用MILES-II进行演化恒星布居合成。定标太阳和α增强模型
Evolutionary stellar population synthesis with MILES - II. Scaled-solar and α-enhanced models
摘要：
我们提出了模型，预测具有不同[α/Fe]丰度的2.51 Å（FWHM）的老年和中老年恒星星族的光谱。这些模型是基于MILES库和理论恒星光谱的修正。该模型采用最近的[Mg/Fe]测定MILES星和BaSTI标度的太阳和α增强等时线。我们计算模型的一套IMF的形状和斜率，涵盖了广泛的年龄/金属丰度范围。使用BaSTI，我们还计算“基本模型”匹配银河丰度模式。我们证实，α增强模型显示出相对于标度太阳模型向蓝$\sim$ 4500的通量过剩，这随着年龄和金属丰度的增加。我们还证实了[MgFe]和[MgFe]'指数都是[α/Fe]不敏感的。我们发现高阶Balmer线对[α/Fe]的敏感性存在于它们的伪连续体中，较窄的折射率定义产生较低的敏感性。我们证实，α增强模型产生蓝（红）光谱范围内的蓝（红）色。为了匹配大质量星系的光学颜色，我们需要α增强和底部重的IMF。比较球状星团线强度与我们的预测相匹配的[Mg/Fe]测定从他们的个别恒星。我们得到了很好的拟合全光谱和指数的星系与不同的[α/Fe]。使用数千个SDSS星系光谱，我们得到了一个线性关系之间的代理的丰度，[Z $_{\rm Mg}$/Z $_{\rm Fe}$] $_{\rm SS(BaSTI)}$，使用单独的缩放太阳模型和[Mg/Fe]与不同的丰度模型（[Mg/Fe]= 0.59 [Z $_{\rm Mg}$/Z $_{\rm Fe}$] $_{\rm SS(BaSTI)}$）。最后，我们提供了一个用户友好的，基于Web的设施，它允许不同的IMF和[α/Fe]的复合人群（www.example.com）。
英文摘要：
We present models that predict spectra of old- and intermediate-aged stellar populations at 2.51Å (FWHM) with varying [α/Fe] abundance. The models are based on the MILES library and on corrections from theoretical stellar spectra. The models employ recent [Mg/Fe] determinations for the MILES stars and BaSTI scaled-solar and α-enhanced isochrones. We compute models for a suite of IMF shapes and slopes, covering a wide age/metallicity range. Using BaSTI, we also compute "base models" matching The Galactic abundance pattern. We confirm that the α-enhanced models show a flux excess with respect to the scaled-solar models blue-ward $\sim$4500Å, which increases with age and metallicity. We also confirm that both [MgFe] and [MgFe]' indices are [α/Fe]-insensitive. We show that the sensitivity of the higher order Balmer lines to [α/Fe] resides in their pseudo-continua, with narrower index definitions yielding lower sensitivity. We confirm that the α-enhanced models yield bluer (redder) colours in the blue (red) spectral range. To match optical colours of massive galaxies we require both α-enhancement and a bottom-heavy IMF. The comparison of Globular Cluster line-strengths with our predictions match the [Mg/Fe] determinations from their individual stars. We obtain good fits to both full spectra and indices of galaxies with varying [α/Fe]. Using thousands of SDSS galaxy spectra we obtain a linear relation between a proxy for the abundance, [Z$_{\rm Mg}$/Z$_{\rm Fe}$]$_{\rm SS(BaSTI)}$, using solely scaled-solar models and the [Mg/Fe] derived with models with varying abundance ([Mg/Fe]=0.59[Z$_{\rm Mg}$/Z$_{\rm Fe}$]$_{\rm SS(BaSTI)}$). Finally we provide a user-friendly, web-based facility, which allows composite populations with varying IMF and [α/Fe] ( http://miles.iac.es ).
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