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arXiv 2203.09540astro-ph.HEastro-ph.COastro-ph.GAastro-ph.IM
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AGN时间序列数据的LSST节奏策略评估

LSST Cadence Strategy Evaluations for AGN Time-series Data in Wide-Fast-Deep Field

Xinyue Sheng, Nicholas Ross, Matt Nicholl

摘要:

机器学习是一种很有前途的工具,可以从稀疏采样数据中重建时间序列现象,例如活动星系核(AGN)的变化。在这里,我们使用三个连续自回归移动平均(CARMA)表示AGN可变性-阻尼随机游走(DRW)和(过/欠)阻尼谐振子(DHO)-模拟10年AGN光变曲线,因为它们将出现在即将到来的维拉鲁宾天文台遗产空间和时间调查(LSST),并提供一个公共工具来生成这些任何调查节奏。我们调查活动星系核科学的五个建议的节奏策略LSST的主要宽快深(WFD)调查的影响。我们首次在天文学中应用一种新的随机递归神经网络(SRNN)算法从模拟LSST数据重建输入光变曲线,并提供一个度量来评估SRNN如何帮助恢复底层CARMA参数。我们发现,光变曲线重建是最敏感的观察季节之间的间隙的持续时间,和建议的节奏,那些改变过滤器之间的平衡,或避免在{g}-波段的长间隙执行更好。总的来说,SRNN是一种很有前途的手段来重建密集采样的活动星系核光变曲线和恢复DRW过程的长期结构函数(SF $_\infty$)相当不错。然而,我们发现,对于所有的节奏,CARMA/SRNN模型的斗争,以恢复去相关时间尺度($τ$),由于调查观察的长间隙。这可能表明在活动星系核变率科学中使用LSST WFD数据的主要局限性。

英文摘要:

Machine learning is a promising tool to reconstruct time-series phenomena, such as variability of active galactic nuclei (AGN), from sparsely-sampled data. Here we use three Continuous Auto-Regressive Moving Average (CARMA) representations of AGN variability -- the Damped Random Walk (DRW) and (over/under-)Damped Harmonic Oscillator (DHO) -- to simulate 10-year AGN light curves as they would appear in the upcoming Vera Rubin Observatory Legacy Survey of Space and Time (LSST), and provide a public tool to generate these for any survey cadence. We investigate the impact on AGN science of five proposed cadence strategies for LSST's primary Wide-Fast-Deep (WFD) survey. We apply for the first time in astronomy a novel Stochastic Recurrent Neural Network (SRNN) algorithm to reconstruct input light curves from the simulated LSST data, and provide a metric to evaluate how well SRNN can help recover the underlying CARMA parameters. We find that the light curve reconstruction is most sensitive to the duration of gaps between observing season, and that of the proposed cadences, those that change the balance between filters, or avoid having long gaps in the {g}-band perform better. Overall, SRNN is a promising means to reconstruct densely sampled AGN light curves and recover the long-term Structure Function of the DRW process (SF$_\infty$) reasonably well. However, we find that for all cadences, CARMA/SRNN models struggle to recover the decorrelation timescale ($τ$) due to the long gaps in survey observations. This may indicate a major limitation in using LSST WFD data for AGN variability science.

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