Improving the Flux Calibration in Reverberation Mapping by Spectral Fitting: Application to the Seyfert Galaxy MCG--6-30-15

• Published in: arXiv.org 2016-08
• Main Authors: Hu, Chen, Wang, Jian-Min, Ho, Luis C, Jin-Ming, Bai, Yan-Rong, Li, Du, Pu, Kai-Xing, Lu
• Format: Article
• Language: English
• Subjects: Active galactic nuclei; Calibration; Flux; Galaxies; Light curve; Mapping; Seyfert galaxies; Spectra; Time lag; Virial coefficients
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.1608.06869

We propose a method for the flux calibration of reverberation mapping spectra based on accurate measurement of [O III] \(\lambda 5007\) emission by spectral fitting. The method can achieve better accuracy than the traditional method of van Groningen & Wanders (1992), allowing reverberation mapping measurements for object with variability amplitudes as low as \(\sim\) 5%. As a demonstration, we reanalyze the data of the Seyfert 1 galaxy MCG--6-30-15 taken from the 2008 campaign of the Lick AGN Monitoring Project, which previously failed to obtain a time lag for this weakly variable object owing to a relatively large flux calibration uncertainty. We detect a statistically significant rest-frame time lag of \(6.38_{-2.69}^{+3.07}\) days between the H\(\beta\) and \(V\)-band light curves. Combining this lag with FWHM(H\(\beta\)) = \(1933\pm81\) \(\rm km~s^{-1}\) and a virial coefficient of \(f\) = 0.7, we derive a virial black hole mass of \(3.26_{-1.40}^{+1.59}\times10^6\) \(M_{\odot}\), which agrees well with previous estimates by other methods.