银盘倾角和分辨率对观测到的GMC性质和Larson标度关系的影响
Effects of Galactic Disc Inclination and Resolution on Observed GMC Properties and Larson's Scaling Relations
摘要：
随着ALMA使解决其他星系中的巨分子云（GMC）成为可能，量化测量GMC属性的观测偏差变得必要。通过对一个棒旋星系的流体动力学模拟，比较了位置-位置-位置空间（PPP）和观测位置-位置-速度空间（PPV）中形成的巨星系团的物理性质.我们评估了光盘倾斜度的影响：面对（PPV_face）和边缘（PPV_edge），和分辨率：1.5 pc与24 pc，对GMC属性和进一步的影响，使用拉森的缩放关系的质量半径和速度色散半径。低分辨率PPV数据是通过使用CASA软件包模拟ALMA周期3观测而生成的。结果表明，在两种分辨率下，PPP和PPV_face云的中值特性没有很大差异，但PPV_edge云偏离了这两者。当切换到较低但更真实的分辨率时，差异会被放大。这种差异可能导致维里参数对引力结合的测量结果相反，从而导致云的动力学状态。两个Larson标度关系的幂律指数从PPP、PPV_face到PPV_edge递减，并且从高分辨率到低分辨率递减。我们的结论是，这些关系并不完全是由潜在的物理起源，因此必须谨慎使用时，考虑环境的依赖性，动力学状态，和河外的CO到H2的转换因子的GMCs。
英文摘要：
With ALMA making it possible to resolve giant molecular clouds (GMCs) in other galaxies, it is becoming necessary to quantify the observational bias on measured GMC properties. Using a hydrodynamical simulation of a barred spiral galaxy, we compared the physical properties of GMCs formed in position-position-position space (PPP) to the observational position-position-velocity space (PPV). We assessed the effect of disc inclination: face-on (PPV_face) and edge-on (PPV_edge), and resolution: 1.5 pc versus 24 pc, on GMC properties and the further implications of using Larson's scaling relations for mass-radius and velocity dispersion-radius. The low-resolution PPV data are generated by simulating ALMA Cycle 3 observations using the CASA package. Results show that the median properties do not differ strongly between PPP and PPV_face under both resolutions, but PPV_edge clouds deviate from these two. The differences become magnified when switching to the lower, but more realistic resolution. The discrepancy can lead to opposite results for the virial parameter's measure of gravitational binding, and therefore the dynamical state of the clouds. The power-law indices for the two Larson's scaling relations decrease going from PPP, PPV_face to PPV_edge and decrease from high to low resolutions. We conclude that the relations are not entirely driven by the underlying physical origin and therefore have to be used with caution when considering the environmental dependence, dynamical state, and the extragalactic CO-to-H2 conversion factor of GMCs.
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