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 I 0 is found, n ∝ I 0.14 0 , 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 e I 0.13 0 , assuming a constant stellar mass‐to‐light ratio, is consistent with that determined for ellipticals in the B band, n ∝ R 0.09 e I 0.15 0 , and for K ‐band remnants, n ∝ R 0.11 e I 0.14 0 . We find that the surface defined by Sérsic parameters { n , R e , μ 0 } 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 e ρ 0.09 0 . 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.