We present CO(1-0) and H I (21?cm) observations of the central region of the wet merger remnant NGC?34. The Combined Array for Research in Millimeter-wave Astronomy observations detect a regularly rotating disk in CO with a diameter of 2.1?kpc and a total molecular hydrogen mass of (2.1 ± 0.2) × 109 M ☉. The rotation curve of this gas disk rises steeply, reaching maximum velocities at 1'' (410?pc) from the center. Interestingly, H I observations performed with the Karl G. Jansky Very Large Array show that the absorption against the central continuum has the exact same velocity range as the CO in emission. This strongly suggests that the absorbing H I also lies within 1'' from the center, is mixed in, and corotates with the molecular gas. A comparison of H I absorption profiles taken at different resolutions (5''-45'') shows that the spectra at lower resolutions are less deep at the systemic velocity. This provides evidence for H I emission in the larger beams, covering the region from 1?kpc to 9?kpc from the center. The central rapidly rotating disk was likely formed either during the merger or from fall-back material. Lastly, the radio continuum flux of the central source at mm wavelengths (5.4 ± 1.8?mJy) is significantly higher than expected from an extrapolation of the synchrotron spectrum, indicating the contribution of thermal free-free emission from the central starburst.
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机译：我们提出湿合并残余NGC？34中心区域的CO（1-0）和H I（21？cm）观测值。用于毫米波天文学研究的组合阵列可检测到CO中规则旋转的圆盘，直径为2.1？kpc，总分子氢质量为（2.1±0.2）×109 M☉。该气盘的旋转曲线陡峭上升，在距中心1''（410？pc）处达到最大速度。有趣的是，用卡尔·J·詹斯基（Karl G. Jansky）超大型阵列进行的H I观测表明，对中央连续谱的吸收具有与发射CO完全相同的速度范围。这有力地表明，吸收的H I也位于距中心1''的范围内，与分子气体混合并共同旋转。比较以不同分辨率（5''-45''）采集的H I吸收曲线，发现较低分辨率的光谱在系统速度下的深度较小。这提供了较大光束中H I发射的证据，该光束覆盖了从中心1？kpc到9？kpc的区域。中心快速旋转的圆盘可能是在合并过程中或由后备材料形成的。最后，在毫米波波长（5.4±1.8？mJy）处，中心源的无线电连续通量明显高于同步加速器频谱的外推预期，表明来自中心星爆的无热辐射的贡献。
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