Radio-emitting narrow-line Seyfert 1 galaxies in the JVLA perspective

Abstract

We report the first results of a survey on 74 narrow-line Seyfert 1 galaxies (NLS1s) carried out in 2015 with the Karl G. Jansky Very Large Array (JVLA) at 5 GHz in A-configuration. So far, this is the largest survey aimed to image the radio continuum of NLS1s. We produced radio maps in order to compare the general properties of three different samples of objects: radio-quiet NLS1s (RQNLS1s), steep-spectrum radio-loud NLS1s (S-NLS1s), and flat-spectrum radio-loud NLS1s (F-NLS1s). We find that the three classes correspond to different radio morphologies, with F-NLS1s being more compact, and RQNLS1s often showing diffuse emission on kpc scales. We also find that F-NLS1s might be low-luminosity and possibly young blazars, and that S-NLS1s are part of the parent population of F-NLS1s. Dedicated studies to RQNLS1s are needed in order to fully understand their role in the unification pictures.

Absorbed relativistic jets in radio-quiet narrow-line Seyfert 1 galaxies

“…However, they will be directly comparable with those already derived for different classes of NLS1s by Berton et al (2018a), whose observations were also carried out with the JVLA in A configuration. For this reason, we limit our brightness temperature estimate at 5.2 GHz, where the sources in Berton et al (2018a) were studied. The radio maps of the detected sources are shown in Figures 2 to 6.…”

“…As before, J1614+3454 has a constant spectral index, while J1232+4957 becomes steeper. When our results are compared to the in-band spectral indexes measured in at 5.2 GHz by Berton et al (2018a), they turn out to be comparable either to those of typical radioquiet and putatively non-jetted NLS1s, or with those of jetted steep-spectrum radio-loud NLS1s (i.e. misaligned objects, see Berton et al 2016a).…”

“…The detection of γ rays is associated with a beamed relativistic jet which, typically, has a flat radio spectrum in the JVLA range. However, its low-frequency spectrum is clearly steep, its brightness temperature is rather low (albeit still consistent with a misaligned jet), and its radio luminosity is very low, the lowest ever measured for a γ-ray NLS1 (e.g., Berton et al 2018a;Paliya 2019). Even in this object, therefore, Fig.…”

“…If these low-mass objects had relativistic jets they would have a rather low radio luminosity due to the low jet power, which would lead to the radio-quiet classification. Furthermore, even relatively powerful relativistic jets, when misaligned, could be faint at radio frequencies because we would not see any relativistic beaming effects (Berton et al 2018a). Therefore, sources with relativistic jets could be hidden among the radio-quiet/silent population (Foschini 2011(Foschini , 2012Berton et al 2015).…”

TXS 2116−077: A Gamma-Ray Emitting Relativistic Jet Hosted in a Galaxy Merger

“…The detection of variable γ-ray emission from about half-a-dozen radio-loud NLSy1 objects with the Fermi Large Area Telescope (e.g., Abdo et al 2009) has provided the strongest evidence in support of the relativistic beaming. These enigmatic sources, in general, are thought to be rapidly accreting (Boroson & Green 1992), low-luminosity AGN in the early phase of their evolution (Mathur 2000;Grupe & Mathur 2004;Berton et al 2018). They have also been found to reside in spiral/late-type galaxies Berton et al 2019;Olguín-Iglesias et al 2020) providing supportive evidences about their young nature.…”