论文标题
估计银河光谱的灰尘衰减。 I.方法和测试
Estimating dust attenuation from galactic spectra. I. methodology and tests
论文作者
论文摘要
我们开发了一种方法来估计星系的尘埃衰减曲线，这些曲线是通过其光谱的完整光谱拟合的。从以前的研究中，我们通过对观察到的光谱和简单的恒星种群模型光谱进行移动平均方法来将小规模特征与大规模光谱形状分开。然后，通过拟合与SSP模型的S/L比的小尺度和大尺度（S/L）组件的观察到的比率来得出固有的无尘模型光谱。然后，通过将观察到的光谱与无尘模型频谱进行比较来确定选择性的灰尘衰减曲线。该方法的一个重要优点是，估计的灰尘衰减曲线与理论灰尘衰减曲线的形状无关。我们已经对一系列模拟光谱进行了一系列测试，其中涵盖了恒星年龄和金属性的广泛范围。我们表明，我们的方法能够准确地恢复输入灰尘衰减曲线，尽管精度略微取决于光谱的信噪比。我们已经将方法应用于许多带有漫画调查中明显的尘埃道的边缘星系，得出了灰尘衰减曲线和$ e（B-V）$地图，以及$ g $，$ r $和$ i $ $ bands中的无尘图像。这些星系在其原始图像中显示出明显的灰尘车道特征，在我们纠正了灰尘衰减的效果之后，它们在很大程度上消失了。这些星系的垂直亮度轮廓成为轴对称，并且可以通过为磁盘垂直结构提出的简单模型拟合。将估计的尘埃衰减曲线与三个常用模型曲线进行比较，我们发现Calzetti曲线提供了对星系内部区域的估计曲线的最佳描述，而银河系和SMC曲线则在外部区域更有效。
We develop a method to estimate the dust attenuation curve of galaxies from full spectral fitting of their optical spectra. Motivated from previous studies, we separate the small-scale features from the large-scale spectral shape, by performing a moving average method to both the observed spectrum and the simple stellar population model spectra. The intrinsic dust-free model spectrum is then derived by fitting the observed ratio of the small-scale to large-scale (S/L) components with the S/L ratios of the SSP models. The selective dust attenuation curve is then determined by comparing the observed spectrum with the dust-free model spectrum. One important advantage of this method is that the estimated dust attenuation curve is independent of the shape of theoretical dust attenuation curves. We have done a series of tests on a set of mock spectra covering wide ranges of stellar age and metallicity. We show that our method is able to recover the input dust attenuation curve accurately, although the accuracy depends slightly on signal-to-noise ratio of the spectra. We have applied our method to a number of edge-on galaxies with obvious dust lanes from the ongoing MaNGA survey, deriving their dust attenuation curves and $E(B-V)$ maps, as well as dust-free images in $g$, $r$, and $i$ bands. These galaxies show obvious dust lane features in their original images, which largely disappear after we have corrected the effect of dust attenuation. The vertical brightness profiles of these galaxies become axis-symmetric and can well be fitted by a simple model proposed for the disk vertical structure. Comparing the estimated dust attenuation curve with the three commonly-adopted model curves, we find that the Calzetti curve provides the best description of the estimated curves for the inner region of galaxies, while the Milky Way and SMC curves work better for the outer region.
