Double-Peaked Profiles: Ubiquitous Signatures of Disks in the Broad Emission Lines of Active Galactic Nuclei
Abstract
Broad (∼10,000 km s-1), double-peaked emission-line profiles of Balmer lines emitted by active galactic nuclei (AGN) are thought to originate in the outer parts of an accretion disk surrounding a nuclear supermassive black hole (SMBH), at ∼1000 gravitational radii, and are most frequently observed in the nuclear spectra of low-luminosity AGN (LLAGN) and radio galaxies. In the present paper we argue that broad double-peaked profiles are present also in the spectra of other type 1 AGN, such as Seyfert 1 galaxies, suggesting that the inner part of the broad-line region (BLR) is also the outer part of the accretion disk. We use the Palomar spectral survey of nearby galaxies to show that the only difference between Seyfert 1 BLR line profiles and “bona fide” double-peakers is that, in most cases, besides a disk component, we need an additional Gaussian component attributed to nondisk clouds. The recognition that the inner and most variable part of the BLR has a disk geometry suggests that the factor f in the expression to obtain the SMBH mass in type 1 AGN, {M}{BH}=f({R}{BLR}{{Δ }}{V}2/G), is f=1/{\sin }2I for the disk-dominated sources. Our median I = 27° implies f = 4.5, very close to the most recent value of f = 4.3 ± 1.05, obtained from independent studies. We derive a relation between f and the FWHM of the broad profile that may help to reduce the uncertainties in the SMBH mass determinations of AGN.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- February 2017
- DOI:
- 10.3847/1538-4357/835/2/236
- arXiv:
- arXiv:1612.06843
- Bibcode:
- 2017ApJ...835..236S
- Keywords:
-
- accretion;
- accretion disks;
- galaxies: active;
- galaxies: nuclei;
- galaxies: Seyfert;
- line: profiles;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- doi:10.3847/1538-4357/835/2/236