Research summary
Kiloparsec-scale semirelativistic Fe Kα emission in NGC 5728
Paper II analyzes the combined NW and SE extended-bicone spectrum from 1.5–8 arcsec (approximately 300–1600 pc) and energy-resolved morphology from eleven Chandra/ACIS-S observations totaling approximately 260.8 ks. The bicone contains 2625 ± 51 net 0.3–8 keV counts. One-eighth-native-pixel imaging, adaptively binned or smoothed products, observation-specific MARX PSFs, an empirical PKS 1055+201 PSF, and a Her X-1 calibration comparison show PSF-relative extension along the bicone: the 5.0–6.3 keV red wing reaches approximately 6 arcsec (1.2 kpc), while the 6.3–6.5 keV rest-frame and 6.5–7.5 keV blue-wing emission reach approximately 5 arcsec (1 kpc). The bicone contains 120 red-wing, 70 rest-frame, 73 blue-wing, and 32 normalized hard-continuum counts; its 4–7 keV excess is 317 counts (approximately 15σ), while the cross-cone excess is 17 counts (1.4σ). A phenomenological fit gives red- and blue-wing significances of 5.4σ and 3.7σ, but across 33 tested spectral models the red wing remains robust at approximately 3σ or greater in nearly all cases, whereas rest-frame Fe XXV, Fe XXVI, and Fe Kβ can reduce the blue-wing significance to 1.4σ–3.7σ. Line-of-sight velocities near ±0.1c apply only if both wings are Doppler-shifted neutral Fe Kα; deprojected velocities and symmetry additionally depend on the adopted bicone geometry. Paper II does not directly measure a gas velocity field, gas mass, mass-outflow rate, kinetic energy, kinetic power, feedback efficiency, or causal feedback. Paper I morphology and spectral-mixture results are background, and Paper III multiwavelength circumnuclear results are not Paper II measurements.