In this paper , a possible relation between the high dispersion in metallicity of metal-poor halo stars and the minor merger processes in the history of the Galaxy is presented .
Observations show that satellite galaxies have been falling into the gravitational well of the Galaxy and then disrupted by the tidal force through minor merger processes .
As a result , the foreign populations of stars in the satellites make considerable contributions to the Galactic halo , therefore alter the intrinsic distribution of metallicities of the halo stars .
A model for the distribution of metallicities of halo stars with [ Fe / H ] < -2 is made , which is constrained by observations .
We show that most of the metal-poor halo field stars come from the satellite galaxies mergered into the Galaxy .
Assuming the bulk of stars in a satellite galaxy were formed in a cloud which had been enriched by previous type II supernova events , our model reproduces the observed trends in the metallicity distribution of the extremely metal-poor halo field stars in the Galaxy .
Taken all the parameters for our model , through mergering satellite galaxies into the Galactic halo , a density of 1.9 \times 10 ^ { -3 } kpc ^ { -3 } of extremely metal-poor halo stars in -5 < [ Fe / H ] < -4 is predicted , which explains why no such stars have been observed so far .