THE VARIABLE HARD X-RAY EMISSION OF NGC 4945 AS OBSERVED BYNUSTAR

Spatially resolved Fe K spectroscopy of NGC 4945

“…This can be ascribed to superwind-starburst-driven, metal-enriched galactic-scale outflows (Veilleux, Cecil & Bland-Hawthorn 2005) that are dominated by emission from hot plasma, as shown by Schurch, Roberts & Warwick (2002). A detailed investigation is beyond the scope of this work but the inclusion of a simple thermal component (mekal model in Xspec) gives a gas temperature kT=2.0 +1.5 −1.0 keV with a contribution of ∼ 15% to the total 3-10 kV flux, in agreement with Schurch, Roberts & Warwick (2002) and Puccetti et al (2014).…”

“…Indeed, the five spectra were fitted with a model consisting of a reflection continuum (model PEXRAV, Magdziarz & Zdziarski 1995) and five emission lines for neutral Fe Kα at 6.4 keV, Fe xxv He-α (actually a triplet, with the two most intense lines, the forbidden and the resonant, at 6.637 keV and 6.700 keV), Fe xxvi Ly-α at 6.966 keV, Fe Kβ at 7.058 keV and for the Compton Shoulder (CS) redwards of the line core (with energy fixed at 6.3 keV and σ = 40 eV, Matt 2002). A value of Γ = 1.9 was used for the illuminating continuum, as measured from the NuSTAR high energy spectra (Puccetti et al 2014), and the cosine of the inclination angle of the reflector is fixed to 0.45. A Galactic absorption of 1.38 × 10 21 cm −2 has been taken into account (Kalberla et al 2005).…”

“…By inverting the previous equation and using a 2-10 keV luminosity LX = 4 × 10 42 erg s −1 (Puccetti et al 2014), we can derive a density n cl ≃ 10 2 cm −3 for the clump.…”

“…NGC 4945 is one of the nearest AGN (D ∼3.7 Mpc) and the brightest Seyfert 2 in the 100 keV sky (Done, Madejski & Smith 1996), with a highly absorbed (NH = 3.5 × 10 24 cm −2 , Puccetti et al 2014) and extremely variable primary continuum Madejski et al 2000;Done et al 2003). Such a strong absorption along the line of sight completely blocks the nuclear emission below 10 keV and allows it to be observed only at higher energies, though heavily affected by Compton scattering and photoelectric absorption.…”

“…Such a strong absorption along the line of sight completely blocks the nuclear emission below 10 keV and allows it to be observed only at higher energies, though heavily affected by Compton scattering and photoelectric absorption. Broadband analyses of its high energy variability (Yaqoob 2012;Puccetti et al 2014) led to important constraints Merged ACIS-S image of the central 40×40 arcsec region of NGC 4945, in the 6.2-6.5 keV energy band. Right panel: Merged ACIS-S image of the central 40×40 arcsec region of NGC 4945, in the 6.6-7.0 keV energy band.…”