发表机构
Indiana University; Olivet Nazarene University; Knox College; University of Texas, Austin; Macalester College; ASTRON, The Netherlands Institute for Radio Astronomy; University of Groningen; Cornell University; Morgan State University（印第安纳大学; 奥利特纳扎伦大学; 诺克斯学院; 德克萨斯大学奥斯汀分校; 麦卡莱斯特学院; 荷兰射电天文研究所; 格罗宁根大学; 康奈尔大学; 摩根州立大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本文对SHIELD矮星系样本进行H-alpha窄带观测，探测到55/82个星系的发射并计算恒星形成率，发现低SFR下H-alpha示踪不佳且与质量无关，总体恒星形成效率低。
AI 中文摘要
极低质量矮星系中性氢巡天（SHIELD）星系样本是一个以中性氢（HI）选择的星系目录，这些星系占据了HI质量函数的极低质量端。我们的团队正在开展一项全面的多波段观测计划，针对这些富含气体、正在形成恒星的矮星系。本文介绍了对完整SHIELD样本的H-alpha窄带观测。我们在82个星系中的55个（67%）探测到星云H-alpha发射，并为27个未探测到的星系推断出灵敏的H-alpha通量上限。我们推导了所有82个SHIELD星系的H-alpha光度与恒星形成率（SFR），或上限。我们还首次展示了深宽带及连续谱扣除后的H-alpha图像，以及整个样本的性质总结。我们对H-alpha数据的分析再次证实了先前的结果，即在低恒星形成水平（log(SFR_{H-alpha}) < -2.5）下，H-alpha作为由远紫外（FUV）光度测量的近期平均SFR的示踪剂变得越来越差。然而，我们表明这种效应并非严格与星系质量相关。一些具有较高基于H-alpha的SFR的极低质量SHIELD星系与SFR_{FUV}表现出良好的一致性。SHIELD星系在H-alpha SFR与气体质量分数之间未显示出相关性，但在H-alpha比恒星形成率与气体质量分数之间揭示了适度的相关性。总体而言，SHIELD矮星系展现的恒星形成效率相当低，尽管该样本富含气体（68%的星系M_{gas} > M_{stellar}）。
英文摘要
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}).
Comments29 pages, 16 figures, submitted to ApJ and revised based on initial referee report
