极环星系的分子含量
Molecular content of polar-ring galaxies
摘要：
我们已经在21个新的形态确定的极环星系（其中9个是运动学证实）的样本中搜索了CO线，这些星系是Moiseev和合作者在银河动物园项目中进行广泛搜索获得的。极环星系（Polar-ring galaxies，PRG）是一类独特的天体，追踪星系质量组合中的特殊事件：它们可以通过星系相互作用和合并形成，也可以通过宇宙细丝的吸积形成。此外，它们使三维空间中的暗物质晕研究成为可能。极环本身是一个富含气体的子系统，预计分子气体会在那里形成，并形成新的恒星。在21个PRG样本中，我们检测到了5个富含CO的系统，现在可以用更高的空间分辨率进行跟踪。它们的平均分子质量为9.4 × 10**9 Mo，平均气体分数为重子质量的27%，范围从15%到43%，这意味着它们只是吸积了大量的气体。在速度-星等图中检测到的物体的位置偏离了正常螺旋的塔利-费舍尔关系，正如已经发现的PRG。这项工作是我们的多波长项目的一部分，以确定极环星系的详细形态和动力学，通过数值模型测试其形成方案，并推断其暗物质含量和3D形状。
英文摘要：
We have searched for CO lines in a sample of 21 new morphologically determined polar-ring galaxies (of which nine are kinematically confirmed), obtained from a wide search in the Galaxy Zoo project by Moiseev and collaborators. Polar-ring galaxies (PRG) are a unique class of objects, tracing special episodes in the galaxy mass assembly: they can be formed through galaxy interaction and merging, but also through accretion from cosmic filaments. Furthermore, they enable the study of dark matter haloes in three dimensions. The polar ring itself is a sub-system rich in gas, where molecular gas is expected, and new stars are formed. Among the sample of 21 PRG, we have detected five CO-rich systems, that can now be followed up with higher spatial resolution. Their average molecular mass is 9.4 10**9 Mo, and their average gas fraction is 27% of their baryonic mass, with a range from 15 to 43%, implying that they just accreted a large amount of gas. The position of the detected objects in the velocity-magnitude diagram is offset from the Tully-Fisher relation of normal spirals, as was already found for PRGs. This work is part of our multi-wavelength project to determine the detailed morphology and dynamics of polar-ring galaxies, test through numerical models their formation scenario, and deduce their dark matter content and 3D-shape.
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