scholarly journals Optical Properties of the Radio Source B2 0828+32

1996 ◽  
Vol 175 ◽  
pp. 254-255
Author(s):  
M.-H. Ulrich-Demoulin ◽  
J. Rönnback
Keyword(s):  
Optical Properties ◽  
Radio Source ◽  
Spectral Index ◽  
Surface Brightness ◽  
Gravitational Interaction ◽  
Radio Galaxies ◽  
Host Galaxy ◽  
Radio Structure ◽  
Close Pair ◽  
Different Ages

A small number of radio galaxies have two sets of classical double radio lobes with the radio axes aligned in different directions. Furthermore differences in the properties of the radio lobes such as the surface brightness and spectral index indicate that the two sets of double radio structure have different ages. The radio ejection axis has therefore changed direction with time. In the first two known radio galaxies of this type, 3C 315 and B2 0055+26, the host galaxy is a member of a close pair of ellipticals in a common optical envelope suggesting that the complex radio structure is caused by gravitational interaction.

scholarly journals X-shaped Radio Galaxies: Optical Properties, Large-scale Environment, and Relationship to Radio Structure

2019 ◽  
Vol 887 (2) ◽  
pp. 266 ◽  
Author(s):  
Ravi Joshi ◽  
Gopal Krishna ◽  
Xiaolong Yang ◽  
Jingjing Shi ◽  
Si-Yue Yu ◽  
...  
Keyword(s):  
Optical Properties ◽  
Large Scale ◽  
Radio Galaxies ◽  
Radio Structure

scholarly journals VLA Images of Two Extended Radio Galaxies

2002 ◽  
Vol 199 ◽  
pp. 193-194
Author(s):  
W. Junor ◽  
F. Mantovani ◽  
R. Morganti ◽  
L. Padrielli
Keyword(s):  
Radio Source ◽  
Low Frequency ◽  
Detection Limits ◽  
Radio Galaxies ◽  
Radio Structure ◽  
Polarization Effects ◽  
Compact Component ◽  
Instrumental Polarization ◽  
Extended Radio

There is some evidence from earlier studies that the two sources 0235 — 197 and 1203 + 043 exhibit low frequency (< 1 GHz) variability. This work shows that both sources have linear polarizations, if any, below the detection limits at 320 MHz, so we cannot explain the variability as being due to instrumental polarization effects as has been suggested for 3C159. Refractive scintillation may be the cause of the variability in 0235—197. The radio source 1203+043 lacks any bright compact component thereby ruling out a refractive scintillation mechanism for its variability. Consequently, it is possible that claims of variability in this source are spurious. However, the 320 MHz VLA observations show that 1203+043 has an ‘X'-shaped radio structure.

scholarly journals Different Types of Radio Sources and Possible Evolution of Radio Galaxies

2002 ◽  
Vol 184 ◽  
pp. 301-303
Author(s):  
Gabriel A. Ohanian
Keyword(s):  
Radio Source ◽  
Large Scale ◽  
Large Range ◽  
Host Galaxy ◽  
Radio Sources ◽  
Powerful Radio ◽  
Host Galaxies ◽  
Radio Structure ◽  
Different Types ◽  
The Universe

Extragalactic radio sources have been studied for many years, but it is still unclear how they are formed and evolve. The sizes of the most powerful radio emitters in the Universe vary from less than one parsec to more than 1 Mpc. This large range of sizes has been interpreted as evidence for the evolution of the linear sizes of radio structure (e.g., O’Dea and Baum, 1997). A crucial element in the study of their evolution is the identification of the young compact counterparts of “old” FRI/FRII extended objects. Good candidates for young radio sources are those with peaked spectra (Gigahertz Peaked Spectrum - GPS and Compact Steep Spectrum - CSS, e.g., O’Dea 1998). Radio sources are presumably born in the very compact GPS phase, then they expand beyond 1 kpc into the CSS regime and finally, they reach a size of 20 kpc, and afterwards evolve into large-scale radio sources (young scenario, e.g., O’Dea 1998). Alternatively, GPS sources may be compact because a particularly dense environment prevents them from growing larger (old scenario, e.g., O’Dea 1998). In either scenario, the radio source host galaxy determines the time evolution of the radio structure. By studying the optical environments and host galaxies we hope to obtain clues to the evolution of the radio sources. Similarities or differences in host galaxy properties over a range of radio source types and sizes enable us to investigate possible differences or similarities of the radio size class as a whole.

scholarly journals Relations Between Radio and Optical Properties of Radio Sources - Radio Astronomer's Point of View

1977 ◽  
Vol 74 ◽  
pp. 237-243
Author(s):  
J. M. Riley ◽  
C. J. Jenkins
Keyword(s):  
Optical Properties ◽  
Radio Galaxies ◽  
Point Of View ◽  
Radio Sources ◽  
Optical Identification ◽  
Complete Sample ◽  
Radio Structure ◽  
Quasars And Radio Galaxies

One particular aspect of the relations between the radio and optical properties of radio sources has been examined for a complete sample of 3CR sources, namely the relation between the radio structure of a source and its optical identification. Possible differences between the radio structures of quasars and radio galaxies are investigated, and the data provide clues as to the optical nature of the unidentified sources.

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 The SINFONI survey of powerful radio galaxies at z ~ 2: Jet-driven AGN feedback during the Quasar Era

2017 ◽  
Vol 599 ◽  
pp. A123 ◽  
Author(s):  
N. P. H. Nesvadba ◽  
C. De Breuck ◽  
M. D. Lehnert ◽  
P. N. Best ◽  
C. Collet
Keyword(s):  
Kinetic Energy ◽  
Interstellar Medium ◽  
Large Scale ◽  
High Redshift ◽  
Radio Galaxies ◽  
Energy Output ◽  
Host Galaxy ◽  
Powerful Radio ◽  
Massive Galaxies ◽  
Gas Kinematics

We present VLT/SINFONI imaging spectroscopy of the rest-frame optical emission lines of warm ionized gas in 33 powerful radio galaxies at redshifts z ≳ 2, which are excellent sites to study the interplay of rapidly accreting active galactic nuclei and the interstellar medium of the host galaxy in the very late formation stages of massive galaxies. Our targets span two orders of magnitude in radio size (2−400 kpc) and kinetic jet energy (a few 1046– almost 1048 erg s-1). All sources have complex gas kinematics with broad line widths up to ~1300 km s-1. About half have bipolar velocity fields with offsets up to 1500 km s-1 and are consistent with global back-to-back outflows. The others have complex velocity distributions, often with multiple abrupt velocity jumps far from the nucleus of the galaxy, and are not associated with a major merger in any obvious way. We present several empirical constraints that show why gas kinematics and radio jets seem to be physically related in all galaxies of the sample. The kinetic energy in the gas from large scale bulk and local outflow or turbulent motion corresponds to a few 10-3 to 10-2 of the kinetic energy output of the radio jet. In galaxies with radio jet power ≳ 1047 erg s-1, the kinetic energy in global back-to-back outflows dominates the total energy budget of the gas, suggesting that bulk motion of outflowing gas encompasses the global interstellar medium. This might be facilitated by the strong gas turbulence, as suggested by recent analytical work. We compare our findings with recent hydrodynamic simulations, and discuss the potential consequences for the subsequent evolution of massive galaxies at high redshift. Compared with recent models of metal enrichment in high-z AGN hosts, we find that the gas-phase metallicities in our galaxies are lower than in most low-z AGN, but nonetheless solar or even super-solar, suggesting that the ISM we see in these galaxies is very similar to the gas from which massive low-redshift galaxies formed most of their stars. This further highlights that we are seeing these galaxies near the end of their active formation phase.

scholarly journals Observations of Southern Radio Galaxies at 1415 MHz

1992 ◽  
Vol 45 (6) ◽  
pp. 797 ◽  
Author(s):  
PA Jones
Keyword(s):  
Spectral Index ◽  
Angular Size ◽  
Radio Galaxies ◽  
Beam Size

The structures of 23 strong radio galaxies, all with angular size larger than 3 arcmin, have been observed with the Fleurs Synthesis Telescope (FST) at 1415 MHz with a resolution of 22 arcsec. Spectral index differences within the sources were investigated by omparing 843 MHz images made with the Molonglo Observatory Synthesis Telescope (MOST) with FST images convolved to the same beam-size of 44 arcsec.

scholarly journals A Novel Method for Estimating the Ambient Medium Density Around Distant Radio Sources from Their Observed Radio Spectra

2021 ◽  
Vol 922 (2) ◽  
pp. 197
Author(s):  
Anna Wójtowicz ◽  
Łukasz Stawarz ◽  
Jerzy Machalski ◽  
Luisa Ostorero
Keyword(s):  
Radio Emission ◽  
Ambient Medium ◽  
Radio Galaxies ◽  
Radiative Properties ◽  
Radio Continuum ◽  
Physical Parameters ◽  
Radio Sources ◽  
Data Set ◽  
Radio Structure ◽  
5 Ghz

Abstract The dynamical evolution and radiative properties of luminous radio galaxies and quasars of the FR II type, are well understood. As a result, through the use of detailed modeling of the observed radio emission of such sources, one can estimate various physical parameters of the systems, including the density of the ambient medium into which the radio structure evolves. This, however, requires rather comprehensive observational information, i.e., sampling the broadband radio continua of the targets at several frequencies, and imaging their radio structures with high resolution. Such observations are, on the other hand, not always available, especially for high-redshift objects. Here, we analyze the best-fit values of the source physical parameters, derived from extensive modeling of the largest currently available sample of FR II radio sources, for which good-quality multiwavelength radio flux measurements could be collected. In the analyzed data set, we notice a significant and nonobvious correlation between the spectral index of the nonthermal radio emission continuum, and density of the ambient medium. We derive the corresponding correlation parameters, and quantify the intrinsic scatter by means of Bayesian analysis. We propose that the discovered correlation could be used as a cosmological tool to estimate the density of ambient medium for large samples of distant radio galaxies. Our method does not require any detailed modeling of individual sources, and relies on limited observational information, namely, the slope of the radio continuum between the rest-frame frequencies 0.4 and 5 GHz, possibly combined with the total linear size of the radio structure.

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