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We present numerical simulations aimed at exploring the effects of varyingthe sub-grid physics parameters on the evolution and the properties of thegalaxy formed in a low-mass dark matter halo (~7 times 10^10 Msun/h at redshiftz=0). The simulations are run within a cosmological setting with a nominalresolution of 218 pc comoving and are stopped at z = 0.43. In all of oursimulations, an extended old/intermediate-age stellar halo and a more compactyounger stellar disk are formed. We found that a non negligible fraction of thehalo stars are formed in situ in a spheroidal distribution. Changes in thesub-grid physics parameters affect significantly and in a complex way theevolution and properties of the galaxy: (i) Lower threshold densities nsfproduce larger stellar effective radii Re, less peaked circular velocity curvesV_c(R), and greater amounts of low-density and hot gas in the disk mid-plane;(ii) When stellar feedback is modeled by temporarily switching off radiativecooling in the star forming regions, Re increases (by a factor of ~ 2 in ourparticular model), the circular velocity curve becomes flatter, and a complexmulti-phase gaseous disk structure develops; (iii) A more efficient localconversion of gas mass to stars, measured by a stellar particle massdistribution biased toward larger values, increases the strength of thefeedback energy injection -driving outflows and inducing burstier SF histories;iv) If feedback is too strong, gas loss by galactic outflows -which are easierto produce in low-mass galaxies- interrupts SF, whose history becomes episodic.The simulations exhibit two important shortcomings: the baryon fractions arehigher, and the specific SF rates are much smaller, than observationallyinferred values for redshifts ~ 0.4-1.

Low-mass galaxy formation in cosmological AMR simulations: the effects of varying the sub-grid physics parameters