VLBI Imaging of the Double Peaked Emission Line Seyfert KISSR1494

TL;DR

This study uses VLBI observations to analyze the radio emission in Seyfert galaxy KISSR1494, suggesting a non-thermal origin likely from a coronal wind or accretion disk edge, with implications for understanding AGN outflows.

Contribution

First VLBI imaging of KISSR1494 revealing the nature of its radio emission and proposing a coronal wind origin over jet models.

Findings

Radio emission is steep-spectrum and non-thermal.

Estimated black hole mass is ~1.4×10^8 solar masses.

Outflow kinetic power is typical of low-luminosity AGN.

Abstract

We present here the results from dual-frequency phase-referenced VLBI observations of the Seyfert galaxy KISSR1494, which exhibits double peaked emission lines in its SDSS spectrum. We detect a single radio component at 1.6 GHz, but not at 5 GHz implying a spectral index steeper than $-1.5\pm0.5$ ($S_\nu\propto\nu^\alpha$). The high brightness temperature of the radio component ($\sim1.4\times10^7$ K) and the steep radio spectrum support a non-thermal synchrotron origin. A crude estimate of the black hole mass derived from the $M_{BH}-\sigma_{\star}$ relation is $\sim1.4\pm1.0\times10^8$ Msun; it is accreting at an Eddington rate of $\sim0.02$. The radio data are consistent with either the radio emission coming from the parsec-scale base of a synchrotron wind originating in the magnetised corona above the accretion disk, or from the inner ionised edge of the accretion disk or torus. In the former case, the narrow line region (NLR) clouds may form a part of the broad outflow, while in the latter, the NLR clouds may form a part of an extended disk beyond the torus. The radio and NLR emission may also be decoupled so that the radio emission originates in an outflow while the NLR is in a disk, and vice versa. While with the present data, it is not possible to clearly distinguish between these scenarios, there appears to be greater circumstantial evidence supporting the coronal wind picture in KISSR1494. From the kiloparsec-scale radio emission, the time-averaged kinetic power of this outflow is estimated to be $Q\approx1.5\times10^{42}$ erg s$^{-1}$, which is typical of radio outflows in low-luminosity AGN. This supports the idea that radio "jets" and outflowing coronal winds are indistinguishable in Seyfert galaxies.