The Sloan Digital Sky Survey Reverberation Mapping Project: Mg II Lag Results from Four Years of Monitoring
Abstract
We present reverberation mapping results for the Mg II λ2800 Å broad emission line in a sample of 193 quasars at $0.35\lt z\lt 1.7$ with photometric and spectroscopic monitoring observations from the Sloan Digital Sky Survey Reverberation Mapping project during 2014-2017. We find significant time lags between the Mg II and continuum lightcurves for 57 quasars, and define a "gold sample" of 24 quasars with the most reliable lag measurements. We estimate false-positive rates for each lag that range from 1% to 24%, with an average false-positive rate of 11% for the full sample and 8% for the gold sample. There are an additional ∼40 quasars with marginal Mg II lag detections, which may yield reliable lags after additional years of monitoring. The Mg II lags follow a radius-luminosity relation with a best-fit slope that is consistent with $\alpha =0.5$ , but with an intrinsic scatter of 0.36 dex that is significantly larger than found for the Hβ radius-luminosity relation. For targets with SDSS-RM lag measurements of other emission lines, we find that our Mg II lags are similar to the Hβ lags and ∼2-3 times larger than the C IV lags. This work significantly increases the number of Mg II broad-line lags and provides additional reverberation-mapped black hole masses, filling the redshift gap at the peak of supermassive black hole growth between the Hβ and C IV emission lines in optical spectroscopy.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- September 2020
- DOI:
- 10.3847/1538-4357/ababa9
- arXiv:
- arXiv:2005.03663
- Bibcode:
- 2020ApJ...901...55H
- Keywords:
-
- Active galaxies;
- Galaxy nuclei;
- Quasars;
- Active galactic nuclei;
- 17;
- 609;
- 1319;
- 16;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- Accepted for publication in ApJ. 18 pages and 12 figures. The complete figure set (193 images) similar to Figure 4 in the manuscript are available at http://phys.uconn.edu/~jtrump/Fig4_lags.tar.gz. The complete figure set (57 images) similar to Figure 6 in the manuscript are available at http://phys.uconn.edu/~jtrump/Fig6_lightcurves.tar.gz