Spatially Resolved HCN Absorption Features in the Circumnuclear Region of NGC 1052

Abstract

We present the first VLBI detection of HCN molecular absorption in the nearby active galactic nucleus NGC 1052. Utilizing the 1 milliarcsecond resolution achieved by the Korean VLBI Network, we have spatially resolved the HCN absorption against a double-sided nuclear jet structure. Two velocity features of HCN absorption are detected significantly at the radial velocity of 1656 and 1719 km/s, redshifted by 149 and 212 km/s with respect to the systemic velocity of the galaxy. The column density of the HCN molecule is estimated to be 10^{15}-10^{16} cm^{-2}, assuming the excitation temperature of 100-230 K. The absorption features show high optical depth localized on the receding jet side, where the free-free absorption occurred due to the circumnuclear torus. The size of the foreground absorbing molecular gas is estimated to be on approximately one-parsec scales, which agrees well with the approximate size of the circumnuclear torus. HCN absorbing gas is likely to be several clumps smaller than 0.1 parsec inside the circumnuclear torus. The redshifted velocities of the HCN absorption features imply that HCN absorbing gas traces ongoing infall motion inside the circumnuclear torus onto the central engine.

5 pages, 3 figures, accepted for publication in ApJ Letters

References in corpus (4)

• Vibrationally Excited HCN in the Luminous Infrared Galaxy NGC 4418
• Positional Coincidence of H2O Maser and a Plasma Obscuring Torus in Radio Galaxy NGC 1052
• A New Hardware Correlator in Korea: Performance Evaluation using KVN observations
• The relation between star formation rate and accretion rate in LINERs

Cited by in corpus (9)

• The Two-sided Jet Structures of NGC 1052 at Scales from 300 to $4\times 10^7$ Schwarzschild Radii
• A Massive Molecular Torus inside a Gas-Poor Cirnumnuclear Disk in the Radio Galaxy NGC 1052 Discovered with ALMA
• A Compact Jet at the Infrared Heart of the Prototypical Low-Luminosity AGN in NGC 1052
• Properties of the Obscuring Torus in NGC 1052 from Multi-epoch Broadband X-ray Spectroscopy
• A broad HCO+ absorption line associated with the circumnuclear torus of NGC 1052
• Probing Jet-Torus Interaction in the Radio Galaxy NGC 1052 by Sulfur-Bearing Molecules
• ALMA Detection of 321 GHz water maser emission in the radio galaxy NGC 1052
• Searching For the 380 GHz H2O emission from the High-z lensed QSO MG J0414+0534
• Very Long Baseline Interferometry imaging of H2O maser emission in the nearby radio galaxy NGC 4261