The star formation history ( SFH ) and the properties of the dwarf galaxy LGS 3 are analyzed using color-magnitude ( CM ) diagrams plotted from VRI photometry of 736 stars .
The distance to the galaxy is estimated through the position of the tip or the red giant branch .
Two acceptable results have been obtained : 0.77 \pm 0.07 Mpc and 0.96 \pm 0.07 Mpc , although the first value is favored by complementary considerations on the stellar content of the galaxy .
Both values make LGS 3 a possible satellite of M31 or of M33 .
The SFH is investigated for each of the two adopted distances comparing the observed ( CM ) diagrams with model CM diagrams computed for different star formation rates ( \psi ( t ) ) and chemical enrichment laws ( Z ( t ) ) .

The results are compatible with LGS 3 having been forming stars since an early epoch , 15–12 Gyr ago , at an almost constant rate if distance is 0.77 Mpc or at an exponentially decreasing rate if distance is 0.96 Mpc .
According to our models , the current metallicity would range from Z \simeq 0.0007 to Z \simeq 0.002 .
Other results are the current \psi ( t ) : ( 0.55 \pm 0.04 ) \times 10 ^ { -10 } M _ { \odot } yr ^ { -1 } pc ^ { -2 } or ( 0.47 \pm 0.07 ) \times 10 ^ { -10 } M _ { \odot } yr ^ { -1 } pc ^ { -2 } , depending of the distance , and its average for the entire life of the galaxy , \bar { \psi } = ( 1.4 \pm 0.1 ) \times 10 ^ { -10 } M _ { \odot } yr ^ { -1 } pc ^ { -2 } .
At the present \psi ( t ) , the probability of LGS 3 having an HII region is 0.2 , which is compatible with the fact that no HII regions have been found in the galaxy .
Its fraction of gas relative to the mass intervening in the chemical evolution is about 0.40 and its percentage of dark matter ( that which can not be explained as stellar remnants or by extrapolation of the used IMF to low masses ) is 95 % .
The results for \psi ( t ) and Z ( t ) for d = 0.77 Mpc are compatible with a moderate outflow of well mixed material ( \lambda = 3 ) , but large outflow rate ( \lambda = 30 ) is required to account for the results for d = 0.96 Mpc .
The latter would imply that , if the amount of dark mass associated to the galaxy is constant , the initial dark matter fraction was about 50 % .
In both cases , a large fraction of freshly made metals ( \gamma = 0.85 for the case of d = 0.77 Mpc and \gamma = 0.36 for d = 0.96 Mpc ) should also escape from the galaxy before mixing with the interstellar medium to make the results compatible with the theoretical yields .

LGS 3 is considered an intermediate type between dIr and dE .
However we find that it shows characteristics typical of dIrs ( the M _ { gas } / L _ { B } ratio and the SFH shape ) , the main difference being that its mass and star formation rate ( present and averaged ) are one to two orders of magnitude smaller than those of other dIrs .
This makes the absence of HII regions a simple probabilistic effect .
Considering this and the fact that LGS 3 can continue to form stars for a further 10 Gyr at a rate equal to that averaged for its past history , we conclude that this galaxy may be considered just a dIr in the tail of the distributions of mass , luminosity and star formation rate .