M33中的巨大分子云：它们对动力学摩擦敏感吗？
Giant molecular clouds in M 33: are they susceptible to dynamical friction?
摘要：
M33中的大部分巨分子云（GMC）都与螺旋状的气体臂（细丝）相连，但内部2 kpc区域除外，在那里臂与GMC之间的联系消失了（参见Tosaki et al. 2011）。我们检查它是否可能是由于动力摩擦使云减速而引起的。利用该星系的半解析模型，计算了盘平面内不同初始星系心距离处不同质量巨星系团的动力学。我们证明，动力学摩擦可能会真正改变GMC的轨道在中央2 kpc大小的区域。然而，在这种情况下，GMC的典型寿命应该接近或大于$10^8$ ~yr，这比通常接受的值大。
英文摘要：
Most of giant molecular clouds (GMCs) in M 33 are connected with spiral-like gaseous arms (filaments) with the exception of the inner 2 kpc region where the link between the arms and GMCs disappears (see Tosaki et al. 2011). We check whether it may be caused by the dynamic friction retarding the clouds. Using semi-analytical model for this galaxy we calculate the dynamics of GMCs of different masses situated at different initial galactocentric distances in the disk plane. We demonstrate that the dynamical friction may really change the orbits of GMCs in the central 2 kpc-size region. However in this case the typical lifetimes of GMCs should be close to or greater than $10^8$~yr, which is larger than the usually accepted values.
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