Spectral line

Redshift

Luminous infrared galaxy

Galaxy

Star formation

Infrared

Interstellar medium

Astrophysics

Velocity dispersion

Physics

Virial theorem

Mathematics

Active galactic nucleus

Astronomy

Virial mass

Supermassive black hole

Geometry

Stars

Line (geometry)

Photometry (optics)

The Astrophysical Journal Supplement Series

Virial black hole (BH) mass ( M BH ) determination directly involves knowing the broad-line region (BLR) clouds’ velocity distribution, their distance from the central supermassive BH ( R BLR ), and the virial factor ( f ). Understanding whether biases arise in M BH estimation with increasing obscuration is possible only by studying a large ( N &gt; 100) statistical sample of obscuration-unbiased (hard) X-ray-selected active galactic nuclei (AGNs) in the rest-frame near-infrared (0.8–2.5 μ m) since it penetrates deeper into the BLR than the optical. We present a detailed analysis of 65 local Burst Alert Telescope (BAT) selected Seyfert galaxies observed with Magellan/FIRE. Adding these to the near-infrared BAT AGN spectroscopic survey database, we study a total of 314 unique near-infrared spectra. While the FWHMs of H α and near-infrared broad lines (He i , Pa β , Pa α ) remain unbiased to either BLR extinction or X-ray obscuration, the H α broad-line luminosity is suppressed when N H ≳ 10 21 cm −2 , systematically underestimating M BH by 0.23–0.46 dex. Near-infrared line luminosities should be preferred to H α until N H &lt; 10 22 cm −2 , while at higher obscuration a less-biased R BLR proxy should be adopted. We estimate f for Seyfert 1 and 2 using two obscuration-unbiased M BH measurements, i.e., the stellar velocity dispersion and a BH mass prescription based on near-infrared and X-ray, and find that the virial factors do not depend on the redshift or obscuration, but some broad lines show a mild anticorrelation with M BH . Our results show the critical impact obscuration can have on BLR characterization and the importance of the near-infrared and X-rays for a less-biased view of the BLR.

BASS. XXIX. The Near-infrared View of the Broad-line Region (BLR): The Effects of Obscuration in BLR Characterization*