Ionized Gas Motions and the Structure of Feedback near a Forming Globular Cluster in NGC 5253
Ionized Gas Motions and the Structure of Feedback near a Forming Globular Cluster in NGC 5253
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DOI：
10.3847/1538-4357/aac170
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发表时间：
2018-05
期刊：
影响因子：
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通讯作者：
D. Cohen;J. Turner;S. Consiglio;E. Martin;S. Beck
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文献类型：
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作者：
D. Cohen;J. Turner;S. Consiglio;E. Martin;S. Beck
利用Keck II上的NIRSPEC自适应光学模式（NIRSPAO）观测了NGC 5253超星云的Brackett α 4.05 μm辐射，以探测来自其激发的嵌入超星星团（SSC）的反馈。同时使用NIRSPEC的狭缝观察相机以100.″1的分辨率对K波段连续谱成像。我们将红外光谱与HST成像进行了对比，发现可见光团簇偏离了K带峰，而K带峰与超星云及其相关分子云的Brα峰重合。该超星云的光谱显示出Brα发射，具有强而窄的核心。线宽为65-76 km s-1，FWHM，与我们银河系中单个超紧凑H ii区域的线宽相当。在这条线的底部探测到一个弱而宽（半高宽为150-175 km s−1）的分量，它可以追踪一群具有高速风的源。Brα辐射的核心速度在整个超星云中从东北向西南移动了+13 km s−1，这可能表明来自嵌入物体的双极流出或与前景红移气体细丝的联系。结果可以解释，如果超级星云包括数千个电离风区域围绕单个大质量恒星，由于临界辐射冷却而停止膨胀，并且无法合并以驱动相干的星团风。基于没有大量质量损失的外流，我们得出结论，反馈目前在分散气体方面是无效的，SSC保留了丰富的物质，从中可以继续形成恒星。
We observed Brackett α 4.05 μm emission toward the supernebula in NGC 5253 with NIRSPEC on Keck II in adaptive optics mode, NIRSPAO, to probe feedback from its exciting embedded super star cluster (SSC). NIRSPEC's Slit-viewing Camera was simultaneously used to image the K-band continuum at ∼0.″1 resolution. We register the IR continuum with HST imaging, and find that the visible clusters are offset from the K-band peak, which coincides with the Brα peak of the supernebula and its associated molecular cloud. The spectra of the supernebula exhibit Brα emission with a strong, narrow core. The linewidths are 65–76 km s−1, FWHM, comparable to those around individual ultra-compact H ii regions within our Galaxy. A weak, broad (FWHM ≃ 150–175 km s−1) component is detected on the base of the line, which could trace a population of sources with high-velocity winds. The core velocity of Brα emission shifts by +13 km s−1 from NE to SW across the supernebula, possibly indicating a bipolar outflow from an embedded object or a link to a foreground redshifted gas filament. The results can be explained if the supernebula comprises thousands of ionized wind regions around individual massive stars, stalled in their expansion due to critical radiative cooling and unable to merge to drive a coherent cluster wind. Based on the absence of an outflow with large mass loss, we conclude that feedback is currently ineffective at dispersing gas, and the SSC retains enriched material out of which it may continue to form stars.