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

Title: PHYSICAL CONDITIONS IN THE X-RAY EMISSION-LINE GAS IN NGC 1068

Abstract

We present a detailed, photoionization modeling analysis of XMM-Newton/Reflection Grating Spectrometer observations of the Seyfert 2 galaxy NGC 1068. The spectrum, previously analyzed by Kinkhabwala et al., reveals a myriad of soft X-ray emission lines, including those from H- and He-like carbon, nitrogen, oxygen, and neon, and M- and L-shell iron. As noted in the earlier analysis, based on the narrowness of the radiative recombination continua, the electron temperatures in the emission-line gas are consistent with photoionization, rather than collisional ionization. The strengths of the carbon and nitrogen emission lines, relative to those of oxygen, suggest unusual elemental abundances, which we attribute to the star formation history of the host galaxy. Overall, the emission lines are blueshifted with respect to systemic, with radial velocities ∼160 km s{sup –1}, similar to that of [O III] λ5007, and thus consistent with the kinematics and orientation of the optical emission-line gas and, hence, likely part of an active galactic nucleus driven outflow. We were able to achieve an acceptable fit to most of the strong emission lines with a two-component photoionization model, generated with CLOUDY. The two components have ionization parameters and column densities of logU = –0.05 and 1.22 and logN {sub H} = 20.85more » and 21.2 and covering factors of 0.35 and 0.84, respectively. The total mass of the X-ray gas is roughly an order of magnitude greater than the mass of ionized gas determined from optical and near-IR spectroscopy, which indicates that it may be the dominant component of the narrow-line region. Furthermore, we suggest that the medium that produces the scattered/polarized optical emission in NGC 1068 possesses similar physical characteristics to those of the more highly ionized of the X-ray model components.« less

Authors:
 [1]; ; ;  [2]
  1. Institute for Astrophysics and Computational Sciences, Department of Physics, The Catholic University of America, Washington, DC 20064 (United States)
  2. Department of Physics, University of Maryland Baltimore County, Baltimore, MD 21250 (United States)
Publication Date:
OSTI Identifier:
22364700
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal
Additional Journal Information:
Journal Volume: 798; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0004-637X
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; CARBON; COMPUTERIZED SIMULATION; ELECTRON TEMPERATURE; INFRARED SPECTRA; IRON; L SHELL; MASS; NEON; NITROGEN; OXYGEN; PHOTOIONIZATION; RADIAL VELOCITY; RECOMBINATION; REFLECTION; SEYFERT GALAXIES; SOFT X RADIATION; STAR CLUSTERS; STARS; X-RAY GALAXIES

Citation Formats

Kraemer, S. B., Sharma, N., Turner, T. J., George, Ian M., and Crenshaw, D. Michael, E-mail: kraemer@yancey.gsfc.nasa.gov. PHYSICAL CONDITIONS IN THE X-RAY EMISSION-LINE GAS IN NGC 1068. United States: N. p., 2015. Web. doi:10.1088/0004-637X/798/1/53.
Kraemer, S. B., Sharma, N., Turner, T. J., George, Ian M., & Crenshaw, D. Michael, E-mail: kraemer@yancey.gsfc.nasa.gov. PHYSICAL CONDITIONS IN THE X-RAY EMISSION-LINE GAS IN NGC 1068. United States. https://doi.org/10.1088/0004-637X/798/1/53
Kraemer, S. B., Sharma, N., Turner, T. J., George, Ian M., and Crenshaw, D. Michael, E-mail: kraemer@yancey.gsfc.nasa.gov. 2015. "PHYSICAL CONDITIONS IN THE X-RAY EMISSION-LINE GAS IN NGC 1068". United States. https://doi.org/10.1088/0004-637X/798/1/53.
@article{osti_22364700,
title = {PHYSICAL CONDITIONS IN THE X-RAY EMISSION-LINE GAS IN NGC 1068},
author = {Kraemer, S. B. and Sharma, N. and Turner, T. J. and George, Ian M. and Crenshaw, D. Michael, E-mail: kraemer@yancey.gsfc.nasa.gov},
abstractNote = {We present a detailed, photoionization modeling analysis of XMM-Newton/Reflection Grating Spectrometer observations of the Seyfert 2 galaxy NGC 1068. The spectrum, previously analyzed by Kinkhabwala et al., reveals a myriad of soft X-ray emission lines, including those from H- and He-like carbon, nitrogen, oxygen, and neon, and M- and L-shell iron. As noted in the earlier analysis, based on the narrowness of the radiative recombination continua, the electron temperatures in the emission-line gas are consistent with photoionization, rather than collisional ionization. The strengths of the carbon and nitrogen emission lines, relative to those of oxygen, suggest unusual elemental abundances, which we attribute to the star formation history of the host galaxy. Overall, the emission lines are blueshifted with respect to systemic, with radial velocities ∼160 km s{sup –1}, similar to that of [O III] λ5007, and thus consistent with the kinematics and orientation of the optical emission-line gas and, hence, likely part of an active galactic nucleus driven outflow. We were able to achieve an acceptable fit to most of the strong emission lines with a two-component photoionization model, generated with CLOUDY. The two components have ionization parameters and column densities of logU = –0.05 and 1.22 and logN {sub H} = 20.85 and 21.2 and covering factors of 0.35 and 0.84, respectively. The total mass of the X-ray gas is roughly an order of magnitude greater than the mass of ionized gas determined from optical and near-IR spectroscopy, which indicates that it may be the dominant component of the narrow-line region. Furthermore, we suggest that the medium that produces the scattered/polarized optical emission in NGC 1068 possesses similar physical characteristics to those of the more highly ionized of the X-ray model components.},
doi = {10.1088/0004-637X/798/1/53},
url = {https://www.osti.gov/biblio/22364700}, journal = {Astrophysical Journal},
issn = {0004-637X},
number = 1,
volume = 798,
place = {United States},
year = {Thu Jan 01 00:00:00 EST 2015},
month = {Thu Jan 01 00:00:00 EST 2015}
}