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tokens: explosions, exceeds its binding energy (see Matteucci 1994 ; Bradamante, Matteucci D’Ercole 1998 ; Vincenzo et al. 2014 ): The thermal energy of the gas is produced by SN explosions (of all types) and by stellar winds, while the binding energy of the gas is computed as where W L ( t ) is the potential well due to the luminous matter and W LD ( t ) represents the potential well due to the interaction between dark and luminous matter. This last term mainly depends on the mass of the DM halo ( M DM ) and on the ratio S = R L / R DM between the galaxy effective radius ( R L ) and the radius of the DM core ( R DM ) (see Bertin, Saglia Stiavelli 1992 ). The last term R i ( t ) represents the fraction of matter that is returned by stars into the ISM through stellar winds, SN explosions, and MNS, in the form of the element i . In other words, it represents the rate at which each chemical element is restored into the ISM by all stars dying at the time t . R i ( t ) depends also on the initial mass function (IMF). Here we adopt a Salpeter ( 1955 ) IMF for all galaxies: normalized to unity between 0.1 and 100 M ⊙ . 4 NUCLEOSYNTHESIS PRESCRIPTIONS For all the stars sufficiently massive to die in a Hubble time, the following stellar yields have been adopted. For LIMS we included the metallicity-dependent stellar yields of Karakas ( 2010 ). For massive stars we assumed yields of Kobayashi et al. ( 2006 ). For Type Ia SNe (SNeIa) we included yields of Iwamoto et al. ( 1999 ). We adopted the single-degenerate scenario for SNeIa, in which SNe arise from the explosion via C-deflagration of a C–O white dwarf in a close binary system as it has reached the Chandrasekhar mass due to accretion from its red giant companion. The same stellar yields have been adopted in Vincenzo et al. ( 2015 ). Also, a complete and detailed description of those yields can be found in Romano et al. ( 2010 ). 4.1 Eu and Ba yields For both Eu and the r-process fraction of Ba we considered two different production sites: MNS and MRD-SNe. We assume r-process elements to be produced by (i) only MNS, (ii) only MRD-SNe, (iii) both MNS and MRD-SNe. In our simulations, MNS are systems of two 1.4 M ⊙ neutron stars with progenitors in the 9–50 M ⊙ mass range. In order to include the production of r-process elements from MNS in our chemical evolution code, we need to specify the following parameters (see Matteucci et al. 2014 ): the mass of each elements that is produced per merging event, and ; the time delay between the formation of the double neutron star system and the merging event, τ; the fraction of neutron stars in binaries that produce a MNS, α MNS . For what it concerns the yields of r-process elements from MNS, they have been obtained by assuming that there is a scaling relation between them and those of strontium (Sr). The adopted scaling factors are equal to 0.03 for Eu and to 3.16 for Ba, and have been found from the Solar system r-process contribution, as determined by Simmerer et