Space Telescope and Optical Reverberation Mapping ("STORM")

Calibrated spectra and models are provided for NGC 5548 from HST/COS observations in the Space Telescope and Optical Reverberation Mapping (STORM) Campaign. The STORM campaign used HST/COS, Swift, Chandra and ground-based facilities in a six-month long reverberation-mapping experiment during 2014. HST observations were made in single-orbit COS visits approximately daily from 2014 February 1 through July 27. Of the 179 scheduled visits, 171 observations were executed successfully. In each visit, the team used the G130M and G160M gratings to observe the UV spectrum over the range 1153—1796 Angstroms in four separate exposures. Exposure times were selected to provide S/N > 100 when measured over velocity bins of ~500 km/s. During each visit, we obtained two 200-second exposures with G130M centered at 1291 Angstroms and 1327 Angstroms, and two 590-second exposures with G160M centered at 1600 Angstroms and 1623 Angstroms. As described in De Rosa et al. (2015) the team customized the calibrations of these spectra to improve the wavelength calibration, the S/N with better flat fields, and more accurate and repeatable flux calibrations. These reprocessed spectra obtained with the various central wavelength and FPPOS settings were then combined into single spectra for G130M and G160M for each individual observation.

The team have also modeled these UV spectra of NGC 5548 to correct for intervening absorption and to deblend the individual emission lines. These spectral models, described by Kriss et al. (2019) are based on merged G130M and G160M spectra for each observation that have been binned by 4 pixels (half a resolution element). Using the modeled spectra, the team produce spectra where absorption intrinsic to NGC 5548 and in the intervening interstellar medium of the Milky Way has been replaced by their emission model to remove the absorption features. The models themselves consist of 91 components. Finally, modeled continuum fluxes, deblended emission line fluxes, and the strengths of absorption lines intrinsic to NGC 5548, as tabulated in Kriss et al. (2019) are collected here as well.

本数据集提供了空间望远镜与光学反响映射（STORM）计划中，哈勃空间望远镜/宇宙起源光谱仪（HST/COS）对NGC 5548的观测所得校准光谱与模型。该STORM计划于2014年开展为期六个月的反响映射实验，使用了HST/COS、斯威夫特（Swift）、钱德拉（Chandra）以及地面观测设施。2014年2月1日至7月27日期间，研究团队大致每日开展单次轨道的COS观测任务，累计计划观测179次，实际成功执行171次。每次观测中，团队使用G130M与G160M光栅对1153—1796埃波段的紫外光谱进行四次独立曝光。曝光时长的选取原则为：在约500 km/s的速度分档下测量时，信噪比（S/N）大于100。每次观测中，研究团队以1291埃与1327埃为中心，使用G130M光栅完成两次200秒曝光；并以1600埃与1623埃为中心，使用G160M光栅完成两次590秒曝光。正如De Rosa等人（2015）所述，团队针对这些光谱的校准流程进行了定制优化，以提升波长校准精度、通过优化平场校正改善信噪比，并实现更精准且可重复的流量校准。针对不同中心波长与FPPOS设置所获取的经重新处理的光谱，随后被整合为单次观测对应的G130M与G160M单张光谱。

研究团队还对NGC 5548的这批紫外光谱进行建模，以校正居间吸收效应并分离单条发射谱线。Kriss等人（2019）所描述的这批光谱模型，基于每次观测中合并得到的G130M与G160M光谱，且已按4个像素（即半个分辨率单元）进行分箱处理。借助该光谱模型，研究团队生成了新的光谱：其中NGC 5548自身的吸收特征以及银河系居间星际介质的吸收特征，均被对应的发射模型替代，以消除吸收谱线特征。该模型本身包含91个组成分量。最终，本数据集同时收录了Kriss等人（2019）中列出的建模连续谱流量、分离得到的发射线流量，以及NGC 5548自身的吸收线强度数据。