Sérsic parameters characterising the density profiles of remnants formed in collision-less disc galaxy mergers are obtained ; no bulge is included in our simulations .
For the luminous component we find that the Sérsic index is n \in ( 1.5 , 5.3 ) with \langle n \rangle \approx 3 \pm 1 and an effective radius of R _ { e } \in ( 1.6 , 12.9 ) kpc with \langle R _ { e } \rangle \approx 5 \pm 3 kpc .
The mean values of these quantities increases as the radial interval of fitting is reduced .
A strong correlation of n with the central projected density I _ { 0 } is found ( n \propto I _ { 0 } ^ { -0.14 } ) which is consistent with observations .
No positive linear correlation between the size ( R _ { e } ) and structure ( n ) of our remnants is found ; we do not advocate the existence of this .
The photometric plane ( PHP ) of the luminous component ( n \propto R _ { e } ^ { 0.05 } I _ { 0 } ^ { 0.15 } ) agrees well , within the uncertainties and the assumption of a constant mass-to-light ratio , with those observationally determined for ellipticals in the B -band ( n \propto R _ { e } ^ { 0.09 } I _ { 0 } ^ { 0.15 } ) and for K -band remnants ( n \propto R _ { e } ^ { 0.11 } I _ { 0 } ^ { 0.14 } ) .
We found that the surface defined by Sérsic parameters \ { n,R _ { e } , \mu _ { 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 the remnants have a 3-dimensional Sérsic index of \langle n \rangle \approx 4 \pm 0.5 that are smaller than the ones obtained for dark haloes in \Lambda CDM cosmologies n \approx 6 \pm 1 .
A tight dark Sérsic “ plane ” ( DSP ) is also defined by the parameters of the remnants haloes with n \propto r _ { e } ^ { 0.07 } \rho _ { 0 } ^ { 0.10 } .
We conclude that collision-less merger remnants of pure disc galaxies have Sérsic properties and correlations consistent with those of observed in early-type galaxies and local remnants .
It seems that a “ primordial ” bulge in spirals is not a necessary condition to form bona fide ellipticals on grounds of the Sérsic properties of remnants .