We present the eddington bias corrected Specific Star Formation Rate Function (sSFRF) at different stellar mass scales from a sub-sample of the Sloan Digital Sky Survey Data Release DR7 (SDSS), which is considered complete both in terms of stellar mass (${ \rm M_{ \star}}$) and star formation rate (SFR). The above enable us to study qualitatively and quantitatively quenching, the distribution of passive/star-forming galaxies and perform comparisons with the predictions from state-of-the-art cosmological models, within the same ${ \rm M_{ \star}}$ and SFR limits. We find that at the low mass end (${ \rm M_{ \star}} = 10^{ 9.5} - 10^{ 10} \, { \rm M_{ \odot}}$) the sSFRF is mostly dominated by star-forming objects. However, moving to the two more massive bins (${ \rm M_{ \star}} = 10^{ 10} - 10^{ 10.5} \, { \rm M_{ \odot}}$ and ${ \rm M_{ \star}} = 10^{ 10.5} - 10^{ 11} \, { \rm M_{ \odot}}$) a bi-modality with two peaks emerges. One peak represents the star-forming population, while the other describes a rising passive population. The bi-modal form of the sSFRFs is not reproduced by a range of cosmological simulations (e.g. Illustris, EAGLE, Mufasa, IllustrisTNG) which instead generate mostly the star-forming population, while a bi-modality emerges in others (e.g. L-Galaxies, Shark, Simba). Our findings reflect the need for the employed quenching schemes in state-of-the-art models to be reconsidered, involving prescriptions that allow "quenched galaxies" to retain a small level of SF activity (sSFR $=$ ${ \rm 10^{ -11} { \rm yr^{ -1}}}$-${ \rm 10^{ -12} { \rm yr^{ -1}}}$) and generate an adequate passive population/bi-modality even at intermediate masses (${ \rm M_{ \star}} = 10^{ 10} - 10^{ 10.5} \, { \rm M_{ \odot}}$).
Categories: astro-ph.GA astro-ph.IM