We investigate how cluster morphology is affected by the cosmological constant in low-density universes .
Using high-resolution cosmological N-body/SPH simulations of flat ( \Omega _ { 0 } = 0.3 , \lambda _ { 0 } = 0.7 , \Lambda CDM ) and open ( \Omega _ { 0 } = 0.3 , \lambda _ { 0 } = 0 , OCDM ) cold dark matter universes , we calculate statistical indicators to quantify the irregularity of the cluster morphologies .
We study axial ratios , center shifts , cluster clumpiness , and multipole moment power ratios as indicators for the simulated clusters at z = 0 and 0.5 .
Some of these indicators are calculated for both the X-ray surface brightness and projected mass distributions .
In \Lambda CDM all these indicators tend to be larger than those in OCDM at z = 0 .
This result is consistent with the analytical prediction of Richstone , Loeb , & Turner , that is , clusters in \Lambda CDM are formed later than in OCDM , and have more substructure at z = 0 .
We make a Kolmogorov-Smirnov test on each indicator for these two models .
We then find that the results for the multipole moment power ratios and the center shifts for the X-ray surface brightness are under the significance level ( 5 % ) .
We results also show that these two cosmological models can be distinguished more clearly at z = 0 than z = 0.5 by these indicators .