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2.10. Mass, Luminosity, and Mass-to-Luminosity Ratio
The typical dynamical mass of rich clusters within 1.5h-1 Mpc radius sphere (determined from the virial theorem for an isothermal distribution) is
The approximate range of masses for R 0 clusters (within 1.5h-1 Mpc) is
Comparable masses are obtained using the X-ray temperature and distribution of the hot intracluster gas (Hughes 1989; Bahcall and Cen 1993; Lubin and Bahcall 1993; Section 3).
The typical (median) blue luminosity of rich clusters (within 1.5h-1 Mpc) is
The approximate range of rich cluster blue luminosities is
The typical mass-to-luminosity ratio of rich clusters is thus
The inferred mass-density in the universe based on cluster dynamics is
(if mass follows light, M L, on scales 1h-1 Mpc). = 1 corresponds to the critical mass-density needed for a closed universe and / LB ( = 1) 1500h.