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arXiv · 2205.07034

The intermediate-ionization lines as virial broadening estimators for Population A quasars

P. Marziani·A. del Olmo·C. A. Negrete·D. Dultzin·E. Piconcelli·G. Vietri·M. L. Martinez-Aldama·Mauro D'Onofrio·E. Bon·N. Bon·A. Deconto Machado·G. M. Stirpe·T. Buendia Rios
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Abstract

The identification of a virial broadening estimator in the quasar UV rest frame suitable for black hole mass computation at high redshift has become an important issue. We compare the HI Balmer H-beta line width to the ones of two intermediate ionization lines: the Aliii 1860 doublet and the Ciii] 1909 line, over a wide interval of redshift and luminosity (0 < z < 3.5; 43 < logL < 48.5 [erg a/]), for 48 sources belonging to the quasar population characterized by mid-to-high values of the Eddington ratio (Population A). The present analysis indicates that the line width of Aliii 1860 and H-beta are highly correlated, and can be considered equivalent for most Population A quasars over five orders of magnitude in luminosity; forCiii] 1909, multiplication by a constant correction factor xi ~ 1.25 is sufficient to bring the FWHM of Ciii] in agreement with the one of H-betaa. The statistical concordance between low-ionization and intermediate-ionization lines suggests that they predominantly arise from the same virialized part of the broad line region. However, blueshifts of modest amplitude (few hundred km /s) with respect to the quasar rest frame and an excess (~ 1.1) Aliii broadening with respect to H-beta are found in a fraction of our sample. Scaling laws to estimate M_BH of high redshift quasar using the Aliii and the Ciii] line widths have rms scatter ~ 0.3 dex. The Aliii scaling law takes the form log M_BH ~ 0.58 log L1700,44 + 2 log FWHM + 0.49 [solar masses].

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P. Marziani, A. del Olmo, C. A. Negrete, D. Dultzin, E. Piconcelli, G. Vietri, M. L. Martinez-Aldama, Mauro D'Onofrio, E. Bon, N. Bon, A. Deconto Machado, G. M. Stirpe, T. Buendia Rios. 2022-05-14. The intermediate-ionization lines as virial broadening estimators for Population A quasars. https://doi.org/10.3847/1538-4365/ac6fd6

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