skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

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

Abstract

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

Citation Formats

Okuda, Takeshi, Iguchi, Satoru, and Kohno, Kotaro, E-mail: okuda@a.phys.nagoya-u.ac.jp. A MILLIMETER-WAVE INTERFEROMETRIC SEARCH FOR A MOLECULAR TORUS IN THE RADIO GALAXY NGC 4261. United States: N. p., 2013. Web. doi:10.1088/0004-637X/768/1/19.
Okuda, Takeshi, Iguchi, Satoru, & Kohno, Kotaro, E-mail: okuda@a.phys.nagoya-u.ac.jp. A MILLIMETER-WAVE INTERFEROMETRIC SEARCH FOR A MOLECULAR TORUS IN THE RADIO GALAXY NGC 4261. United States. doi:10.1088/0004-637X/768/1/19.
Okuda, Takeshi, Iguchi, Satoru, and Kohno, Kotaro, E-mail: okuda@a.phys.nagoya-u.ac.jp. 2013. "A MILLIMETER-WAVE INTERFEROMETRIC SEARCH FOR A MOLECULAR TORUS IN THE RADIO GALAXY NGC 4261". United States. doi:10.1088/0004-637X/768/1/19.
@article{osti_22126850,
title = {A MILLIMETER-WAVE INTERFEROMETRIC SEARCH FOR A MOLECULAR TORUS IN THE RADIO GALAXY NGC 4261},
author = {Okuda, Takeshi and Iguchi, Satoru and Kohno, Kotaro, E-mail: okuda@a.phys.nagoya-u.ac.jp},
abstractNote = {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.},
doi = {10.1088/0004-637X/768/1/19},
journal = {Astrophysical Journal},
number = 1,
volume = 768,
place = {United States},
year = 2013,
month = 5
}
  • Observations of the radio galaxy 3C 111 show this source to have a very strong and very compact component at millimeter wavelengths, 3000 times more luminous than that recently found in Cen A. This component is coincident with the optical galaxy and may also be related to the X-ray source 3U 0430+37. The spectrum of the north-following, extended outer component remains power-law even at 3.3 mm wavelength. At least five spectral components of 3C 111 may be distinguished. (AIP)
  • A large number of previously unreported molecular transitions have been detected in the submillimeter wavelength band toward OMC-1 and M17 SW using the Texas 4.9 m radio antenna. The emission components in OMC-1 that come from the unresolved plateau and hot core regions are stronger in these higher energy transitions than in the lower-energy, lower-frequency lines. Intense, probably thermalized high J SiO lines require a very hot core if they arise in a region the same size as that mapped in J = 2-1 SiO by interferometer measurements. Despite the high energy levels of the submillimeter lines of CN andmore » CCH, there is no broad emission component evident, consistent with their greatly reduced abundance due to removal by chemical reactions. 33 references.« less
  • Millimeter wave (MMW) radiometry can be used for simultaneous measurement of emissivity and temperature of materials under extreme environments (high temperature, pressure, and corrosive environments) such as in slagging coal gasifiers, where sensors have been identified as a key enabling technology need for process optimization. We present a state-of-the-art dual-channel MMW heterodyne radiometer with active interferometric capability that allows simultaneous radiometric measurements of sample temperature, emissivity, and flow dynamics to over 1873 K. Interferometric capability is supplied via a probe signal originating from the 137 GHz radiometer local oscillator (LO). The interferometric 'video' channels allow measurement of additional parameters simultaneously,more » such as volume expansion, thickness change, and slag viscosity along with temperature or emissivity. This capability has been used to demonstrate measurement of temperature and simulated coal slag infiltration into a chromia refractory brick sample as well as slag flow down a vertically placed refractory brick. Observed phenomena include slag melting and slumping, slag reboil and foam with oxygen evolution, and eventual failure of the alumina crucible through corrosion by the molten slag. These results show the promise of the MMW system for extracting quantitative and qualitative process parameters from operating slagging coal gasifiers, providing valuable information for process efficiency, control, and increased productivity.« less
  • A high-resolution map of 113 GHz dust continuum emission from OMC-1 is presented. Maps in several bands confirm the detection of true continuum, free of contamination by molecular lines. The emission arises from a region approximately 10 arcsec in extent centered on IRc2 and coincident with the region of NH3 emission detected at the VLA. The peak column density near IRc2 is N(H2) = 10 to the 24th/sq cm. No continuum flux was detected from the SO emission region, indicating the column density there is less than 10 to the 23rd/sq cm. This suggests that the SO emission, previously modeledmore » as a high-density torus surrounding IRc2, arises from a zone of abnormally high SO/H2 abundance at the surface of cavity around IRc2. In this new picture, the hot core is viewed as dense clumps of gas and dust left behind as the cavity was cleared by winds from IRc2. 27 references.« less