Inner spiral structure of the galaxy M51
Inner spiral structure of the galaxy M51
复制标题
M51星系的内螺旋结构
作者：
D. Zaritsky;H. Rix;M. Ricke
螺旋星系的结构和运动学模型需要精确的质量追踪恒星群图。但是，由于尘埃的遮蔽和明亮的年轻恒星的存在，这一点迄今为止一直很困难。为了最大限度地减少尘埃的影响，并最大限度地提高对主要恒星群体的敏感性，我们获得了附近“宏伟设计”螺旋星系NGC 5194（M51）的K波段（2.2 μm）图像。我们的观察揭示了显着的动力学结构在传统的光学图像中不可见。我们发现，螺旋臂向星系中心的延伸比以前观察到的要远得多，并且可以通过几乎三次旋转连续跟踪-大约是光学图像的两倍。在这个大的径向范围内的臂的连贯性挑战了目前的螺旋结构理论。我们认为，几种机制的组合，如M51与邻近星系NGC 5195的相互作用，迫使中央“酒吧”，或密度波的扭曲，需要产生观察到的结构。
MODELLING the structure and kinematics of spiral galaxies requires accurate maps of the mass-tracing stellar population. But this has hitherto been difficult because of dust obscuration and the presence of luminous young stars. To minimize the effects of dust and maximize sensitivity to the dominant stellar population, we have obtained K-band (2.2-μm) images of the nearby 'grand-design' spiral galaxy NGC5194 (M51). Our observations reveal remarkable dynamical structures not visible in conventional optical images. We find that the spiral arms extend significantly further towards the galaxy's centre than previously observed and can be traced continuously through almost three revolutions — roughly twice as far as with optical images. The coherence of the arms over this large radial range challenges current theories of spiral structure. We suggest that a combination of several mechanisms, such as the interaction of M51 with the neighbouring galaxy NGC5195, forcing by the central 'bar', or distortions from density waves, is required to generate the observed structure.