贫金属星系中的HI：SBS 0335-052系统
HI in very metal-poor galaxies: the SBS 0335-052 system
摘要：
我们提出了巨型米波射电望远镜（GMRT），HI 21厘米的观测SBS 0335- 052 E和SBS 0335- 052 W，一对近距离的矮星系，这是进一步不寻常的是最贫金属的恒星形成星系已知的。我们提供了几个角分辨率的图像，范围从~40到4角秒。这些图像显示SBS 0335-052是一个强相互作用的系统，在低分辨率下可以看到微弱的弥漫HI桥，在高分辨率下可以看到细长的尾巴。整体形态表明，这对星系代表了一个非常富含气体的星系的主要合并。低分辨率的速度场主要由两个星系之间的速度差和沿潮汐特征的速度梯度所决定。然而，至少对于SBS 0335- 052 W，在高角分辨率下，可以看到中心速度场，其可以与原始未扰动盘的自旋相关联。最高角分辨率的HI图像显示，Thuan，Izotov和Lipovetsky（1997）在哈勃空间望远镜（HST）拍摄的SBS 0335- 052 E图像中发现的电离超级气泡沿着一个扩散潮汐特征延伸，在超级气泡的另一端有一个高密度的HI团块。SBS 0335- 052 E的恒星形成主要发生在一组具有明显年龄梯度的超级巨星团（SSC）中;随着接近致密的HI团，年龄降低。我们认为，这种传播的恒星形成是由超级气泡膨胀到一个潮汐产生的密度梯度的介质。与压缩物质相关的高压也自然地解释了为什么目前的恒星形成主要集中在超级巨星团中。
英文摘要：
We present Giant Metrewave Radio Telescope (GMRT), HI 21cm observations of SBS 0335-052E and SBS 0335-052W, a close pair of dwarf galaxies, which are further unusual in being the most metal-poor star-forming galaxies known. We present images at several angular resolutions, ranging from ~40 to 4 arcsec. These images show that SBS 0335-052 is a strongly interacting system, with a faint diffuse HI bridge seen at low resolution, and elongated tails seen at the higher resolutions. The overall morphology suggests that the pair represents a major merger of extremely gas-rich galaxies. The low-resolution velocity field is dominated by the velocity difference between the two galaxies and the velocity gradient along the tidal features. However, for SBS 0335-052W at least, at high angular resolution, one sees a central velocity field that could be associated with the spin of the original undisturbed disc. The highest angular resolution HI images show that the ionized superbubble, identified by Thuan, Izotov & Lipovetsky (1997), in the Hubble Space Telescope (HST) images of SBS 0335-052E, is extended along one of the diffuse tidal features, and that there is a high-density HI clump at the other end of the superbubble. The star formation in SBS 0335-052E occurs mainly in a group of superstar clusters (SSCs) with a clear age gradient; the age decreases as one approaches the dense HI clump. We suggest that this propagating star formation is driven by the superbubble expanding into a medium with a tidally-produced density gradient. The high pressures associated with the compressed material would also naturally explain why current star formation is mainly concentrated in superstar clusters.
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