We present new VLA observations of the H I medium of the Local Group dwarf galaxies Sag DIG, LGS 3, and Phoenix. Sag DIG is a gas-rich, blue dwarf irregular with some known recent star formation, whereas LGS 3 and Phoenix are gas-poor, red galaxies of intermediate irregular/spheroidal type with little recent star formation. These galaxies complete a small sample of Local Group and near-Local Group irregular and elliptical galaxies that have been mapped in H I and, where possible, in CO. We compare the properties and kinematics of the ISM in these different galaxy types in order to gain some insights into the relationship between galaxy properties, star formation, and the ISM. Both Sag DIG and LGS 3 have larger H I extents and higher H I fluxes than previously known, and in both cases the H I extends significantly farther than the stellar component. Neither one shows convincing signs of rotation; both seem to derive a significant amount of their support against gravity from random motions in the gas. The dwarf galaxies of the sample support the idea that there are large variations in the dark/luminous mass ratio at a given luminosity. The high sensitivity and high spectral and spatial resolution of these observations also make it possible to study the physical properties of the H I medium. The H I in Sag DIG is decomposed into broad (σ = 10 km s-1) and narrow (σ = 5 km s-1) components, with the broad component distributed throughout the galaxy and the narrow component concentrated into a small number of prominent clumps of about 8 × 105 M☉. It is argued that these H I components are in fact cold and warm phases of the H I medium, as in Galactic H I and in the dwarf irregular Leo A. LGS 3, on the other hand, shows little sign of such a two-phase H I structure. This new information on the phase structure of the ISM in dwarf galaxies is consistent with theoretical models of the H I medium if the H I line width is greater than purely thermal widths. The lack of a cold H I phase may be a reason for the lack of recent star formation in LGS 3; we suggest that the presence of a cold H I phase serves as a better indicator of conditions appropriate for star formation than measures of total H I content. The Phoenix dwarf and LGS 3 have been interpreted as two dwarf spheroidal galaxies which are unusual in that they contain H I. The presence of H I in LGS 3 is interesting, then, in the context of models that remove the gas from dwarf spheroidals by a burst of star formation. Either LGS 3 has not had a burst of star formation sufficient to remove its gas, or gas removal was not complete. It is not clear whether the Phoenix dwarf has H I. The current observations show emission in the vicinity of the galaxy at +55 km s-1 and -23 km s-1 (heliocentric). However, none of this emission is coincident with the optical galaxy. Until the stellar velocities in Phoenix are known, we cannot distinguish whether any of the detected H I is actually associated with the galaxy or is perhaps associated with the Magellanic Stream.
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机译：我们介绍了本地群矮星系Sag DIG，LGS 3和Phoenix的H I介质的新VLA观测结果。凹陷DIG是富含气体的蓝矮星不规则星体，具有一些已知的近来恒星形成，而LGS 3和Phoenix则是中度不规则/球体类型的贫气，红色星系，几乎没有新星形成。这些星系完成了在HI和可能的情况下在CO中映射的局部群和近局部群不规则和椭圆形星系的一小部分样本。我们比较了这些不同星系类型中ISM的特性和运动学，关于银河性质，恒星形成和ISM之间关系的一些见解。 Sag DIG和LGS 3都具有比以前已知的更大的H I范围和更高的H I通量，并且在这两种情况下，H I的延伸远比恒星分量远。没有人显示令人信服的旋转迹象。两者似乎都从气体中的随机运动获得了大量的重力支持。样品的矮星系支持这样的想法：在给定的亮度下，暗/光质量比存在很大的变化。这些观测结果的高灵敏度以及高光谱和空间分辨率也使得研究H I介质的物理性质成为可能。凹陷DIG中的HI分解为宽分量（σ= 10 km s-1）和窄分量（σ= 5 km s-1），宽分量分布在整个银河系中，而窄分量集中成少量突出的约8×105M☉的团块。有人认为，这些HI成分实际上是HI介质的冷热相，如Galactic HI和矮小不规则LeoA。LGS 3另一方面，几乎没有这种两相HI结构的迹象。 。如果H I线宽大于纯热宽度，则有关矮星系中ISM相结构的新信息与H I介质的理论模型是一致的。缺乏冷的H I相可能是LGS 3缺乏近期恒星形成的原因。我们认为，相比于总H I含量，冷I I相的存在可以更好地指示适合恒星形成的条件。凤凰矮星和LGS 3被解释为两个矮球体星系，它们不常见，因为它们包含HI。LGS 3中HI的存在很有趣，因此，在模型中，通过爆发的恒星形成。 LGS 3尚未爆发出足以清除其气体的恒星爆发，或者气体清除不完全。目前尚不清楚凤凰矮人是否具有HI。目前的观测结果表明，在星系附近的发射在+55 km s-1和-23 km s-1（日心）。但是，这些发射都与光学星系不一致。在知道凤凰城的恒星速度之前，我们无法区分检测到的任何H I是否实际上与星系相关或与麦哲伦流相关。
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