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Register a new userThe Mass of the Black Hole in the Quasar PG 2130+099
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We present the results of a recent reverberation-mapping campaign undertaken to improve measurements of the radius of the broad line region and the central black hole mass of the quasar PG 2130+099. Cross correlation of the 5100 angstrom continuum and H-beta emission-line light curves yields a time lag of 22.9 (+4.4 - 4.3) days, corresponding to a central black hole mass MBH= 3.8 (+/- 1.5) x 10^7 Msun. This value supports the notion that previous measurements yielded an incorrect lag. We re-analyzed previous datasets to investigate the possible sources of the discrepancy and conclude that previous measurement errors were apparently caused by a combination of undersampling of the light curves and long-term secular changes in the H-beta emission-line equivalent width. With our new measurements, PG 2130+099 is no longer an outlier in either the R-L or the MBH-Sigma relationships.
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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.
In order to investigate the dependence of quasar variability on fundamental physical parameters like black hole mass, we have matched quasars from the QUEST1 Variability Survey with broad-lined objects from the Sloan Digital Sky Survey. The matched sample contains approximately 100 quasars, and the Sloan spectra are used to estimate black hole masses and bolometric luminosities. Variability amplitudes are measured from the QUEST1 light curves. We find that black hole mass correlates with several measures of the variability amplitude at the 99% significance level or better. The correlation does not appear to be caused by obvious selection effects inherent to flux-limited quasar samples, host galaxy contamination or other well-known correlations between quasar variability and luminosity/redshift. We evaluate variability as a function of rest-frame time lag using structure functions, and find further support for the variability--black hole mass correlation. The correlation is strongest for time lags of the order a few months up to the QUEST1 maximum temporal resolution of approximately 2 years, and may provide important clues for understanding the long-standing problem of the origin of quasar optical variability. We discuss whether our result is a manifestation of a relation between characteristic variability timescale and black hole mass, where the variability timescale is typical for accretion disk thermal timescales, but find little support for this. Our favoured explanation is that more massive black holes have larger variability amplitudes, and we highlight the need for larger samples with more complete temporal sampling to test the robustness of this result.
We use the microlensing variability observed for nine gravitationally lensed quasars to show that the accretion disk size at 2500 Angstroms is related to the black hole mass by log(R_2500/cm) = (15.6+-0.2) + (0.54+-0.28)log(M_BH/10^9M_sun). This scaling is consistent with the expectation from thin disk theory (R ~ M_BH^(2/3)), but it implies that black holes radiate with relatively low efficiency, log(eta) = -1.29+-0.44 + log(L/L_E) where eta=L/(Mdot c^2). These sizes are also larger, by a factor of ~3, than the size needed to produce the observed 0.8 micron quasar flux by thermal radiation from a thin disk with the same T ~ R^(-3/4) temperature profile. More sophisticated disk models are clearly required, particularly as our continuing observations improve the precision of the measurements and yield estimates of the scaling with wavelength and accretion rate.
In order to investigate the dependence of quasar optical-UV variability on fundamental physical parameters like black hole mass, we have matched quasars from the QUEST1 variability survey with broad-lined objects from the SDSS. Black hole masses and bolometric luminosities are estimated from Sloan spectra, and variability amplitudes from the QUEST1 light curves. Long-term variability amplitudes (rest-frame time scales 0.5--2 yrs) are found to correlate with black hole mass at the 99% significance level or better. This means that quasars with larger black hole masses have larger percentage flux variations. Partial rank correlation analysis shows that the correlation cannot explained by obvious selection effects inherent to flux-limited samples. We discuss whether the correlation is a manifestation of a relation between BH mass and accretion disk thermal time scales, or if it is due to changes in the optical depth of the accretion disk with black hole mass. Perhaps the most likely explanation is that the more massive black holes are starving, and produce larger flux variations because they do not have a steady inflow of gaseous fuel.
The evolution of galaxies is connected to the growth of supermassive black holes in their centers. During the quasar phase, a huge luminosity is released as matter falls onto the black hole, and radiation-driven winds can transfer most of this energy back to the host galaxy. Over five different epochs, we detected the signatures of a nearly spherical stream of highly ionized gas in the broadband X-ray spectra of the luminous quasar PDS 456. This persistent wind is expelled at relativistic speeds from the inner accretion disk, and its wide aperture suggests an effective coupling with the ambient gas. The outflows kinetic power larger than 10^46 ergs per second is enough to provide the feedback required by models of black hole and host galaxy co-evolution.
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