1999/08/27 by M. Cappi, M. Persic, Cappi, M. +17
Environmental Science · Physics and Astronomy · #Astrophysics (astro-ph) #FOS: Physical sciences #Galaxies: Formation, Evolution, Phenomena #Impact of Light on Environment and Health #X-ray Spectroscopy and Fluorescence Analysis #astro-ph
paper · pdf · doi:10.48550/arxiv.astro-ph/9908312
17 Latex pages, 7 figures, uses psfig.sty. Accepted for publication in Astronomy and Astrophysics
arxiv created 1999/08/27 · openalex publication_date 1999/08/27 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
BeppoSAX observations of the nearby archetypical starburst galaxies NGC253 and M82 are presented. Spectral analysis shows that the 2-10 keV spectra of both galaxies, extracted from the central 4' regions, are best fitted by a thermal emission model with kT~6-9 keV and metal abundances ~ 0.1-0.3 solar. The spatial analysis yields clear evidence that this emission is extended in NGC 253, and possibly also in M82. These results clearly rule out a LLAGN as the \it main origin of the X-ray emission in NGC 253. For M82, the presence of an Fe-K line at ~ 6.7 keV, and the convex profile of its 2-10 keV continuum, indicate a significant thermal component. Contributions from point sources (e.g. X-ray binaries, supernova remnants, and/or a LLAGN) and Compton emission are also likely. Altogether, BeppoSAX results provide compelling evidence for the existence of a hot interstellar plasma in both galaxies, possibly in the form of superwind outflows from the disks of these galaxies. Order-of-magnitude estimates and some implications, such as the expelled mass and the energetics of the outflowing gas of this superwind scenario, are discussed. These new results also suggest some similarity between the X-ray emission from these galaxies and that from the Galactic Ridge.