Radio morphology of southern narrow-line Seyfert 1 galaxies with Very Large Array observations

Abstract

We present the results of new radio observations carried out with the Karl G. Jansky Very Large Array C-configuration at 5.5 GHz for a sample of southern narrow-line Seyfert 1 galaxies (NLS1s). This work increases the number of known radio-detected NLS1s in the southern hemisphere, and confirms that the radio emission of NLS1s is mainly concentrated in a central region at kpc-scale and only a few sources show diffuse emission. In radio-quiet NLS1s, the radio luminosity tends to be higher in steep-spectrum sources and be lower in flat-spectrum sources, which is opposite to radio-loud NLS1s. This may be because the radio emission of steep NLS1s is dominated by misaligned jets, AGN-driven outflows, or star formation superposing on a compact core. Instead the radio emission of flat NLS1s may be produced by a central core which has not yet developed radio jets and outflows. We discover new NLS1s harboring kpc-scale radio jets and confirm that a powerful jet does not require a large-mass black hole to be generated. We also find sources dominated by star formation. These NLS1s could be new candidates in investigating the radio emission of different mechanisms.

Jetted Narrow-Line Seyfert 1 Galaxies & Co.: Where Do We Stand?

“…I would like to stress that the point worth noting in the work by Lähteenmäki et al is the change radio quiet/loud many times per year. There are known examples of radio quiet AGN with relics of a past jet activity (e.g., [7][8][9]), but, in these cases, their jet was switched off as a consequence of the cosmological evolution. Today, they can safely be labeled as radio quiet.…”

“…In 2012, there were just a handful of jetted NLS1s showing large scale radio structures, but many more were discovered within a few years. Doi et al were the most prolific hunters of kiloparsec radio structures [95][96][97][98][99], but other significant contributions were either from surveys or individual studies [8,9,[100][101][102][103][104][105][106][107][108][109][110]. Nevertheless, despite the multiple efforts, the number of jetted NLS1s viewed at large angles, with kiloparsec scale structures, increased to a few tens, is still too low with respect to the expected thousands of objects.…”

“…Although there are many ways to identify an AGN, the optical spectroscopy is still the best one, the richest of information. The Sloan Digital Sky Survey (SDSS 9 ) played a key role in the identification of NLS1s and the generation of flux-limited samples, with its impressive wealth of high-quality spectra freely available. The forthcoming SDSS-V 10 is a guarantee of continuity.…”

“…Works worth noting are those based on 15 GHz VLBA observations of the MOJAVE Program 11 , which made it possible to study the kinematic of the jet components, and hence to measure superluminal β app (up to ∼ 11c), and the polarization [266][267][268]. It is also worth mentioning the work by Chen et al [9] on the first sample of NLS1s in the Southern Hemisphere.…”

Jet-Induced Feedback in the [O III] Lines of Early Evolution Stage Active Galactic Nuclei

“…It is worth noting that since the radio observations were carried out in the most extended configuration of JVLA, some large-scale extended emission may had been resolved out. However, a sample of NLS1s were investigated at the same frequency by Chen et al [73] using the JVLA in a more compact configuration. Their results seem to indicate that the morphology of jetted sources is typically compact, with no signs of large-scale radio lobes as those seen in other classes of jetted AGN.…”