arXiv 1811.045902018-11-12astro-ph.GA

Messier 33恒星形成的多尺度研究

A Multi-Scale Study of Star Formation in Messier 33

E. C. Elson, S. Z. Kam, L. Chemin, C. Carignan, T. H. Jarrett

备注：: 16 pages, 13 figures, accepted for publication in MNRAS
DOI：: 10.1093/mnras/sty3091

摘要：

本文对本星系群Scd星系M 33的基于12 $μ$ m辐射的单色星形成率（SFR）估算值与基于远紫外和24 $μ$ m辐射组合的总SFR估算值之间的关系进行了多尺度研究。我们表明，12 $μ$ m排放量是一个线性估计的总SFR的空间尺度从782 PC下降到49 PC，在几乎四个量级的SFR。因此，这些结果扩展到亚千秒差距的长度尺度从其他研究的全球长度尺度的类似结果。我们使用高分辨率HI和$^{12}\mathrm{CO}(J=2-1)$图像集从文献中比较恒星形成的中性气体。对于整个范围内的长度尺度，我们发现12个$μ$ m衍生的SFR表面密度和中性气体表面密度之间定义良好的幂律关系。对于H $_\mathrm{2}$气体组分，几乎所有的相关性都是线性的。没有发现其他作者报道的M33恒星形成定律在小尺度上崩溃的证据。我们发现，在M 33的平均恒星形成效率大约是$10^{-9}$年$^{-1}$，它保持不变，以巨大的分子云长度尺度。Toomre和剪切为基础的模型的恒星形成阈值不准确占恒星形成活动的内部盘的M 33。最后，我们清楚地表明，HI饱和极限的$\approx 9$ M $_{\odot}$ PC $^{-2}$在文献中报道的其他星系不是一个固有的属性M 33 -它是系统地介绍了作为一个人工制品的空间平滑的数据。

英文摘要：

For the Local Group Scd galaxy M 33 this paper presents a multi-scale study of the relationship between the monochromatic star formation rate (SFR) estimator based on 12 $μ$m emission and the total SFR estimator based on a combination of far-ultraviolet and 24 $μ$m emission. We show the 12 $μ$m emission to be a linear estimator of total SFR on spatial scales from 782 pc down to 49 pc, over almost four magnitudes in SFR. These results therefore extend to sub-kpc length scales the analogous results from other studies for global length scales. We use high-resolution HI and $^{12}\mathrm{CO}(J=2-1)$ image sets from the literature to compare the star formation to the neutral gas. For the full range of length scales we find well-defined power-law relationships between 12 $μ$m-derived SFR surface densities and neutral gas surface densities. For the H$_\mathrm{2}$ gas component almost all correlations are consistent with being linear. No evidence is found for a breakdown in the star formation law at small length scales in M 33 reported by other authors. We show that the average star formation efficiency in M 33 is roughly $10^{-9}$ yr$^{-1}$ and that it remains constant down to giant molecular cloud length scales. Toomre and shear-based models of the star formation threshold are shown to inaccurately account for the star formation activity in the inner disc of M 33. Finally, we clearly show that the HI saturation limit of $\approx 9$ M$_{\odot}$ pc$^{-2}$ reported in the literature for other galaxies is not an intrinsic property of M 33 - it is systematically introduced as an artefact of spatially smoothing the data.

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