HALOGAS：NGC 3198中的面外气体
HALOGAS: Extraplanar gas in NGC 3198
摘要：
我们提出了新的，深HI观测的螺旋星系NGC 3198的分析，作为HALOGAS（Westerbork氢吸积在LOCAL GALAXIES）调查的一部分，主要目的是调查的存在，数量，形态和运动学的面外气体。我们提出了NGC 3198的HI观测模型：与观测数据立方体最匹配的模型具有厚盘的特征，其标度高度为~3 kpc，HI质量约为总HI质量的15%;这个厚盘的旋转速度也随着高度（滞后）的降低而降低7-15 km/s/kpc（尽管有很大的不确定性）。这种面外气体是在NGC 3198中首次发现的。从径向上看，这种气体似乎稍微超出了活跃的恒星形成星系（由H α辐射跟踪），但它并不比恒星盘的外部更暗的部分径向延伸。与以前的研究相比，由于灵敏度的提高，我们跟踪旋转曲线到更大的半径。我们模型的旋转曲线的框架MOND（修改后的牛顿动力学），我们确认，在允许的距离范围内，我们假设，适合质量是适度的，在这个星系，但新的外部部分的解释令人满意的方式。
英文摘要：
We present the analysis of new, deep HI observations of the spiral galaxy NGC 3198, as part of the HALOGAS (Westerbork Hydrogen Accretion in LOcal GAlaxieS) survey, with the main aim of investigating the presence, amount, morphology and kinematics of extraplanar gas. We present models of the HI observations of NGC 3198: the model that matches best the observed data cube features a thick disk with a scale height of ~3 kpc and an HI mass of about 15% of the total HI mass; this thick disk also has a decrease in rotation velocity as a function of height (lag) of 7-15 km/s/kpc (though with large uncertainties). This extraplanar gas is detected for the first time in NGC 3198. Radially, this gas appears to extend slightly beyond the actively star-forming body of the galaxy (as traced by the Halpha emission), but it is not more radially extended than the outer, fainter parts of the stellar disk. Compared to previous studies, thanks to the improved sensitivity we trace the rotation curve out to larger radii. We model the rotation curve in the framework of MOND (Modified Newtonian Dynamics) and we confirm that, with the allowed distance range we assumed, fit quality is modest in this galaxy, but the new outer parts are explained in a satisfactory way.
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