Recent observations have discovered a number of extremely gas-rich very faint dwarf galaxies possibly embedded in low-mass dark matter halos .
We investigate star formation histories of these gas-rich dwarf ( “ almost dark ” ) galaxies both for isolated and interacting/merging cases .
We find that although star formation rates ( SFRs ) are very low ( < 10 ^ { -5 } { M } _ { \odot } yr ^ { -1 } ) in the simulated dwarfs in isolation for the total halo masses ( M _ { h } ) of 10 ^ { 8 } -10 ^ { 9 } { M } _ { \odot } , they can be dramatically increased to be \sim 10 ^ { -4 } { M } _ { \odot } yr ^ { -1 } when they interact or merge with other dwarfs .
These interacting faint dwarfs with central compact H ii regions can be identified as isolated emission line dots ( “ ELdots ” ) owing to their very low surface brightness envelopes of old stars .
The remnant of these interacting and merging dwarfs can finally develop central compact stellar systems with very low metallicities ( Z / Z _ { \odot } < 0.1 ) , which can be identified as extremely metal-deficient ( “ XMD ” ) dwarfs .
These results imply that although there would exist many faint dwarfs that can be hardly detected in the current optical observations , they can be detected as isolated ELdots or XMD dwarfs , when they interact with other galaxies and their host environments .
We predict that nucleated ultra-faint dwarfs formed from the darkest dwarf merging can be identified as low-mass globular clusters owing to the very low surface brightness stellar envelopes .