An FMOS Survey of Moderate-luminosity, Broad-line AGNs in COSMOS, SXDS, and E-CDF-S

Abstract

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 10 43  ≲   ≲ 10 45 erg s −1 . We provide emission-line properties and derived virial black hole mass estimates, bolometric luminosities, and Eddington ratios, based on H α (211), H β (63), and Mg ii (4). We compare line widths, luminosities, and black hole mass estimates from H α and H β , and augment these with commensurate measurements of Mg ii and C iv detected in optical spectra. We demonstrate the robustness of using H α , H β , 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 H α 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 (∼10 8 M ⊙ ) among current near-IR samples at this redshift and is in a state of fast growth.