Sérsic properties of disc galaxy mergers

Sérsic parameters characterizing the density profiles of remnants formed in collisionless disc galaxy mergers are obtained; no bulge is included in our simulations. The Sérsic index range for the luminous matter, n ∈ (1.7, 5.2), is similar to that found in early-type galaxies, for about the same luminous mass range, while the effective radius tends to be higher, R_e ∈ (1.6, 12.3)kpc. A strong correlation of n with the central projected surface density I₀ is found, n ~ I^0.14₀, which is consistent with observations. No strong positive linear correlation between the size, R_e, and structure, n, of our remnants is found. The derived scaling of the index n with luminous mass, n ~ M^0.20_L, compares favourably with its observational counterpart, n ~ L^0.27. The dependence of the effective radius with luminous mass for our remnants, R_e ~ M^0.48_L, compares well with that determined from early-type galaxies of the Sloan Digital Sky Survey, R_e ~ M^0.56_L. The photometric plane scaling found for the luminous component, n ~ R^0.14_eI^0.13₀, assuming a constant stellar mass-to-light ratio, is consistent with that determined for ellipticals in the B band, n ~ R^0.09_eI^0.15₀, and for K-band remnants, n ~ R^0.11_eI^0.14₀. We find that the surface defined by Sérsic parameters {n, R_e, μ₀} in log space is not a true plane, but a pseudo-plane with a small curvature at low values of n owed to intrinsic properties of the Sérsic model. The dark haloes of our remnants have a mean 3D Sérsic index of <n> ~ 4 +/- 0.5, that is somewhat smaller than the one obtained for dark haloes in Lambda cold dark matter cosmologies, <n> ~ 6 +/- 1. Also, a tight dark Sérsic `plane' is found to be defined by the parameters of the remnants haloes with n ~ r^0.10_eρ^0.09₀. We conclude that collisionless merger remnants of pure disc galaxies have Sérsic properties and correlations consistent with those of observed in early-type galaxies and local remnants.