching for correlated optical and radio variability in large temporal data sets of 22 extragalactic radio sources. The optical data were obtained with the 76-cm reflector at the Rosemary Hill Observatory in Florida, USA. The radio data were obtained at two different sites: 22, 37 and some of the 90 GHz data at the Metsähovi Radio Research Station, Finland, and 90 and 230 GHz data at the Swedish-ESO Submillimetre Telescope (SEST) on La Silla, Chile. Because the SEST data unfortunately reaches only back to 1988, the 90 and 230 GHz data were complemented by the IRAM data from Steppe et al. (A&AS 75, 1988 and A&AS 96, 1992).

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 Relativistic plasma and ICM/radio source interaction

2010 ◽  
Vol 6 (S274) ◽  
pp. 340-347 ◽  
Author(s):  
Luigina Feretti ◽  
Gabriele Giovannini ◽  
Federica Govoni ◽  
Matteo Murgia
Keyword(s):  
Magnetic Fields ◽  
Radio Source ◽  
Large Scale ◽  
Large Scale Structure ◽  
Radio Sources ◽  
Relativistic Electrons ◽  
Coma Cluster ◽  
Cluster Of Galaxies ◽  
Formation And Evolution ◽  
The Universe

AbstractThe first detection of a diffuse radio source in a cluster of galaxies, dates back to the 1959 (Coma Cluster, Large et al. 1959). Since then, synchrotron radiating radio sources have been found in several clusters, and represent an important cluster component which is linked to the thermal gas. Such sources indicate the existence of large scale magnetic fields and of a population of relativistic electrons in the cluster volume. The observational results provide evidence that these phenomena are related to turbulence and shock-structures in the intergalactic medium, thus playing a major role in the evolution of the large scale structure in the Universe. The interaction between radio sources and cluster gas is well established in particular at the center of cooling core clusters, where feedback from AGN is a necessary ingredient to adequately describe the formation and evolution of galaxies and host clusters.

scholarly journals Unveiling the high-frequency radio source population with the AT20G survey

2013 ◽  
Vol 9 (S304) ◽  
pp. 205-208
Author(s):  
Elizabeth K. Mahony
Keyword(s):  
Radio Source ◽  
Flux Density ◽  
High Frequency ◽  
Gamma Ray ◽  
Low Frequency ◽  
Radio Sources ◽  
Source Population ◽  
Frequency Source ◽  
Galaxy Population ◽  
5 Ghz

AbstractUntil recently, the radio sky above 5 GHz was relatively unexplored. This has changed with the completion of the Australia Telescope 20 GHz survey (AT20G; Murphy et al., 2010); a blind survey of the southern sky down to a limiting flux density of 40 mJy. The AT20G survey provides by far the largest and most complete sample of high-frequency radio sources yet obtained, offering new insights into the nature of the high-frequency active galaxy population. Whilst the radio data provides a unique sample of objects, these data alone are insufficient to completely constrain models of radio source properties and the evolution of radio galaxies. Complementary multiwavelength data is vital in understanding the physical properties of the central black hole.In this talk I will provide a brief overview of the AT20G survey, followed by a discussion of the multiwavelength properties of the high-frequency source population. In particular, I will focus on the optical properties of AT20G sources, which are very different to those of a low-frequency selected sample, along with the gamma-ray properties where we find a correlation between high-frequency radio flux density and gamma-ray flux density. By studying the multiwavelength properties of a large sample of high-frequency radio sources we gain a unique perspective on the inner dynamics of some of the most active AGN.

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