222 research outputs found
Hard X-ray Emission from the M87 AGN Detected with NuSTAR
M87 hosts a 3-6 billion solar mass black hole with a remarkable relativistic
jet that has been regularly monitored in radio to TeV bands. However, hard
X-ray emission \gtrsim 10keV, which would be expected to primarily come from
the jet or the accretion flow, had never been detected from its unresolved
X-ray core. We report NuSTAR detection up to 40 keV from the the central
regions of M87. Together with simultaneous Chandra observations, we have
constrained the dominant hard X-ray emission to be from its unresolved X-ray
core, presumably in its quiescent state. The core spectrum is well fitted by a
power law with photon index Gamma=2.11 (+0.15 -0.11). The measured flux density
at 40 keV is consistent with a jet origin, although emission from the
advection-dominated accretion flow cannot be completely ruled out. The detected
hard X-ray emission is significantly lower than that predicted by synchrotron
self-Compton models introduced to explain emission above a GeV.Comment: 5 pages, 4 figures, updated to better match the published version in
the Astrophysical Journal Letters. A minor typo in the published version
(angular scale should be 1 arcsec = 78 pc instead, no result of the paper is
affected) is fixed her
Prospects for AGN Studies with AXIS: AGN Fueling -- Resolving Hot Gas inside Bondi Radius of SMBHs
Hot gas around a supermassive black hole (SMBH) should be captured within the
gravitational "sphere of influence", characterized by the Bondi radius. Deep
Chandra observations have spatially resolved the Bondi radii of at least five
nearby SMBHs. Contrary to earlier hot accretion models that predicted a steep
temperature increase within the Bondi radius, none of the resolved temperature
profiles exhibit such an increase. The temperature inside the Bondi radius
appears to be complex, indicative of a multi-temperature phase of hot gas with
a cooler component at about 0.2-0.3 keV. The density profiles within the Bondi
regions are shallow, suggesting the presence of strong outflows. These findings
might be explained by recent realistic numerical simulations that suggest that
large-scale accretion inside the Bondi radius can be chaotic, with cooler gas
raining down in some directions and hotter gas outflowing in others. With an
angular resolution similar to Chandra and a significantly larger collecting
area, AXIS will collect enough photons to map the emerging accretion flow
within and around the "sphere of influence" of a sample of active galactic
nuclei (AGNs). AXIS will reveal transitions in the inflow that ultimately fuels
the AGN, as well as outflows that provide feedback to the environment.Comment: 7 pages, 3 figures. This White Paper is part of a series commissioned
for the AXIS Probe Concept Mission; additional AXIS White Papers can be found
at the AXIS website http://axis.astro.umd.edu/ with a mission overview here
arXiv:2311.0078
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