What question did this study set out to answer?

This research aims to investigate various geometries influencing the intrinsic nuclear flux related to neutrino production in NGC 1068.

May 9, 2026

NGC 1068: Exploring various geometries based on hard X-ray observations and their implications for neutrino production models in the source

Key Points

This research aims to investigate various geometries influencing the intrinsic nuclear flux related to neutrino production in NGC 1068.
Analyzed NuSTAR spectra from two different time periods and combined results from INTEGRAL/IBIS/ISGRI and INTEGRAL/SPI ranging from 2.5 to 500 keV.
Utilized MYTorus models to compare different scenarios of X-ray absorption and infer intrinsic nuclear components.
Examined multiple Compton-thick AGN models to establish comparisons and constraints on neutrino spectra.
The intrinsic nuclear spectrum yielded a normalization around ∼0.017 ph/cm²/s/keV, indicating significant differences with some neutrino models.
Comparison with published models shows the best-fit nuclear spectrum is lower than predictions for one model and marginally agrees with another.
Luminosities ranged from 1.2 × 10^42 erg/s to 6.4 × 10^42 erg/s, suggesting intricate interactions affecting observed neutrinos.

Abstract

The Compton-thick active galactic nucleus NGC 1068 has received increased attention since IceCube results reported high-energy neutrinos associated with the source. Numerous models attribute neutrino production to the region in or near the corona. The very high absorption column makes the X-ray/soft gamma-ray characteristics of the core not directly visible. Using broadband hard X-ray observations, we investigated various geometries to constrain the intrinsic nuclear flux from the core. We compare our results with both the assumed corona models (the main ingredient of the cascade process) and the predicted cascade spectra of the neutrino production models. We analyzed NuSTAR spectra from two periods along with the long-term average spectra from INTEGRAL/IBIS/ISGRI and INTEGRAL/SPI from 2. 5--500, keV using MYTorus models. We tested multiple MYTorus scenarios based on analyses of other Compton-thick AGN. ̧irc) and (0^ ̧irc) compared to a ``coupled'' scenario or a decoupled scenario with only a (90^ ̧irc) or (0^ ̧irc) component. In this scenario, the differences between the datasets can be explained by changes in the line-of-sight absorption column. For that geometry, the spectrum of the intrinsic nuclear component has a (Γ = 1. 96), (E_ cut) fixed to 500 keV, best-fit normalization (∼ 0. 017), ph/cm (^ 2) /s/keV and a 99% upper-limit normalization of (∼ 0. 095), ph/cm (^ 2) /s/keV at 1 keV, which corresponds to 2--10, keV intrinsic luminosities of (1. 2 10^ 42), erg/s and (6. 4 10^ 42), erg/s, respectively. A comparison with four published neutrino production models in NGC 1068 found that our best-fit intrinsic nuclear spectrum is significantly lower than the predicted cascade spectrum for one of them, while for two others, our results are below the assumed X-ray model ( (∼ 5-10 questioning the resulting cascade spectra. Finally, the fourth model is marginally consistent with our results. However, this does not exclude neutrino production in the central part of the source.

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