In this work we analyze the dark matter ( DM ) fraction , f _ { DM } , and mass-to-light ratio mismatch parameter , \delta _ { IMF } ( computed with respect to a Milky-Way-like IMF ) , for a sample of 39 dwarf early-type galaxies ( dEs ) in the Virgo cluster .
Both f _ { DM } and \delta _ { IMF } are estimated within the central ( one effective radius ) galaxy regions , with a Jeans dynamical analysis that relies on galaxy velocity dispersions , structural parameters , and stellar mass-to-light ratios from the SMAKCED survey .
In this first attempt to constrain , simultaneously , the IMF normalization and the dark matter content , we explore the impact of different assumptions on the DM model profile .
On average , for a NFW profile , the \delta _ { IMF } is consistent with a Chabrier-like normalization ( \mbox { $ \delta _ { IMF } $ } \sim 1 ) , with \mbox { $f _ { DM } $ } \sim 0.35 .
One of the main results of the present work is that for at least a few systems the \delta _ { IMF } is heavier than the Milky-Way-like value ( i.e .
either top- or bottom-heavy ) .
When introducing tangential anisotropy , larger \delta _ { IMF } and smaller f _ { DM } are derived .
Adopting a steeper concentration–mass relation than that from simulations , we find lower \delta _ { IMF } ( \mathrel { \hbox to 0.0 pt { \lower 3.5 pt \hbox { $ \sim$ } } \raise 0.5 pt \hbox { $ < $ } } 1 ) and larger f _ { DM } .
A constant M / L profile with null f _ { DM } gives the heaviest \delta _ { IMF } ( \sim 2 ) .
In the MONDian framework , we find consistent results to those for our reference NFW model .
If confirmed , the large scatter of \delta _ { IMF } for dEs would provide ( further ) evidence for a non-universal IMF in early-type systems .
On average , our reference f _ { DM } estimates are consistent with those found for low- \sigma _ { e } ( \sim 100 kms ^ { -1 } ) early-type galaxies ( ETGs ) .
Furthermore , we find f _ { DM } consistent with values from the SMAKCED survey , and find a double-value behavior of f _ { DM } with stellar mass , which mirrors the trend of dynamical M / L and global star formation efficiency ( from abundance matching estimates ) with mass .