BRACKETT LINE-BASED MBHESTIMATORS AND HOT DUST TEMPERATURES OF TYPE 1 AGNs FROM AKARI SPECTROSCOPIC DATA

Abstract

We provide results of near-infrared (NIR) spectroscopic observations of 83 nearby (0.002 5 mag and J K>1.3 mag; Glikmanet al. 2007; Urrutia et al. 2009) have been found, andthey are now thought to be galaxies in an intermediatestage. However, their BH masses and activities are stillveiled by their massive dust extinction.It is common to use UV or optical lines such as CIV,Mg II, H , or H emission lines to estimate BH masses,but the usual BH mass estimators su er from dust ex-tinction and cannot give us correct information for BHmasses for the red AGNs. Therefore, previous studieshave tried to establish BH mass estimators using NIRspectrum (e.g., Paschen series: Kim et al. 2010). Inthis study, we derive BH mass estimators using Brack-ett lines, and expect that the Brackett-based BH massestimators will give us correct BH masses of the redAGNs even in type 2 AGNs.In order to use Brackett lines (Br : 2.63m and Br :4.05m), we need NIR spectra above 2.5m. However,http://pkas.kas.orgNIR (>2.5m) spectrum of AGNs are scarce due toobservational limitation by atmospheric absorption. Inorder to get the NIR spectra of AGNs, we used theinfrared astronomy satellite AKARI with IRC for 83nearby and bright AGNs. The IRC on AKARI pro-vides us spectroscopic observations with a wide wave-length coverage of 2.5{5.0m and a low resolution ofR˘120 at 3.6m.2. RESULTS2.1. BH Mass Estimators with Brackett LinesWe derive new BH mass estimators based on the Br and Br lines, with luminosities serving as a BLR size,and ˙as a velocity. In order to derive BH mass esti-mators, we need three parameters, a, b, and c, in theequation log(M