The star formation reference survey - IV. Stellar mass distribution of local star-forming galaxies

We constrain the mass distribution in nearby, star-forming galaxies with the Star Formation Reference Survey (SFRS), a galaxy sample constructed to be representative of all known combinations of star formation rate, dust temperature, and specific star formation rate (sSFR) that exist in the Local Universe. An innovative 2D bulge/disc decomposition of the 2MASS/K_s-band images of the SFRS galaxies yields global luminosity and stellar mass functions (MFs), along with separate MFs for their bulges and discs. These accurate MFs cover the full range from dwarf galaxies to large spirals, and are representative of star-forming galaxies selected based on their infrared luminosity, unbiased by active galactic nucleus content and environment. We measure an integrated luminosity density j = 1.72 ± 0.93 × 10⁹ L$_{\odot }\, h^{-1}$ Mpc^-3 and a total stellar mass density ρ_M = 4.61 ± 2.40 × 10⁸ M$_{\odot }\, h^{-1}$ Mpc^-3. While the stellar mass of the average star-forming galaxy is equally distributed between its sub-components, discs globally dominate the mass density budget by a ratio 4:1 with respect to bulges. In particular, our functions suggest that recent star formation happened primarily in massive systems, where they have yielded a disc stellar mass density larger than that of bulges by more than 1 dex. Our results constitute a reference benchmark for models addressing the assembly of stellar mass on the bulges and discs of local (z = 0) star-forming galaxies.