International Astronomy and Astrophysics Research Journal

On Extragalactic Radio Sources and Dark Energy

Ezeugo Jeremiah Chukwuemerie *

Department of Physics and Industrial Physics, Nnamdi Azikiwe University, Awka, Nigeria.

*Author to whom correspondence should be addressed.

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Abstract

In this work, we use statistical methods of analyses to find effects of the intergalactic medium (IGM) and interstellar medium (ISM) of some extragalactic radio sources on dark energy. We carry out linear regression analysis of observed source linear sizes (D) of the more extended radio quasars against their corresponding observed redshifts (Z) in our sample. Also, we carry out similar analysis on the observed linear sizes of compact steep spectrum (CSS) quasars against their corresponding observed redshifts. Results of the regression indicate that if we take D to be distance between any two positions in the IGM/ISM, then cosmic evolution shows an inverse power-law function with the magnitude of the distance between the two positions according to the relation, \((1+z) \sim D^{-\psi}\); where \(\psi=0.6\) and 0.4 for the more extended quasars and CSS quasars respectively. Since “a higher redshift implies an earlier epoch”, and redshift has a direct dependence on expansion velocity between any two points in space, the results of the analyses simply suggest that at earlier epoch, the expansion rate of the universe is higher. Our results also indicate that the effect of cosmic evolution in the extended quasars is more than the effect in the CSS quasars \({ (i. e. } \left.D_{z(E G R Q)}>D_{z(\operatorname{css} Q)}\right)\). Since the linear sizes of the extended radio-loud quasars are projected into the IGM, while the linear sizes of the CSS radio-loud quasars are confined within their individual host galaxies, the result \(\left(D_{z(E G R Q)}>D_{z(\operatorname{cSS} Q)}\right)\) can be interpreted to mean that cosmic evolution shows greater effect in the IGM (i.e. more rarefied medium) than in the ISM (i.e. less rarefied medium). Hence, from the results of the analyses, we may state that if dark energy is defined as the intrinsic tendency of vacuum (or free space) to increase in volume, then the inconsistency in \(D_{z(E G R Q)}\) and \(D_{z(CSSQ)}\) is simply a manifestation of dark energy. Therefore, we may conclusively say that dark energy constitutes a driving parameter behind cosmic evolution. Moreover, we estimate the percentage dilution on dark energy caused by the presence of matter to be \(\approx\) 33%. This implies that if we assume IGM to be approximately an ideal vacuum, then matter present in the ISM offers \(\approx\) 33% dilution effect on dark energy.

Keywords: Dark energy, cosmic evolution, linear size, radio sources, quasars, redshifts

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References

Robson I. Active Galactic Nuclei, John Wiley and Sons Ltd, England;1996.

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

Ezeugo JC. On Cosmic Epoch and Linear Size/Luminosity Evolution of Compact Steep Spectrum Sources. American Journal of Astronomy and Astrophysics. 2021;9(1):8–12.

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.

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.

Jackson JC. Radio Source Evolution and Unified Schemes. Publications of Astronomical Society of the Pacific. 1999;16:124–129.

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

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.

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.

O’Dea CP. The Compact Steep Spectrum and Gigahertz peaked spectrum radio sources. Publications of the Astronomical Society of the Pacific. 1998;110:493– 532.

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.

Ezeugo JC. Compact Steep 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.

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.

Mahatma VH, Hardcastleand 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.

Friedman JA, Turner MS, Huterer D. Dark Energy and the Accelerating Universe. Annual Review of Astronomy. 2008;46: 385–432.