On the Significance of Absorption Features in HST/COS Data
On the Significance of Absorption Features in HST/COS Data
复制标题
论HST/COS数据中吸收特征的意义
DOI：
10.1086/667392
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发表时间：
2012
影响因子：
3.5
通讯作者：
J. Green
中科院分区：
文献类型：
--
作者：
B. Keeney;C. Danforth;J. Stocke;K. France;J. Green
我们提出了经验尺度关系的意义，在中等分辨率，远紫外光谱与宇宙起源光谱仪（COS）检测到的吸收功能。这些关系正确地解释了COS线扩展函数的扩展翼和数据的非泊松噪声特性，我们首次描述了这些特性，并预测了当波长和多普勒参数在λ = 1150-1750 nm和B > 10 km s-1的范围内时，偏离经验行为≤ 5%的极限等效宽度。我们已经测试了一些共同添加的算法，并发现在所有情况下，个人曝光的噪声属性比共同添加的数据更接近泊松理想。对于未分辨的吸收线，共同添加的数据的限制等效宽度比从具有相同信噪比的单独曝光获得的限制等效宽度大6%。该比率与分辨吸收线的b值成比例，当B = 150 km s-1时，共同添加的数据具有比单独曝光大25%的极限等效宽度。
We present empirical scaling relations for the significance of absorption features detected in medium-resolution, far-UV spectra obtained with the Cosmic Origins Spectrograph (COS). These relations properly account for both the extended wings of the COS line-spread function and the non-Poissonian noise properties of the data, which we characterize for the first time, and predict limiting equivalent widths that deviate from the empirical behavior by ≤ 5% when the wavelength and Doppler parameter are in the ranges of λ = 1150–1750 Å and b > 10 km s-1. We have tested a number of co-addition algorithms and find the noise properties of individual exposures to be closer to the Poissonian ideal than are co-added data in all cases. For unresolved absorption lines, limiting equivalent widths for co-added data are 6% larger than limiting equivalent widths derived from individual exposures with the same signal-to-noise ratio. This ratio scales with b-value for resolved absorption lines, with co-added data having a limiting equivalent width that is 25% larger than individual exposures when b ≈ 150 km s-1.