An infrared study of local galaxy mergers
  We combine a large, homogeneous sample of $\sim$3000 local mergers with the
Imperial IRAS Faint Source Redshift Catalogue (IIFSCz), to perform a blind
far-infrared (FIR) study of the local merger population. The IRAS-detected
mergers are mostly ($98\%$) spiral-spiral systems, residing in low density
environments, a median FIR luminosity of $10^{11} L_\odot$ (which translates to
a median star formation rate of around 15$M_\odot yr^{-1}$). The FIR luminosity
-- and therefore the star formation rate -- shows little correlation with group
richness and scales with the total stellar mass of the system, with little or
no dependence on the merger mass ratio. In particular, minor mergers (mass
ratios $<1:3$) are capable of driving strong star formation (between 10 and
$173 M_\odot yr^{-1}$) and producing systems that are classified as LIRGs,
luminous infrared galaxies ($65\%$ of our LIRGs are minor mergers), with some
minor-merging systems being close to the ultra luminous infrared galaxy (ULIRG)
limit. Optical emission line ratios indicate that the AGN fraction increases
with increasing FIR luminosity, with all ULIRG mergers having some form of AGN
activity. Finally, we estimate that the LIRG-to-ULIRG transition along a merger
sequence typically takes place over a relatively short timescale of $\sim$160
Myr.
