A Broad HCO+ Absorption Line Associated with the Circumnuclear Torus of NGC 1052

We present the first subparsec-scale maps of HCO+ J = 1–0 absorption in the circumnuclear region of the nearby radio galaxy NGC 1052. Our λ3 mm very-long-baseline-interferometry (VLBI) observations with the Korean VLBI Network have spatially resolved the broad HCO+ absorption at a velocity range of 1350–1850 km s−1 against a double-sided nuclear jet, and have revealed that the HCO+ absorption is concentrated on the receding jet and the nuclear components. The distribution of the HCO+ absorbing gas strongly supports the circumnuclear torus surrounding the supermassive black hole. From the estimations of the column density and the volume density of molecular hydrogen, the size of the molecular gas region in the torus is at least 1 pc. The broad spectral profile of HCO+ is likely to be a blend of multiple gas clumps with various velocities. The HCO+ absorption of NGC 1052 could trace complex kinematics in the vicinity of the active galactic nucleus, such as inflow, outflow, turbulence, and so on.

[1]  Sang-Sung Lee,et al.  SPATIALLY RESOLVED HCN ABSORPTION FEATURES IN THE CIRCUMNUCLEAR REGION OF NGC 1052 , 2016, 1609.08771.

[2]  Duk-Gyoo Roh,et al.  AMPLITUDE CORRECTION FACTORS OF KOREAN VLBI NETWORK OBSERVATIONS , 2015 .

[3]  China.,et al.  A NEW HARDWARE CORRELATOR IN KOREA: PERFORMANCE EVALUATION USING KVN OBSERVATIONS , 2015, 1503.07972.

[4]  A. Fuente,et al.  Molecular line emission in NGC 1068 imaged with ALMA - II. The chemistry of the dense molecular gas , 2014, 1407.4940.

[5]  A. Fuente,et al.  Molecular line emission in NGC 1068 imaged with ALMA: I. An AGN-driven outflow in the dense molecular gas , 2014, 1405.7706.

[6]  D. Meier,et al.  Submillimeter ALMA Observations of the Dense Gas in the Low-Luminosity Type-1 Active Nucleus of NGC 1097 , 2013, 1306.0507.

[7]  Do-Young Byun,et al.  Korean VLBI Network Receiver Optics for Simultaneous Multifrequency Observation: Evaluation , 2013 .

[8]  S. Iguchi,et al.  Design and Development of a High-Speed Data-Acquisition System for the Korean VLBI Network , 2011 .

[9]  Richard Dodson,et al.  HIGH-PRECISION ASTROMETRIC MILLIMETER VERY LONG BASELINE INTERFEROMETRY USING A NEW METHOD FOR ATMOSPHERIC CALIBRATION , 2011, 1101.2051.

[10]  J. Pety,et al.  The CO luminosity and CO-H2 conversion factor of diffuse ISM: does CO emission trace dense molecular gas? , 2010, 1005.2157.

[11]  S. Y. Park,et al.  Development of Software Correlator for KJJVC , 2009 .

[12]  M. Inoue,et al.  Positional Coincidence of H2O Maser and a Plasma-Obscuring Torus in Radio Galaxy NGC 1052 , 2008, 0802.4149.

[13]  Jungwon Lee,et al.  Millimeter-wave Receiver Optics for Korean VLBI Network , 2008 .

[14]  B. Drouin,et al.  Rotational Spectrum of the Formyl Cation, HCO+, to 1.2 THz , 2007 .

[15]  A. T. Deller,et al.  DiFX: A Software Correlator for Very Long Baseline Interferometry Using Multiprocessor Computing Environments , 2007, astro-ph/0702141.

[16]  Emergence of a Narrow H2O Maser Feature in NGC 1052 , 2005 .

[17]  H. Falcke,et al.  VLBI observations of weak sources using fast frequency switching , 2004, astro-ph/0412564.

[18]  H. Liszt,et al.  Mm-wave HCO+, HCN and CO absorption toward NGC 1052 , 2004, astro-ph/0409298.

[19]  H. Falcke,et al.  The twin-jet system in NGC 1052: VLBI-scrutiny of the obscuring torus , 2004, astro-ph/0407283.

[20]  H. Falcke,et al.  Jet emission in NGC 1052 at radio, optical, and X-ray frequencies , 2004, astro-ph/0403165.

[21]  Eric W. Greisen,et al.  AIPS, the VLA, and the VLBA , 2003 .

[22]  K. Wajima,et al.  Dense Plasma Torus in the GPS Galaxy NGC 1052 , 2002, Publications of the Astronomical Society of Australia.

[23]  Rodger I. Thompson,et al.  Measuring Distances and Probing the Unresolved Stellar Populations of Galaxies Using Infrared Surface Brightness Fluctuations , 2002, astro-ph/0210129.

[24]  M. Cohen,et al.  The Shroud Around the Twin Radio Jets in NGC 1052 , 2002, astro-ph/0212030.

[25]  M. Rupen,et al.  VLA detection of OH absorption from the elliptical galaxy NGC 1052 , 2001, astro-ph/0111268.

[26]  K. Wajima,et al.  The dense plasma torus around the nucleus of an active galaxy ngc 1052 , 2001, astro-ph/0104039.

[27]  D. Flower.  Rotational excitation of HCO+ by H2 , 1999 .

[28]  L. A. Antonelli,et al.  The flat X-ray spectrum of the LINER NGC 1052 , 1999 .

[29]  K. Weaver,et al.  X-Ray Emission from the Prototypical LINER Galaxy NGC 1052 , 1999, astro-ph/9902269.

[30]  British Ornithologists,et al.  Bulletin of the , 1999 .

[31]  Noordwijk,et al.  The flat X-ray spectrum of the LINER NGC1052 , 1998, astro-ph/9812385.

[32]  L. Gurvits,et al.  Sub-Milliarcsecond Imaging of Quasars and Active Galactic Nuclei. IV. Fine-Scale Structure , 2005, astro-ph/0505536.

[33]  C. Henkel,et al.  The discovery of five new H2O megamasers in active galaxies , 1994 .

[34]  S. Faber,et al.  Distribution and kinematics of H I in the active elliptical galaxy NGC 1052 , 1986 .

[35]  J. Wrobel.  Radio continuum activity in the elliptical galaxy NGC 1052 , 1984 .

[36]  D. Jones,et al.  Structure of the compact radio sources in NGC 1052 and NGC 4278 , 1984 .

[37]  R. Woods,et al.  Configuration interaction electric dipole moments for HCN, HNC, HNN+, HCO+ HBO, HBF+, and HCNH+☆ , 1979 .

[38]  R. W. Haas,et al.  Absolute calibration of millimeter-wavelength spectral lines , 1976 .