During a wide-field narrowband Hα imaging survey, we noted the presence of numerous isolated emission-line point sources in the data. These objects could represent ultra-low-luminosity galaxies at low-redshift (detection via Hα), isolated extragalactic H II regions associated with the galaxy targeted by the original observation, or background galaxies or QSOs where strong emission lines (most often [O III] λ5007) redshift into our narrowband filter. We have carried out a systematic search for these "Hα dots" in over 200 15 × 15 arcmin fields. To date we have cataloged 61 candidate emission-line sources in roughly 11.7?deg2. The sample has a median R magnitude of 19.5, and detects objects as faint as R = 22.6. Follow-up spectroscopy reveals that ~85% of the candidates are bona fide emission-line objects, with roughly 60% of the real sources being lower-redshift objects (detection via Hα) and 40% being higher-redshift objects detected via [O III] emission or some other emission line. Here we present the results of our initial survey and follow-up spectroscopy. We use our sample to study the properties (including star-formation rates and metal abundances) of low-luminosity star-forming galaxies in the nearby universe and of low-metallicity star-forming galaxies at z ≈ 0.33.
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机译：在宽频窄带Hα成像调查中，我们注意到数据中存在许多孤立的发射线点源。这些物体可能代表处于低红移状态的超低发光星系（通过Hα探测），与原始观测所针对的星系相关的孤立的银河外H II区域，或者是背景星系或QSO，在这些星系中有强发射线（通常是[O III ]λ5007）红移到我们的窄带滤波器中。我们已经在200多个15×15 arcmin场中对这些“Hα点”进行了系统搜索。迄今为止，我们已经分类了大约11.7？deg2的61个候选发射线源。样本的中值R值为19.5，并且检测到的物体像R = 22.6一样微弱。后续光谱显示，约有85％的候选物是真正的发射线物体，其中大约60％的真实源是较低的红移物体（通过Hα检测），而40％的是较高的红移物体，通过[O III]发射或其他一些发射线。在这里，我们介绍了我们的初步调查和后续光谱学的结果。我们使用样本研究附近宇宙中低发光度恒星形成星系和z≈0.33的低金属度恒星形成星系的特性（包括恒星形成率和金属丰度）。
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