Abstract
Stability of the nearest 14 groups of galaxies is investigated by means of Jacobi's criterion. In this way these groups are found strongly unstable, except perhaps two. The result is unaltered when we discuss the validity of the assumptions needed for the computations and when we take into account the inaccuracy of the data. This apparent instability is tentatively explained by presence of intergalactic ionized hydrogen in each group. Physical parameters of the gas are derived by means of the general modified form of the virial theorem and through the assumption of the equiparatition among several modes of energy.
The main results are the following: the ratios of the gas mass to the sum of the masses of the member galaxies are of the order of 10, densitiesϱg of the gas are about 10−29 to 10−28 g cm−3, and temperatures are of the order of 105K. Values of each physical parameter of the gas show little change from one group to the next. As significant correlation:ϱG ∝ϱg 0.9 is obtained betweenϱg and the densityϱG of the visible matter for the various groups; it may be compatible with the assumption that the intergalactic gas is a remnant of the condensation of the galaxies. Then it is shown that, at present, the observations are not opposed to our treatment. Finally, it is noticed that detection of intergalactic gas in the groups investigated will be very difficult, except if this gas is strongly cloudy.
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Chamaraux, P., Montmerle, T. & Tadokoro, M. Intergalactic ionized hydrogen in nearby groups of galaxies. Astrophys Space Sci 15, 383–394 (1972). https://doi.org/10.1007/BF00649766
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DOI: https://doi.org/10.1007/BF00649766