In this paper, we utilize high-quality rest-UV spectra of three radio galaxies at $z \sim$ 3 observed with VLT/FORS2 to measure the flux of several emission lines including relatively faint ones, such as NIV]$λ$1486, OIII]$λ$1663, and [NeIV]$λ$2424. Additionally, we collect fluxes of faint rest-UV emission lines in 12 $z \sim$ 3 radio galaxies from the literature. Previously, physical and chemical properties of narrow-line regions (NLRs) in high-$z$ active galactic nuclei (AGNs) have been investigated mostly by using only strong rest-UV emission-lines (e.g., NV$λ$1240, CIV$λ$1549, HeII$λ$1640, and CIII]$λ$1909). Such strong-line diagnostics are based on various assumptions due to the limitation in the number of available emission-line constraints. In this work, both physical and chemical properties of NLR clouds in each object are estimated by fitting detailed photoionization models to the measured emission-line fluxes. We confirm that the metallicity of NLRs in AGNs at $z \sim$ 3 is solar or super-solar, without assuming the gas density and ionization parameter thanks to the constrains from the faint emission lines. This result suggests that high-$z$ radio galaxies are already chemically matured at $z \sim$ 3.
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. Thi…
The last decade has witnessed a steadily increasing number of observational studies concerning the rare class of radio loud narrow-line Seyfert 1 galaxies, of which several hundred are currently known. According to the current AGN paradigm, the low black hole masses and high accretion rates of narrow-line Seyfert 1 galaxies (NLSy1) should make them unlikely to launch jets, and indeed the vast majority ($\sim 90\%$) are very radio weak. The remainder, however, display a wide range of radio power, from $\simeq 10^{21}$- $10^{28}$ W/Hz. In this review I discuss recent radio imaging surveys that s…
The [O III] $λλ$ 4959,5007 lines are a useful proxy to test the kinematic of the narrow-line region (NLR) in active galactic nuclei (AGN). In AGN, and particularly in narrow-line Seyfert 1 galaxies (NLS1s) these lines often show few peculiar features, such as blue wings, often interpreted as outflowing component, and a shift $-$ typically toward lower wavelengths $-$ of the whole spectroscopic feature in some exceptional sources, the so-called blue outliers, which are often associated to strong winds. We investigated the incidence of these peculiarities in two samples of radio-emitting NLS1s, …
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 RQN…
In recent years, several Radio-Loud Narrow-Line Seyfert 1 galaxies (RL-NLS1) possessing relativistic jets have come into attention with their detections in Very Large Baseline Array (VLBA) and in $γ$-ray observations. In this paper we attempt to understand the nature of radio-jets in NLS1s by examining the kpc-scale radio properties of, hitherto, the largest sample of 11101 optically-selected NLS1s. Using 1.4 GHz FIRST, 1.4 GHz NVSS, 327 MHz WENNS, and 150 MHz TGSS catalogues we find the radio-detection of merely $\sim$ 4.5 per cent (498/11101) NLS1s, with majority (407/498 $\sim$ 81.7 per cen…
SDSS J094857.3+002225 is a very radio-loud narrow-line Seyfert 1 (NLS1) galaxy. Here, we report our discovery of the intranight optical variability (INOV) of this galaxy through the optical monitoring in the B and R bands that covered seven nights in 2009. Violent rapid variability in the optical bands was identified in this RL-NLS1 for the first time, and the amplitudes of the INOV reaches 0.5 mag in both the B and R bands on the timescale of several hours. The detection of the INOV provides a piece of strong evidence supporting the fact that the object carries a relativistic jet with a small…
Radio Properties of Narrow-Line and Broad-Line Seyfert 1 Galaxies
HUN-REN Research Centre for Astronomy and Earth Sciences（匈牙利研究科学院天文学与地球科学研究中心）；Konkoly Observatory（孔科利天文台）；HUN-REN--ELTE Extragalactic Astrophysics Research Group（匈牙利研究科学院-厄特沃什·洛兰大学河外天体物理学研究组）；Nicolaus Copernicus University（尼古拉·哥白尼大学）；HUN-REN--SZTE Stellar Astrophysics Research Group（匈牙利研究科学院-塞格德大学恒星天体物理学研究组）
Narrow-line Seyfert 1 (NLS1) galaxies are active galactic nuclei (AGN) believed to be in the early stages of their evolution. A fraction of them have been found to host relativistic jets. Due to the lack of large-scale diffuse radio emission they are believed to be experiencing one of their first activity cycles, and can offer us an opportunity to study the early evolution of more powerful AGN, such as radio galaxies and flat-spectrum radio quasars. Recently, a group of intriguing jetted NLS1s was discovered: based on high radio frequency data they host relativistic jets, but in the JVLA obser…
In order to study the ram-pressure interaction between radio galaxies and the intracluster medium, we analyse a sample of 208 highly-bent narrow-angle tail radio sources (NATs) in clusters, detected by the LOFAR Two-metre Sky Survey. For NATs within $7\,R_{500}$ of the cluster centre, we find that their tails are distributed anisotropically with a strong tendency to be bent radially away from the cluster, which suggests that they are predominantly on radially inbound orbits. Within $0.5\,R_{500}$, we also observe an excess of NATs with their jets bent towards the cluster core, indicating that …
Narrow-line Seyfert 1 galaxies (NLS1) are an intriguing subclass of active galactic nuclei. Their observed properties indicate low central black hole mass and high accretion rate. The extremely radio-loud NLS1 sources often show relativistic beaming and are usually regarded as younger counterparts of blazars. Recently, the object SDSS J110006.07+442144.3 was reported as a candidate NLS1 source. The characteristics of its dramatic optical flare indicated its jet-related origin. The spectral energy distribution of the object was similar to that of the gamma-ray detected radio-loud NLS1, PMN J094…
Among the large varieties of active galactic nuclei (AGN) known, narrow line Seyfert 1 (NLSy1) galaxies are a puzzling class, particularly after the discovery of $γ$-ray emission in a handful of them using observations from the Fermi Gamma-ray Space Telescope. Here, we report the discovery of a rare large double lobed radio source with its radio core associated with a NLSy1 galaxy SDSS J103024.95+551622.7 at z = 0.435. The lobe separation is 116 kpc which is the second largest known projected size among NLSy1 radio sources. This finding is based on the analysis of 1.4 GHz data from the Faint I…
Narrow-Line Seyfert 1 galaxies (NLS1s) are generally believed to be radio-quiet Active Galactic Nuclei (AGN) with relatively less-massive (10$^{5}$$-$10$^{8}$~M$_{\odot}$) Super-Massive Black Holes (SMBH). Using the FIRST radio detections of hitherto the largest sample of 11101 optically-selected NLS1s we find a rather uncommon population of 55 NLS1s with Kiloparsec-Scale Radio structures (KSRs). We note that the number of NLS1s with KSRs found in our study is only a lower limit considering the effects of sensitivity, spatial resolution and projection, and hence, the number of NLS1s with KSRs …
We critically analyze the Bell et al. findings on "anomalous" widths of high-order Hydrogen radio recombination lines in the Orion Nebula at 6 GHz. We review their method of modified frequency switching and show that the way this method is used for large Δn is not optimal and can lead to misinterpretation of measured spectral line parameters. Using a model of the Orion Nebula, conventional broadening theory and Monte Carlo simulation, we determine a transition-zone n = 224, ..., 241 (Δn = 11, ..., 14), where measurement errors grow quickly with n and become comparable with the measurement valu…
This work provides evidence that a large fraction of \ion{C}{IV} narrow absorption lines (NALs) seen along the line of sight to distant quasars are due to accretion disk winds, while also seeking to understand the relationship between NALs and certain quasar-intrinsic properties. We extend the results from past work in the literature using $\sim105,000$ NALs from a sample of $\sim58,000$ SDSS quasars. The primary results of this work are summarized as follows: (1) the velocity distribution (${\rm d}N/{\rm d}β$) of NALs is not a function of radio loudness (or even detection) once marginalized b…
Radio-Loud narrow-line Seyfert 1 galaxies (NLS1s), especially the extremely radio-loud ones, are widely accepted as the jetted versions of NLS1s. We explore the radio-loud fraction for NLS1s with recently released LoTSS DR1 at 150 MHz. The radio detection rate is about 28\% for LoTSS DR1. The radio detected NLS1s have lower redshift than the non-detected ones. Moreover, the 150 MHz radio luminosity of NLS1s detected by LoTSS are about two orders of magnitude weaker than that of the previous samples. By defining the radio loudness with the ratio between 150 MHz radio flux and SDSS \textit{r} ba…
We have detected six narrow-line Seyfert 1 (NLS1) galaxies at 37 GHz that were previously classified as radio silent and two that were classified as radio quiet. These detections reveal the presumption that NLS1 galaxies labelled radio quiet or radio silent and hosted by spiral galaxies are unable to launch jets to be incorrect. The detections are a plausible indicator of the presence of a powerful, most likely relativistic jet because this intensity of emission at 37 GHz cannot be explained by, for example, radiation from supernova remnants. Additionally, one of the detected NLS1 galaxies is …
We present an analysis of 2.05 $μ$m Hubble Space Telescope (HST) polarimetric data for a sample of 13 nearby Fanaroff-Riley type II (FRII) 3CR radio sources ($0.03<z<0.11$) that are classified as narrow line radio galaxies (NLRG) at optical wavelengths. We find that the compact cores of the NLRG in our sample are intrinsically highly polarised in the near-IR ($6 < P_{2.05μm} < 60$ per cent), with the electric-vector (E-vector) perpendicular to the radio axis in 54 per cent of the sources. The levels of extinction required to produce near-infrared polarisation by the dichroic extinction mechani…
Problems where impact broadened radio recombination lines appeared narrower than predicted first showed up ~40 years ago at frequencies below ~3 GHz. But it was soon found that the observations could be explained by throwing out the uniform density models and replacing them with variable density ones. However, this problem re-appeared recently when a mysterious line narrowing above quantum numbers of (n,Δn) = (202,8) was reported from sensitive observations of Orion and W51 near 6 GHz. Here it is demonstrated that the narrowing is unlikely to be caused by the data processing technique and ther…
We have examined a subset of 18 active galactic nuclei (AGNs) drawn from a sample of 81 galaxies that possess double-peaked narrow optical emission line spectra in the Sloan Digital Sky Survey, have two optical AGN emission components separated by >0.2", and are detected in the Faint Images of the Radio Sky at Twenty-centimeters survey. Without follow-up observations, the sources of the double-peaked narrow emission lines are uncertain, and may be produced by kpc-scale separation dual active supermassive black holes, AGN outflows, or disk rotation. In this work, we propose a new methodology to…
We present the first results of a radio survey of 79 narrow-line Seyfert 1 (NLS1) carried out with the Karl G. Jansky Very Large Array (JVLA) at 5 GHz in A configuration aimed at studying the radio properties of these sources. We report the detection of extended emission in one object: Mrk 783. This is intriguing, since the radio-loudness parameter R of this object is close to the threshold between radio-quiet and radio-loud active galactic nuclei (AGN). The galaxy is one of the few NLS1 showing such an extended emission at z < 0.1. The radio emission is divided in a compact core component and…
In this paper, we present the analysis of new radio and optical observations of the narrow-line Seyfert 1 galaxy Mrk 783. 1.6 GHz observations performed with the e-MERLIN interferometer confirm the presence of the diffuse emission previously observed. The Very Long Baseline Array (VLBA) also detects the nuclear source both at 1.6 GHz (L-Band) and 5 GHz (C-band). While the L-band image shows only an unresolved core, the C-band image shows the presence of a partially resolved structure, at a position angle of 60°. The brightness temperature of the emission in both bands ($>10^6$ K) suggests that…
We present radio spectral analyses for a sample of 29 radio-quiet (RQ) and three radio-loud (RL) narrow-line Seyfert 1 galaxies (NLS1s) detected with the Australia Telescope Compact Array at both 5.5 GHz and 9.0 GHz. The sample is characterized by L_bol/L_Edd > 0.15. The radio slopes in 25 of the 29 RQ NLS1s are steep (alpha_5.5-9.0 < -0.5), as found in earlier studies of RQ high L_bol/L_Edd AGN. This steep radio emission may be related to AGN-driven outflows, which are likely more prevalent in high L_bol/L_Edd AGN. In two of the three RL NLS1s, the radio slopes are flat or inverted (alpha_5.5…
We study a sample of Narrow-line Seyfert 1 galaxies (NLS1) in their optical and radio features, in order to understand the differences between their radio silent, radio-loud and radio-quiet subclasses. We first show that the different redshift and mass distributions of radio-loud and -quiet NLS1s could be ascribed to observational biases. We then present a geometrical model according to which most of the different observational features of radio-loud and radio-quiet NLS1s are ascribed to the orientation of an intrinsically structured jet. We estimate the fraction of intrinsically jetted source…
We present the analysis of infrared HST and Spitzer data for a sample of 13 FRII radio galaxies at 0.03<z<0.11 that are classified as narrow-line radio galaxies (NLRG). In the context of the unified schemes for active galactic nuclei (AGN), our direct view of the AGN in NLRG is impeded by a parsec-scale dusty torus structure. Our high resolution infrared observations provide new information about the degree of extinction induced by the torus, and the incidence of obscured AGN in NLRG. We find that the point-like nucleus detection rate increases from 25 per cent at 1.025$μ$m, to 80 per cent at …
We present a new accurate catalog of narrow-line Seyfert 1 galaxies (NLS1s) in the southern hemisphere from the Six-degree Field Galaxy Survey (6dFGS) final data release, which is currently the most extensive spectroscopic survey available in the southern sky whose database has not yet been systematically explored. We classified 167 sources as NLS1s based on their optical spectral properties. We derived flux-calibrated spectra for the first time that the 6dFGS indeed does not provide. By analyzing these spectra, we obtained strong correlations between the monochromatic luminosity at 5100 A and…
High-energy γ-rays, which are produced by powerful relativistic jets, are usually associated with blazars and radio galaxies. In the current active galactic nuclei (AGN) paradigm, such jets are almost exclusively launched from massive elliptical galaxies. Recently, however, Fermi/LAT detected γ-rays from a few narrow-line Seyfert 1 galaxies and thus confirmed the presence of relativistic jets in them. Since NLS1 galaxies are assumed to be young evolving AGN, they offer a unique opportunity to study the production of relativistic jets in late-type galaxies. Our aim is to estimate by which proce…
We investigate the mid-infrared properties of the largest (42 objects) sample of radio-loud narrow-line Seyfert 1 (RL NLS1) collected to date, using data from the Wide-field Infrared Survey Explorer (WISE). We analyse the mid-IR colours of these objects and compare them to what is expected from different combinations of AGN and galaxy templates. We find that, in general, the host-galaxy emission gives an importan contribution to the observed mid-IR flux in particular at the longest wavelengths (W3, at 12micron, and W4, at 22micron). In about half of the sources (22 objects) we observe a very r…
We analyze the 11-year long-term light curve of the Radio-loud Narrow-line Seyfert 1 (NLSy1) galaxy J0849+5108 and the nearly simultaneous $γ$-ray data of the source. The data were obtained with the Owens Valley Radio Observatory 40-m telescope at 15~GHz and with the Large Area Telescope onboard Fermi Gamma-ray Space Telescope, respectively. A quasi-periodic oscillation (QPO) signal at a significance of $>$5$σ$ is found in the radio light curve, but no similar modulation is seen in the $γ$-ray light curve. The QPO signal was present for 21 cycles, the longest among the reported radio QPOs, and…
Narrow-line Seyfert 1 (NLS1) galaxies are believed to be active galactic nuclei (AGN) in the early stages of their evolution. Some dozens of them have been found to host relativistic jets, whilst the majority has not even been detected in radio, emphasising the heterogeneity of the class in this band. In this paper, our aim is to determine the predominant source of radio emission in a sample of 44 NLS1s, selected based on their extended kpc-scale radio morphologies at 5.2 GHz. We accomplish this by analysing their spatially resolved radio spectral index maps, centred at 5.2 GHz. In addition, w…
Until recently, relativistic jets were ubiquitously found to be launched from giant elliptical galaxies. However, the detection by the Fermi-LAT of gamma-ray emission from radio-loud narrow-line Seyfert 1 (RL-NLSy1) galaxies raised doubts on this relation. Here, we morphologically characterize a sample of 29 RL-NLSy1s (including 12 gamma-ray emitters, gamma-NLSy1s) in order to find clues on the conditions needed by AGN to produce relativistic jets. We use deep near-infrared images from the Nordic Optical Telescope and the ESO VLT to analyze the surface brightness distribution of the galaxies i…
Narrow-line Seyfert 1 (NLS1) galaxies are peculiar active galactic nuclei (AGN). Most of them do not show strong radio emission, but recently seven radio-quiet (or -silent) NLS1s have been detected flaring multiple times at 37 GHz by the Metsähovi Radio Telescope, indicating the presence of relativistic jets in these peculiar sources. We observed them with the Karl G. Jansky Very Large Array (JVLA) in A configuration at 1.6, 5.2, and 9.0 GHz. Our results show that these sources are either extremely faint or not detected in the JVLA bands. At those frequencies, the radio emission from their rel…
Aims. Narrow-angle tailed (NAT) sources in clusters of galaxies can show on the large scale very narrow tails that are unresolved even at arcsecond resolution. These sources could therefore be classified as one-sided jets. The aim of this paper is to gain new insight into the structure of these sources, and establish whether they are genuine one-sided objects, or if they are two-sided sources. Methods. We observed a sample of apparently one-sided NAT sources at subarcsecond resolution to obtain detailed information on their structure in the nuclear regions of radio galaxies. Results. Most radi…
We report finding kiloparsec-scale radio emissions aligned with parsec-scale jet structures in the narrow-line Seyfert 1 (NLS1) galaxy Mrk 1239 using the Very Large Array and the Very Long Baseline Array. Thus, this radio-quiet NLS1 has a jet-producing central engine driven by essentially the same mechanism as that of other radio-loud active galactic nuclei (AGNs). Most of the radio luminosity is concentrated within 100 parsecs and overall radio morphology looks edge-darkened; the estimated jet kinetic power is comparable to Fanaroff--Riley Type I radio galaxies. The conversion from accretion …
As hybrids of narrow-line Seyfert 1 (NLS1) galaxies and blazars, γ-ray emitting NLS1s are important probes of jet physics in the high Eddington-ratio regime. Only very few of them are known to date; the majority of them below redshift z = 0.5. Here we present the identification of the γ-ray emitting AGN TXS 0943+105 (SDSS J094635.06+101706.1) as a high-redshift NLS1 galaxy. It turns out to be one of the radio-loudest NLS1s known, highly variable at all wavelengths, and shows widely extended radio emission at a (projected) > 100 kpc scale. It is a known strong γ-ray emitter with a luminous flar…
Recently, Rakshit et al. (2018) reported the discovery of SDSS J103024.95$+$551622.7, a radio-loud narrow-line Seyfert 1 galaxy having a $\sim 100$ kpc scale double-lobed radio structure. Here we analyse archival radio interferometric imaging data taken with the Very Large Array (VLA) at 5 GHz, and with the Very Long Baseline Array (VLBA) at 4.3 and 7.6 GHz. Two hotspots and a compact core are detected with the VLA at arcsec scale, while a single milliarcsec-scale compact radio core is seen with the highest resolution VLBA observations. The Fermi Large Area Telescope did not detect $γ$-ray emi…
The supermassive black holes (SMBHs) of narrow-line Seyfert 1 galaxies (NLS1s) are at the lowest end of mass function of active galactic nuclei (AGNs) and preferentially reside in late-type host galaxies with pseudobulges, which are thought to be formed by internal secular evolution. On the other hand, the population of radio-loud NLS1s presents a challenge for the relativistic jet paradigm that powerful radio jets are exclusively associated with very high mass SMBHs in elliptical hosts, which are built-up through galaxy mergers. We investigated distorted radio structures associated with the n…
We present the detection of compact radio structures of fourteen radio-loud narrow line Seyfert 1 (NLS1) galaxies from Very Long Baseline Array observations at 5 GHz, which were performed in 2013. While 50\% of the sources of our sample show a compact core only, the remaining 50\% exhibit a core-jet structure. The measured brightness temperatures of the cores range from $10^{8.4}$ to $10^{11.4}$ K with a median value of $10^{10.1}$ K, indicating that the radio emission is from non-thermal jets, and that, likely, most sources are not strongly beamed, then implying a lower jet speed in these rad…
Radio-loud Narrow-line Seyfert 1 (NLS1) galaxies are unique probes of the formation of powerful radio jets at extreme (near-Eddington) accretion rates and low black hole masses, in a regime very different from classical blazars and, therefore, not probed before. Further, strong thermal and non-thermal components simultaneously present in their spectral energy distributions (SEDs), shed new light on the jet-disk connection at much shorter timescales, given their low SMBH masses. While NLS1 galaxies have been studied thoroughly at optical and X-ray energies for decades, the populations of radio-…
We conducted Very Long Baseline Array (VLBA) observations of seven nearby narrow-line Seyfert 1 (NLS1) galaxies at 1.7 GHz (18cm) with milli-arcsecond resolution. This is the first systematic very long baseline interferometry (VLBI) study focusing on the central parsec-scale regions of radio-quiet NLS1s. Five of the seven were detected at a brightness temperature of >~5x10^6 K and contain radio cores with high brightness temperatures of >6x10^7 K, indicating a nonthermal process driven by jet-producing central engines as is observed in radio-loud NLS1s and other active galactic nucleus (AGN) c…
1H 0323+342 is optically one of the nearest and brightest very radio loud narrow line Seyfert 1 galaxies (vRL NLSy1). It is also one of the first vRLNLSy1s detected at gamma-ray energies by the Fermi-LAT. We report the results of monitoring the optical flux of 1H 0323+342 during more than six and a half years. In some cases, we, for the first time, simultaneously use two telescopes to monitor the optical flux of 1H 0323+342 on timescales ranging from minutes to hours, demonstrating the reality of low amplitude microvariability whole events with durations of a few hours for this object. Based o…
Flat-spectrum radio-loud Narrow-Line Seyfert 1 galaxies (NLS1s) are a recently discovered class of $γ$-ray emitting Active Galactic Nuclei (AGN), that exhibit some blazar-like properties which are explained with the presence of a relativistic jet viewed at small angles. When blazars are observed at larger angles they appear as radio-galaxies, and we expect to observe an analogue parent population for beamed NLS1s. However, the number of known NLS1s with the jet viewed at large angles is not enough. Therefore, we tried to understand the origin of this deficit. Current hypotheses about the natur…
We report the finding of kiloparsec (kpc)-scale radio structures in three radio-loud narrow-line Seyfert 1 (NLS1) galaxies from the Faint Images of the Radio Sky at Twenty-centimeters (FIRST) of the Very Large Array (VLA), which increases the number of known radio-loud NLS1s with kpc-scale structures to six, including two gamma-ray emitting NLS1s (PMN J0948+0022 and 1H 0323+342) detected by the Fermi Gamma-ray Space Telescope. The detection rate of extended radio emissions in NLS1s is lower than that in broad-line active galactic nuclei (AGNs) with a statistical significance. We found both cor…
We present SDSSJ143244.91+301435.3, a new case of radio-loud narrow line Seyfert 1 (RL NLS1) with a relatively high radio power (P1.4GHz=2.1x10^25 W Hz^-1) and large radioloudness parameter (R1.4=600+/-100). The radio source is compact with a linear size below ~1.4 kpc but, contrary to most of the RL NLS1 discovered so far with such a high R1.4, its radio spectrum is very steep (alpha=0.93) and not supporting a 'blazar-like' nature. Both the small mass of the central super-massive black-hole and the high accretion rate relative to the Eddington limit estimated for this object (3.2x10^7 Msun an…
Observations at 37 GHz, performed at Metsähovi Radio Observatory, are presented for a sample of 78 radio-loud and radio-quiet narrow-line Seyfert 1 (NLS1) galaxies, together with additional lower and higher frequency radio data from RATAN-600, Owens Valley Radio Observatory, and the Planck satellite. Most of the data have been gathered between February 2012 and April 2015 but for some sources even longer lightcurves exist. The detection rate at 37 GHz is around 19%, comparable to other populations of active galactic nuclei presumed to be faint at radio frequencies, such as BL Lac objects. Vari…
We studied the radio emission from four radio-loud and gamma-ray-loud narrow-line Seyfert 1 galaxies. The goal was to investigate whether a relativistic jet is operating at the source, and quantify its characteristics. We relied on the most systematic monitoring of such system in the cm and mm radio bands which is conducted with the Effelsberg 100 m and IRAM 30 m telescopes and covers the longest time-baselines and the most radio frequencies to date. We extract variability parameters and compute variability brightness temperatures and Doppler factors. The jet powers were computed from the ligh…
The $γ$-ray narrow-line Seyfert 1 (NLS1) galaxies can be considered to be the third class of $γ$-ray active galactic nuclei possessing relativistic jets. In this paper, we present multi-band high resolution Very Long Baseline Array (VLBA) images of the $γ$-ray NLS1, SDSS J211852.96$-$073227.5 (J2118$-$0732, $z=0.26$). We find a core-jet radio morphology and significant flux density variations in the radio core. The high brightness temperature estimated from VLBA images and core variability demonstrate that it exhibits substantial relativistic beaming effects. From considering radio emission in…
We conducted a high-sensitivity radio detection survey for forty narrow-line Seyfert 1 (NLS1) galaxies using very-long-baseline interferometry (VLBI) at 22 GHz through phase-referencing long-time integration and using a newly developing recorder with a data rate of 8 Gbps, which is a candidate of the next generation VLBI data recording systems for the Japanese VLBI Network. The baseline sensitivity was typically a few mJy. The observations resulted in a detection rate of 12/40 for our radio-selected NLS1 sample; 11 out of the detected 12 NLS1s showed inverted radio spectra between 1.4 and 22 G…
We have discovered kiloparsec-scale extended radio emission in three narrow-line Seyfert 1 galaxies (NLS1s) in sub-arcsecond resolution 9 GHz images from the Karl G. Jansky Very Large Array (VLA). We find all sources show two-sided, mildly core-dominated jet structures with diffuse lobes dominated by termination hotspots. These span 20-70 kpc with morphologies reminiscent of FR II radio galaxies, while the extended radio luminosities are intermediate between FR I and FR II sources. In two cases the structure is linear, while a $45^{\circ}$ bend is apparent in the third. Very Long Baseline Arra…
Most of the radio-loud narrow-line Seyfert 1 (NLS1) galaxies resemble compact steep-spectrum sources. However, the extremely radio-loud ones show blazar-like characteristics, like flat radio spectra, compact radio cores, substantial variability and high brightness temperatures. These objects are thought to be similar to blazars as they possess relativistic jets seen at small angle to the line of sight. This claim has been further supported by the Fermi satellite discovery of gamma-ray emission from a handful of these sources. Using the Wide-Field Infrared Survey Explorer (WISE) data, we analyz…
Narrow-line Seyfert 1 galaxies (NLS1s) are active galactic nuclei (AGN) recently identified as a new class of $γ$-ray sources. The high energy emission is explained by the presence of a relativistic jet observed at small angles, just like in the case of blazars. When the latter are observed at larger angles they appear as radio-galaxies, but an analogue parent population for beamed NLS1s has not yet been determined. In this work we analyze this problem by studying the physical properties of three different samples of parent sources candidates: steep-spectrum radio-loud NLS1s, radio-quiet NLS1s…
We studied optical variability (OV) of a large sample of narrow-line Seyfert 1 (NLSy1) and broad-line Seyfert 1 (BLSy1) galaxies with z<0.8 to investigate any differences in their OV properties. Using archival optical V-band light curves from the Catalina Real Time Transient Survey that span 5-9 years and modeling them using damped random walk, we estimated the amplitude of variability. We found NLSy1 galaxies as a class show lower amplitude of variability than their broad-line counterparts. In the sample of both NLSy1 and BLSy1 galaxies, radio-loud sources are found to have higher variability…
We present a 3D magnetohydrodynamic (MHD) study of narrow-angle tail (NAT) radio galaxy (RG) dynamics, including passive cosmic ray electrons. We follow evolution of a bipolar-jet RG in a persistent crosswind through hundreds of Myr. We confirm traditional jet-bending models, while noting that our NAT exhibits a transitional morphology reminiscent of wide-angle radio tails. Once deflected, jets remain internally stable, but are intermittently disrupted by external disturbances induced by the NAT dynamics itself. The disruptions enhance jet and tail magnetic fields. Disrupted jet plasma is hete…
