EVIDENCE OF ONGOING RADIAL MIGRATION IN NGC 6754: AZIMUTHAL VARIATIONS OF THE GAS PROPERTIES
EVIDENCE OF ONGOING RADIAL MIGRATION IN NGC 6754: AZIMUTHAL VARIATIONS OF THE GAS PROPERTIES
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DOI：
10.3847/2041-8205/830/2/l40
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发表时间：
2016-10
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通讯作者：
L. Sánchez-Menguiano;S. S'anchez;D. Kawata;L. Chemin;I. P'erez;T. Ruiz-Lara;P. S'anchez-Bl'azquez;L. Galbany;J. Anderson;R. Grand;I. Minchev;F. G'omez
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作者：
L. Sánchez-Menguiano;S. S'anchez;D. Kawata;L. Chemin;I. P'erez;T. Ruiz-Lara;P. S'anchez-Bl'azquez;L. Galbany;J. Anderson;R. Grand;I. Minchev;F. G'omez
了解盘状星系中螺旋结构的本质是星系天文学中一个主要的、尚未解决的问题。然而，理论工作提出了新的可测试的预测，随着仪器仪表的最新发展，这些预测的检测变得可行。特别是，沿旋臂的流运动预计会在给定的星系半径处引起星系化学成分的方位角变化。本文利用VLT/MUSE数据分析了NGC 6754的气体含量，表征了其二维化学成分和Hα视线速度分布。我们发现，NGC 6754旋臂的后缘（前缘）显示出在很大半径范围内，富金属（贫）气体流运动的特征：切向慢，径向向外（切向快，径向向内）。这些结果首次提供了气体径向运移的直接证据。我们将我们的结果与n体圆盘模拟中的气体行为进行了比较，显示出螺旋形态特征，在每个半径处以与气体相似的速度旋转，与观察到的趋势很好地一致。这表明NGC 6754中的旋臂特征可能是短暂的，并且在很大的半径范围内与气体相似地旋转。
Understanding the nature of spiral structure in disk galaxies is one of the main, and still unsolved, questions in galactic astronomy. However, theoretical works are proposing new testable predictions whose detection is becoming feasible with recent development in instrumentation. In particular, streaming motions along spiral arms are expected to induce azimuthal variations in the chemical composition of a galaxy at a given galactic radius. In this Letter, we analyze the gas content in NGC 6754 with VLT/MUSE data to characterize its 2D chemical composition and Hα line of sight velocity distribution. We find that the trailing (leading) edge of the NGC 6754 spiral arms show signatures of tangentially slower, radially outward (tangentially faster, radially inward) streaming motions of metal-rich (poor) gas over a large range of radii. These results show direct evidence of gas radial migration for the first time. We compare our results with the gas behavior in an N-body disk simulation showing spiral morphological features rotating with a similar speed as the gas at every radius, in good agreement with the observed trend. This indicates that the spiral arm features in NGC 6754 may be transient and rotate similarly as the gas does at a large range of radii.