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arXiv 2104.07227astro-ph.GA
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用ALMA CO（2-1）数据对双棒星系NGC 3504的形态学和运动学分析

Morphological and Kinematical Analysis of the Double-barred Galaxy NGC 3504 Using ALMA CO (2-1) Data

Yu-Ting Wu, Alfonso Trejo, Daniel Espada, Yusuke Miyamoto

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Accepted for publication in MNRAS, 18 pages, 18 figures, 1 table
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摘要：

本文给出了双棒星系NGC 3504的ALMACO（2-1）数据。具有三倍高的角分辨率（~ 0.“8）与以前的研究相比，我们的观测揭示了一个内部分子气棒，一个核环和四个内部螺旋臂状结构。此外，CO的排放是明确的对齐外酒吧区的两个尘埃带，它们之间的形状和强度的差异。在观测区域（50“x57”）的总分子气体质量估计为$\sim 3.1\times 10^9 \, {\rm M}_{\odot}$，占恒星质量的17%。我们使用Kinemetron软件包来拟合速度场，发现圆周运动在$R= 0.3-0.8$ kpc处占主导地位，但径向运动在$R<0.3$ kpc和$R=1.0-2.5$ kpc处变得重要，这是由于内外杆的存在而预期的。最后，假设气体沿尘埃带在酒吧旋转框架，我们推导出的模式速度的外酒吧是$ 18\pm5$公里秒$^{-1}$千分之$^{-1}$，平均流动速度的两个尘埃带分别为165和221公里秒$^{-1}$，和总质量流入率沿尘埃带为12 M $_{\odot}$年$^{-1}$。我们的研究结果给出了一个新的例子，一个内部的气体酒吧在一个富含气体的双棒星系，并建议双棒星系的形成可能与这种气体结构的存在。

英文摘要：

We present results obtained from ALMA CO (2-1) data of the double-barred galaxy NGC 3504. With three times higher angular resolution (~ 0."8) than previous studies, our observations reveal an inner molecular gas bar, a nuclear ring, and four inner spiral arm-like structures in the central 1 kpc region. Furthermore, the CO emission is clearly aligned with the two dust lanes in the outer bar region, with differences in shape and intensity between them. The total molecular gas mass in the observed region (50"x57") is estimated to be $\sim 3.1\times 10^9 \, {\rm M}_{\odot}$, which is 17 per cent of the stellar mass. We used the Kinemetry package to fit the velocity field and found that circular motion strongly dominates at $R= 0.3-0.8$ kpc, but radial motion becomes important at $R<0.3$ kpc and $R=1.0-2.5$ kpc, which is expected due to the presence of the inner and outer bars. Finally, assuming that the gas moves along the dust lanes in the bar rotating frame, we derived the pattern speed of the outer bar to be $ 18\pm5$ km s$^{-1}$ kpc$^{-1}$, the average streaming velocities on each of the two dust lanes to be 165 and 221 km s$^{-1}$, and the total mass inflow rate along the dust lanes to be 12 M$_{\odot}$ yr$^{-1}$. Our results give a new example of an inner gas bar within a gas-rich double-barred galaxy and suggest that the formation of double-barred galaxies could be associated with the existence of such gas structures.

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