Final published version
Research output: Contribution in Book/Report/Proceedings - With ISBN/ISSN › Conference contribution/Paper
Research output: Contribution in Book/Report/Proceedings - With ISBN/ISSN › Conference contribution/Paper
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TY - GEN
T1 - Revealing X-ray luminous AGN in apparent starburst galaxies
AU - Jackson, F. E.
AU - Roberts, T. P.
AU - Gelbord, J. M.
AU - Ward, M. J.
AU - Wardlow, J. L.
AU - Alexander, D. M.
AU - Watson, M. G.
PY - 2010/8/26
Y1 - 2010/8/26
N2 - It is commonly assumed in deep survey work that all galaxies with X-ray luminosities above about 1042ergs-1 harbour AGN, regardless of their optical spectrum, due to the absence of starburst galaxies in the local Universe reaching such extreme luminosities. We investigate the validity of this assumption using new Chandra and XMM-Newton observations of three relatively nearby (z∼0.1) starburst galaxies, chosen on the basis of their SDSS optical spectrum, and their coincidence with a bright X-ray source from the 2XMMp catalogue. If originating from the galaxy in question, the X-ray luminosity is in each case greater than 1042ergs-1 (and in one case reaches 1043ergs-1), meaning these would be the most X-ray luminous starburst galaxies yet discovered if no AGN were present. However, the new X-ray data shows two of the three sources to display X-ray spectral and temporal variability between observations, with all three appearing point-like at Chandra resolution. Furthermore they are spectrally dissimilar to starburst X-ray emission, possessing power-law dominated spectra more reminiscent of AGN. We therefore conclude that otherwise innocuous AGN are indeed fuelling the X-ray emission from these galaxies, and that the assumption starburst galaxies do not exceed 1042ergs-1 remains observationally justified.
AB - It is commonly assumed in deep survey work that all galaxies with X-ray luminosities above about 1042ergs-1 harbour AGN, regardless of their optical spectrum, due to the absence of starburst galaxies in the local Universe reaching such extreme luminosities. We investigate the validity of this assumption using new Chandra and XMM-Newton observations of three relatively nearby (z∼0.1) starburst galaxies, chosen on the basis of their SDSS optical spectrum, and their coincidence with a bright X-ray source from the 2XMMp catalogue. If originating from the galaxy in question, the X-ray luminosity is in each case greater than 1042ergs-1 (and in one case reaches 1043ergs-1), meaning these would be the most X-ray luminous starburst galaxies yet discovered if no AGN were present. However, the new X-ray data shows two of the three sources to display X-ray spectral and temporal variability between observations, with all three appearing point-like at Chandra resolution. Furthermore they are spectrally dissimilar to starburst X-ray emission, possessing power-law dominated spectra more reminiscent of AGN. We therefore conclude that otherwise innocuous AGN are indeed fuelling the X-ray emission from these galaxies, and that the assumption starburst galaxies do not exceed 1042ergs-1 remains observationally justified.
KW - active galactic nuclei
KW - star formation
U2 - 10.1063/1.3475293
DO - 10.1063/1.3475293
M3 - Conference contribution/Paper
AN - SCOPUS:77955828917
SN - 9780735407954
T3 - AIP Conference Proceedings
SP - 449
EP - 450
BT - X-ray Astronomy-2009
T2 - International Conference on X-ray Astronomy-2009: Present Status, Multi-Wavelength Approach and Future Perspectives
Y2 - 7 September 2009 through 11 September 2009
ER -