BASS. XXVI. DR2 Host Galaxy Stellar Velocity Dispersions

Abstract

We present new central stellar velocity dispersions for 484 Sy 1.9 and Sy 2 from the second data release of the Swift/BAT AGN Spectroscopic Survey (BASS DR2). This constitutes the largest study of velocity dispersion measurements in X-ray-selected obscured active galactic nuclei (AGN) with 956 independent measurements of the Ca ii H and K λ3969, 3934 and Mg I λ5175 region (3880–5550 Å) and the calcium triplet region (8350–8730 Å) from 642 spectra mainly from VLT/X-Shooter or Palomar/DoubleSpec. Our sample spans velocity dispersions of 40–360 km s1, corresponding to 4–5 orders of magnitude in black hole mass (M BH = 105.5−9.6 M ⊙), bolometric luminosity (L bol ∼ 1042–46 erg s−1), and Eddington ratio (L/L Edd ∼ 10−5 to 2). For 281 AGN, our data and analysis provide the first published central velocity dispersions, including six AGN with low-mass black holes (M BH = 105.5−6.5 M ⊙), discovered thanks to high spectral resolution observations (σ inst ∼ 25 km s−1). The survey represents a significant advance with a nearly complete census of velocity dispersions of hard X-ray–selected obscured AGN with measurements for 99% of nearby AGN (z < 0.1) outside the Galactic plane (∣b∣ > 10°). The BASS AGN have much higher velocity dispersions than the more numerous optically selected narrow-line AGN (i.e., ∼150 versus ∼100 km s−1) but are not biased toward the highest velocity dispersions of massive ellipticals (i.e., >250 km s−1). Despite sufficient spectral resolution to resolve the velocity dispersions associated with the bulges of small black holes (∼104–5 M ⊙), we do not find a significant population of super-Eddington AGN. Using estimates of the black hole sphere of influence from velocity dispersion, direct stellar and gas black hole mass measurements could be obtained with existing facilities for more than ∼100 BASS AGN.

BASS. XXIV. The BASS DR2 Spectroscopic Line Measurements and AGN Demographics

“…We used the penalized pixel fitting method (Cappellari & Emsellem 2004, pPXF) and employed the synthesized stellar population models (Bruzual & Charlot 2003) and the empirical stellar libraries (Sánchez-Blázquez et al 2006;MILES) for most of the objects, whereas the X-Shooter spectral library (Chen et al 2014) was used for the X-Shooter spectra. More details regarding stellar velocity dispersion measurements within BASS DR2 are provided in a separate publication (Koss et al 2022c). The templates were convolved and rebinned to match the spectral resolution.…”

“…The observed anticorrelation still holds in the higher redshift regime, up to z ∼ 1.7 (Oh et al 2019; green filled dots in Figure 16). We show the anticorrelation in Figure 16 using the measurements of black hole mass (Koss et al 2022c;Mejía-Restrepo et al 2022), bolometric luminosity (Ricci et al 2017a), and the [N II]λ6583/Hα ratio of 639 BAT AGNs. We report α and β values of −0.46 ± 0.03 and −0.18 ± 0.02, respectively, where α and β are the intercept and slope of the Bayesian linear regression as follows:…”

BASS. XXV. DR2 Broad-line-based Black Hole Mass Estimates and Biases from Obscuration

“…The virial factor f of M BH,BLR in Figure12has been rescaled to 1.14 to better match the virial factor used inKormendy & Ho (2013), which is in turn used to estimate M BH,s in BASS/DR2(Koss et al 2022c). …”

BASS. XXX. Distribution Functions of DR2 Eddington Ratios, Black Hole Masses, and X-Ray Luminosities

“…For narrow-line (Type 2) AGNs,Koss et al (2017) andKoss et al (2022a) rely on measurements of the stellar velocity dispersion (σ å ) in the AGN host galaxies and the well-known M BH − σ å relation. Specifically, σ å was measured from the Ca H + K, Mg I, and/or the Ca II triplet spectral complexes, as described in detail inKoss et al (2022c). We then used the relation…”