Scatter Analysis along the Multidimensional RadiusLuminosity Relations for Reverberationmapped Mg II Sources
Abstract
The usage of the radiusluminosity (RL) relation for the determination of black hole masses across the cosmic history, as well as its application for cosmological studies, motivates us to analyze its scatter, which has recently increased significantly for both the optical (Hβ) and UV (Mg II) lines. To this purpose, we determined the scatter along the RL relation for an uptodate reverberationmapped Mg II sample. Studying linear combinations of the luminosity at 3000 Å with independent parameters such as the FWHM, the UV Fe II strength (R_{Fe II}), and the fractional variability (F_{var}) for the whole sample, we get only a small decrease in the scatter ( ${\sigma }_{\mathrm{rms}}=0.29\,0.30$ dex). Linear combinations with the dimensionless accretion rate ( $\dot{\,{ \mathcal M }}$ ) and the Eddington ratio lead to significant reductions of the scatter ( ${\sigma }_{\mathrm{rms}}\sim 0.1$ dex), albeit both suffering from the interdependency on the observed time delay. After the division into two subsamples considering the median value of the $\dot{\,{ \mathcal M }}$ in the full sample, we find that the scatter decreases significantly for the highly accreting subsample. In particular, the smallest scatter of ${\sigma }_{\mathrm{rms}}=0.17$ dex is associated with the independent parameter R_{Fe II}, followed by the combination with F_{var} with ${\sigma }_{\mathrm{rms}}=0.19$ dex. Both of these independent observationally inferred parameters are in turn correlated with $\dot{{ \mathcal M }}$ and ${L}_{\mathrm{bol}}/{L}_{\mathrm{Edd}}$ . These results suggest that the large scatter along the RL relation is driven mainly by the accretion rate intensity.
 Publication:

The Astrophysical Journal
 Pub Date:
 November 2020
 DOI:
 10.3847/15384357/abb6f8
 arXiv:
 arXiv:2007.09955
 Bibcode:
 2020ApJ...903...86M
 Keywords:

 Active galaxies;
 Supermassive black holes;
 17;
 1663;
 Astrophysics  Astrophysics of Galaxies
 EPrint:
 20 pages, 9 figures, 2 tables. Accepted for publication in ApJ