The Star Forming Main Sequence of Dwarf Low Surface Brightness Galaxies

TL;DR

This paper investigates the star formation properties of low surface brightness dwarf galaxies, revealing a steep main sequence slope and abundant gas supply, distinct from more massive spirals, with implications for galaxy evolution.

Contribution

It characterizes the star forming main sequence of LSB dwarf galaxies and compares it to more massive spirals, highlighting differences in slope and gas properties.

Findings

LSB dwarfs have a steep SFR-$M_*$ slope (~1.04).

The main sequence break occurs around $10^{10} M_\odot$.

LSB galaxies have gas depletion times exceeding a Hubble time.

Abstract

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.