Smooth dark spiral arms in the flocculent galaxy NGC2841
Smooth dark spiral arms in the flocculent galaxy NGC2841
复制标题
絮状星系NGC2841中光滑的暗旋臂
作者：
D. Block;B. Elmegreen;R. Wainscoat
螺旋星系旋臂的光学图像总是显示出在星际气体和尘埃的脊中形成的大质量蓝色恒星。这些现象在“宏大设计”星系中尤其引人注目，在这些星系中，恒星的位置受到螺旋密度波的影响。相比之下，许多星系有一个“絮状”的外观，在可见光波段没有明显的螺旋结构的证据。在这里，我们报告的原型絮状星系NGC 2841的红外观测，揭示了一个显着的系统长，暗旋臂。这些臂由灰尘聚集而成;它们被灰尘散射的光隐藏在光学波长处。将气体和尘埃组织成这些暗臂的机制目前尚不清楚;这些臂可能是高度剪切的致密云，或者它们可能对应于星际介质中由细长的中央隆起驱动的密度波，这不会影响稳定的恒星盘。
OPTICAL images of the arms of spiral galaxies invariably show massive blue stars forming in ridges of interstellar gas and dust1. These are particularly striking in 'grand-design' galaxies, in which the stellar positions are influenced by spiral density waves1. By contrast, many galaxies have a 'flocculent' appearance, with no obvious evidence of spiral structure at visible wavelengths. Here we report infrared observations of the prototype flocculent galaxy NGC2841, which reveal a remarkable system of long, dark spiral arms. These arms arise from concentrations of dust; they are hidden at optical wavelengths by light scattered from the dust. The mechanism that has organized the gas and dust into these dark arms is at present unclear; the arms might be highly sheared dense clouds, or they might correspond to density waves in the interstellar medium driven by an elongated central bulge, which would not affect the stable stellar disk.