The Star Forming Main Sequence of Dwarf Low Surface Brightness Galaxies
  We explore the star forming properties of late type, low surface brightness
(LSB) galaxies. The star forming main sequence (SFR-$M_*$) of LSB dwarfs has a
steep slope, indistinguishable from unity ($1.04 \pm 0.06$). They form a
distinct sequence from more massive spirals, which exhibit a shallower slope.
The break occurs around $M_* \approx 10^{10}\;M_{\odot}$, and can also be seen
in the gas mass-stellar mass plane. The global Kennicutt-Schmidt law
(SFR-$M_g$) has a slope of $1.47 \pm 0.11$ without the break seen in the main
sequence. There is an ample supply of gas in LSB galaxies, which have gas
depletion times well in excess of a Hubble time, and often tens of Hubble
times. Only $\sim 3\%$ of this cold gas need be in the form of molecular gas to
sustain the observed star formation. In analogy with the faint, long-lived
stars of the lower stellar main sequence, it may be appropriate to consider the
main sequence of star forming galaxies to be defined by thriving dwarfs (with
$M_* < 10^{10}\;M_{\odot}$) while massive spirals (with $M_* >
10^{10}\;M_{\odot}$) are weary giants that constitute more of a turn-off
population.
