X-Ray Emission of the γ-ray-loud Young Radio Galaxy NGC 3894
Abstract
The radio source 1146+596 is hosted by the elliptical/S0 galaxy NGC 3894, with a low-luminosity active nucleus. The radio structure is compact, suggesting a very young age for the jets in the system. Recently, the source has been confirmed as a high-energy (HE; >0.1 GeV) γ-ray emitter in the most recent accumulation of Fermi Large Area Telescope data. Here we report on the analysis of the archival Chandra X-ray Observatory data for the central part of the galaxy, consisting of a single 40 ks long exposure. We have found that the core spectrum is best fitted by a combination of an ionized thermal plasma with a temperature of ≃0.8 keV, and a moderately absorbed power-law component (photon index Γ = 1.4 ± 0.4, hydrogen column density N H/1022 cm-2 = 2.4 ± 0.7). We have also detected the iron Kα line at 6.5 ± 0.1 keV, with a large equivalent width of ${1.0}_{-0.5}^{+0.9}$ keV. Based on the simulations of Chandra's point-spread function, we have concluded that while the soft thermal component is extended on the scale of the galaxy host, the hard X-ray emission within the narrow photon energy range 6.0-7.0 keV originates within the unresolved core (effectively the central kiloparsec radius). The line is therefore indicative of the X-ray reflection from a cold neutral gas in the central regions of NGC 3894. We discuss the implications of our findings in the context of the X-ray Baldwin effect. NGC 3894 is the first young radio galaxy detected in HE γ-rays with the iron Kα line.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- November 2021
- DOI:
- 10.3847/1538-4357/ac1ff5
- arXiv:
- arXiv:2106.13193
- Bibcode:
- 2021ApJ...922...84B
- Keywords:
-
- 2035;
- 2033;
- 17;
- 1390;
- 1343;
- 633;
- Astrophysics - High Energy Astrophysical Phenomena;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- Revised version, accepted for publication in the Astrophysical Journal