scholarly journals The Origin and Evolution of Giant Radio Galaxies

2022 ◽  
Vol 8 ◽  
Author(s):  
David Garofalo
Keyword(s):  
Black Hole ◽  
Active Galactic Nuclei ◽  
Spiral Galaxies ◽  
Radio Galaxy ◽  
Galactic Nuclei ◽  
Radio Galaxies ◽  
High Excitation ◽  
Origin And Evolution ◽  
Black Hole Spin ◽  
Upper Limit

Giant radio galaxies are arguably the least understood of jetted active galactic nuclei (AGN). We propose that radio galaxies are the product of large mergers that do not involve radio galaxies or radio quasars, such as in merging spiral galaxies, while giant radio galaxies emerge from a merger involving a parent that in the not-too-distant past harbored a radio galaxy. Predictions following from this are an upper limit to the number fraction of giant radio galaxies to radio galaxies, lower average redshift for giant radio galaxies, a higher incidence of high excitation for giant radio galaxies compared with radio galaxies, and lower average prograde black hole spin values for giant radio galaxies compared to radio galaxies and to bright radio quiet quasars.

scholarly journals H i absorption towards radio active galactic nuclei of different accretion modes

2020 ◽  
Vol 494 (4) ◽  
pp. 5161-5177
Author(s):  
Yogesh Chandola ◽  
D J Saikia ◽  
Di Li
Keyword(s):  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Radio Galaxies ◽  
High Excitation ◽  
Host Galaxies ◽  
Detection Rates ◽  
Systemic Velocity ◽  
Wide Range ◽  
Significant Difference ◽  
Absorption Experiment

ABSTRACT We present results of H i absorption experiment done using the Giant Metrewave Radio Telescope (GMRT) towards 27 low- and intermediate-luminosity ($P_{\rm 1.4 GHz}\, \sim 10^{23}$-1026 W Hz−1) radio active galactic nuclei (AGNs), classified as either low excitation radio galaxies (LERGs) or high excitation radio galaxies (HERGs) and with WISE colour W2[4.6 μm]−W3[12  μm]> 2. We report H i absorption detection towards seven radio AGNs, six of which are new. Combined with other sources from literature classified as LERGs or HERGs, we confirm our earlier result that compact radio AGNs with WISE colour W2−W3 > 2 have higher detection rates compared to those with W2−W3 < 2. We find that H i absorption detection rate is higher for HERGs (37.0$^{+15.8}_{-11.5}$ per cent) compared to LERGs (22.0$^{+3.9}_{-3.4}$ per cent), mainly due to a larger fraction of HERGs being gas and dust rich with a younger stellar population compared to LERGs. However, for similar compact radio structures and host galaxies with WISE colours W2−W3 > 2, we don’t find any significant difference in detection rates of two types of AGNs implying detection of H i gas may not necessarily mean high excitation mode AGN. We further analysed the kinematics towards these sources. We find that while LERGs show a wide range in the shift of centroid velocities ($\sim \, -$479 to +356 km s−1) relative to the optical systemic velocity, most of the HERGs have centroid velocity shift less than 200 km s−1, possibly due to differences in jet-interstellar medium interaction.

scholarly journals ARE RADIO ACTIVE GALACTIC NUCLEI POWERED BY ACCRETION OR BLACK HOLE SPIN?

2010 ◽  
Vol 727 (1) ◽  
pp. 39 ◽  
Author(s):  
B. R. McNamara ◽  
Mina Rohanizadegan ◽  
P. E. J. Nulsen
Keyword(s):  
Black Hole ◽  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Black Hole Spin

scholarly journals A Comparison of Two Methods for Estimating Black Hole Spin in Active Galactic Nuclei

2017 ◽  
Vol 836 (1) ◽  
pp. L8 ◽  
Author(s):  
Daniel M. Capellupo ◽  
Gaylor Wafflard-Fernandez ◽  
Daryl Haggard
Keyword(s):  
Black Hole ◽  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Black Hole Spin

scholarly journals Radio Galaxies at VHE Energies

Galaxies ◽  
2018 ◽  
Vol 6 (4) ◽  
pp. 116 ◽  
Author(s):  
Frank Rieger ◽  
Amir Levinson
Keyword(s):  
Black Hole ◽  
Active Galactic Nuclei ◽  
Gamma Ray ◽  
Galactic Nuclei ◽  
Radio Galaxies ◽  
Concise Overview ◽  
Recent Developments ◽  
Γ Ray ◽  
Very High

Radio Galaxies have by now emerged as a new γ-ray emitting source class on the extragalactic sky. Given their remarkable observed characteristics, such as unusual gamma-ray spectra or ultrafast VHE variability, they represent unique examples to probe the nature and physics of active galactic nuclei (AGN) in general. This review provides a compact summary of their observed characteristics at very high γ-ray energies (VHE; greater than 100 GeV) along with a discussion of their possible physics implications. A particular focus is given to a concise overview of fundamental concepts concerning the origin of variable VHE emission, including recent developments in black hole gap physics.

M 87 — TEN YEARS OF TEV GAMMA-RAY OBSERVATIONS

2010 ◽  
Vol 19 (06) ◽  
pp. 849-857
Author(s):  
MATTHIAS BEILICKE
Keyword(s):  
Active Galactic Nuclei ◽  
Gamma Ray ◽  
Radio Galaxy ◽  
Galactic Nuclei ◽  
Plasma Jet ◽  
Radio Galaxies ◽  
Jet Physics ◽  
X Ray ◽  
High Energies ◽  
Very High

The giant radio galaxy M 87 is located 16.7 Mpc away and harbours a supermassive black hole in its center. Structures of its relativistic plasma jet are resolved at radio, optical and X–ray energies. M 87 belongs to the class of active galactic nuclei and is one of only a few radio galaxies detected at very-high energies (E > 100 GeV ). This makes it a unique laboratory to study jet physics and the corresponding emission processes. The results obtained from TeV gamma-ray observations during the last decade are discussed.

Radio galaxies with and without emission lines

2020 ◽  
Vol 15 (S359) ◽  
pp. 396-401
Author(s):  
Grażyna Stasińska ◽  
Natalia Vale Asari ◽  
Dorota Kozieł-Wierzbowska
Keyword(s):  
Black Hole ◽  
Active Galactic Nuclei ◽  
Equivalent Width ◽  
Galactic Nuclei ◽  
Optical Emission ◽  
Radio Galaxies ◽  
Emission Lines ◽  
The Common ◽  
Black Hole Masses

AbstractUsing the recent ROGUE I catalogue of galaxies with radio cores (Kozie_l-Wierzbowska et al. 2020) and after selecting the objects which are truly radio active galactic nuclei, AGNs, (which more than doubles the samples available so far), we perform a thorough comparison of the properties of radio galaxies with and without optical emission lines (galaxies where the equivalent width of Hα is smaller than 3Å are placed in the last category). We do not find any strong dichotomy between the two classes as regards the radio luminosities or black hole masses. The same is true when using the common classification into high- and low-excitation radio galaxies (HERGs and LERGs respectively).

scholarly journals Discovery of Rare Dying Radio Galaxies Using MeerKAT

Galaxies ◽  
2021 ◽  
Vol 9 (4) ◽  
pp. 102
Author(s):  
Nadeem Oozeer ◽  
Lawrence Rudnick ◽  
Michael F. Bietenholz ◽  
Tiziana Venturi ◽  
Kenda Knowles ◽  
...  
Keyword(s):  
Active Galactic Nuclei ◽  
Radio Galaxy ◽  
Galaxy Cluster ◽  
Galactic Nuclei ◽  
Radio Galaxies ◽  
Radio Sources ◽  
Central Black Hole ◽  
Massive Galaxies ◽  
Multi Wavelength ◽  
Radio Power

Dying radio galaxies represent a stage of the evolution of active galactic nuclei (AGN), during which the accreting central black hole has switched off and/or falls to such a low level that the plasma outflow can no longer be sustained. When this happens, the radio source undergoes a period of fading, the dying phase, before it disappears completely. We present the study of three potential dying radio sources using the MeerKAT radio telescope: MKT J072851.2-752743, MKT J001940.4-654722, and ACO 548B. The identification as dying radio sources came from the MeerKAT Galaxy Cluster Legacy Survey (MGCLS). We carry out a multi-wavelength analysis of the sources and derive their energetics. The ages of the sources are ∼30–70 Myr, they have magnetic fields of the order of a few μG, and they have relatively low radio power. Their potential optical counterparts are associated with massive galaxies. We show that ACO 548B, previously classified as two peripheral relic radio sources, is a dying radio galaxy. With its good sensitivity and resolution, MeerKAT is an ideal instrument to detect potential dying radio sources, and contribute to the understanding of the evolution of AGN population.

scholarly journals Radio Active Nuclei

1983 ◽  
Vol 6 ◽  
pp. 481-490
Author(s):  
K. I. Kellermann
Keyword(s):  
Active Galactic Nuclei ◽  
Time Scale ◽  
Galactic Nuclei ◽  
Extreme Case ◽  
Radio Galaxies ◽  
Radio Sources ◽  
Great Similarity ◽  
Radio Flux ◽  
Active Nucleus ◽  
Origin And Evolution

For the purpose of this survey we shall use the term radio active nucleus to refer to compact radio sources which are found in galactic nuclei and which show activity either in the form of flux density variations or outward flow of material from the nucleus. There is great similarity between the observed properties of radio active nuclei with those of radio active quasars, and it is widely supposed that the quasar phenomena represents an extreme case of an active galaxy. In this paper however, we shall concentrate on compact radio sources found in the nuclei of identifiable galaxies, and quasars are discussed only to the extent that they help to understand the origin and evolution of radio active galactic nuclei.Since radio active nuclei are typically in extent, they can be mapped only with VLBI techniques. Detailed maps are available for only a few of the strongest nuclei, but a much larger number can be identified from conventional interferometry with a resolution ~ 1”. In the few radio galaxies where most of the observed radio flux comes from the active nucleus, activity is observed directly on a time scale of months or even weeks. In others, it may be inferred from arguments based on synchrotron lifetime.

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