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Register a new userEvidence for Two Distinct Broad-Line Regions from Reverberation Mapping of PG 0026+129
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Chen Hu
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We report on the results of a new spectroscopic monitoring campaign of the quasar PG 0026+129 at the Calar Alto Observatory 2.2m telescope from July 2017 to February 2020. Significant variations in the fluxes of the continuum and broad-emission lines, including H$beta$ and He II, were observed in the first and third years, and clear time lags between them are measured. The broad H$beta$ line profile consists of two Gaussian components: an intermediate-width H$beta_{rm IC}$ with a full width at half-maximum (FWHM) of 1964$pm$18 $rm km~s^{-1}$ and another very broad H$beta_{rm VBC}$ with a FWHM of 7570$pm$83 $rm km~s^{-1}$. H$beta_{rm IC}$ has long time lags of $sim$40--60 days in the rest frame, while H$beta_{rm VBC}$ shows nearly zero time delay with respect to the optical continuum at 5100 AA. The velocity-resolved delays show consistent results: lags of $sim$30--50 days at the core of the broad H$beta$ line and roughly zero lags at the wings. H$beta_{rm IC}$ has a redshift of $sim$400 $rm km~s^{-1}$ which seems to be stable for nearly 30 years by comparing with archived spectra, and may originate from an infall. The root mean square (rms) spectrum of H$beta_{rm VBC}$ shows a double-peaked profile with brighter blue peak and extended red wing in the first year, which matches the signature of a thin disk. Both the double-peaked profile and the near-zero lag suggest that H$beta_{rm VBC}$ comes from a region associated with the part of the accretion disc that emits the optical continuum. Adopting the FWHM (in the rms spectrum) and the time lag measured for the total H$beta$ line, and a virial factor of 1.5, we obtain a virial mass of $2.89_{-0.69}^{+0.60} times10^7 M_{odot}$ for the central black hole in this quasar.
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As one of the most interesting Seyfert 1 galaxies, PG 2130+099 has been the target of several reverberation mapping (RM) campaigns over the years. However, its measured broad H$beta$ line responses have been inconsistent, with time lags of $sim$200 days, $sim$25 days, and $sim$10 days being reported for different epochs while its optical luminosity changed no more than 40%. To investigate this issue, we conducted a new RM-campaign with homogenous and high cadence (about $sim$3 days) for two years during 2017--2019 to measure the kinematics and structure of the ionized gas. We successfully detected time lags of broad H$beta$, He II, He I, and Fe II lines with respect to the varying 5100AA continuum, revealing a stratified structure that is likely virialized with Keplerian kinematics in the first year of observations, but an inflow kinematics of the broad-line region from the second year. With a central black hole mass of $0.97_{-0.18}^{+0.15}times 10^7~M_{odot}$, PG 2130+099 has an accretion rate of $10^{2.1pm0.5}L_{rm Edd}c^{-2}$, where $L_{rm Edd}$ is the Eddington luminosity and $c$ is speed of light, implying that it is a super-Eddington accretor and likely possesses a slim, rather than thin, accretion disk. The fast changes of the ionization structures of the three broad lines remain puzzling.
A detailed analysis of the data from a high sampling rate, multi-month reverberation mapping campaign, undertaken primarily at MDM Observatory with supporting observations from telescopes around the world, reveals that the Hbeta emission region within the broad line regions (BLRs) of several nearby AGNs exhibit a variety of kinematic behaviors. While the primary goal of this campaign was to obtain either new or improved Hbeta reverberation lag measurements for several relatively low luminosity AGNs (presented in a separate work), we were also able to unambiguously reconstruct velocity-resolved reverberation signals from a subset of our targets. Through high cadence spectroscopic monitoring of the optical continuum and broad Hbeta emission line variations observed in the nuclear regions of NGC 3227, NGC 3516, and NGC 5548, we clearly see evidence for outflowing, infalling, and virialized BLR gas motions, respectively.
We report the results of a multi-year spectroscopic and photometric monitoring campaign of two luminous quasars, PG~0923+201 and PG~1001+291, both located at the high-luminosity end of the broad-line region (BLR) size-luminosity relation with optical luminosities above $10^{45}~{rm erg~s^{-1}}$. PG~0923+201 is for the first time monitored, and PG~1001+291 was previously monitored but our campaign has a much longer temporal baseline. We detect time lags of variations of the broad H$beta$, H$gamma$, Fe {sc ii} lines with respect to those of the 5100~{AA} continuum. The velocity-resolved delay map of H$beta$ in PG~0923+201 indicates a complicated structure with a mix of Keplerian disk-like motion and outflow, and the map of H$beta$ in PG~1001+291 shows a signature of Keplerian disk-like motion. Assuming a virial factor of $f_{rm BLR}=1$ and FWHM line widths, we measure the black hole mass to be $118_{-16}^{+11}times 10^7 M_{odot}$ for PG~0923+201 and $3.33_{-0.54}^{+0.62}times 10^7 M_{odot}$ for PG~1001+291. Their respective accretion rates are estimated to be $0.21_{-0.07}^{+0.06} times L_{rm Edd},c^{-2}$ and $679_{-227}^{+259}times L_{rm Edd},c^{-2}$, indicating that PG~0923+201 is a sub-Eddington accretor and PG~1001+291 is a super-Eddington accretor. While the H$beta$ time lag of PG~0923+201 agrees with the size-luminosity relation, the time lag of PG~1001+291 shows a significant deviation, confirming that in high-luminosity AGN the BLR size depends on both luminosity and Eddington ratio. Black hole mass estimates from single AGN spectra will be over-estimated at high luminosities and redshifts if this effect is not taken into account.
We carried out photometric and spectroscopic observations of the well-studied broad-line radio galaxy 3C 120 with the Las Cumbres Observatory (LCO) global robotic telescope network from 2016 December to 2018 April as part of the LCO AGN Key Project on Reverberation Mapping of Accretion Flows. Here, we present both spectroscopic and photometric reverberation mapping results. We used the interpolated cross-correlation function (ICCF) to perform multiple-line lag measurements in 3C 120. We find the H$gamma$, He II $lambda 4686$, H$beta$ and He I $lambda 5876$ lags of $tau_{text{cen}} = 18.8_{-1.0}^{+1.3}$, $2.7_{-0.8}^{+0.7}$, $21.2_{-1.0}^{+1.6}$, and $16.9_{-1.1}^{+0.9}$ days respectively, relative to the V-band continuum. Using the measured lag and rms velocity width of the H$beta$ emission line, we determine the mass of the black hole for 3C 120 to be $M=left(6.3^{+0.5}_{-0.3}right)times10^7,(f/5.5)$ M$_odot$. Our black hole mass measurement is consistent with similar previous studies on 3C 120, but with small uncertainties. In addition, velocity-resolved lags in 3C 120 show a symmetric pattern across the H$beta$ line, 25 days at line centre decreasing to 17 days in the line wings at $pm4000$ km s$^{-1}$. We also investigate the inter-band continuum lags in 3C 120 and find that they are generally consistent with $tauproptolambda^{4/3}$ as predicted from a geometrically-thin, optically-thick accretion disc. From the continuum lags, we measure the best fit value $tau_{rm 0} = 3.5pm 0.2$ days at $lambda_{rm 0} = 5477$A. It implies a disc size a factor of $1.6$ times larger than prediction from the standard disc model with $L/L_{rm Edd} = 0.4$. This is consistent with previous studies in which larger than expected disc sizes were measured.
Reverberation results of a flat spectrum radio quasar PKS 1510-089 are presented from 8.5-years long spectroscopic monitoring carried out in 9 observing seasons between December 2008 to June 2017 at Steward Observatory. Optical spectra show strong H$beta$, H$gamma$, and Fe II emission lines overlaying on a blue continuum. All the continuum and emission line light curves show significant variability with a fractional root-mean-square variation of $37.30pm0.06$% ($f_{5100}$), $11.88pm0.29$% (H$beta$) and $9.61pm0.71$% (H$gamma$), however, along with thermal radiation from accretion disk non-thermal emission from jet also contribute to $f_{5100}$. Several methods of time series analysis (ICCF, DCF, von Neumann, Bartels, JAVELIN, $chi^2$) are used to measure lag between continuum and line light curves. The observed frame BLR size is found to be $61.1^{+4.0}_{-3.2}$ ($64.7^{+27.1}_{-10.6}$) light-days for H$beta$ (H$gamma$). Using $sigma_{mathrm{line}}$ of $1262pm247$ km s$^{-1}$ measured from the rms spectrum, the black hole mass of PKS 1510-089 is estimated to be $5.71^{+0.62}_{-0.58} times 10^{7} M_{odot}$.
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