Temperature and abundance profiles of hot gas in galaxy groups - II.
  Implications for feedback and ICM enrichment
  We investigate the history of galactic feedback and chemical enrichment
within a sample of 15 X-ray bright groups of galaxies, on the basis of the
inferred Fe and Si distributions in the hot gas and the associated metal masses
produced by core-collapse and type Ia supernovae (SN). Most of these cool-core
groups show a central Fe and Si excess, which can be explained by prolonged
enrichment by SN Ia and stellar winds in the central early-type galaxy alone,
but with tentative evidence for additional processes contributing to core
enrichment in hotter groups. Inferred metal mass-to-light ratios inside r_500
show a positive correlation with total group mass but are generally
significantly lower than in clusters, due to a combination of lower global ICM
abundances and gas-to-light ratios in groups. This metal deficiency is present
for products from both SN Ia and SN II, and suggests that metals were either
synthesized, released from galaxies, or retained within the ICM less
efficiently in lower-mass systems. We explore possible causes, including
variations in galaxy formation and metal release efficiency, cooling-out of
metals, and gas and metal loss via AGN- or starburst-driven galactic winds from
groups or their precursor filaments. Loss of enriched material from filaments
coupled with post-collapse AGN feedback emerge as viable explanations, but we
also find evidence for metals to have been released less efficiently from
galaxies in cooler groups and for the ICM in these to appear chemically less
evolved, possibly reflecting more extended star formation histories in less
massive systems. Some implications for the hierarchical growth of clusters from
groups are briefly discussed.
