Radio jets in NGC 4151: where eMERLIN meets HST

Journal
Date Issued
2017
Author(s)
Williams, D. R. A.
•
McHardy, I. M.
•
•
Beswick, R. J.
•
Argo, M. K.
•
Dullo, B. T.
•
Knapen, J. H.
•
Brinks, E.
•
Fenech, D. M.
•
Mundell, C. G.
•
Muxlow, T. W. B.
•
•
Rampadarath, H.
•
Westcott, J.
DOI
Abstract
We present high-sensitivity eMERLIN radio images of the Seyfert galaxy NGC 4151 at 1.51 GHz. We compare the new eMERLIN images to those from archival MERLIN observations in 1993 to determine the change in jet morphology in the 22 yr between observations. We report an increase by almost a factor of 2 in the peak flux density of the central core component, C4, thought to host the black hole, but a probable decrease in some other components, possibly due to adiabatic expansion. The core flux increase indicates an active galactic nucleus (AGN) that is currently active and feeding the jet. We detect no significant motion in 22 yr between C4 and the component C3, which is unresolved in the eMERLIN image. We present a spectral index image made within the 512 MHz band of the 1.51 GHz observations. The spectrum of the core, C4, is flatter than that of other components further out in the jet. We use HST emission-line images (H α, [O III] and [O II]) to study the connection between the jet and the emission-line region. Based on the changing emission-line ratios away from the core and comparison with the eMERLIN radio jet, we conclude that photoionization from the central AGN is responsible for the observed emission-line properties further than 4 arcsec (360 pc) from the core, C4. Within this region, a body of evidence (radio-line co-spatiality, low [O III]/H α and estimated fast shocks) suggests additional ionization from the jet.
Volume
472
Issue
4
Start page
3842
Uri
Url
Issn Identifier
0035-8711
Ads BibCode
2017MNRAS.472.3842W
Rights
open.access
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