Using dust, gas and stellar mass selected samples to probe dust sources and sinks in low metallicity galaxies
2017
We combine samples of nearby galaxies with Herschel photometry selected on their dust, metal,
Hi, and stellar mass content, and compare these to chemical evolution models in order to discriminate
between different dust sources. In a companion paper, we used a Hi-selected sample of nearby
galaxies to reveal a sub-sample of very gas rich (gas fraction > 80 per cent) sources with dust masses
significantly below predictions from simple chemical evolution models, and well below Md/M∗ and
Md/Mgas scaling relations seen in dust and stellar-selected samples of local galaxies. We use a chemical
evolution model to explain these dust-poor, but gas-rich, sources as well as the observed star
formation rates (SFRs) and dust-to-gas ratios. We find that (i) a delayed star formation history is
required to model the observed SFRs; (ii) inflows and outflows are required to model the observed
metallicities at low gas fractions; (iii) a reduced contribution of dust from supernovae (SNe) is
needed to explain the dust-poor sources with high gas fractions. These dust-poor, low stellar mass
galaxies require a typical core-collapse SN to produce 0.01−0.16 M� of dust. To match the observed
dust masses at lower gas fractions, significant grain growth is required to counteract the reduced
contribution from dust in SNe and dust destruction from SN shocks. These findings are statistically
robust, though due to intrinsic scatter it is not always possible to find one single model that successfully
describes all the data. We also show that the dust-to-metals ratio decreases towards lower
metallicity.
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