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This paper presents an alternative scenario to explain the observedproperties of the Milky Way dwarf Spheroidals (MW dSphs). We show that insteadof resulting from large amounts of dark matter (DM), the large velocitydispersions observed along their lines of sight can be entirely accounted forby dynamical heating of DM-free systems resulting from MW tidal shocks. Such aregime is expected if the progenitors of the MW dwarfs are infallinggas-dominated galaxies. In this case, gas lost through ram-pressure leads to astrong decrease of self-gravity, a phase during which stars can radiallyexpand, while leaving a gas-free dSph in which tidal shocks can easily develop.  The DM content of dSphs is widely derived from the measurement of the dSphsself-gravity acceleration projected along the line of sight. We show that thelatter strongly anti-correlates with the dSph distance from the MW, and that itis matched in amplitude by the acceleration caused by MW tidal shocks onDM-free dSphs. If correct, this implies that the MW dSphs would have negligibleDM content, putting in question, e.g., their use as targets for DM directsearches, or our understanding of the Local Group mass assembly history. Mostof the progenitors of the MW dSphs are likely extremely tiny dIrrs, and deeperobservations and more accurate modeling are necessary to infer their propertiesas well as to derive star formation histories of the faintest dSphs.

On the absence of dark matter in dwarf galaxies surrounding the Milky Way