ROSAT
ASCA observations of X-ray luminous starburst galaxies: NGC 3310 and 3690 |
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| Authors: | A L Zezas I Georgantopoulos & M J Ward |
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| Institution: | Department of Physics and Astronomy, University of Leicester, Leicester LE1 7RH,;National Observatory of Athens, Lofos Koufou, Palaia Penteli, 15236 Athens Greece |
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| Abstract: | We present ROSAT High Resolution Imager (HRI) and Position Sensitive Proportional Counter (PSPC)] and ASCA observations of the two luminous ( L x ∼ 1041−42 erg s−1) star-forming galaxies NGC 3310 and 3690. The HRI shows clearly that the sources are extended with the X-ray emission in NGC 3690 coming from at least three regions. The combined 0.1–10 keV spectrum of NGC 3310 can be described by two components, a Raymond–Smith plasma with temperature kT = 0.81+0.09−0.12 keV and a hard power law, Γ = 1.44−0.20−0.11 (or alternatively a harder Raymond–Smith plasma with kT ∼ 15 keV), while there is no substantial excess absorption above the Galactic column value. The soft component emission is probably a super wind while the nature of the hard emission is more uncertain with the likely origins being X-ray binaries, inverse Compton scattering of infrared photons, an active galactic nucleus or a very hot gas component (∼108 K). The spectrum of NGC 3690 is similar, with kT = 0.83+0.02−0.04 keV and Γ = 1.56+0.11−0.11. We also employ more complicated models such as a multi-temperature thermal plasma, a non-equilibrium ionization code or the addition of a third softer component, which improve the fit but not at a statistically significant level (2σ). These results are similar to recent results on the archetypal star-forming galaxies M82 and NGC 253. |
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| Keywords: | galaxies: individual: NGC 3690 galaxies: individual: NGC 3310 galaxies: interactions galaxies: starburst X-rays: galaxies |
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