skip to main content

Title: OzDES Reverberation Mapping Programme: the first Mg  ii lags from 5 yr of monitoring
ABSTRACT Reverberation mapping is a robust method to measure the masses of supermassive black holes outside of the local Universe. Measurements of the radius–luminosity (R−L) relation using the Mg ii emission line are critical for determining these masses near the peak of quasar activity at z ≈ 1−2, and for calibrating secondary mass estimators based on Mg ii that can be applied to large samples with only single-epoch spectroscopy. We present the first nine Mg ii lags from our 5-yr Australian Dark Energy Survey reverberation mapping programme, which substantially improves the number and quality of Mg ii lag measurements. As the Mg ii feature is somewhat blended with iron emission, we model and subtract both the continuum and iron contamination from the multiepoch spectra before analysing the Mg ii line. We also develop a new method of quantifying correlated spectroscopic calibration errors based on our numerous, contemporaneous observations of F-stars. The lag measurements for seven of our nine sources are consistent with both the H β and Mg ii R−L relations reported by previous studies. Our simulations verify the lag reliability of our nine measurements, and we estimate that the median false positive rate of the lag measurements is $4{{\ \rm per\ cent}}$.
Authors:
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; more » ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; « less
Award ID(s):
1814440
Publication Date:
NSF-PAR ID:
10348513
Journal Name:
Monthly Notices of the Royal Astronomical Society
Volume:
507
Issue:
3
Page Range or eLocation-ID:
3771 to 3788
ISSN:
0035-8711
Sponsoring Org:
National Science Foundation
More Like this
  1. ABSTRACT 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 to perform multiple-line lag measurements in 3C 120. We find the H γ, He ii λ4686, H β, and He i λ5876 lags of $\tau _{\text{cen}} = 18.8_{-1.0}^{+1.3}$, $2.7_{-0.8}^{+0.7}$, $21.2_{-1.0}^{+1.6}$, and $16.9_{-1.1}^{+0.9}$ d, respectively, relative to the V-band continuum. Using the measured lag and rms velocity width of the H β emission line, we determine the mass of the black hole for 3C 120 to be $M=(6.3^{+0.5}_{-0.3})\times 10^7\, (f/5.5)$ M⊙. 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 β line, 25 d at line centre decreasing to 17 d in the line wings at ±4000 km s−1. We also investigate the inter-band continuum lags in 3C 120 and find that they are generally consistent with τ ∝ λ4/3 as predicted from a geometrically thin, optically thick accretion disc. From the continuum lags,more »we measure the best-fitting value τ0 = 3.5 ± 0.2 d at $\lambda _{\rm 0} = 5477\, \mathring{\rm A}$. It implies a disc size a factor of 1.6 times larger than prediction from the standard disc model with L/LEdd = 0.4. This is consistent with previous studies in which larger than expected disc sizes were measured.« less
  2. Abstract In order to constrain the size of the optical continuum emission region in the dwarf Seyfert 1 galaxy NGC 4395 through reverberation mapping, we carried out high-cadence photometric monitoring in the griz filter bands on two consecutive nights in 2022 April using the four-channel MuSCAT3 camera on the Faulkes Telescope North at Haleakalā Observatory. Correlated variability across the griz bands is clearly detected, and the r -, i -, and z -band light curves show lags of 7.72 − 1.09 + 1.01 , 14.16 − 1.25 + 1.22 , and 20.78 − 2.09 + 1.99 minutes with respect to the g band when measured using the full-duration light curves. When lags are measured for each night separately, the Night 2 data exhibit lower cross-correlation amplitudes and shorter lags than the Night 1 light curves. Using the full-duration lags, we find that the lag–wavelength relationship is consistent with the τ ∝ λ 4/3 dependence found for more luminous active galactic nuclei. Combining our results with continuum lags measured for other objects, the lag between g and z band scales with optical continuum luminosity as τ gz ∝ L 0.56±0.05 , similar to the scaling of broad-line region size with luminosity,more »reinforcing recent evidence that diffuse continuum emission from the broad-line region may contribute substantially to optical continuum variability and reverberation lags.« less
  3. Abstract We carried out spectroscopic monitoring of 21 low-redshift Seyfert 1 galaxies using the Kast double spectrograph on the 3 m Shane telescope at Lick Observatory from 2016 April to 2017 May. Targeting active galactic nuclei (AGNs) with luminosities of λ L λ (5100 Å) ≈ 10 44 erg s −1 and predicted H β lags of ∼20–30 days or black hole masses of 10 7 –10 8.5 M ⊙ , our campaign probes luminosity-dependent trends in broad-line region (BLR) structure and dynamics as well as to improve calibrations for single-epoch estimates of quasar black hole masses. Here we present the first results from the campaign, including H β emission-line light curves, integrated H β lag times (8–30 days) measured against V -band continuum light curves, velocity-resolved reverberation lags, line widths of the broad H β components, and virial black hole mass estimates (10 7.1 –10 8.1 M ⊙ ). Our results add significantly to the number of existing velocity-resolved lag measurements and reveal a diversity of BLR gas kinematics at moderately high AGN luminosities. AGN continuum luminosity appears not to be correlated with the type of kinematics that its BLR gas may exhibit. Follow-up direct modeling of this datamore »set will elucidate the detailed kinematics and provide robust dynamical black hole masses for several objects in this sample.« less
  4. Abstract We present accretion-disk structure measurements from UV–optical reverberation mapping (RM) observations of a sample of eight quasars at 0.24 < z < 0.85. Ultraviolet photometry comes from two cycles of Hubble Space Telescope monitoring, accompanied by multiband optical monitoring by the Las Cumbres Observatory network and Liverpool Telescopes. The targets were selected from the Sloan Digital Sky Survey Reverberation Mapping project sample with reliable black hole mass measurements from H β RM results. We measure significant lags between the UV and various optical griz bands using JAVELIN and CREAM methods. We use the significant lag results from both methods to fit the accretion-disk structure using a Markov Chain Monte Carlo approach. We study the accretion disk as a function of disk normalization, temperature scaling, and efficiency. We find direct evidence for diffuse nebular emission from Balmer and Fe ii lines over discrete wavelength ranges. We also find that our best-fit disk color profile is broadly consistent with the Shakura & Sunyaev disk model. We compare our UV–optical lags to the disk sizes inferred from optical–optical lags of the same quasars and find that our results are consistent with these quasars being drawn from a limited high-lag subset of themore »broader population. Our results are therefore broadly consistent with models that suggest longer disk lags in a subset of quasars, for example, due to a nonzero size of the ionizing corona and/or magnetic heating contributing to the disk response.« less
  5. We present new near-infrared VLTI/GRAVITY interferometric spectra that spatially resolve the broad Br γ emission line in the nucleus of the active galaxy IRAS 09149−6206. We use these data to measure the size of the broad line region (BLR) and estimate the mass of the central black hole. Using an improved phase calibration method that reduces the differential phase uncertainty to 0.05° per baseline across the spectrum, we detect a differential phase signal that reaches a maximum of ∼0.5° between the line and continuum. This represents an offset of ∼120  μ as (0.14 pc) between the BLR and the centroid of the hot dust distribution traced by the 2.3 μ m continuum. The offset is well within the dust sublimation region, which matches the measured ∼0.6 mas (0.7 pc) diameter of the continuum. A clear velocity gradient, almost perpendicular to the offset, is traced by the reconstructed photocentres of the spectral channels of the Br γ line. We infer the radius of the BLR to be ∼65  μ as (0.075 pc), which is consistent with the radius–luminosity relation of nearby active galactic nuclei derived based on the time lag of the H β line from reverberation mapping campaigns. Our dynamicalmore »modelling indicates the black hole mass is ∼1 × 10 8   M ⊙ , which is a little below, but consistent with, the standard M BH – σ * relation.« less