Galaxy-halo size relation from Sloan Digital Sky Survey Data Release 7 and the ELUCID simulation

Based on galaxies in the Sloan Digital Sky Survey Data Release 7 and dark matter haloes in the dark matter only, cosmological, and constrained ELUCID simulation, we investigate the relation between the observed radii of central galaxies with stellar mass greater than or similar to 10(8) h(-2) M-circle dot and the virial radii of their host dark matter haloes with virial mass greater than or similar to 10.5 h(-1) M-circle dot, and the dependence of galaxy-halo size relation on the halo spin and concentration. Galaxies in observation are matched to dark matter (sub)haloes in the ELUCID simulation using a novel neighbourhood subhalo abundance matching method. For galaxy two-dimensional (2D) half-light radii R-50, we find that early- and late-type galaxies have the same power-law index 0.55 with R-50 proportional to R-vir(0.55), although early-type galaxies have smaller 2D half-light radii than late-type galaxies at fixed halo virial radii. When converting the 2D half-light radii R-50 to 3D half-mass radii r(1/2), both early- and late-type galaxies display similar galaxy-halo size relations with log r(1/2) = 0.55 log(R-vir/210 h(-1) kpc) + 0.39. We find that the galaxy-halo size ratio r(1/2)/R-vir decreases with increasing halo mass. At fixed halo mass, there is no significant dependence of galaxy-halo size ratio on the halo spin or concentration.

Automated summary

This study investigates the relationship between the observed radii of central galaxies and the virial radii of their host dark matter haloes, as well as the dependence on the halo spin and concentration. The results suggest that early- and late-type galaxies have similar galaxy-halo size relations, with a decreasing ratio at higher halo masses.