Velocity dispersion, mass and the luminosity function of the fossil cluster RX J1416.4+2315
Abstract
We study the properties of the fossil cluster RX J1416.4+2315 through g' and i'-band imaging and spectroscopy of 25 member galaxies. The system is at a mean redshift of 0.137 and has a velocity dispersion of 584 km s-1. Superimposed onto one quadrant of the cluster field there is a group of five galaxies at a mean redshift of 0.131, which, if included as part of the cluster, increases the velocity dispersion to 846 km/s. The central object of RX J1416.4+2315 is a normal elliptical galaxy, with no cD envelope. The luminosity function of the system, estimated by the number counts, and statistical background correction, in the range -22.6< Mg'< -16.6, is well fitted by a Schechter function with Mg'* = -21.2 +/- 0.8 and alpha = -1.2 +/- 0.2 (H0 = 70 km s-1 Mpc-1, OmegaM=0.3, OmegaLambda=0.7). The luminosity function obtained from the spectroscopically confirmed members in both g' and i' bands agrees with the photometric results. The mass of the system, M 0.9 × 1014 h-170 Msun, its M/L of 445 h70 Msun/LBsun and LX of 11 1043 h-270 ergs s-1 (bolometric) suggest that this system is the second example of known fossil cluster, after RX J1552.2+2013, confirmed in the literature.
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