标题： 美杜莎合并星系中的亚角秒射电连续谱和中性氢成像 显示英文标题

标题： Sub-arcsecond imaging of the radio continuum and neutral hydrogen in the Medusa merger

摘要： 我们展示了亚角秒级分辨率的多功能射电干涉仪联测系统（MERLIN）观测到的星爆星系 NGC 4194（美杜莎合并）核区的分米波段无线电连续谱结构和中性氢（HI）吸收。 美杜莎核心一千秒差距的连续谱结构已经被成像，显示出一对被更弥散且较弱的射电辐射包围的紧凑射电分量。 利用这些观测结果以及文献中的数据，我们得出结论，认为大部分这种射电信号与该合并系统中的持续恒星形成有关。 通过这些观测，我们也追踪了穿过检测到的射电连续谱结构的深层 HI 吸收。 吸收 HI 气体结构显示出柱密度的巨大变化。 最大的柱密度出现在核区射电连续谱南部，与核尘埃带和$^{12}$CO (1->0) 辐射峰值共空间分布。 HI 吸收的动力学特征与较低分辨率的$^{12}$CO 辐射观测一致，显示约 320 km/s/kpc 的浅南北速度梯度。 这一梯度被解释为核区内旋转气体结构的一部分。 HI 和 CO 的速度结构，结合观测到的气体柱密度和分布，在此次合并中心正在进行的恒星爆发的供气和气体物理环境中进一步讨论。 显示英文摘要

摘要： We present sub-arcsecond, Multi-Element Radio Linked Interferometer (MERLIN) observations of the decimetre radio continuum structure and neutral hydrogen (HI) absorption from the nuclear region of the starburst galaxy NGC 4194 (the Medusa Merger). The continuum structure of the central kiloparsec of the Medusa has been imaged, revealing a pair of compact radio components surrounded by more diffuse, weak radio emission. Using the constraints provided by these observations and those within the literature we conclude that the majority of this radio emission is related to the ongoing star-formation in this merger system. With these observations we also trace deep HI absorption across the detected radio continuum structure. The absorbing HI gas structure exhibits large variations in column densities. The largest column densities are found toward the south of the nuclear radio continuum, co-spatial with both a nuclear dust lane and peaks in $^{12}$CO (1->0) emission. The dynamics of the HI absorption, which are consistent with lower resolution $^{12}$CO emission observations, trace a shallow north-south velocity gradient of ~320km/s/kpc. This gradient is interpreted as part of a rotating gas structure within the nuclear region. The HI and CO velocity structure, in conjunction with the observed gas column densities and distribution, is further discussed in the context of the fuelling and gas physics of the ongoing starburst within the centre of this merger.