New HI observations are presented for a complete sample of 109 low luminosity star-forming galaxies taken from the KPNO International Spectroscopic Survey ( KISS ) , the first CCD-based wide-field objective-prism survey for emission-line galaxies .
This sample consists of all star-forming galaxies with M _ { B } > -18.0 and cz < 11,000 km s ^ { -1 } from the first H \alpha -selected survey list .
The galaxies in this list lie within a 1.3 deg wide strip centered on \delta ( B 1950 ) = 29 \arcdeg 30 \arcmin that spans the range \alpha ( B 1950 ) = 12 ^ { \mbox { \scriptsize h } } 15 ^ { \mbox { \scriptsize m } } to \alpha ( B 1950 ) = 17 ^ { \mbox { \scriptsize h } } 0 ^ { \mbox { \scriptsize m } } .
Overall , 97 out of 109 galaxies have been detected in HI .
We confirm the weak trend of increasing gas richness with decreasing luminosity found by previous authors .
Gas richness is also shown to be weakly anti-correlated with metallicity .
The dependence of star formation rates ( SFRs ) and HI gas depletion timescales on metallicity is examined .
The median solar metallicity based SFR and gas depletion timescale are 0.1639 M _ { \odot } yr ^ { -1 } and 5 Gyrs , respectively .
Corrections for variations in metallicity decreases SFRs by \sim 0.5 dex and increases gas depletion timescales by an average of \sim 8 Gyrs .
The majority of galaxies in this sample still have large reservoirs of HI gas , and despite their large current star formation rates , could have formed stars in a quasi-continuous manner for a Hubble time .
Finally , we present the first HI mass function for low luminosity star-forming galaxies and show that this subpopulation contributes 10-15 % of the overall HI density in the local universe .
We conclude that if the HI mass function of the Universe does indeed have a steeply rising low-mass slope as suggested by previous authors , it is not due to the population of low luminosity star-forming galaxies .
Comparison of the number densities from the HIMFs in the range 10 ^ { 8 } < M _ { HI } / M _ { \odot } < 10 ^ { 9 } implies that 25-50 % of galaxies in this regime are currently undergoing a strong episode of star formation .