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OzDES Reverberation Mapping of Active Galactic Nuclei: Final Data Release, Black-Hole Mass Results, & Scaling Relations

H. McDougall, T. M. Davis, Z. Yu, P. Martini, C. Lidman, U. Malik, A. Penton, G. F. Lewis, B. E. Tucker, B. J. S. Pope, S. Allam, F. Andrade-Oliveira, J. Asorey, D. Bacon, S. Bocquet, D. Brooks, A. Carnero Rosell, D. Carollo, A. Carr, J. Carretero, T. Y. Cheng, L. N. da Costa, M. E. da Silva Pereira, J. De Vicente, H. T. Diehl, P. Doel, S. Everett, J. García-Bellido, K. Glazebrook, D. Gruen, G. Gutierrez, K. Herner, S. R. Hinton, D. L. Hollowood, D. J. James, A. G. Kim, K. Kuehn, S. Lee, M. March, J. L. Marshall, J. Mena-Fernández, F. Menanteau, R. Miquel, J. Myles, R. L. C. Ogando, A. Porredon, E. Sanchez, D. Sanchez Cid, R. Sharp, M. Smith, E. Suchyta, M. E. C. Swanson, C. To, D. L. Tucker, A. R. Walker, N. Weaverdyck

Abstract

Over the last decade, the Australian Dark Energy (OzDES) collaboration has used Reverberation Mapping to measure the masses of high redshift supermassive black holes. Here we present the final review and analysis of this OzDES reverberation mapping campaign. These observations use 6-7 years of photometric and spectroscopic observations of 735 Active Galactic Nuclei (AGN) in the redshift range $z\in [0.13, 3.85]$ and bolometric luminosity range $\log_{10}(L_{\mathrm{bol}})\in [44.3, 47.5] \mathrm{erg/s}$. Both photometry and spectra are observed in visible wavelengths, allowing for the physical scale of the AGN broad line region to be estimated from reverberations of the Hbeta, MgII and CIV emission lines. We successfully use reverberation mapping to constrain the masses of 62 super-massive black holes, and combine with existing data to fit a power law to the lag-luminosity relation for the Hbeta and MgII lines with a scatter of $\sim0.25$ dex, the tightest and most robust fit yet identified. We fit a similarly constrained relation for CIV, resolving a tension with the low luminosity literature AGN by accounting for selection effects. We also examine the impact of emission line width and luminosity (related to accretion rate) in reducing the scatter of these scaling relationships and find no significant improvement over the lag-only approach for any of the three lines. Using these relations, we further estimate the masses and accretion rates of 246 AGN. We also use these relations to estimate the relative sizes of the Hbeta, MgII and CIV emitting regions, and find evidence that the MgII emission may occur further out than Hbeta. In short, we provide a comprehensive benchmark of high redshift AGN reverberation mapping at the close of this most recent generation of surveys, including light curves, time-delays, and the most reliable radius-luminosity relations to date.

OzDES Reverberation Mapping of Active Galactic Nuclei: Final Data Release, Black-Hole Mass Results, & Scaling Relations

Abstract

Over the last decade, the Australian Dark Energy (OzDES) collaboration has used Reverberation Mapping to measure the masses of high redshift supermassive black holes. Here we present the final review and analysis of this OzDES reverberation mapping campaign. These observations use 6-7 years of photometric and spectroscopic observations of 735 Active Galactic Nuclei (AGN) in the redshift range and bolometric luminosity range . Both photometry and spectra are observed in visible wavelengths, allowing for the physical scale of the AGN broad line region to be estimated from reverberations of the Hbeta, MgII and CIV emission lines. We successfully use reverberation mapping to constrain the masses of 62 super-massive black holes, and combine with existing data to fit a power law to the lag-luminosity relation for the Hbeta and MgII lines with a scatter of dex, the tightest and most robust fit yet identified. We fit a similarly constrained relation for CIV, resolving a tension with the low luminosity literature AGN by accounting for selection effects. We also examine the impact of emission line width and luminosity (related to accretion rate) in reducing the scatter of these scaling relationships and find no significant improvement over the lag-only approach for any of the three lines. Using these relations, we further estimate the masses and accretion rates of 246 AGN. We also use these relations to estimate the relative sizes of the Hbeta, MgII and CIV emitting regions, and find evidence that the MgII emission may occur further out than Hbeta. In short, we provide a comprehensive benchmark of high redshift AGN reverberation mapping at the close of this most recent generation of surveys, including light curves, time-delays, and the most reliable radius-luminosity relations to date.

Paper Structure

This paper contains 32 sections, 14 equations, 13 figures, 7 tables.

Table of Contents

  1. Introduction
  2. Technique and limitations
  3. Reverberation Mapping
  4. The Aliasing Problem
  5. Data
  6. OzDES
  7. Light Curve & Spectral Calibration
  8. External data sets
  9. Methods
  10. Lag Recovery
  11. Post-Recovery Quality Cuts
  12. Quality Cuts for H$\beta$ Lags
  13. Quality Cuts for MgII Lags
  14. Quality Cuts for CIV Lags
  15. SDSS Sub-Sampling Criteria
  16. ...and 17 more sections

Figures (13)

  • Figure 1: Simplified model of reverberation mapping, showing the different light travel paths for direct and re-processed light. In its simplest 'single lag' form, RM relies on the assumption that the accretion disk and BLR are homogeneous, that the accretion disk be reasonably small compared to their angular separation, and the kinematics of the BLR be reasonably well characterised by a single radius Shakura_1973Cackett_2021. Additional geometric complexity is characterised by the virial factor $\braket{f}$ defined in equation \ref{['eq:RM_mass']}.
  • Figure 2: Demonstration of the source of the aliasing problem for mock RM light curves generated with a true lag of $360\mathrm{d}$, with shaded bands to demonstrate the overlap / gaps in the observations. When observational seasons of our windowing function are of similar or smaller size to the gaps, lags that give no overlap cannot be easily identified as bad fits. This creates local optima in many fitting procedures, inducing 'aliasing peaks' in lag recovery distributions every $\approx \! 180 \mathrm{d}$ which can obscure the true lag.
  • Figure 3: Demonstration of the spectral warping procedure from OzDES-Hoormann_2019. The top panel shows a smoothed version of the spectrum of AGN DES J022828.19-040044.30. The second panel shows the $gri$ filter transmission functions, while the third shows the wavelength-dependent transmission coefficients, found by integrating the spectrum with these filters, and the quadratic fit between them, each in units of $10^{-16} \text{erg}\; {\rm s}^{-1} \text{cm}^{-2} \hbox{\normalfont\AA}^{-1} \text{counts}^{-1}$. The bottom panel shows the spectrum after correcting by these scale factors to produce a fully calibrated spectrum in units of $10^{-16} \text{erg}\; {\rm s}^{-1} \text{cm}^{-2} \hbox{\normalfont\AA}^{-1}$.
  • Figure 4: A summary of all OzDES reverberation mapping (circles) and single epoch findings (squares) as well as comparison with literature RM results (plus signs). The top row plots measured and estimated lags (left, estimates from the R-L relationship) and accretion rates (right) against redshift, while the bottom row shows SBMH mass plotted against redshift (left) and bolometric luminosity (right). In each plot, the top panel colours sources by emission line, while the bottom colours by data source. On the mass vs luminosity plot, we also overlay power laws of index $0.5, 1.0$ and $2.0$ as a way to illustrate the slope of the relation.
  • Figure 5: Rest-frame lags and monochromatic luminosities for all data sources from all lines, plotted on a log-log scale to show the linear trend that forms the basis for the $R-L$ relationship. Sources marked with a circle contribute to the constraint of the shown $R-L$ relationship, while sources marked with a cross do not. Sub-plots from top to bottom are for H$\beta$, MgII and CIV lags with their 'best fit' $R-L$ relationships overlaid (see Table \ref{['tab:R-L_Summary']}). The monochromatic luminosity is measured at $5100 \hbox{\normalfont\AA}$, $3000 \hbox{\normalfont\AA}$ and $1350 \hbox{\normalfont\AA}$ from top to bottom.
  • ...and 8 more figures