A new measurement of the baryonic fraction using the sparse NGC 3258 group of galaxies
نویسندگان
چکیده
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 240h 50 kpc is found to be 0.065 −0.020 for h50 = 1, where h50 ≡ H0/50 km s Mpc, in good agreement with the universal value of 0.05 ± 0.01 predicted by standard Big Bang nucleosynthesis for a Universe with Ω0 = 1 and h50 = 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. Subject headings: dark matter — galaxies: individual (NGC 3258) — intergalactic medium — X-rays: galaxies
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