The role of minor mergers in the recent star formation history of early-type galaxies
Nov, 2007Citations per year
Abstract: (arXiv)
We demonstrate that the large scatter in the ultra-violet (UV) colours of luminous (L* and above) early-type galaxies in the local Universe and the inferred low-level recent star formation in these objects can be reproduced by minor mergers in the standard LCDM cosmology. Numerical simulations of mergers with mass ratios less than or equal to 1:4, with reasonable assumptions for the ages, metallicities and dust properties of the merger progenitors, produce good agreement to the observed UV colours of the early-type population, if the infalling satellites are assumed to have (cold) gas fractions greater than ~20%. Early-types that satisfy (NUV-r)<3.8 are likely to have experienced mergers with mass ratios between 1:4 and 1:6 within the ~1.5 Gyrs, while those that satisfy 3.8<(NUV-r)<5.5 are consistent with either recent mergers with mass ratios less than ~1:6 or mergers with higher mass ratios that occurred more than 1.5 Gyrs in the past. The UV colour distribution as a whole is consistent with the expected frequency of minor merging activity in the LCDM cosmology at low redshift. We speculate that minor mergers may be the primary cause for the large scatter in the early-type UV colours, although small contributions from largely dry major mergers and gas accretion from the halo cannot be completely ruled out.References(28)
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