The Radius–Luminosity Relationship Depends on Optical Spectra in Active Galactic Nuclei

Abstract

The radius-luminosity (R Hβ -L 5100 ) relationship of active galactic nuclei (AGNs) established by the reverberation mapping (RM) observations has been widely used as a single-epoch black hole mass estimator in the research of large AGN samples. However, the recent RM campaigns discovered that the AGNs with high accretion rates show shorter time lags by factors of a few comparing with the predictions from the R Hβ -L 5100 relationship. The explanation of the shortened time lags has not been finalized yet. We collect 8 different singleepoch spectral properties to investigate how the shortening of the time lags correlate with those properties and to understand what is the origin of the shortened lags. We find that the flux ratio between Fe II and Hβ emission lines shows the most prominent correlation, thus confirm that accretion rate is the main driver for the shortened lags. In addition, we establish a new scaling relation including the relative strength of Fe II emission. This new scaling relation can provide less biased estimates of the black hole mass and accretion rate from the single-epoch spectra of AGNs.

Extreme Quasars as Distance Indicators in Cosmology

“…This second effect related to the disk anisotropy is especially severe if the line emitting gas is located close to the equatorial plane of the disk: in this case, following Wang et al (2014c), we expect a drastic reduction of the number of ionizing photons which would affect L 0 . Precisely quantifying the effect on line emission is not trivial, as it depends on the distribution of the line emitting gas around the equatorial plane of the disk, in terms of both angular and radial distance (Du and Wang, 2019), the black hole mass as well as the accretion disk model. Differences in the accretion disk SED are also expected from object to object because of different black hole spins (Wang et al, 2014b).…”

The spatially resolved broad line region of IRAS 09149−6206

“…For the Keplerian model, Table 3 shows that the best fitting value is 1. The black circles are the RM measurements collected from the literature by Du & Wang (2019), which mainly include data from Bentz et al (2013) and the SEAMBH campaign (see text for details). The blue squares are based on Hβ time lags from the SDSS-RM project Grier et al (2017b).…”

“…10, we compare the BLR radius of IRAS 09149−6206 and 3C 273 measured with GRAVITY to the radius-luminosity (R-L) relation of the RM results. Du & Wang (2019) provide the most recent collection of 75 Hβ time lags from various reverberation campaigns during the past two decades 6 . The collection primarily includes 41 AGNs from Bentz et al (2013) and 25 AGNs with high accretion rate from the SEAMBH campaign (Du et al 2014(Du et al , 2015(Du et al , 2016b(Du et al , 2018b.…”

“…Towards the high luminosity end of the R-L relation, the RM results also show large scatter and tend to drop below the bestfit relation from Bentz et al (2013), which we refer to as the "standard" R-L relation. A study of high accretion rate AGNs finds a deviation from this relation that is primarily driven by accretion rate (Du et al 2015;Du & Wang 2019). These authors proposed that the size of the BLR is reduced at high accretion rate due to the anisotropic emission of the "slim" accretion disk (Abramowicz et al 1988).…”

Quasars from LSST as dark energy tracers: first steps

“…Thus, the super-Eddington sources tend to be related with strong FeII emitters, and vice-versa. Based on this fact, Du and Wang (2019) and Yu et al (2020a) explored the possibility to decrease the scatter in the R Hβ −L 5100 relation using R FeII and thus skip the self-correlation presented byṀ c . They proposed a new radius-luminosity relation with the next form: log (R Hβ /lt-day)= α + β logL 5100 + γ R FeII .…”