Intergalactic Media Densities of Extragalactic Radio Sources and Source Ages
Ezeugo Jeremiah Chukwuemerie
Issue:
Volume 9, Issue 2, June 2021
Pages:
13-17
Received:
16 March 2021
Accepted:
30 March 2021
Published:
20 April 2021
Abstract: In this paper, we use analytical methods with some plausible assumptions to develop a mathematical model which may be used to obtain estimate of density of the intergalactic medium (IGM). This relation suggests that the plot of the linear sizes against the bolometric luminosities of the extragalactic radio sources in our sample should be able to furnish us with an estimate of the density of IGM in which the radio sources are domiciled. Moreover, for the purpose of obtaining an empirical relation similar to the theoretical model, we carry out linear regression analysis of linear sizes and luminosities of the 31 radio galaxies in our sample. The regression result shows an empirical relationship between observed source linear sizes and observed bolometric luminosities with slight correlation whose coefficient is 4. Moreover, we compared the theoretical relation and the empirical relation to obtain an estimate of the particle number density of the IGM in which the radio sources are located. The estimate indicates a very low density when compared with the values obtained by authors for the compact steep spectrum (CSS) sources. However, while the linear sizes of the CSS sources are of sub-galactic dimensions – they are located within the interstellar media (ISM) – those of the large extended extragalactic radio sources extend into the intergalactic media. The staggering difference in these obtained densities of IGM and ISM simply supports the general notion that there is a sharp decrease in the density at the IGM–ISM interface. Moreover, using theoretical approach again, with some plausible assumptions, we find another relation which may be used to estimate the ages of extragalactic radio sources. This relation possibly indicates that the plot of the linear sizes against velocities of the radio jets of the radio sources in our sample should be able to supply us with an estimate of the sources’ ages. We find from the simple linear regression analysis of linear sizes and jet velocities of the radio galaxies in our sample, a relation with correlation coefficient given as 4, which is also marginal. Comparison of the two relations – theoretical and the empirical relations – gives an estimate of age of the radio sources. The value shows that these large extended extragalactic radio sources are old sources.
Abstract: In this paper, we use analytical methods with some plausible assumptions to develop a mathematical model which may be used to obtain estimate of density of the intergalactic medium (IGM). This relation suggests that the plot of the linear sizes against the bolometric luminosities of the extragalactic radio sources in our sample should be able to fu...
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About the Free and Forced Nutation: The Daily Nutation
Issue:
Volume 9, Issue 2, June 2021
Pages:
18-21
Received:
22 March 2021
Accepted:
14 April 2021
Published:
8 May 2021
Abstract: To explain the nutation phenomenon, Euler chose a geocentric frame of coordinates to present his dynamical equations. In accordance with his formulas, the nutation is caused by a momentum relative to the Earth's center, due to certain external forces. Further, Poinsot presented a special case of the Euler's equations, when any momentum of those certain external forces does not exist. Due to a problematic approximation, Poinsot announced that in this case may take place a nutation period of 10 month, named “free period”, to distinguish it from the Euler's dynamical solution, known as “forced nutation”. After Poinsot, the notion of “free nutation” was extended also to those nutation phenomena which have only a geophysical origin, without a momentum of certain external forces. Usually, the daily nutation is considered as being a free nutation phenomenon. In order to search for a forced daily nutation component, the daily trajectory of the Earth-Moon barycenter inside the Earth is used (a simple scheme of this barycenter trajectory is presented in a geocentric system of axes). Finally, if the ecliptic line is accepted to be described by the Earth-Moon barycenter, it must be accepted, too, that a torque due the Sun and the Moon acts during a sideral day interval on diurnal Earth rotation around its axis. Due to the small value of the nutation constant, a period of 18,6 years is needed to correctly and completely detect the forced daily nutation; this phenomenon permanently presents very fine variations depending on the longitude of the ascending lunar node, the Moon’s declination and the Sun’s ecliptic longitude.
Abstract: To explain the nutation phenomenon, Euler chose a geocentric frame of coordinates to present his dynamical equations. In accordance with his formulas, the nutation is caused by a momentum relative to the Earth's center, due to certain external forces. Further, Poinsot presented a special case of the Euler's equations, when any momentum of those cer...
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