Galaxy Populations in Groups and Clusters: Evidence for a Characteristic Stellar Mass Scale at M _∗ ∼ 10^9.5 M _⊙

We use the most recent data release (DR9) of DESI legacy imaging survey and SDSS galaxy groups to measure conditional luminosity function (CLF) for with halo mass $M_{\rm h}\ge 10^{12}M_{\odot}$ redshift $0.01\le z\le 0.08$, down a limiting $r$-band magnitude r}=-10\sim-12$. For given we CLF total satellite population, as well separately red blue populations classified using $(g-z)$ color. find clear faint-end upturn in satellites, slope $\alpha\approx-1.8$ which is almost independent mass. This not seen satellites population. Our stellar population synthesis modeling shows that color provides clean red/blue division, group galaxies defined by are all dominated old populations. The fraction minimum at r}\sim-18$, corresponding $M_\ast\sim10^{9.5}M_\odot$. scale comparable characteristic show dichotomy surface brightness size, suggesting structure may have common origin. rising faint end Milky Way (MW)-sized halos found here good agreement quenched measured both MW/M31 system from ELVES survey. discuss implications our results formation evolution low-mass galaxies, functions be observed high redshift.