从GALEX到斯皮策的椭圆的颜色
Colors of Ellipticals from GALEX to Spitzer
摘要：
本文提出了一种利用形态学和孤立度方法选取大样本局部椭圆星系的多色测光方法。该样本使用GALEX、SDSS、2 MASS和Spitzer的数据，以涵盖NUV、ugri、JHK和3.6 μ m滤光片。使用2 MASS J滤波器中定义的半光孔径的各种双色图从颜色到颜色都非常一致，这意味着定义为红色的星系在一种颜色中总是红色的。与球状星团颜色的比较表明，椭圆星系不是由单一的年龄、单一的金属丰度组成的（例如，[Fe/H]）恒星星族，但需要使用化学富集情景的多金属丰度模型。这样一个模型足以解释双色图和所有颜色的颜色-星等关系，只使用金属丰度作为一个变量，在一个单独的12 Gyrs恒星星族没有证据的恒星年龄小于10 Gyrs。与星系颜色相匹配的[Fe/H]值在-0.5到+0.4之间，比从Lick/IDS线强度系统研究中推导出的人口特征要高得多（也更老），表明星系颜色和线指数值之间的不一致性，原因不明。NUV的颜色有不寻常的行为信号的上升和下降的紫外线上升与椭圆光度。具有BHB轨迹的模型可以再现这种行为，表明UV上升严格地说是金属丰度效应。
英文摘要：
Multi-color photometry is presented for a large sample of local ellipticals selected by morphology and isolation. The sample uses data from GALEX, SDSS, 2MASS and Spitzer to cover the filters NUV, ugri, JHK and 3.6mum. Various two-color diagrams, using the half-light aperture defined in the 2MASS J filter, are very coherent from color to color, meaning that galaxies defined to be red in one color are always red in other colors. Comparison to globular cluster colors demonstrates that ellipticals are *not* composed of a single age, single metallicity (e.g., [Fe/H]) stellar population, but require a multi-metallicity model using a chemical enrichment scenario. Such a model is sufficient to explain two-color diagrams and the color-magnitude relations for all colors using only metallicity as a variable on a solely 12 Gyrs stellar population with no evidence of stars younger than 10 Gyrs. The [Fe/H] values that match galaxy colors range from -0.5 to +0.4, much higher (and older) than population characteristics deduced from Lick/IDS line-strength system studies, indicating an inconsistency between galaxy colors and line indices values for reasons unknown. The NUV colors have unusual behavior signaling the rise and fall of the UV upturn with elliptical luminosity. Models with BHB tracks can reproduce this behavior indicating the UV upturn is strictly a metallicity effect.
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