3C 33: another case of photoionized soft X-ray emission in radio galaxies

TL;DR

This study analyzes the X-ray spectral properties of the radio galaxy 3C 33, revealing a complex spectrum with a heavily obscured nucleus and soft X-ray emission likely originating from photoionized gas, using archival Chandra and XMM-Newton data.

Contribution

It provides a comprehensive X-ray spectral analysis of 3C 33, highlighting the nature of its soft X-ray emission and supporting the photoionization origin through combined X-ray and optical data.

Findings

The nucleus shows heavy obscuration with N_H~10^23 cm^-2.

Soft X-ray emission is consistent with photoionized gas.

Jet contribution to soft X-ray emission is minimal.

Abstract

All the observations available in the Chandra and XMM-Newton archives have been used to investigate the X-ray spectral properties of 3C 33. In this paper is presented a complete X-ray analysis of the nuclear emission of this narrow line radio galaxy. The broad band spectrum of 3C 33 is complex. The hard part resembles that of Seyfert 2 galaxies, with a heavily obscured nuclear continuum (N_H~10^23 cm^-2) and a prominent Fe Kalpha line. This represents the nuclear radiation directly observed in transmission through a cold circumnuclear gas. On the other hand an unabsorbed continuum plus emission lines seem to fit well the soft part of the spectrum (0.5-2 keV) suggesting that the jet does not significantly contribute to the X-ray emission. We discuss the possible collisional or photoionized origin of the gas that emits the soft X-ray lines. Our results, strengthened by optical spectroscopy favor the photoionization scenario.