The Star-forming Main Sequence of Dwarf Low Surface Brightness Galaxies
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 ± 0.06). They form a distinct sequence from more massive spirals, which exhibit a shallower slope. The break occurs around {M}* ≈ {10}10 {M}⊙ , 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 ± 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 ∼ 3 % of this cold gas needs 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}⊙ ), while massive spirals (with {M}* > {10}10 {M}⊙ ) are weary giants that constitute more of a turn-off population.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- December 2017
- DOI:
- 10.3847/1538-4357/aa9790
- arXiv:
- arXiv:1710.11236
- Bibcode:
- 2017ApJ...851...22M
- Keywords:
-
- galaxies: dwarf;
- galaxies: evolution;
- galaxies: formation;
- galaxies: irregular;
- galaxies: spiral;
- galaxies: star formation;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- Accepted for publication in the Astrophysical Journal. 11 pages, 3 figures. Second version identical to original version