1. Deep XMM-Newton Observations Reveal the Origin of Recombining Plasma in the Supernova Remnant W44
- Author
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Smith, Randall K., Orlando, Salvatore, Bocchino, Fabrizio, Miceli, Marco, Okon, Hiromichi, Tanaka, Takaaki, Uchida, Hiroyuki, Yamaguchi, Hiroya, Tsuru, Takeshi Go, Seta, Masumichi, Yoshiike, Satoshi, Okon H., Tanaka T., Uchida H., Yamaguchi H., Tsuru T.G., Seta M., Smith R.K., Yoshiike S., Orlando S., Bocchino F., and Miceli M.
- Subjects
010504 meteorology & atmospheric sciences ,Astrophysics::High Energy Astrophysical Phenomena ,Supernova remnants (1667) ,FOS: Physical sciences ,Astrophysics ,Molecular cloud ,01 natural sciences ,X-ray astronomy ,Settore FIS/05 - Astronomia E Astrofisica ,Plasma astrophysics (1261) ,Supernova remnant ,0103 physical sciences ,Plasma astrophysics ,Adiabatic process ,Spectroscopy ,010303 astronomy & astrophysics ,Astrophysics::Galaxy Astrophysics ,0105 earth and related environmental sciences ,High Energy Astrophysical Phenomena (astro-ph.HE) ,Physics ,Astronomy and Astrophysics ,Plasma ,Supernova ,Space and Planetary Science ,Molecular clouds (1072) ,Electron temperature ,X-ray astronomy (1810) ,Astrophysics - High Energy Astrophysical Phenomena - Abstract
Recent X-ray studies revealed over-ionized recombining plasmas (RPs) in a dozen mixed-morphology (MM) supernova remnants (SNRs). However, the physical process of the over-ionization has not been fully understood yet. Here we report on spatially resolved spectroscopy of X-ray emission from W44, one of the over-ionized MM-SNRs, using XMM-Newton data from deep observations, aiming to clarify the physical origin of the over-ionization. We find that combination of low electron temperature and low recombination timescale is achieved in the region interacting with dense molecular clouds. Moreover, a clear anti-correlation between the electron temperature and the recombining timescale is obtained from each of the regions with and without the molecular clouds. The results are well explained if the plasma was over-ionized by rapid cooling through thermal conduction with the dense clouds hit by the blast wave of W44. Given that a few other over-ionized SNRs show evidence for adiabatic expansion as the major driver of the rapid cooling, our new result indicates that both processes can contribute to over-ionization in SNRs, with the dominant channel depending on the evolutionary stage., 10 pages, 7 figures Accepted for publication in ApJ
- Published
- 2020