The size-mass and other structural parameter (n, mu(z), R-z) relations for local bulges/spheroids from multicomponent decompositions

We analyse the bulge/spheroid size-(stellar mass), R-e, S-ph - M-*,M-Sph, relation and spheroid structural parameters for 202 local (predominantly less than or similar to 110 Mpc) galaxies spanning M-* similar to 3 x 10(9)-10(12) M-circle dot and 0.1 less than or similar to R-e,R-Sph less than or similar to 32 kpc from multicomponent decomposition. The correlations between the spheroid Sersic index (n(Sph)), central surface brightness (mu(0,) (Sph)), effective half-light radius (R-e, (Sph)), absolute magnitude (M-Sph), and stellar mass (M-*,M-Sph) are explored. We also investigate the consequences of using different scale radii, R-z,R-Sph, encapsulating a different fraction (z, from 0 to 1) of the total spheroid luminosity. The correlation strengths for projected mass densities, Sigma(z) and (z), vary significantly with the choice of z. Spheroid size (R-z,R-Sph) and mass (M-*,M-Sph) are strongly correlated for all light fractions z. We find log(R-e,R-Sph/kpc) = 0.88 log(M-*,M-Sph/M-circle dot) - 9.15 with a small scatter of Delta(rms) = 0.24 dex in the log (R-e,R-Sph) direction. This result is discussed relative to the curved size-mass relation for early-type galaxies due to their discs yielding larger galaxy radii at lower masses. Moreover, the slope of our spheroid size-mass relation is a factor of similar to 3, steeper than reported bulge size-mass relations, and with bulge sizes at M-*,M-sph similar to 3 x 10(9) M-circle dot which are 2-3 times smaller. Our spheroid size-mass relation present no significant flattening in slope in the low-mass end (M-*,M-sph similar to 10(9) - 10(10) M circle dot). Instead of treating galaxies as single entities, future theoretical and evolutionary models should also attempt to recreate the strong scaling relations of specific galactic components. Additional scaling relations, such as log (n(Sph)) - log (M-*,M-Sph), log (Sigma(0,Sph)) - log (n(Sph)), and log (n(Sph)) - log (R-e,R-Sph), are also presented. Finally, we show that the local spheroids align well with the size-mass distribution of quiescent galaxies at z similar to 1.25-2.25. In essence, local spheroids and high- z quiescent galaxies appear structurally similar, likely dictated by the virial theorem.

Automated summary

We analyzed the relation between bulge/spheroid size-stellar mass and spheroid structural parameters for 202 local galaxies. We found a strong correlation between spheroid size and mass, and the local spheroids are structurally similar to high-z quiescent galaxies.