The Seoul National University AGN monitoring project. II. BLR size and black hole mass of two AGNs

TL;DR

This study presents reverberation-mapping results for two luminous AGNs, measuring BLR sizes and black hole masses to test the high-luminosity end of the size-luminosity relation.

Contribution

First reverberation-mapping measurements for high-luminosity AGNs, extending the BLR size-luminosity relation to more luminous objects.

Findings

BLR sizes of 41.8 and 52.6 days in observed frame

Black hole masses of approximately 3.65 and 23.02 million solar masses

Results support the size-luminosity relation at high luminosities

Abstract

Active galactic nuclei (AGNs) show a correlation between the size of the broad line region (BLR) and the monochromatic continuum luminosity at 5100 \AA, allowing black hole mass estimation based on single-epoch spectra. However, the validity of the correlation is yet to be clearly tested for high-luminosity AGNs. We present the first reverberation-mapping results of the Seoul National University AGN monitoring program (SAMP), which is designed to focus on luminous AGNs for probing the high end of the size-luminosity relation. We report time lag measurements of two AGNs, namely, 2MASS J10261389+5237510 and SDSS J161911.24+501109.2, using the light curves obtained over a $\sim$1000 day period with an average cadence of $\sim$10 and $\sim$20 days, respectively for photometry and spectroscopy monitoring. Based on a cross-correlation analysis and H$\beta$ line width measurements, we determine the H$\beta$ lag as $41.8^{+4.9}_{-6.0}$ and $52.6^{+17.6}_{-14.7}$ days in the observed-frame, and black hole mass as $3.65^{+0.49}_{-0.57} \times 10^7 M_{\odot}$ and $23.02^{+7.81}_{-6.56} \times 10^7 M_{\odot}$, respectively for 2MASS J1026 and SDSS J1619.