The Hα Broadband Photometric Reverberation Mapping of Four Seyfert 1 Galaxies

• Published in: The Astrophysical journal Vol. 949; no. 1; pp. 22 - 39
• Main Authors: Ma, Qinchun, Wu, Xue-Bing, Gu, Huapeng, Wen, Yuhan, Fu, Yuming
• Format: Journal Article
• Language: English
• Published: Philadelphia The American Astronomical Society 01.05.2023; IOP Publishing
• Subjects: Accretion; Accretion disks; Active galactic nuclei; Astrophysics; Black holes; Broadband; Chi-square test; Consistency; Emission lines; Galaxies; H alpha line; Mapping; Photometry; Reliability analysis; Reverberation; Reverberation mapping; Seyfert galaxies; Stars & galaxies
• ISSN: 0004-637X; 1538-4357
• DOI: 10.3847/1538-4357/acc4c1

Abstract Broadband photometric reverberation mapping (PRM) has been investigated for active galactic nuclei (AGNs) in recent years, but mostly on accretion disk continuum RM. Due to the small fraction of broad emission lines in the broad band, PRM for emission lines is very challenging. Here, we present an ICCF-Cut method for broadband PRM to obtain the H α broad-line lag and apply it to four Seyfert 1 galaxies: MCG+08-11-011, NGC 2617, 3C 120, and NGC 5548. All of them have high-quality broadband lightcurves with daily/subdaily cadences, which enable us to extract H α lightcurves from the line band by subtracting the contributions from the continuum and host galaxy. Their extracted H α lightcurves are compared with the lagged continuum-band lightcurves, as well as the lagged H β lightcurves obtained by spectroscopic RM (SRM) at the same epochs. The consistency of these lightcurves and the comparison with the SRM H β lags provide support for the H α lags of these AGNs, in a range from 9 to 19 days, obtained by the ICCF-Cut, JAVELIN, and χ 2 methods. The simulations for evaluating the reliability of the H α lags and the comparisons between the SRM H β and PRM H α lags indicate that the consistency of the ICCF-Cut, JAVELIN, and χ 2 results can ensure the reliability of the derived H α lags. These methods may be used to estimate the broad-line region sizes and black hole masses of a large sample of AGNs in large multi-epoch, high-cadence photometric surveys such as LSST in the future.