International Astronomy and Astrophysics Research Journal

Unification of Extragalactic Radio Sources and Re-Acceleration of Radio Jets

Ezeugo Jeremiah Chukwuemerie *

Department of Physics and Industrial Physics, NnamdiAzikiwe University, Awka, Anambra State, Nigeria.

*Author to whom correspondence should be addressed.

---

Abstract

We use statistical methods of analysis to show that Large extended extragalactic radio sources (large EGRS) and compact steep spectrum (CSS) sources are similar sources evolving in different environments. Because of the diversity of their ambient media, one suffers higher magnitude of jet re-acceleration than the other. Linear regression analysis of observed source linear sizes, , of large extended extragalactic radio quasars against their individual observed redshifts,  was carried out. With appreciable correlation coefficient, result shows that  relates with redshift according to the equation, ; where  is a constant. The relation shows that projected source size is smaller at earlier epoch in the evolution of the universe. In addition, if we take  to be distance between any two points in space, then the relation may mean that the diameter of the universe is smaller at earlier epoch of its evolution. Moreover, with some plausible assumption, we find that jet velocity may be written as, . This indicates that mechanism of jet production derives from the source central core (presumed to house a super massive blackhole), as well as, from cosmic evolution. Since cosmic evolution is propelled by dark energy, the relation simply shows that dark energy enhances jet expansion more than blackhole power. Dark energy creates more empty spaces. It is anti-gravity in nature, and is believed to be the driving force behind cosmic dilation. Moreover, we estimate the magnitude of the effect of dark energy on the jet expansion to be three times the effect caused by blackhole power. Therefore, this result suggests that in addition to other factors, a culprit for re-acceleration mechanism for radio jets is dark energy. In order to check the authenticity of the assertion, we carry out linear regression analyses of observed luminosities,, against observed redshifts for both the extended extragalactic radio quasars and CSS quasars. With good correlations in both cases, we obtain ; where  and  for the extended quasars and CSS quasars respectively. The results show strong dependence of source luminosity on redshift. Moreover, the staggering difference in their indices suggestively implies that if we match the two samples at similar redshifts, luminosities of CSS quasars will be higher than those of the more extended sources. Hence, the results show that at similar epoch, luminosities of the more extended quasars are more extinguished (or more attenuated) than those of the CSS quasars. The jets and lobes of the larger/extended quasars are located in the intergalactic medium (IGM). This medium is very much rarefied and dark energy should be expected to exhibit more effect there than in the interstellar medium (ISM). On the other hand, the components of the CSS sources are sub-galactic. This means that they are buried in the dense ISM. In this medium, there is lesser manifestation of dark energy. Therefore, the disparity in the two indices (0.04 and 4.33) simply indicates manifestation of dark energy. Due to more rapid expansion of the IGM in which the jets and lobes of the extended sources are located, their luminosities are diluted more by more spaces created by dark energy in that medium. This shows that Large EGRS and CSS sources are similar sources evolving in different ambient media. Therefore, because of the diversity of their ambient media, large EGRS suffers higher magnitude of jet re-acceleration than the CSS source. In addition to this, we may state that dark energy is a suspect in enhancement of re-acceleration of the extragalactic jets. In conclusion, our results suggest that in addition to being similar sources evolving in different ambient media, a factor which fuels re-acceleration of extragalactic radio jets is dark energy.

Keywords: Cosmic evolution, linear size, astronomical distance, luminosity, radio sources, quasars, dynamical evolution, re-acceleration, dark energy

---

---

---

References

Ezeugo JC. Jet in the more extended radio sources and unification with compact steep spectrum sources. The Pacific Journal of Science and Technology. 2021;22:14–19.

Ubah OL, Ezeugo JC. Relativistic jet propagation: Its evolution and linear size cosmic dilation. International Astronomy and Astrophysics Research Journal. 2021;3(3):1–6.

Urry CM. AGN Unification: An update. Astronomical Society of the Pacific conference series 1; 2004.

Readhead AC. Evolution of powerful extragalactic radio sources. In proc. Colloquium on Quasars and Active Galactic Nuclei, ed. Kohen, M., and Kellermann, K. (USA: National Academy of Sciences, Berkman Center, Irvine). 1995;92:11447–11450.

Robson I. Active galactic nuclei, John Wiley and Sons Ltd, England; 1996.

Jackson JC. Radio source evolution and unified schemes. Publications of Astronomical Society of the Pacific. 1999;16:124–129.

Kawakatu N, Kino M. The velocity of large-scale jets in a declining density medium. In Serie de Conferencias. Triggering Relativistic Jets, ed. W.H. Lee and E. Ramirez-Ruiz. 2007;27:192–197.

Ezeugo JC. On the intergalactic media densities, dynamical ages of some powerful radio sources and implications. Journal of Physical Sciences and Application. 2021;11(1):29–34.

Mahatma VH, Hardcastle MJ, Williams WL. LoTSS DR1: Double-double Radio Galaxies in the HETDEX Field. Astronomy and Astrophysics. 2019;622:A13.

Mingo B, Croston JH, Hardcastle MJ. Revisiting the Fanaroff-Riley Dichotomy and Radio Galaxy Morphology with the LOFAR Two-Meter Sky Survey (LoTSS). Monthly Notices of the Royal Astronomical Society. 2019;488:2701-2721.

Hardcastle MJ, Williams WL, Best PN. Radio-loud AGN in the First LoTSS Data Release — The Lifetimes and Environmental Impact of Jet-Driven Sources. Astronomy and Astrophysics. 2019;622:A12.

Dabhade P, Gaikwad M, Bagchi J. Discovery of giant radio galaxies from NVSS: Radio and infrared properties. Monthly Notices of the Royal Astronomical Society. 2017;469(3):2886–2906.

Ezeugo JC. Compact steep-spectrum radio sources and ambient medium density. International Journal of Astrophysics and Space Science. 2015;3(1):1–6.

Ezeugo JC. On the dependence of spectral turnover on linear size of compact steep-spectrum radio sources. International Journal of Astrophysics and Space Science. 2015;3(2):20–24.

Ezeugo JC, Ubachukwu AA. The spectral turnover–linear size relation and the dynamical evolution of compact steep spectrum sources. Monthly Notices of the Royal Astronomical Society. 2010;408:2256–2260.

O’Dea CP. The Compact Steep Spectrum and Gigahertz peaked spectrum radio sources. Publications of the Astronomical Society of the Pacific. 1998110:493–532.

Fanti C, Fanti R, Dallacasa D, Schillizzi RT, Spencer RE, Stanghellini C. Are compact steep spectrum sources young? Astronomy and Astrophysics. 1995;302:317–326.

Ezeugo JC. Compact spectrum source size and cosmological implication. Journal of Research in Applied Mathematics. 2021;7(2):1–4.

Nilsson K. Kinematical models of double radio sources and unified scheme. Monthly Notices of the Royal Astronomical Society. 1998;132:31–37.

Ezeugo JC. On the components of large extended extragalactic radio sources. The Pacific Journal of Science and Technology. 2021;22(1):20–23.

Cavalho JC. The evolution of GHZ-peaked spectrum radio sources. Astronomy and Astrophysics. 1998;329:845–852.

Friedman JA, Turner MS, Huterer D. Dark energy and the accelerating universe annual review of astronomy. 2008;46:385–432.