2001/02/01 by Stefan Immler, S. Immler, Q. Daniel Wang · 2 citations
Physics and Astronomy · #Astronomy #Astrophysical Phenomena and Observations #Astrophysics #Astrophysics and Cosmic Phenomena #Bulge #Galaxies: Formation, Evolution, Phenomena #Galaxy #Luminosity #Physics #ROSAT #Spiral galaxy #Supernova #astro-ph
paper · pdf · doi:10.1086/321335
15 pages, 8 tables, 9 figures, accepted for publication in the Astrophysical Journal
arxiv created 2001/02/01 · openalex publication_date 2001/06/10 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
We present results from the analysis of deep ROSAT HRI and PSPC observations of the spiral galaxy M81. The inferred total (0.5-2 keV band) luminosity of M81 is ~3 × 10 40 ergs s -1 , excluding the contribution from identified interlopers found within the D 25 ellipse. The nucleus of the galaxy alone accounts for about 65% of this luminosity. The rest is due to 26 other X-ray sources (contributing ~10%) and to apparently diffuse emission, which is seen across much of the galactic disk and is particularly bright in the bulge region around the nucleus. Spectral analysis further gives evidence for a soft component, which can be characterized by a two-temperature optically thin plasma with temperature at ~0.15 and 0.60 keV and an absorption of the galactic foreground only. These components, accounting for ~13% of the X-ray emission from the region, apparently arise in a combination of hot gas and faint discrete sources. We find interesting spatial coincidences of luminous (10 37 -10 40 ergs s -1 ) and variable X-ray sources with shock-heated optical nebulae. Three of them are previously classified as supernova remnant candidates. The other one is far off the main body of M81 but is apparently associated with a dense H I concentration produced most likely by the tidal interactions of the galaxy with its companions. These associations suggest that such optical nebulae may be powered by outflows from luminous X-ray binaries, which are comparable to, or more luminous than, Galactic "microquasars."