Possible gamma-ray emission of radio intermediate AGN III Zw 2 and its implication on the evolution of jets in AGNs

TL;DR

This study models the spectral energy distribution of the radio intermediate AGN III Zw 2, suggesting it may emit gamma rays and be a young, early-stage jet source, with implications for understanding AGN jet evolution.

Contribution

It provides the first detailed SED modeling of III Zw 2, indicating potential gamma-ray emission and its place in jet evolution, bridging radio intermediate and gamma-ray AGNs.

Findings

The inverse Compton peak of III Zw 2 is at a few MeV.

The gamma-ray flux is below Fermi/LAT detection sensitivity.

III Zw 2 exhibits jet properties similar to gamma-ray AGNs.

Abstract

AGNs with hard $\gamma$-ray emission identified so far are radio-loud. III Zw 2 is a radio intermediate AGN with a relativistic jet. We study its spectral energy distribution (SED) and find that the broad band emissions are dominated by the non-thermal emissions from the jet. We model its SED through a synchrotron + inverse Compton (IC) model. The results show that the IC component of III Zw 2 peaks at a few MeV, and the flux density drops rapidly at higher energy with photon index $\Gamma\approx3.3$ above 0.1 GeV. The predicted flux is slightly over the sensitivity of $Fermi$/LAT, but it is not included in the first $Fermi$/LAT AGN catalog. The reason for this may be: 1) that the IC peak is low and the spectrum is very steep above 0.1 GeV, 2) that III Zw 2 is in the low state during the period of the $Fermi$/LAT operation. We also find that III Zw 2 follows similar jet processes as those in $\gamma$-ray AGNs, e.g., the relation between jet power and radiation power, called the blazar sequence. We suggest that III Zw 2 may be a young source at an earlier stage of jet activity.