Local galaxies with specific star-formation rates ( star-formation rate per unit mass ; sSFR \sim 0.2-10 Gyr ^ { -1 } ) as high as distant galaxies ( z \approx 1-3 ) , are very rich in H i .
Those with low stellar masses , M _ { \star } =10 ^ { 8 - 9 } M _ { \sun } , for example , have M _ { HI } /M _ { \star } \approx 5-30 .
Using continuity arguments of Peng et al .
( 2014 ) , whereby the specific merger rate is hypothesized to be proportional to the specific star-formation rate , and H i gas mass measurements for local galaxies with high sSFR , we estimate that moderate mass galaxies , M _ { \star } =10 ^ { 9 - 10.5 } M _ { \sun } , can acquire sufficient gas through minor mergers ( stellar mass ratios \sim 4-100 ) to sustain their star formation rates at z \sim 2 .
The relative fraction of the gas accreted through minor mergers declines with increasing stellar mass and for the most massive galaxies considered , M _ { \star } =10 ^ { 10.5 - 11 } M _ { \sun } , this accretion rate is insufficient to sustain their star formation .
We checked our minor merger hypothesis at z=0 using the same methodology but now with relations for local normal galaxies and find that minor mergers can not account for their specific growth rates , in agreement with observations of H i -rich satellites around nearby spirals .
We discuss a number of attractive features , like a natural down-sizing effect , in using minor mergers with extended H i disks to support star formation at high redshift .
The answer to the question posed by the title , “ Can galaxy growth be sustained through H i -rich minor mergers ? ” , is maybe , but only for relatively low mass galaxies and at high redshift .