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arXiv 1109.6360astro-ph.CO
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矮星暴星系NGC 5253的电离锥

An Ionization Cone in the Dwarf Starburst Galaxy NGC 5253

Jordan Zastrow, M. S. Oey, Sylvain Veilleux, Michael McDonald, Crystal L. Martin

备注：
5 pages, 4 figures, Accepted to ApJ Letters
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摘要：

关于电离光子从星暴星系逃逸如何取决于星系参数，几乎没有观测限制。在这里，我们报告的第一个主要检测的电离锥在NGC 5253，附近的星暴星系。利用Las Campanas天文台的Maryland-Magellan可调谐滤波器拍摄的[S III] lambda 9069、[S II] lambda 6716和H_alpha窄带图像，通过绘制星系的发射线比率图来确定这种高激发特征。电离锥在光学上看起来很薄，这暗示了电离光子的逃逸。锥状的形态很窄，估计立体角仅覆盖4pi球面度的3%，而年轻的大质量核星爆星团可以很容易地产生覆盖锥状所需的辐射。虽然可能性较小，但我们不能排除活动星系核来源被遮蔽的可能性。沿短轴的阶梯光谱显示出与外流活动相一致的复杂运动学。电离锥的狭窄形态支持的情况下，在检测从星爆和莱曼break星系莱曼连续辐射的困难的方向偏差。

英文摘要：

There are few observational constraints on how the escape of ionizing photons from starburst galaxies depends on galactic parameters. Here, we report on the first major detection of an ionization cone in NGC 5253, a nearby starburst galaxy. This high-excitation feature is identified by mapping the emission-line ratios in the galaxy using [S III] lambda 9069, [S II] lambda 6716, and H_alpha narrow-band images from the Maryland-Magellan Tunable Filter at Las Campanas Observatory. The ionization cone appears optically thin, which is suggestive of the escape of ionizing photons. The cone morphology is narrow with an estimated solid angle covering just 3% of 4pi steradians, and the young, massive clusters of the nuclear starburst can easily generate the radiation required to ionize the cone. Although less likely, we cannot rule out the possibility of an obscured AGN source. An echelle spectrum along the minor axis shows complex kinematics that are consistent with outflow activity. The narrow morphology of the ionization cone supports the scenario that an orientation bias contributes to the difficulty in detecting Lyman continuum emission from starbursts and Lyman break galaxies.

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