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We report the first results of a survey on 74 narrow-line Seyfert 1 galaxies (NLS1s) carried out in 2015 with the Karl J. 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 sam...
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Citations
... Nonetheless, despite a double-humped spectral energy distribution (SED) like the blazars for a few RLNLSy1s (e.g., Abdo et al., 2009c, Paliya et al., 2013b, a small fraction of RLNLSy1s, especially very radio-loud (R > 100) RLNLSy1s exhibit interesting multi-wavelength characteristics such as compactness of the radio core, high brightness temperature, superluminal motion, flat radio and X-ray spectra, and rapid infrared and X-ray flux variability similar to blazar class of AGN (Boller et al., 1996, Grupe et al., 1998, Berton et al., 2018. All these characteristics provide indirect evidence for the presence of jets in them. ...
... The DC of the jetted and non-jetted RLNLSy1s samples would be more reliable if it were possible to remove thermal contamination from the disc due to their higher Eddington accretion rates in NLSy1s. A relatively lower DC of the jetted-RLNLSy1s sample could be attributed to either the sub-luminal speed of jets (e.g., see Ojha et al., 2019) or their primarily misaligned relativistic jets towards the observer line of sight (Berton et al., 2018). Therefore, we divided our sample of jetted-RLNLSy1s into two subsamples: J-γ-RLNLSy1s (8 sources) and J-RLNLSy1s (7 sources), based on their detection in γ-ray by Fermi-LAT. ...
The innermost regions of Active Galactic Nuclei (AGN) are critical for understanding galaxy evolution and the dynamics of matter near a Supermassive Black Hole (SMBH). Yet, due to smaller angular projections, it is very difficult to resolve these regions. This thesis explores indirect methods to understand these objects. We use the reverberation mapping technique to estimate accretion disk sizes for a sample of AGN, finding that the computed disk sizes are, on average, 3.9 times larger than the Shakura Sunyev (SS) standard disk model predictions. We also find a weak correlation between the obtained accretion disk sizes and the SMBH mass. We present initial results from a new accretion disk monitoring program to probe the accretion disk structure of Super Eddington Accreting AGN. We report that the disk sizes are about 4 times larger than the SS disk model. We calibrate the narrow-band photometric reverberation mapping (PRM) technique to develop tools for a large systematic narrow-band PRM project. We use simulations to test the effect of cadence, variability of the light curves, and the length of light curves in recovering the reverberation lags. We study the dichotomy between AGNs with and without detected jets using the method of microvariability observed in the accretion disk continuum. We find that AGNs with confirmed jets are about 3 times more variable on short time scales than the AGNs without a confirmed jet. By performing statistical analysis on a large sample of low luminosity AGNs, we find that the NLSy1 galaxies are more likely to have outflow signatures than their broad-line counterparts, hinting toward the disk wind origin of the material in BLR. We find that the principal components for NLSy1 galaxies differ from the BLSy1 galaxies, suggesting that the NLSy1 galaxies could be occupying their own parameter space.
... Therefore, non-detection of jet activity in JVLA observations from the current sample may be due to their low-integrated luminosity which is indeed low ≤1.0 × 10 39 erg s −1 (see table 2 of Berton et al. 2020b ). Such scenario straightens with integrated luminosity ≥1.5 × 10 39 erg s −1 found in jetted sources (see Berton et al. 2018 ). In addition to the lo w po wer of jets, non-detection of jet activity in JVLA observations might be due to absorbed jets because of a more tied connection of optical emission to nuclear jet emission at millimetre wavelengths as compared to its emission at lower radio frequencies (see Gopal-Krishna et al. 2023 ), which is largely attenuated due to a high opacity around the nuclear jet, as interpreted from very long baseline interferometry studies (Gopal-Krishna & Steppe 1991 ;Boccardi et al. 2017 ). ...
Variability studies of active galactic nuclei are a powerful diagnostic tool in understanding the physical processes occurring in disk-jet regions, unresolved by direct imaging with currently available techniques. Here, we report the first attempt to systematically characterize intra-night optical variability (INOV) for a sample of seven apparently radio-quiet narrow-line Seyfert 1 galaxies (RQNLSy1s) that had shown recurring flaring at 37 GHz in the radio observations at Metsähovi Radio Observatory (MRO), indicating the presence of relativistic jets in them, but no evidence for relativistic jets in the recent radio observations of Karl G. Jansky Very Large Array (JVLA) at 1.6, 5.2, and 9.0 GHz. We have conducted a total of 28 intra-night sessions, each lasting ≥ 3 hrs for this sample, resulting in an INOV duty cycle ($\overline{DC} ~\sim$20 %) similar to that reported for γ-ray-NLSy1s (DC ∼25 % - 30 %), that display blazar-like INOV. This in turn infers the presence of relativistic jet in our sample sources. Thus, it appears that even lower-mass (MBH ∼ 106 M⊙) RQNLSy1 galaxies can maintain blazar-like activities. However, we note that the magnetic reconnection in the magnetosphere of the black hole can also be a viable mechanism to give rise to the INOV from these sources.
... Indeed, the general NLSy1 population has been considered as rapidly accreting, low-luminosity AGN in the early stage of their evolution (cf. Mathur 2000 ;Berton et al. 2018 ). ...
Narrow-line Seyfert 1 (NLSy1) galaxies are an enigmatic class of active galactic nuclei (AGN) that exhibit peculiar multiwavelength properties across the electromagnetic spectrum. For example, these sources have allowed us to explore the innermost regions of the central engine of AGN using X-ray observations and have also provided clues about the origin of relativistic jets considering radio and γ-ray bands. Keeping in mind the ongoing and upcoming wide-field, multi-frequency sky surveys, we present a new catalogue of NLSy1 galaxies. This was done by carrying out a detailed decomposition of >2 million optical spectra of quasars and galaxies from the Sloan Digital Sky Survey Data Release 17 (SDSS-DR17) using the publicly available software “Bayesian AGN Decomposition Analysis for SDSS Spectra”. The catalogue contains 22656 NLSy1 galaxies which is more than twice the size of the previously identified NLSy1s based on SDSS-DR12. As a corollary, we also release a new catalogue of 52273 broad-line Seyfert 1 (BLSy1) galaxies. The estimated optical spectral parameters and derived quantities confirm the previously known finding of NLSy1 galaxies being AGN powered by highly accreting, low-mass black holes. We conclude that this enlarged sample of NLSy1 and BLSy1 galaxies will enable us to explore the low-luminosity end of the AGN population by effectively utilizing the sensitive, high-quality observations delivered by ongoing/upcoming wide-field sky surveys. The catalogue has been made public at https://www.ucm.es/blazars/seyfert.
... The ratio of peak intensity (measured in μJy beam −1 ) and the fitted flux density (measured in μJy), denoted here by C , is characteristic to the compactness of the emission (e.g. Ger éb, Morganti & Oosterloo 2014 ; Berton et al. 2018 ;Berghea et al. 2020 ;Chen et al. 2020 ). For an unresolved source confined to within the restoring beam, one would expect C = 1 beam −1 . ...
Using empty-field ‘Quick Look’ images from the first two epochs of the VLA Sky Survey (VLASS) observations, centred on the positions of ∼3700 individually radio-non-detected active galactic nuclei (AGNs) at z ≥ 4, we performed image stacking analysis to examine the sub-mJy emission at 3 GHz. We found characteristic monochromatic radio powers of Pchar = (2–13) × 1024 W Hz−1, indicating that AGN-related radio emission is widespread in the sample. The signal-to-noise ratios of the redshift-binned median stacked maps are between 4–6, and we expect that with the inclusion of the yet to be completed third-epoch VLASS observations, the detection limit defined as signal-to-noise ratio SNR ≥ 6 could be reached, and the redshift dependence can be determined. To obtain information on the general spectral properties of the faint radio emission in high-redshift AGNs, we confined the sample to ∼3000 objects covered by both the VLASS and the Faint Images of the Radio Sky at Twenty-centimeters (FIRST) survey. We found that the flux densities from the median stacked maps show a characteristic spectral index of α* = −0.30 ± 0.15, which is in agreement with the median spectral index of the radio-detected z ≥ 4 AGNs from our high-redshift AGN catalogue. The three-band mid-infrared colour–colour diagram based on Wide-field Infrared Survey Explorer observations provides further support regarding the AGN contribution to the radio emission in the sub-mJy sample.
... The BH mass and bolometric luminosity are from Davis & Laor (2011) or Laor et al. (2019). Reference: (a) Kellermann et al. (1989), (b) Berton et al. (2018), (c) Alhosani et al. (2022). Table 5. ...
The origin of the radio emission in radio-quiet quasars (RQQ) is not established yet. We present new VLBA observations at 1.6 and 4.9 GHz of ten RQQ (nine detected), which together with published earlier observations of eight RQQ (five detected), forms a representative sample of 18 RQQ drawn from the Palomar-Green sample of low z (< 0.5) AGN. The spectral slope of the integrated emission extends from very steep (alpha < -1.98) to strongly inverted (alpha = +2.18), and the slopes of nine of the 14 objects are flat (alpha > -0.5). Most objects have an unresolved flat-spectrum core, which coincides with the optical Gaia position. The extended emission is generally steep-spectrum, has a low brightness temperature (< 10^7 K), and is displaced from the optical core (the Gaia position) by ~ 5-100 pc. The VLBA core flux is tightly correlated with the X-ray flux, and follows a radio to X-ray luminosity relation of log L_R/L_X = -6, for all objects with a black hole mass log M_BH/M_Sun < 8.5. The flatness of the core emission implies a compact source size (< 0.1 pc), which likely originates from the accretion disk corona. The mas-scale extended emission is optically thin and of clumpy structure, and is likely produced by an outflow from the center. Radio observations at higher frequencies can further test the accretion disk coronal emission interpretation for the core emission in RQQ.
... It is interesting to compare our results with the distribution of spins estimated in Chen et al. [34] (see Figure 6 in their work) for various types of active galaxies. It can be observed that our distribution of spin values for NLS1 looks very similar to their distribution for radio galaxies, which may indicate that these two types of objects are closely related [35,36]. In addition, it can be seen that our spin distribution for Seyfert 1-type galaxies resembles their distribution for flat-spectrum radio quasars (FSRQ), which in turn could mean that Seyfert 1 galaxies and FSRQs are related (for example, it may mean that these are objects of the same type observed from different directions). ...
... This is generally consistent with the results of Liu et al. [33]. Our distribution of spin values for NLS1 looks very similar to the distribution for radio galaxies from Chen et al. [34], which may indicate that these two types of objects are closely related [35,36]. In addition, it can be seen that our spin distribution for Seyfert 1-type galaxies in our previous works resembles the distribution from Chen et al. [34] for flat-spectrum radio quasars (FSRQ), which in turn could mean that Seyfert 1 galaxies and FSRQs are related (for example, it may mean that these are objects of the same type observed from different directions). ...
We estimated the spin values of the supermassive black holes (SMBHs) of the active galactic nuclei (AGN) for a large set of Narrow Line Seyfert 1 (NLS1) galaxies assuming the inclination angle between the line of sight and the axis of the accretion disk to be approximately 45 degrees. We found that for these objects the spin values are on average less than for the Seyfert 1 galaxies that we studied previously. In addition, we found that the dependencies of the spin on the bolometric luminosity and the SMBH mass are two to three times stronger that for Seyfert 1 galaxies, which could mean that at early stages of evolution NLS1 galaxies either have a low accretion rate or chaotic accretion, while at later stages they have standard disk accretion, which very effectively increases the spin value.
... The physical properties of RLNLS1s are similar to that of Fermi blazars (e.g. Foschini et al. 2015 ;Sun et al. 2015 ;Berton et al. 2018 ;Paliya et al. 2019 ). Chen et al. ( 2021a ) found that there is a weak anticorrelation between synchrotron peak frequency and peak luminosity for both Fermi blazars and RLNLS1s, which suggests that the RLNLS1s belong to the Fermi blazar sequence. ...
The correlation between the kinetic jet power $P_{\rm jet}$, intrinsic $\gamma$-ray luminosity ($L^{\rm int}$) and accretion ($L_{\rm disk}$) may reveal the underlying jet physics in various black hole systems. We study the relation between kinetic jet power, intrinsic $\gamma$-ray luminosity, and accretion by using a large sample of jetted AGN, including flat-spectrum radio quasars (FSRQs), BL Lacertae objects (BL Lacs), gamma-ray Narrow-line Seyfert 1 galaxies ($\gamma$NLS1s) and radio galaxies. Our main results are as follows: (1) The slope indices of the relation between $P_{\rm jet}$ and $L^{\rm int}$ are $0.85\pm0.01$ for the whole sample, $0.70\pm0.02$ for the FSRQs, $0.83\pm0.03$ for the BL Lacs, $0.68\pm0.11$ for the $\gamma$NLS1s, and $0.93\pm0.09$ for the radio galaxies, respectively. The jets in $\gamma$NLS1s and radio galaxies almost follow the same $P_{\rm jet}$-$L^{\rm int}$ correlation that was obtained for Fermi blazars. (2) The slope indices of the relation between $L^{\rm int}$ and $L_{\rm disk}$ are $1.05\pm0.02$ for the whole sample, $0.94\pm0.05$ for the FSRQs, $1.14\pm0.05$ for the BL Lacs, and $0.92\pm0.18$ for the $\gamma$NLS1s, respectively. The $\gamma$NLS1s and radio galaxies almost also follow the $L^{\rm int}$-$L_{\rm disk}$ correlation derived for Fermi blazars. (3) The jet power is larger than the luminosity of accretion disks for almost all jetted AGN. Jet power depends on both the Eddington ratio and black hole mass. We obtain $\log P_{\rm jet}\sim(1.00\pm0.02)\log L_{\rm disk}$ for the whole sample, which is consistent with the theoretically predicted coefficient. These results may imply that the jets of jetted AGN are powered by the Blandford-Znajek mechanism.
... Five sources have been monitored with the Monitoring Of Jets in Active galactic nuclei with VLBA Experiments (MOJAVE) program (Lister et al. 2016), with apparent superluminal motion detected in three NLS1s (1H 0323342, SBS 0846513, PMN J09480022), and subluminal motion in two others (SDSS J12220413, PKS 1502036). Besides these nine bona fide NLS1s, 10 additional sources have radio detection, with most of them being detected the radio emission on the kiloparsec scale (Spencer et al. 1989;Helfand et al. 2015;Gu et al. 2015;Lister et al. 2016;Berton et al. 2018Berton et al. , 2020Singh & Chand 2018), nearly half of them have one-sided parsec-scale core-jet structures (Linford et al. 2012;Orienti et al. 2012;D'Ammando et al. 2012;Lister et al. 2016;An et al. 2017). It has been proposed that γ-ray NLS1s could be regarded as low-luminosity counterparts of powerful blazars (especially flat-spectrum radio quasars (FSRQs); Berton et al. 2016) since they are at the low end of the disk-jet connection for blazars (Foschini et al. 2015;Paliya et al. 2019) and γ-ray NLS1s are likely to be young, low-power, precursors of FSRQs (Paliya 2019). ...
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. By considering radio emission in several bands, we find that the source has an inverted spectrum above 1 GHz but a steep spectrum at low frequencies ranging from 74 MHz–1 GHz; these may arise from the present activity and the old diffuse/extended emission, respectively. The core-jet morphology, significant flux density variations, and beaming effect make J2118-0732 resemble a blazar. Considering the low mass of its central black hole and the ongoing merger environment, J2118-0732 may represent a low-mass, low-power counterpart of blazars, and may finally evolve into a blazar.
... Historically, blazars are classified into two types depending on their optical spectra: the BL Lacertae objects (BL Lacs) typically have very weak or absent features in their optical spectra, and the flat-spectrum radio quasars (FSRQs) show strong broad optical emission lines. Berton et al. ( 2018 ) show that the flatspectrum radio-loud Narrow-Line Seyfert 1 (NLS1) galaxies can host lo w-po wer blazar-type jets aligned with our LOS. The observed broad-band spectral energy distributions (SEDs) of blazars show E-mail: ksushanthreddy1999@gmail.com (SRK); rajprince59.bhu@gmail.com ...
We have presented a multiwavelength temporal and spectral study of the Blazar PKS 0346-27 for the period 2019 January-2021 December (MJD 58484-59575) using data from Fermi-LAT (γ-rays), Swift-XRT (X-rays) and Swift-UVOT (ultra-violet and optical). We identified multiple flaring episodes by analyzing the gamma-ray light curve generated from the Fermi-LAT data over a two-year period. The light curves of these individual gamma-ray flares with one-day binning were then modeled using a sum-of-exponentials fit. We found the minimum variability times for the gamma-ray light curve to be 1.34 ± 0.3 days and a range of 0.1-3.2 days for the Swift wavelengths suggesting the compactness of the source. The broadband emission mechanism was studied by modeling the simultaneous multi-waveband Spectral Energy Distributions (SED) using the one-zone leptonic emission mechanism. We found that the optical-UV and X-ray data can be explained by the synchrotron and Synchrotron Self-Compton (SSC) emissions. However, the disk component of the External Compton radiation is dominant at higher energies with contributions from the EC broad line region component and SSC. Further, we performed a power spectral density (PSD) analysis with data from the gamma-ray light curve using the power spectrum response (PSRESP) method. With the power law model, a best-fit slope of 2.15 ± 0.87 was found. This source could be a promising target for upcoming CTA for its harder spectrum at lower energies (tens of GeV).
... The physical properties of RLNLS1s are similar to that of Fermi blazars (e.g. Foschini et al. 2015 ;Sun et al. 2015 ;Berton et al. 2018 ;Paliya et al. 2019 ). Chen et al. ( 2021a ) found that there is a weak anticorrelation between synchrotron peak frequency and peak luminosity for both Fermi blazars and RLNLS1s, which suggests that the RLNLS1s belong to the Fermi blazar sequence. ...
The correlation between the kinetic jet power Pjet, intrinsic γ-ray luminosity (Lint) and accretion (Ldisk) may reveal the underlying jet physics in various black hole systems. We study the relation between kinetic jet power, intrinsic γ-ray luminosity, and accretion by using a large sample of jetted AGN, including flat-spectrum radio quasars (FSRQs), BL Lacertae objects (BL Lacs), gamma-ray Narrow-line Seyfert 1 galaxies (γNLS1s) and radio galaxies. Our main results are as follows: (1) The slope indices of the relation between Pjet and Lint are 0.85 ± 0.01 for the whole sample, 0.70 ± 0.02 for the FSRQs, 0.83 ± 0.03 for the BL Lacs, 0.68 ± 0.11 for the γNLS1s, and 0.93 ± 0.09 for the radio galaxies, respectively. The jets in γNLS1s and radio galaxies almost follow the same Pjet-Lint correlation that was obtained for Fermi blazars. (2) The slope indices of the relation between Lint and Ldisk are 1.05 ± 0.02 for the whole sample, 0.94 ± 0.05 for the FSRQs, 1.14 ± 0.05 for the BL Lacs, and 0.92 ± 0.18 for the γNLS1s, respectively. The γNLS1s and radio galaxies almost also follow the Lint-Ldisk correlation derived for Fermi blazars. (3) The jet power is larger than the luminosity of accretion disks for almost all jetted AGN. Jet power depends on both the Eddington ratio and black hole mass. We obtain log Pjet ∼ (1.00 ± 0.02)log Ldisk for the whole sample, which is consistent with the theoretically predicted coefficient. These results may imply that the jets of jetted AGN are powered by the Blandford-Znajek mechanism.
