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arXiv 1502.01347astro-ph.GA
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用分辨观测测量恒星形成:M33的测试实例

Measuring star formation with resolved observations: the test case of M33

M. Boquien, D. Calzetti, S. Aalto, A. Boselli, J. Braine, V. Buat, F. Combes, F. Israel, C. Kramer, S. Lord, M. Relano, E. Rosolowsky, G. Stacey, F. Tabatabaei,… 展开作者

M. Boquien, D. Calzetti, S. Aalto, A. Boselli, J. Braine, V. Buat, F. Combes, F. Israel, C. Kramer, S. Lord, M. Relano, E. Rosolowsky, G. Stacey, F. Tabatabaei, F. van der Tak, P. van der Werf, S. Verley, M. Xilouris

摘要:

上下文在局部尺度上测量恒星的形成对于约束恒星形成定律是很重要的。然而,目前尚不清楚恒星形成的测量是否以及如何受到观测星系的空间尺度的影响。目的。我们想了解的空间分辨恒星形成率(SFR)和其他直接相关的物理参数,如衰减的决定的分辨率的影响。方法.我们对附近的星系M33进行了多尺度、逐像素的研究。组装FUV,Halpha,8,24,70,和100微米的地图,我们系统地比较了各个波段的发射与各种SFR估计从33 pc到2084 pc的分辨率。结果我们已经发现,有很强的,规模依赖,差异高达3倍之间的单色SFR估计和Halpha+24微米。单个红外波段和SFR之间的比例因子显示出强烈的依赖于空间尺度和恒星形成的强度。最后,强烈的变化之间的差异变红的星云发射和恒星的连续性,这取决于特定的SFR(sSFR)和分辨率。在最精细的空间尺度上,在高sSFR下几乎没有差异红化。微分红化随sSFR的减小而增大。在粗空间尺度上,微分红化与星爆星系的正则值是一致的。结论.我们的研究结果证实,单色估计的SFR是不可靠的尺度小于1千秒差距。此外,本地校准高红移星系的扩展提出了非平凡的挑战,因为这些系统的属性可能知之甚少。

英文摘要:

Context. Measuring star formation at a local scale is important to constrain star formation laws. Yet, it is not clear whether and how the measure of star formation is affected by the spatial scale at which a galaxy is observed. Aims. We want to understand the impact of the resolution on the determination of the spatially resolved star formation rate (SFR) and other directly associated physical parameters such as the attenuation. Methods. We have carried out a multi-scale, pixel-by-pixel study of the nearby galaxy M33. Assembling FUV, Halpha, 8, 24, 70, and 100 micron maps, we have systematically compared the emission in individual bands with various SFR estimators from a resolution of 33 pc to 2084 pc. Results. We have found that there are strong, scale-dependent, discrepancies up to a factor 3 between monochromatic SFR estimators and Halpha+24 micron. The scaling factors between individual IR bands and the SFR show a strong dependence on the spatial scale and on the intensity of star formation. Finally, strong variations of the differential reddening between the nebular emission and the stellar continuum are seen, depending on the specific SFR (sSFR) and on the resolution. At the finest spatial scales, there is little differential reddening at high sSFR. The differential reddening increases with decreasing sSFR. At the coarsest spatial scales the differential reddening is compatible with the canonical value found for starburst galaxies. Conclusions. Our results confirm that monochromatic estimators of the SFR are unreliable at scales smaller than 1 kpc. Furthermore, the extension of local calibrations to high redshift galaxies presents non-trivial challenges as the properties of these systems may be poorly known.

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