附近Seyfert星系中馈送和反馈的ALMA观测：NGC 1433中活动星系核驱动的外流
ALMA observations of feeding and feedback in nearby Seyfert galaxies: an AGN-driven outflow in NGC 1433
摘要：
本文报道了赛弗特2型双棒星系NGC 1433中CO（3-2）辐射的ALMA观测，空间分辨率达到了前所未有的0.5”=24 pc。我们的目的是通过中央kpc内部气体的形态和动力学来探测活动星系核的馈送和反馈现象。CO地图覆盖了整个核区域（核棒和核环），揭示了一个核气体螺旋结构，在核环内环绕着核恒星棒。这个气体螺旋与哈勃太空望远镜图像中看到的尘埃螺旋有很好的相关性。核螺旋在200 pc半径处缠绕成伪环，这可能对应于内部ILR。连续辐射仅在中心0.87 mm处被探测到，其来源更可能是来自活动星系核的热尘埃辐射而不是非热辐射。它可能对应于塞弗特2星系中预期存在的分子环面。同时观测到HCN（4-3）和HCO+（4-3）线，但仅导出上限，在3sigma下与CO（3-2）线的比率低于1/60，表明非常致密气体的相对低丰度。气体在核盘上的运动学揭示了相当规则的旋转，只是受到螺旋流运动的轻微扰动;初级和次级棒与星系长轴或短轴太接近，在投影速度中留下了签名。在核心附近，有一个强烈的高速CO发射特征，红移到200 km/s（如果位于平面上），蓝移对应物，距离中心2”（100 pc）。虽然CO光谱在中心相当窄，但这一宽的成分被解释为分子量为3.6 × 10^6 Mo且流速为7 Mo/年的外流。这种流动可能部分是由中央恒星形成驱动的，但主要是由活动星系核通过其风或无线电喷流推动的。
英文摘要：
We report ALMA observations of CO(3-2) emission in the Seyfert 2 double-barred galaxy NGC1433, at the unprecedented spatial resolution of 0.5"=24 pc. Our aim is to probe AGN feeding and feedback phenomena through the morphology and dynamics of the gas inside the central kpc. The CO map, which covers the whole nuclear region (nuclear bar and ring), reveals a nuclear gaseous spiral structure, inside the nuclear ring encircling the nuclear stellar bar. This gaseous spiral is well correlated with the dusty spiral seen in Hubble Space Telescope images. The nuclear spiral winds up in a pseudo-ring at 200 pc radius, which might correspond to the inner ILR. Continuum emission is detected at 0.87 mm only at the very centre, and its origin is more likely thermal dust emission than non-thermal emission from the AGN. It might correspond to the molecular torus expected to exist in this Seyfert 2 galaxy. The HCN(4-3) and HCO+(4-3) lines were observed simultaneously, but only upper limits are derived, with a ratio to the CO(3-2) line lower than 1/60 at 3sigma, indicating a relatively low abundance of very dense gas. The kinematics of the gas over the nuclear disk reveal rather regular rotation only slightly perturbed by streaming motions due to the spiral; the primary and secondary bars are too closely aligned with the galaxy major or minor axis to leave a signature in the projected velocities. Near the nucleus, there is an intense high-velocity CO emission feature redshifted to 200 km/s (if located in the plane), with a blue-shifted counterpart, at 2" (100 pc) from the centre. While the CO spectra are quite narrow in the centre, this wide component is interpreted as an outflow involving a molecular mass of 3.6 10^6 Mo and a flow rate 7 Mo/yr. The flow could be in part driven by the central star formation, but is mainly boosted by the AGN through its wind or radio jets.
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