An FMOS Survey of Moderate-luminosity, Broad-line AGNs in COSMOS, SXDS, and E-CDF-S
Résumé
We present near-IR spectroscopy in the J- and H-bands for a large sample of 243 X-ray-selected, moderate-luminosity Type 1 active galactic nuclei (AGNs) in the COSMOS, SXDS, and E-CDF-S survey fields using the multi-object spectrograph Subaru/FMOS. Our sample covers the redshift range 0.5 ≲ z ≲ 3.0 and X-ray luminosity range of 1043 ≲ ≲ 1045 erg s−1. We provide emission-line properties and derived virial black hole mass estimates, bolometric luminosities, and Eddington ratios, based on Hα (211), Hβ (63), and Mg ii (4). We compare line widths, luminosities, and black hole mass estimates from Hα and Hβ, and augment these with commensurate measurements of Mg ii and C iv detected in optical spectra. We demonstrate the robustness of using Hα, Hβ, and Mg ii as reliable black hole mass estimators for high-z moderate-luminosity AGNs, while the use of C iv is prone to large uncertainties (≳0.4 dex). We extend a recently proposed correction based on the C iv blueshift to lower luminosities and black hole masses. While our sample shows an improvement in their C iv black hole mass estimates, the deficit of high blueshift sources reduces its overall importance for moderate-luminosity AGNs compared to the most luminous quasars. In addition, we revisit luminosity correlations between L bol, , L [O iii], L 5100, and L Hα and find them to be consistent with a simple empirical model, based on a small number of well-established scaling relations. Finally, we highlight our highest redshift AGN, CID 781, at z = 4.6, which has the lowest black hole mass (∼108 M ⊙) among current near-IR samples at this redshift and is in a state of fast growth.