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arXiv · 2609.32159

H-alpha Star Formation Rates of the SHIELD Dwarf Galaxies

Madeline Shepley·David G. Gormanous·John J. Salzer·Nathalie Haurberg·Steven Janowiecki·John M. Cannon·Elizabeth A. K. Adams·Martha P. Haynes·Alec S. Hirschauer·Kristen B. W. McQuinn·Katherine L. Rhode·Evan D. Skillman
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Abstract

The Survey of HI in Extremely Low-mass Dwarfs (SHIELD) galaxy sample is an HI-selected catalog of galaxies that occupy the extreme low-mass end of the HI mass function. Our team is carrying out a comprehensive multi-wavelength observational program targeting these gas-rich, star-forming dwarf galaxies. The current paper presents H-alpha narrowband observations of the full SHIELD sample. We detect 55 of the 82 galaxies (67%) with nebular H-alpha emission, and infer sensitive upper limits to the H-alpha fluxes for the 27 non-detections. We derive H-alpha luminosities and star formation rates (SFRs), or upper limits, for all 82 SHIELD galaxies. We also present, for the first time, deep broadband and continuum-subtracted H-alpha images plus a summary of the properties for the entire sample. Our analysis of the H-alpha data re-affirms previous results which show that at low levels of star formation (log(SFR_{H-alpha}) < -2.5), H-alpha becomes an increasingly poor tracer of the recent average SFR as measured by far-UV (FUV) luminosities. However, we show that this effect is not strictly correlated with the mass of the galaxy. Some very low-mass SHIELD galaxies with higher H-alpha-based SFRs show good agreement with SFR_{FUV}. The SHIELD galaxies show no correlation between H-alpha SFR and gas mass fraction, but reveal a modest correlation between H-alpha specific SFR and gas mass fraction. Overall, the star formation efficiency exhibited by the SHIELD dwarfs is rather low, despite the gas-rich nature of the sample (68% have M_{gas} > M_{stellar}).

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Madeline Shepley, David G. Gormanous, John J. Salzer, Nathalie Haurberg, Steven Janowiecki, John M. Cannon, Elizabeth A. K. Adams, Martha P. Haynes, Alec S. Hirschauer, Kristen B. W. McQuinn, Katherine L. Rhode, Evan D. Skillman. 2026-09-26. H-alpha Star Formation Rates of the SHIELD Dwarf Galaxies. https://arxiv.org/abs/2609.32159

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