Searcharxiv⌕ Search
Home/Archive/arXiv

arXiv · 1708.07011

Radio jets in NGC 4151: where eMERLIN meets HST

D. R. A. Williams·I. M. McHardy·R. D. Baldi·R. J. Beswick·M. K. Argo·B. T. Dullo·J. H. Knapen·E. Brinks·D. M. Fenech·C. Mundell·T. W. B. Muxlow·F. Panessa·H. Rampadarath·J. Westcott
View original source ↗Read source document ↗Export metadata ↓

Abstract

We present high-sensitivity eMERLIN radio images of the Seyfert galaxy NGC 4151 at 1.5 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 years 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 AGN which is currently active and feeding the jet. We detect no significant motion in 22 years 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 1.5 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$\alpha$, [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 photoionisation from the central AGN is responsible for the observed emission line properties further than 4" (360 pc) from the core, C4. Within this region, several evidences (radio-line co-spatiality, low [O III]/H$\alpha$ and estimated fast shocks) suggest additional ionisation from the jet.

Explore related subjects

astro-ph.GA

Keep this discovery

BibTeXRIS

D. R. A. Williams, I. M. McHardy, R. D. Baldi, R. J. Beswick, M. K. Argo, B. T. Dullo, J. H. Knapen, E. Brinks, D. M. Fenech, C. Mundell, T. W. B. Muxlow, F. Panessa, H. Rampadarath, J. Westcott. 2017-08-23. Radio jets in NGC 4151: where eMERLIN meets HST. https://doi.org/10.1093/mnras%2Fstx2205

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

Fast Dynamical Modelling of Milky Way Globular Clusters -- II. Impacts of Black Hole Prescriptions

The populations of stellar-mass black holes (BHs) in globular clusters (GCs) play a key role in their dynamical evolution, however the mechanisms surrounding their formation and retention are uncertain. In this work, we extend the analysis of Paper I by fitting coupled rapid cluster evolution and multimass equilibrium models to a large sample of Milky Way GCs, under a variety of prescriptions for stellar evolution, BH formation and supernovae (SN) natal kicks. We explore the impacts of adopting SSE or PARSEC (through SEVN) prescriptions for BH initial-final mass relations, the rapid or delayed SN fallback mechanisms, and an ad hoc grid of kick strengths ejecting between 40 and 80 per cent of all BHs formed. All models reproduce the same present-day conditions despite starting from notably different initial BH populations, due to the correlation found between the initial cluster densities and initial BH mass fractions. A linear relationship is found between the (log) initial half-mass density and the initial BH mass fraction, with the SEVN models resulting in median densities ($\rho_{h,0} \sim 10^{7.2\pm1.1}\,{M_\odot pc^{-3}}$) nearly an order of magnitude higher than those of SSE ($\rho_{h,0} \sim 10^{6.4\pm0.9}\,{M_\odot pc^{-3}}$). We also find that both the bottom-light initial mass functions and the present-day BH mass fractions previously inferred are relatively robust against the stellar evolution models and natal kick prescriptions assumed. Finally, we discuss the implications of these results on the expected numbers and properties of dynamical binary-BH mergers, and the growth of intermediate-mass BHs.

astro-ph.GA↗
arXiv2026

SPURS: An Ultra-deep View Inside the Compact, Nitrogen-Enriched Nuclei of Little Red Dots

We present the first ultra-deep rest-UV spectroscopy of four UV-bright Little Red Dots (LRDs), obtained from the SPURS Cycle 4 Large Program. The spectra reveal broad CIV (FWHM $\approx2700-2800$ km s$^{-1}$) in two LRDs, alongside narrow-line densities elevated above star-forming galaxies ($n_e\sim10^4-10^5$ cm$^{-3}$, reaching $10^6$ cm$^{-3}$ in the most extreme source) and nitrogen-enhancements in all four LRDs. We detect broad HeII emission (FWHM $\approx930$ km s$^{-1}$) in one LRD, and two others with fast P-Cygni absorption ($\gtrsim2200$ km s$^{-1}$). Strong interstellar absorption lines and Ly$\alpha$ damping wings reveal the UV continuum is deeply embedded in neutral gas ($N_{\rm HI}\gtrsim10^{22}$ cm$^{-2}$) in all four LRDs. Detections of fluorescent FeII and OI emission and fine-structure absorption indicate this gas lies close to the UV-emitting region. In archival $z>4$ samples, we find nitrogen and strong CIII] emission are significantly more common in LRDs than in the galaxy population. The transmission of broad CIV, tracing the broad-line region or cocoon, depends on rest-optical color within our sample, consistent with an orientation-dependent picture in which bluer, less obscured sightlines offer a more direct, polar view of the central engine and its outflows. We find several potential signatures of very massive stars, whose winds may contribute to nitrogen enhancement. We investigate other abundance patterns expected from supermassive stars but our results are inconclusive. Our results place the UV-emitting region within $\lesssim8$ pc of the LRD nucleus, consistent with an actively assembling nuclear star cluster. Dynamical interactions in this extremely dense environment, including tidal disruption of stars, may explain the high incidence of nitrogen enhancements in LRDs.

astro-ph.GA↗
arXiv2026

Nitrogen-Loud Quasars from the Dark Energy Spectroscopic Instrument. I. Sample Selection and Basic Properties

We present the largest sample to date of nitrogen-loud (N-loud) quasars with strong broad N IV] $\lambda1486$ and/or N III] $\lambda1750$ emission lines over the redshift range $1.6 < z < 4.3$, selected from the Dark Energy Spectroscopic Instrument (DESI) Data Release 1. The final sample contains 1,993 N-loud quasars, corresponding to about 1.2% of the parent quasar sample. The $L_{1450}$ distribution of the N-loud quasars is broadly similar to that of the DESI parent sample, but their redshift distribution is distinct, with a stronger concentration around $z \sim 2.5$--3. Their composite spectrum displays a broadly similar UV continuum shape to that of the parent quasars, while showing significantly enhanced broad nitrogen emission features, including N V, N IV], and N III]. Other metal emission features also show a moderate enhancement. Relative to a control sample matched in redshift and UV continuum luminosity, the N-loud quasars show systematically narrower broad C IV and Mg II emission lines, lower single-epoch virial black hole masses, and higher Eddington ratios, suggesting that N-loud quasars may preferentially appear during a relatively rapid black hole accretion phase. The radio-loud fraction is 10.1%, with the highest fraction among objects exhibiting both N III] and N IV] emission. The catalog provides a statistical baseline for future studies of nitrogen enhancement and its physical origin.

astro-ph.GA↗