SHIELD: Comparing gas and star formation in low-mass galaxies

Yaron G. Teich, Andrew T. McNichols, Elise Nims, John M. Cannon, Elizabeth A K Adams, Riccardo Giovanelli, Martha P. Haynes, Kristen B W McQuinn, John J. Salzer, Evan D. Skillman, Elijah Z. Bernstein-Cooper, Andrew Dolphin, E. C. Elson, Nathalie Haurberg, Gyula I G Józsa, Jürgen Ott, Amelie Saintonge, Steven R. Warren, Ian Cave, Cedric HagenShan Huang, Steven Janowiecki, Melissa V. Marshall, Clara M. Thomann, Angela Van Sistine

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23 Citations (Scopus)


We analyze the relationships between atomic, neutral hydrogen (H i) and star formation (SF) in the 12 low-mass SHIELD galaxies. We compare high spectral (∼0.82 km s-1 ch-1) and spatial resolution (physical resolutions of 160-640 pc) H i imaging from the VLA with Hα and far-ultraviolet imaging. We quantify the degree of co-spatiality between star-forming regions and regions of high H i column densities. We calculate the global star formation efficiencies (SFE; / ) and examine the relationships among the SFE and H i mass, H i column density, and star formation rate (SFR). The systems are consuming their cold neutral gas on timescales of order a few gigayears. While we derive an index for the Kennicutt-Schmidt relation of N ≈ 0.68 ±0.04 for the SHIELD sample as a whole, the values of N vary considerably from system to system. By supplementing SHIELD results with those from other surveys, we find that H i mass and UV-based SFR are strongly correlated over five orders of magnitude. Identification of patterns within the SHIELD sample allows us to bin the galaxies into three general categories: (1) mainly co-spatial H i and SF regions, found in systems with the highest peak H i column densities and highest total H i masses; (2) moderately correlated H i and SF regions, found in systems with moderate H i column densities; and (3) obvious offsets between H i and SF peaks, found in systems with the lowest total H i masses. SF in these galaxies is dominated by stochasticity and random fluctuations in their ISM.

Original languageEnglish
Article number85
JournalThe Astrophysical Journal
Issue number1
Publication statusPublished - 20 Nov 2016


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