Messier 31：I的宽视场高分辨率HI镶嵌图不透明原子气体与恒星形成率密度
A Wide-field High Resolution HI Mosaic of Messier 31: I. Opaque Atomic Gas and Star Formation Rate Density
摘要：
我们对M31进行了深宽场HI成像调查，在95 x48 kpc区域内达到了约50 pc和2 km/s的最大分辨率。在100 pc分辨率下，对25 km/s宽的光谱特征的HI质量和亮度灵敏度分别为1500M_Sun和0.28K。我们的研究揭示了无处不在的HI自不透明度的功能，在第一个实例中，可辨别的峰值HI亮度温度的图像中的附加局部最小值。局部极小值组织成复杂的长度超过千秒差距，特别是与螺旋臂功能的前缘。就像在银河系中一样，自不透明特征与CO（1-0）发射只有零星的对应关系。在许多情况下，对柱密度的局部不透明度校正超过一个数量级，并且在通常假设可忽略不计的自不透明度下，从积分亮度推断出的原子气体质量在全球范围内增加了30%。不透明原子气体的自旋温度首先从20 K增加到60 K，半径增加到12 kpc，但超过25 kpc后又下降到20 K。我们已经扩展了解决恒星形成法下降到物理尺度的面积和质量比以前可能的小一个数量级以上。总气体质量和恒星形成率密度之间的关系比分子质量的关系紧密得多，并且在斜率和归一化方面都与M51在500 pc分辨率下分子主导的圆盘中发现的幂律指数1.56完全一致。当气体质量密度低于约5 M_Sun/pc ^2时，恒星形成速率密度会下降，这可能代表了在云质量约为5 × 10^4 M_Sun时大质量恒星形成的真正局部阈值。
英文摘要：
We have undertaken a deep, wide-field HI imaging survey of M31, reaching a maximum resolution of about 50 pc and 2 km/s across a 95x48 kpc region. The HI mass and brightness sensitivity at 100 pc resolution for a 25 km/s wide spectral feature is 1500 M_Sun and 0.28 K. Our study reveals ubiquitous HI self-opacity features, discernible in the first instance as filamentary local minima in images of the peak HI brightness temperature. Local minima are organized into complexes of more than kpc length and are particularly associated with the leading edge of spiral arm features. Just as in the Galaxy, there is only patchy correspondence of self-opaque features with CO(1-0) emission. Localized opacity corrections to the column density exceed an order of magnitude in many cases and add globally to a 30% increase in the atomic gas mass over that inferred from the integrated brightness under the usual assumption of negligible self-opacity. Opaque atomic gas first increases from 20 to 60 K in spin temperature with radius to 12 kpc but then declines again to 20 K beyond 25 kpc. We have extended the resolved star formation law down to physical scales more than an order of magnitude smaller in area and mass than has been possible previously. The relation between total-gas-mass- and star-formation-rate-density is significantly tighter than that with molecular-mass and is fully consistent in both slope and normalization with the power law index of 1.56 found in the molecule-dominated disk of M51 at 500 pc resolution. Below a gas-mass-density of about 5 M_Sun/pc^2, there is a down-turn in star-formation-rate-density which may represent a real local threshold for massive star formation at a cloud mass of about 5x10^4 M_Sun.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
