English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Low-power radio sources dominate the radio sky. They tend to be small in sizeand core-dominated, but the origin of their properties and the evolution oftheir radio plasma are not well constrained. Interestingly, there is mountingevidence that low-power radio sources can significantly impact theirsurrounding gaseous medium and, therefore, may be more relevant for galaxyevolution than previously thought. In this paper, we present low radiofrequency observations obtained with LOFAR at 147 MHz of the radio sourcehosted by NGC 3998. This is a rare example of a low-power source which isextremely core-dominated, but which has two large-scale lobes of low surfacebrightness. We combine the new 147 MHz image with available 1400 MHz data toderive the spectral index over the source. Despite the low surface brightness,reminiscent of remnant structures, the lobes show an optically thin synchrotronspectral index (~ 0.6). We interpret this as being due to rapid decollimationof the jets close to the core, to high turbulence of the plasma flow, andentrainment of thermal gas. This could be the result of intermittent activityof the central AGN, or, more likely, temporary disruption of the jet due to theinteraction of the jet with the rich circumnuclear ISM. Both would result insputtering energy injection from the core which would keep the lobes fed,albeit at a low rate. We discuss these results in connection with theproperties of low-power radio sources in general. Our findings show thatamorphous, low surface brightness lobes should not be interpreted, by default,as remnant structures. Large, deep surveys (in particular the LOFAR 150 MHzLoTSS and the recently started 1400 MHz Apertif survey) will identify a growingnumber of objects similar to NGC 3998 where these ideas can be further tested.

The LOFAR view of NGC 3998, a sputtering AGN