A single radio-emitting nucleus in the dual AGN candidate NGC 5515

TL;DR

This study used high-resolution radio and optical observations to investigate whether NGC 5515 hosts one or two active galactic nuclei, finding evidence more consistent with a single AGN.

Contribution

The paper provides multi-wavelength observational analysis that favors a single AGN scenario over a dual AGN in NGC 5515, challenging previous dual nucleus interpretations.

Findings

Detected only one compact radio source at NGC 5515's position.

Optical spectrum shows similar properties for double-peaked lines.

Single radio source and spectral characteristics support a single AGN hypothesis.

Abstract

The Seyfert galaxy NGC 5515 has double-peaked narrow-line emission in its optical spectrum, and it has been suggested that this could indicate that it has two active nuclei. We observed the source with high resolution Very Long Baseline Interferometry (VLBI) at two radio frequencies, reduced archival Very Large Array data, and re-analysed its optical spectrum. We detected a single, compact radio source at the position of NGC 5515, with no additional radio emission in its vicinity. The optical spectrum of the source shows that the blue and red components of the double-peaked lines have very similar characteristics. While we cannot rule out unambiguously that NGC 5515 harbours a dual AGN, the assumption of a single AGN provides a more plausible explanation for the radio observations and the optical spectrum.