The Baryon Content of Cosmic Structures

Understand

We make an inventory of the baryonic and gravitating mass in structures ranging from the smallest galaxies to rich clusters of galaxies.

• We find that the fraction of baryons converted to stars reaches a maximum between M500 = 1E12 and 1E13 Msun, suggesting that star formation is most efficient in bright galaxies in groups.
• The fraction of baryons detected in all forms deviates monotonically from the cosmic baryon fraction as a function of mass.
• On the largest scales of clusters, most of the expected baryons are detected, while in the smallest dwarf galaxies, fewer than 1% are detected.