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Title: CHANDRA ACIS SURVEY OF M33 (ChASeM33): THE ENIGMATIC X-RAY EMISSION FROM IC131

Abstract

We present the first X-ray analysis of the diffuse hot ionized gas and the point sources in IC131, after NGC604 the second most X-ray luminous giant H II region (GHR) in M33. The X-ray emission is detected only in the south eastern part of IC131 (named IC131-se) and is limited to an elliptical region of approx200 pc in extent. This region appears to be confined toward the west by a hemispherical shell of warm ionized gas and only fills about half that volume. Although the corresponding X-ray spectrum has 1215 counts, it cannot conclusively be told whether the extended X-ray emission is thermal, non-thermal, or a combination of both. A thermal plasma model of kT{sub e} = 4.3 keV or a single power law of GAMMA approx = 2.1 fit the spectrum equally well. If the spectrum is purely thermal (non-thermal), the total unabsorbed X-ray luminosity in the 0.35-8 keV energy band amounts to L{sub X} = 6.8(8.7) x 10{sup 35} erg s{sup -1}. Among other known H II regions IC131-se seems to be extreme regarding the combination of its large extent of the X-ray plasma, the lack of massive O stars, its unusually high electron temperature (if thermal), andmore » the large fraction of L{sub X} emitted above 2 keV (approx40%-53%). A thermal plasma of approx4 keV poses serious challenges to theoretical models, as it is not clear how high electron temperatures can be produced in H II regions in view of mass-proportional and collisionless heating. If the gas is non-thermal or has non-thermal contributions, synchrotron emission would clearly dominate over inverse Compton emission. It is not clear if the same mechanisms which create non-thermal X-rays or accelerate cosmic rays in supernova remnants can be applied to much larger scales of 200 pc. In both cases the existing theoretical models for GHRs and superbubbles do not explain the hardness and extent of the X-ray emission in IC131-se. We also detect a variable source candidate in IC131. It seems that this object (CXO J013315.10+304453.0) is a high mass X-ray binary whose optical counterpart is a B2-type star with a mass of approx9 M{sub sun}.« less

Authors:
; ; ;  [1];  [2];  [3];  [4];  [5]; ;  [6]; ;  [7]
  1. Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)
  2. Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)
  3. Space Science Center, Department of Earth and Space Sciences, 235 Martindale Drive, Morehead State University, Morehead, KY 40351 (United States)
  4. Department of Physics, Middlebury College, Middlebury, VT 05753 (United States)
  5. Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195 (United States)
  6. Department of Physics and Astronomy, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218 (United States)
  7. Max-Planck Institut fuer extraterrestrische Physik, Giessenbachstrasse, 85748 Garching (Germany)
Publication Date:
OSTI Identifier:
21392554
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal
Additional Journal Information:
Journal Volume: 707; Journal Issue: 2; Other Information: DOI: 10.1088/0004-637X/707/2/1361; Journal ID: ISSN 0004-637X
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; COSMIC RADIATION; ELECTRON TEMPERATURE; EMISSION; GALAXIES; KEV RANGE 01-10; LUMINOSITY; MASS; PLASMA; POINT SOURCES; STARS; SUPERNOVA REMNANTS; X-RAY SPECTRA; COSMIC RADIO SOURCES; ENERGY RANGE; IONIZING RADIATIONS; KEV RANGE; OPTICAL PROPERTIES; PHYSICAL PROPERTIES; RADIATION SOURCES; RADIATIONS; SPECTRA

Citation Formats

Tuellmann, Ralph, Plucinsky, Paul P, Gaetz, Terrance J, Smith, Randall K, Long, Knox S, Pannuti, Thomas G, Winkler, P Frank, Williams, Ben, Kuntz, Kip D, Blair, William P, Pietsch, Wolfgang, and Haberl, Frank. CHANDRA ACIS SURVEY OF M33 (ChASeM33): THE ENIGMATIC X-RAY EMISSION FROM IC131. United States: N. p., 2009. Web. doi:10.1088/0004-637X/707/2/1361.
Tuellmann, Ralph, Plucinsky, Paul P, Gaetz, Terrance J, Smith, Randall K, Long, Knox S, Pannuti, Thomas G, Winkler, P Frank, Williams, Ben, Kuntz, Kip D, Blair, William P, Pietsch, Wolfgang, & Haberl, Frank. CHANDRA ACIS SURVEY OF M33 (ChASeM33): THE ENIGMATIC X-RAY EMISSION FROM IC131. United States. https://doi.org/10.1088/0004-637X/707/2/1361
Tuellmann, Ralph, Plucinsky, Paul P, Gaetz, Terrance J, Smith, Randall K, Long, Knox S, Pannuti, Thomas G, Winkler, P Frank, Williams, Ben, Kuntz, Kip D, Blair, William P, Pietsch, Wolfgang, and Haberl, Frank. 2009. "CHANDRA ACIS SURVEY OF M33 (ChASeM33): THE ENIGMATIC X-RAY EMISSION FROM IC131". United States. https://doi.org/10.1088/0004-637X/707/2/1361.
@article{osti_21392554,
title = {CHANDRA ACIS SURVEY OF M33 (ChASeM33): THE ENIGMATIC X-RAY EMISSION FROM IC131},
author = {Tuellmann, Ralph and Plucinsky, Paul P and Gaetz, Terrance J and Smith, Randall K and Long, Knox S and Pannuti, Thomas G and Winkler, P Frank and Williams, Ben and Kuntz, Kip D and Blair, William P and Pietsch, Wolfgang and Haberl, Frank},
abstractNote = {We present the first X-ray analysis of the diffuse hot ionized gas and the point sources in IC131, after NGC604 the second most X-ray luminous giant H II region (GHR) in M33. The X-ray emission is detected only in the south eastern part of IC131 (named IC131-se) and is limited to an elliptical region of approx200 pc in extent. This region appears to be confined toward the west by a hemispherical shell of warm ionized gas and only fills about half that volume. Although the corresponding X-ray spectrum has 1215 counts, it cannot conclusively be told whether the extended X-ray emission is thermal, non-thermal, or a combination of both. A thermal plasma model of kT{sub e} = 4.3 keV or a single power law of GAMMA approx = 2.1 fit the spectrum equally well. If the spectrum is purely thermal (non-thermal), the total unabsorbed X-ray luminosity in the 0.35-8 keV energy band amounts to L{sub X} = 6.8(8.7) x 10{sup 35} erg s{sup -1}. Among other known H II regions IC131-se seems to be extreme regarding the combination of its large extent of the X-ray plasma, the lack of massive O stars, its unusually high electron temperature (if thermal), and the large fraction of L{sub X} emitted above 2 keV (approx40%-53%). A thermal plasma of approx4 keV poses serious challenges to theoretical models, as it is not clear how high electron temperatures can be produced in H II regions in view of mass-proportional and collisionless heating. If the gas is non-thermal or has non-thermal contributions, synchrotron emission would clearly dominate over inverse Compton emission. It is not clear if the same mechanisms which create non-thermal X-rays or accelerate cosmic rays in supernova remnants can be applied to much larger scales of 200 pc. In both cases the existing theoretical models for GHRs and superbubbles do not explain the hardness and extent of the X-ray emission in IC131-se. We also detect a variable source candidate in IC131. It seems that this object (CXO J013315.10+304453.0) is a high mass X-ray binary whose optical counterpart is a B2-type star with a mass of approx9 M{sub sun}.},
doi = {10.1088/0004-637X/707/2/1361},
url = {https://www.osti.gov/biblio/21392554}, journal = {Astrophysical Journal},
issn = {0004-637X},
number = 2,
volume = 707,
place = {United States},
year = {Sun Dec 20 00:00:00 EST 2009},
month = {Sun Dec 20 00:00:00 EST 2009}
}