We use deep optical photometry from the Next Generation Virgo Cluster Survey [ NGVS ] to investigate the color-magnitude diagram for the galaxies inhabiting the core of this cluster .
The sensitivity of the NGVS imaging allows us to continuously probe galaxy colors over a factor of \sim 2 \times 10 ^ { 5 } in luminosity , from brightest cluster galaxies to scales overlapping classical satellites of the Milky Way [ M _ { g ^ { \prime } } \sim –9 ; M _ { * } \sim 10 ^ { 6 } M _ { \odot } ] , within a single environment .
Remarkably , we find the first evidence that the RS flattens in all colors at the faint-magnitude end [ starting between –14 \leq M _ { g ^ { \prime } } \leq –13 , around M _ { * } \sim 4 \times 10 ^ { 7 } M _ { \odot } ] , with the slope decreasing to \sim 60 % or less of its value at brighter magnitudes .
This could indicate that the stellar populations of faint dwarfs in Virgo ’ s core share similar characteristics [ e.g .
constant mean age ] over \sim 3 mags in luminosity , suggesting that these galaxies were quenched coevally , likely via pre-processing in smaller hosts .
We also compare our results to galaxy formation models , finding that the RS in model clusters have slopes at intermediate magnitudes that are too shallow , and in the case of semi-analytic models , do not reproduce the flattening seen at both extremes [ bright/faint ] of the Virgo RS .
Deficiencies in the chemical evolution of model galaxies likely contribute to the model-data discrepancies at all masses , while overly efficient quenching may also be a factor at dwarf scales .
Deep UV and near-IR photometry are required to unambiguously diagnose the cause of the faint-end flattening .