New X-ray observations of the sparse NGC 3258 group of galaxies made by the ASCA satellite with good spectral and spatial resolution has revealed that this group has a gravitational potential deep enough to prohibit significant mass removal from the system .
The baryonic fraction within 240 h _ { 50 } ^ { -1 } kpc is found to be 0.065 ^ { +0.051 } _ { -0.020 } for h _ { 50 } = 1 , where h _ { 50 } \equiv H _ { 0 } / 50 km s ^ { -1 } Mpc ^ { -1 } , in good agreement with the universal value of 0.05 \pm 0.01 predicted by standard Big Bang nucleosynthesis for a Universe with \Omega _ { 0 } = 1 and h _ { 50 } = 1 .
Since the deep potential of the NGC 3258 group ensures that all pristine intragroup gas has been retained , the baryonic fraction of the NGC 3258 group is indicative of the universal value .
Consequently it seems premature to rule out a critical Universe .