2005/10/06 by G. Madejski, Greg Madejski, Chris Done +4 · 28 citations
Physics and Astronomy · #Accretion (finance) #Active galactic nucleus #Astronomy #Astrophysical Phenomena and Observations #Astrophysics #Astrophysics and Cosmic Phenomena #Emission spectrum #Galaxies: Formation, Evolution, Phenomena #Galaxy #Ionization #Luminosity #Maser #Megamaser #Observatory #Physics #Spectral line #astro-ph
paper · pdf · doi:10.1086/497894
published in The Astrophysical Journal 636(1), 75-82 (IOP Publishing) · Accepted by the Astrophysical Journal
arxiv created 2005/10/06 · openalex publication_date 2005/12/21 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/06
An observation of the H 2 O megamaser galaxy IC 2560 with the Chandra X-Ray Observatory reveals a complex spectrum composed of soft X-ray emission due to multitemperature thermal plasma and a hard continuum with strong emission lines. The continuum is most likely a Compton reflection (reprocessing) of primary emission that is completely absorbed at least up to 7 keV. The lines can be identified with fluorescence from Si, S, and Fe in the lowest ionization stages. The equivalent widths of the Si and S lines are broadly compatible with those anticipated for reprocessing by optically thick cold plasma of solar abundances, while the large equivalent width of the Fe line requires some overabundance of iron. A contribution to the line from a transmitted component cannot be ruled out, but the limits on the strength of the Compton shoulder make it less likely. From the bolometric luminosity of the nuclear region, we infer that the source radiates at 1%-10% of its Eddington luminosity for an adopted central mass of 3 × 10 6 M ☉ . The overall spectrum is consistent with the hypotheses that the central engines powering the detected megamasers in accretion disks are obscured from direct view by the associated accretion disk material itself and that there is a correlation between the occurrence of megamaser emission and Compton-thick absorption columns. For the 11 known galaxies with both column density measurements and maser emission believed to arise from accretion disks, eight AGNs are Compton thick.