Star formation losses due to tidal debris in "hierarchical" galaxy formation

N-body studies have previously shown that the bottom-up hierarchical format ion of dark matter haloes is not as monotonic as implicitly assumed in the Press-Schechter formalism. During and following halo mergers, matter can be ejected into tidal tails, shells or low density "atmospheres" outside of t he successor haloes' virialisation radii (or group-finder outermost radii). The implications that the possible truncation of star formation in this ti dal "debris" may have for observational galaxy statistics are examined here using the ArFus N-body plus semi-analytical galaxy modelling software for standard star formation hypotheses. In the N-body simulations studied, the debris typically remains close to the successor halo and falls back into th e successor haloes given sufficient time. A maximum debris loss of around 1 6% is found for redshift intervals of around Deltaz = 0.4 at z similar to 1 , with little dependence on the matter density parameter Omega (0) and the cosmological constant lambda (0). Upper and lower bounds on stellar losses implied by a given set of N-body simulation output data can be investigated by choice of the merging/identity criterion of haloes between successive N -body simulation output times. A median merging/identity criterion is defin ed and used to deduce an upper estimate of possible star formation and stel lar population losses. A largest successor merging/identity criterion is de fined to deduce an estimate which minimises stellar losses. The losses for star formation and luminosity functions are strongest for low luminosity ga laxies - a likely consequence of the fact that the debris fraction is highe st for low mass haloes - and at intermediate redshifts (1 less than or simi lar to z less than or similar to 3). The losses in both cases are mostly ar ound 10%-30%, have some dependence on Omega (0) and negligible dependence o n lambda (0). This upper bound on likely losses in star formation rates and stellar populations is smaller than the uncertainties in estimates of corr esponding observational parameters. Hence, it may not be urgent to include a correction for this in Press-Schechter based galaxy formation models, exc ept when statistics regarding dwarf galaxies are under study.