棒星系NGC253的NIR结构
The NIR structure of the barred galaxy NGC253 from VISTA
摘要：
我们使用VISTA望远镜获得的J和Ks波段图像作为科学验证的一部分，以量化棒状Sc星系NGC 253的恒星盘结构。从星系中心向外移动，我们发现明亮的1 kpc直径的核内有一个核环，然后是一个棒，一个半径为2.9 kpc的环。从Ks图像，我们得到一个新的措施，2.5千秒差距的酒吧的dprojected长度。从J-Ks图像中尘埃带的曲率得出的棒的强度是典型的弱棒。由棒的退投影长度，我们确定了共转半径（R_CR=3 kpc）和棒斑图速度（Omega_b = 61.3km/skpc），这提供了盘中高频结构与棒诱导的轨道共振之间的联系。核环位于内林德布拉德共振。第二个环没有共振起源，但它可能是合并残留物或在棒形成的中间阶段形成的瞬态结构。推断出的条形图速度将光盘内的外林德布拉德共振置于4.9千秒差距处，与HI表面密度的峰值处于相同的径向范围内。NGC 253的星盘有一个向下弯曲的轮廓，在R~9.3 kpc处有一个断裂，这相当于内盘尺度长度的3倍。我们讨论了恒星形成效率阈值的证据，作为一个可能的解释，在大半径的表面亮度分布的陡峭梯度。近红外测光揭示了NGC 253星盘对中心棒的动力学响应。棒的形成可能与合并事件有关，合并事件决定了大半径恒星和气体的截断以及盘外缘的扰动。
英文摘要：
[abridged] We used J and Ks band images acquired with the VISTA telescope as part of the science verification to quantify the structures in the stellar disk of the barred Sc galaxy NGC253. Moving outward from the galaxy center, we find a nuclear ring within the bright 1 kpc diameter nucleus, then a bar, a ring with 2.9 kpc radius. From the Ks image we obtain a new measure of the deprojected length of the bar of 2.5 kpc. The bar's strength, as derived from the curvature of the dust lanes in the J-Ks image, is typical of weak bars. From the deprojected length of the bar, we establish the corotation radius (R_CR=3 kpc) and bar pattern speed (Omega_b = 61.3 km /s kpc), which provides the connection between the high-frequency structures in the disk and the orbital resonances induced by the bar. The nuclear ring is located at the inner Lindblad resonance. The second ring does not have a resonant origin, but it could be a merger remnant or a transient structure formed during an intermediate stage of the bar formation. The inferred bar pattern speed places the outer Lindblad resonance within the optical disk at 4.9 kpc, in the same radial range as the peak in the HI surface density. The disk of NGC253 has a down-bending profile with a break at R~9.3 kpc, which corresponds to about 3 times the scale length of the inner disk. We discuss the evidence for a threshold in star formation efficiency as a possible explanation of the steep gradient in the surface brightness profile at large radii. The NIR photometry unveils the dynamical response of the NGC253 stellar disk to its central bar. The formation of the bar may be related to the merger event that determined the truncation of stars and gas at large radii and the perturbation of the disk's outer edge.
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