合成恒星光度学- I。宽带系统的一般考虑和新变换
Synthetic Stellar Photometry - I. General considerations and new transformations for broad-band systems
摘要：
在对合成测光的主要概念进行教学性介绍之后，Johnson-Reynolds，2 MASS和HST-ACS/WFC 3测光系统中的颜色和测辐射热校正由MARCS合成通量产生，用于各种[Fe/H]和[alpha/Fe]组合，几乎任何红化E（B-V）< 0.7的值。的成功和失败的模式通量在复制观测到的震级突出显示。总体而言，现存的合成通量预测相当现实的宽带颜色和测热校正，特别是在光学和较长的波长：进一步改善的预测蓝色和紫外光谱区域等待使用的流体动力学模型的微湍流速度不被视为一个自由参数。我们展示了颜色-星等图（CMD）的形态如何随[Fe/H]和[alpha/Fe]的不同值而变化;特别是，由于CMD中伴随的循环和摆动，合适的颜色组合可以很容易地区分红巨星分支和具有不同[alpha/Fe]的较低主序星群。我们还提供计算机程序来生成合成测辐射热校正表以及在其中进行插值的例程。这些颜色-Teff-金属丰度的关系可以用来转换不同化学成分的等时线到假设观测到的红化值的各种带通，从而绕过了不同光谱类型的恒星的恒定颜色过剩的标准假设。我们还展示了如何这样的假设可能会导致显着的系统误差。本研究中提出的MARCS变换有望为我们理解在球状星团中发现的多个恒星星族提供重要的约束（例如，低主序星的颜色被预测强烈地依赖于[α/Fe]）和那些位于银河系核球附近或核球内的恒星。
英文摘要：
After a pedagogical introduction to the main concepts of synthetic photometry, colours and bolometric corrections in the Johnson-Cousins, 2MASS, and HST-ACS/WFC3 photometric systems are generated from MARCS synthetic fluxes for various [Fe/H] and [alpha/Fe] combinations, and virtually any value of reddening E(B-V) < 0.7. The successes and failures of model fluxes in reproducing the observed magnitudes are highlighted. Overall, extant synthetic fluxes predict quite realistic broad-band colours and bolometric corrections, especially at optical and longer wavelengths: further improvements of the predictions for the blue and ultraviolet spectral regions await the use of hydrodynamic models where the microturbulent velocity is not treated as a free parameter. We show how the morphology of the colour-magnitude diagram (CMD) changes for different values of [Fe/H] and [alpha/Fe]; in particular, how suitable colour combinations can easily discriminate between red giant branch and lower main sequence populations with different [alpha/Fe], due to the concomitant loops and swings in the CMD. We also provide computer programs to produce tables of synthetic bolometric corrections as well as routines to interpolate in them. These colour-Teff-metallicity relations may be used to convert isochrones for different chemical compositions to various bandpasses assuming observed reddening values, thus bypassing the standard assumption of a constant colour excess for stars of different spectral type. We also show how such an assumption can lead to significant systematic errors. The MARCS transformations presented in this study promise to provide important constraints on our understanding of the multiple stellar populations found in globular clusters (e.g., the colours of lower main sequence stars are predicted to depend strongly on [alpha/Fe]) and of those located towards/in the Galactic bulge.
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