NGC 4632：藏着极环的星系

2023年9月13日

NGC 4632: Galaxy with a Hidden Polar Ring
Credit: Jayanne English (U. Manitoba), Nathan Deg (Queen’s University) & WALLABY Survey, CSIRO/ASKAP, NAOJ/Subaru Telescope; Text: Jayanne English (U. Manitoba)

Explanation: Galaxy NGC 4632 hides a secret from optical telescopes. It is surrounded by a ring of cool hydrogen gas orbiting at 90 degrees to its spiral disk. Such polar ring galaxies have previously been discovered using starlight. However, NGC 4632 is among the first in which a radio telescope survey revealed a polar ring. The featured composite image combines this gas ring, observed with the highly sensitive ASKAP telescope, with optical data from the Subaru telescope. Using virtual reality, astronomers separated out the gas in the main disk of the galaxy from the ring, and the subtle color gradient traces its orbital motion. Why do polar rings exist? They could be material pulled from one galaxy as it gravitationally interacts with a companion. Or hydrogen gas flows along the filaments of the cosmic web and accretes into a ring around a galaxy, some of which gravitationally contracts into stars.

Tomorrow’s picture: open space

NGC 4632：藏着极环的星系
影像提供: Jayanne English (U. Manitoba), Nathan Deg (Queen’s University) & WALLABY Survey, CSIRO/ASKAP, NAOJ/Subaru Telescope; 文稿: Jayanne English (U. Manitoba)

说明: 对光学望远镜来说，星系NGC 4632藏着一个看不见的秘密。这个星系的周围，环绕着一圈与它的螺旋星系盘垂直的冰冷氢气环。先前用以发现这种极环星系的手段，是靠观测它所发出的星光。然而，NGC 4632是透过射电望远镜观测所发现的极环星系之一。这幅主题影像，组合了高灵敏ASKAP望远镜所见的这圈气体环及昴宿望远镜的光学数据。利用虚拟实境的技术，天文学家把星系盘和极环的气体分拆出来，并用细致的颜色梯度追踪极环气体的轨道运动。为何会有极环呢？它们可能是星系与其伴星系发生重力互扰时，从该星系拉伸出来的物质。或者是沿着宇宙网细丝流动的氢气，受到星系的吸积聚集成环拱星系的环，其中有部分气体在引力作用下塌缩形成恒星。

明日的图片: open space