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Title: A MILLIMETER-WAVE INTERFEROMETRIC SEARCH FOR A MOLECULAR TORUS IN THE RADIO GALAXY NGC 4261

NGC 4261 is an elliptical galaxy with a pair of symmetric kiloparsec-scale jets. We observed a nucleus of NGC 4261 at 2.6 mm and 1.3 mm with the NRO RAINBOW interferometer, the Nobeyama Millimeter Array, and the IRAM Plateau de Bure Interferometer to determine the excitation state of molecular gas. In this observation, neither CO(J = 2-1) nor CO(J = 1-0) absorption lines were detected even at higher sensitivity than the previous work. The 3{sigma} upper limits on the optical depths of CO lines were 0.098 for J = 2-1 and 0.042 for J = 1-0, respectively. These upper limits are much smaller than the optical depth obtained from the previous claimed detection of CO(J = 2-1) absorption (0.7), indicating that the claimed CO(J = 2-1) absorption profile could be a false feature. Our results suggest that there is a possibility that CO molecules are highly excited by the active galactic nucleus, since the optical depths of low-J CO molecules in NGC 4261 are significantly low.
Authors:
 [1] ;  [2] ;  [3]
  1. Department of Physics and Astrophysics, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8602 (Japan)
  2. National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan)
  3. Institute of Astronomy, University of Tokyo, 2-21-1 Osawa, Mitaka, Tokyo 181-0015 (Japan)
Publication Date:
OSTI Identifier:
22126850
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 768; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ABSORPTION; CARBON MONOXIDE; DEPTH; DETECTION; EXCITATION; INTERFEROMETERS; RADIO GALAXIES; SENSITIVITY