HST unveils a compact mildly relativistic Broad Line Region in the candidate true type 2 NGC 3147

Abstract

NGC 3147 has been considered the best case of a true type 2 AGN: an unobscured AGN, based on the unabsorbed compact X-ray continuum, which lacks a broad line region (BLR). However, the very low luminosity of NGC 3147 implies a compact BLR, which produces very broad lines, hard to detect against the dominant background host galaxy. Narrow (0.1"x0.1") slit HST spectroscopy allowed us to exclude most of the host galaxy light, and revealed an H$\alpha$ line with an extremely broad base (FWZI$\sim 27000$ km s${}^{-1}$). The line profile shows a steep cutoff blue wing and an extended red wing, which match the signature of a mildly relativistic thin accretion disk line profile. It is indeed well fit with a nearly face on thin disk, at $i\sim 23^{\circ }$, with an inner radius at $77\pm 15$ r${}_g$, which matches the prediction of $62_{-14}^{+18}$ r${}_g$ from the $R_{\mathrm{BLR}}\sim L^{1/2}$ relation. This result questions the very existence of true type 2 AGN. Moreover, the detection of a thin disk, which extends below 100 r${}_g$ in an $L/L_{\mathrm{Edd}}\sim 10^{-4}$ system, contradicts the current view of the accretion flow configuration at extremely low accretion rates.

6 pages, 3 figures, accepted for publication in MNRAS Letters

References in corpus (9)

• Constraining Black Hole Spin Via X-ray Spectroscopy
• GHASP : An Halpha kinematic survey of spiral and irregular galaxies - VI. New Halpha data cubes for 108 galaxies
• Dust inflated accretion disc as the origin of the Broad Line Region in Active Galactic Nuclei
• Double-peaked profiles: ubiquitous signatures of disks in the Broad Emission Lines of Active Galactic Nuclei
• Hunting for Supermassive Black Holes in Nearby Galaxies with the Hobby-Eberly Telescope
• Unobscured Type 2 AGNs
• Indecent Exposure in Seyfert 2 Galaxies: A Close Look
• NGC3147: a "true" Seyfert 2 without the broad-line region
• Hidden Double-Peaked Emitters in Seyfert 2 Galaxies

Cited by in corpus (25)

• BASS XXIV: The BASS DR2 Spectroscopic Line Measurements and AGN Demographics
• The 450 days X-ray monitoring of the changing-look AGN 1ES 1927+654
• The Host Galaxy and Rapidly Evolving Broad-line Region in the Changing-look Active Galactic Nucleus 1ES 1927+654
• Time Delay of MgII Emission Response for the Luminous Quasar HE 0435-4312: Towards Application of High-Accretor Radius-Luminosity Relation in Cosmology
• Evolution of a Relativistic Outflow and X-ray Corona in the Extreme Changing-Look AGN 1ES 1927+654
• Evidence for Two Distinct Broad-Line Regions from Reverberation Mapping of PG 0026+129
• $NuSTAR$ Observations of Four Nearby X-ray Faint AGN: Low Luminosity or Heavy Obscuration?
• X-ray absorption in INTEGRAL AGN: Host galaxy inclination
• Constraining the X-ray reflection in low accretion rate AGN using XMM-Newton, NuSTAR and Swift
• Dependence of NLRs sizes on [OIII] luminosity in low redshift AGN with double-peaked broad Balmer emission lines
• Constraining the accretion flow density profile near Sgr A* using the $L^{\prime }$-band emission of the S2 star
• The Main Sequence of quasars: the taming of the extremes
• Dusty plasma in active galactic nuclei
• Surprisingly Strong K-band Emission Found in Low Luminosity Active Galactic Nuclei
• SDSS J1058+5443: A blue quasar does not have optical/NUV broad emission lines
• Systematic research of low redshift optically selected SDSS Type-2 AGN but with apparent long-term optical variabilities from Catalina Sky Survey, I: data sample and basic results
• Optical Observations of the Nearby Type Ia Supernova 2021hpr
• Fundamental Reference AGN Monitoring Experiment (FRAMEx) III: Radio Emission in the Immediate Vicinity of Radio Quiet AGNs
• NGC 3147: a prototypical low-luminosity active galactic nucleus with double-peaked optical and ultraviolet lines
• Long-term variability of the composite galaxy SDSS J103911-000057: A candidate of true Type-2 AGN
• Spectral Energy Distribution profiles from AGN accretion disc in multi-gap setup
• H$\beta$ line shape and radius-luminosity relation in 2.5D FRADO
• Searching for Nuclear Obscuration in the Infrared Spectra of Nearby FR I Radio Galaxies
• Active Galactic Nuclei and their demography through cosmic time
• A radio, optical, UV and X-ray view of the enigmatic changing look Active Galactic Nucleus 1ES~1927+654 from its pre- to post-flare states