SUPERCAL: CROSS-CALIBRATION OF MULTIPLE PHOTOMETRIC SYSTEMS TO IMPROVE COSMOLOGICAL MEASUREMENTS WITH TYPE Ia SUPERNOVAE
SUPERCAL: CROSS-CALIBRATION OF MULTIPLE PHOTOMETRIC SYSTEMS TO IMPROVE COSMOLOGICAL MEASUREMENTS WITH TYPE Ia SUPERNOVAE
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DOI：
10.1088/0004-637x/815/2/117
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发表时间：
2015-08
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通讯作者：
D. Scolnic;S. Casertano;A. Riess;A. Riess;A. Rest;E. Schlafly;R. Foley;D. Finkbeiner;C. Tang;W. Burgett;K. Chambers;P. Draper;H. Flewelling;K. Hodapp;M. Huber;N. Kaiser;R. Kudritzki;E. Magnier;N. Metcalfe;C. Stubbs
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作者：
D. Scolnic;S. Casertano;A. Riess;A. Riess;A. Rest;E. Schlafly;R. Foley;D. Finkbeiner;C. Tang;W. Burgett;K. Chambers;P. Draper;H. Flewelling;K. Hodapp;M. Huber;N. Kaiser;R. Kudritzki;E. Magnier;N. Metcalfe;C. Stubbs
当前利用Ia型超新星观测的宇宙学分析将超新星样本结合起来，以扩大红移范围，使其超出单个样本的范围，并增加总体样本量。不同超新星样本之间不均匀的光度校准是宇宙学参数估计中最大的系统性不确定因素之一。为了将这些不同的样本置于一个统一的系统中，目前的分析利用哈勃太空望远镜系统对一小部分非常明亮的流量标准星的观测。我们提出一种互补的方法，称为“超级校准（Supercal）”，在该方法中，我们利用每个系统中次级标准星的测量值，将其与泛星1号（PS1）系统中相同恒星的测量值进行比较，并确定每个系统相对于PS1的偏差，从而将所有超新星观测置于一个单一、一致的光度系统中。PS1已经观测了天空的3π立体角，其相对校准精度优于5毫星等（对于约15 < griz < 21星等），这使其成为一个理想的参考系统。我们利用这一过程重新校准了以下超新星样本所进行的光学观测：PS1、超新星遗迹巡天、斯隆数字巡天、卡内基超新星项目以及哈佛 - 史密松天体物理中心1 - 4。我们测量到在各种光学波段平均有10毫星等的差异，最大可达35毫星等。我们发现，对这些差异进行校正会使暗能量状态方程参数w的恢复值平均改变2.6%。这一变化大约是当前对w的统计约束大小的一半。这种效应的大小在很大程度上取决于低红移巡天中B - V校准的误差。超级校准方法将使未来的分析能够将过去的样本与校准最佳的样本联系起来。
Current cosmological analyses, which use Type Ia supernova observations, combine supernova (SN) samples to expand the redshift range beyond that of a single sample and increase the overall sample size. The inhomogeneous photometric calibration between different SN samples is one of the largest systematic uncertainties of the cosmological parameter estimation. To place these different samples on a single system, analyses currently use observations of a small sample of very bright flux standards on the Hubble Space Telescope system. We propose a complementary method, called “Supercal,” in which we use measurements of secondary standards in each system, compare these to measurements of the same stars in the Pan-STARRS1 (PS1) system, and determine the offsets for each system relative to PS1, placing all SN observations on a single, consistent photometric system. PS1 has observed 3π of the sky and has a relative calibration of better than 5 mmag (for ∼15 < griz < 21 mag), making it an ideal reference system. We use this process to recalibrate optical observations taken by the following SN samples: PS1, Supernova Legacy Survey, SDSS, CSP, and CfA1-4. We measure discrepancies on average of 10 mmag, but up to 35 mmag, in various optical passbands. We find that correcting for these differences changes the recovered values for the dark energy equation of state parameter, w, by an average of 2.6%. This change is roughly half the size of current statistical constraints on w. The size of this effect strongly depends on the error in the B − V calibration of the low-z surveys. The Supercal method will allow future analyses to tie past samples to the best calibrated sample.