Abstract
In view of the striking similarities between Quasi-Stellar Objects on the one hand and the nuclei of N galaxies, Seyfert galaxies, radio galaxies and normal galaxies on the other, the possibility that QSOs might belong to an early phase in the evolutionary sequence of galaxies is explored. In this connection, considering the fact that nebulosities have been detected around five QSOs, the implications of the hypothesis that a QSO consists of a bright central object embedded in an extended nebulosity have been examined. In particular, the ratio a between the intensity of the bright central object and that of the surrounding nebulosity in the visual band of wavelengths has been calculated by the ‘colour-given method’ for a sample of 81 QSOs with emission redshiftz≤0.76. This ratio a has been used to calculate the apparent visual magnitudem(V) and the absolute visual magnitudeM(V) of the bright central object (Nu) as well as that of the surounding nebulosity (Neb) of the QSOs in the sample and a criterion has been proposed as to the detectability of the surrounding nebulosities. Similar calculations have been made for N galaxies, Seyfert galaxies and normal galaxies. It is found that the values of 〈log a〉, 〈M(V) Nu〉 and 〈M(V) Neb〉 for the four classes of extragalactic objects show a definite trend and suggest an evolutionary sequence: QSOs→N galaxies→Seyfert galaxies→normal galaxies.
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Thakur, R.K., Sapre, A.K. Quasi-stellar objects and evolution of galaxies. Astrophys Space Sci 64, 249–264 (1979). https://doi.org/10.1007/BF00640045
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DOI: https://doi.org/10.1007/BF00640045