J-PLUS: The stellar mass function of quiescent and star forming galaxies at 0.05 <= z <= 0.2

Abstract: Aims. We derive the stellar mass function (SMF) of quiescent and star-forming galaxies at z <= 0.2 using 12-band optical photometry from the third data release (DR3) of the Javalambre Photometric Local Universe Survey (J-PLUS) over 3,284 deg^2. Methods. We select approximately 890,000 galaxies with r <= 20 mag and photometric redshifts in the range 0.05 <= z <= 0.20. Stellar masses and star formation rates were derived through spectral energy distribution fitting with CIGALE, confronted with spectroscopic samples. Galaxies are classified as star-forming or quiescent based on their specific star formation rate (sSFR), adopting log(sSFR [yr^-1]) = -10.2. We compute SMFs for both populations using the 1/Vmax method, apply completeness corrections, and fit Schechter functions. Results. The SMFs from J-PLUS DR3 are well described by Schechter functions and agree with previous photometric and spectroscopic studies. The characteristic mass for quiescent galaxies, log(M*/Msun) = 10.80, is 0.4 dex larger than that of star-forming galaxies. The faint-end slope is steeper for star-forming galaxies (alpha = -1.2) than for quiescent ones (alpha = -0.7). The quiescent fraction rises by 40 percent per dex in stellar mass, reaching fQ > 0.95 at log(M*/Msun) > 11. Comparisons with the GAEA semi-analytic model reveal an excess of star-forming galaxies at intermediate masses. Conclusions. J-PLUS DR3 stellar mass functions and quiescent fractions are consistent with the literature and provide robust constraints for galaxy formation models. Quiescent galaxies represent 45 percent of number density above log(M*) > 9, but 75 percent of stellar mass density. The use of 12 optical bands, including 7 narrow filters, improves redshift precision by 20 percent, enabling more accurate SED fitting and galaxy classification.