Probing the circumnuclear environment of NGC1275 with High-Resolution X-ray spectroscopy

Kavli Affiliate: Erin A. Kara

| First 5 Authors: Christopher S. Reynolds, Robyn N. Smith, Andrew C. Fabian, Yasushi Fukazawa, Erin A. Kara

| Summary:

NGC1275 is the Brightest Cluster Galaxy (BCG) in the Perseus cluster and
hosts the active galactic nucleus (AGN) that is heating the central 100,kpc of
the intracluster medium (ICM) atmosphere via a regulated feedback loop. Here we
use a deep 490ks Cycle-19 Chandra High-Energy Transmission Grating (HETG)
observation of NGC1275 to study the anatomy of this AGN. The X-ray continuum is
adequately described by an unabsorbed power-law with photon index
$Gammaapprox 1.9$, creating strong tension with the detected column of
molecular gas seen via HCN and HCO$^+$ line absorption against the parsec-scale
core/jet. This tension is resolved if we permit a composite X-ray source;
allowing a column of $N_Hsim 8times 10^{22},{rm cm}^{-2}$ to cover $sim
15$% of the X-ray emitter does produce a significant improvement in the
statistical quality of the spectral fit. We suggest that the dominant
unabsorbed component corresponds to the accretion disk corona, and the
sub-dominant X-ray component is the jet working surface and/or jet cocoon that
is expanding into clumpy molecular gas. We suggest that this may be a common
occurence in BCG-AGN. We conduct a search for photoionized absorbers/winds and
fail to detect such a component, ruling out columns and ionization parameters
often seen in many other Seyfert galaxies. We detect the 6.4keV iron-K$alpha$
fluorescence line seen previously by XMM-Newton and Hitomi. We describe an
analysis methodology which combines dispersive HETG spectra, non-dispersive
microcalorimeter spectra, and sensitive XMM-Newton/EPIC spectra in order to
constrain (sub)arcsec-scale extensions of the iron-K$alpha$ emission region.

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