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functions in gadget.i - C


struct CHalo {  
  long   level  ;  
  long   mother;  
  long   firstchild;  
  long   nsisters;  
  long   sister;  
  double rho_saddle;  
  double density;  
  double densmax;  
  double radius ;  
  double mass   ;  
  double position(3);  
// level : integer number corresponding to the level in the tree.  
//         The root, node(1), corresponds to level=0. The root corresponds  
//         to all the selected particles (above the density threshold)  
//         in the simulation box: it is not physically relevant.  
// mother : the id of the mother of this node, i.e. the id of substructure  
//         which contains this substructure (for the root, there is no  
//         mother, i.e. mother=0).  
// firstchild : the id of the first child of this node, i.e. the first  
//         substructure it contains. Other substructures will be found  
//         by running over the list their sisters. If we are sitting  
//         at the end of a branch, firstchild=0 (i.e. this node correspond  
//         to an elementary substructure) .  
// nsisters : the number of sisters of this substructure + 1.  
// sister : the id of the sister ``at the right'' of this structure. A structure  
//         that has not sister at its ``right'' has sister=0.  
// rho_saddle : the density of the saddle(s) point(s) connecting this  
//         structure to its sisters. In principle this could be calculated  
//         uniquely so that a structure would always have at most one  
//         sister, but as explained in the important note above,  
//         rho_saddle is computed approximately, as a result, it can  
//         correspond to more than a single saddle point.  
//         For a given density threshold, rho_th, if rho_th > rho_saddle,  
//         the substructure is connected to its sisters, whereas if  
//         rho_th < rho_saddle, the substructure is disconnected from its  
//         sisters.  
// density : average density of the substructure, calculated from the  
//         average SPH density of all particles with SPH density larger than  
//         rho_saddle and belonging to the substructure.  
// densmax : maximum density within the substructure : it correspond  
//         to the largest SPH density of all the particles within the  
//         substructure.  
// radius : size in Mpc of the substructure calculated by computing the mean  
//         square distance of each particle belonging to it with respect  
//         to its center of mass.  
// mass :  number of particles within the substructure.  
// position(3) : coordinates in Mpc of the center of mass of the  
//         substructure.