Physics and Astronomy
Observational confirmation of hot accretion model predictions has been hindered by the challenge to resolve spatially the Bondi radii of black holes with X-ray telescopes. Here, we use the Megasecond Chandra X-ray Visionary Project observation of the NGC 3115 supermassive black hole to place the first direct observational constraints on the spatially and spectroscopically resolved structures of the X-ray emitting gas inside the Bondi radius of a black hole. We measured temperature and density profiles of the hot gas from a fraction out to tens of the Bondi radius (RB = 24-48 = 112-224 pc). The projected temperature jumps significantly from ~0.3 keV beyond 5'' to ~0.7 keV within ~4''-5'', but then abruptly drops back to ~0.3 keV within ~3''. This is contrary to the expectation that the temperature should rise toward the center for a radiatively inefficient accretion flow. A hotter thermal component of ~1 keV inside 3'' (~150 pc) is revealed using a two-component thermal model, with the cooler ~0.3 keV thermal component dominating the spectra. We argue that the softer emission comes from diffuse gas physically located within ~150 pc of the black hole. The density profile is broadly consistent with ρ∝r –1 within the Bondi radius for either the single temperature or the two-temperature model. The X-ray data alone with physical reasoning argue against the absence of a black hole, supporting that we are witnessing the onset of the gravitational influence of the supermassive black hole.
The Astrophysical Journal
The Megasecond Chandra X-Ray Visionary Project Observation of NGC 3115: Witnessing the Flow of Hot Gas within the Bondi Radius. Wong, K.-W., Irwin, J. A., Shcherbakov, R. V., Yukita, M., Million, E. T., & Bregman, J. N. 2014, ApJ, 780, 9.
Publisher's Copyright and Source
© 2014. The American Astronomical Society. All rights reserved.
Originally published in The Astrophysical Journal, volume 780, issue 1, article 9, 17 pp., 2014, January 1. Available online at: http://doi.org/10.1088/0004-637X/780/1/9.
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