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Register a new userThe distribution of the coronal temperature in Seyfert 1 galaxies
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The Active Galactic Nuclei (AGN) produce copious amounts of X-rays through the corona that is the hot gas that lies close to the accretion disk. The temperature of the corona can be accurately determined by the cut-off signature in the X-ray spectrum. Owing to the large temperatures of the corona, observations well above 10 keV are necessary. Here, we explore the NuSTAR observations of 118 Gehrels/Swift selected Seyfert 1 AGN. We model the spectrum using a single power-law with an exponential cut-off modified by neutral and ionised absorption as well as a reflection component. We find secure spectral cut-off estimates in 62 sources while for the remaining ones we derive only lower limits. The mean value is 103 keV with a skewed distribution towards large energies with large dispersion. When we consider the lower limits using survival analysis techniques, the mean cut-off energy becomes significantly larger, about 200 keV. Because of various limitations (e.g. limited spectral passband, photon statistics, model degeneracies) we perform extensive simulations to explore the underlying spectral cut-off distribution. We find that an intrinsic spectral cut-off distribution which has a Maxwell-Boltzmann shape with a mean value in the range of 160 - 200 keV can reproduce sufficiently well the observations. Finally, our spectral analysis places very stringent constraints on both the photon index (Gamma=1.77+/-0.01) as well as on the reflection component (R=0.69+/-0.04) of the Seyfert 1 population. From the values of the spectral cut-off and the photon-index we deduce that the mean optical depth of the AGN corona is approximately tau=1.82+/-0.14 and its mean temperature approximately kT=65+/-10 keV.
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In this paper, we explore the physics of the accretion and jet in narrow-line Seyfert 1 galaxies (NLS1). Specifically, we compile a sample composed of 16 nearby NLS1 with $L_{rm bol}/L_{rm Edd} gtrsim 0.1$. We investigate the mutual correlation between their radio luminosity $L_{rm R}$, X-ray luminosity $L_{rm X}$, optical luminosity $L_{rm 5100}$ and black hole mass $M_{rm BH}$. By adopting partial correlation analysis: (1) we find a positive correlation between $L_{rm X}$ and $M_{rm BH}$, and (2) we find a weak positive correlation between $L_{rm R}$ and $L_{5100}$. However, we dont find significant correlations between $L_{rm R}$ and $L_{rm X}$ or between $L_{rm X}$ and $L_{5100}$ after considering the effect of the black hole mass, which leads to a finding of the independence of $L_{rm X}/L_{rm Edd}$ on $L_{5100}/L_{rm Edd}$. Interestingly, the findings that $L_{rm X}$ is correlated with $M_{rm BH}$ and $L_{rm X}/L_{rm Edd}$ is not correlated with $L_{5100}/L_{rm Edd}$ support that the X-ray emission is saturated with increasing $dot{M}$ for $L_{rm bol}/L_{rm Edd} gtrsim 0.1$ in NLS1s, which may be understood in the framework of slim disc scenario. Finally, we suggest that a larger NLS1 sample with high quality radio and X-ray data is needed to further confirm this result in the future.
The {gamma}-ray detection from several radio-loud (RL) narrow-line Seyfert 1 (NLS1) galaxies has enabled us to study powerful relativistic jets in active galactic nuclei (AGNs) with smaller black hole masses and higher accretion rates than classical blazars. However, the sample of those {gamma}-ray detected NLS1s available is still not large enough for a comprehensive and statistical study. We provide a summary of our detections and follow-up studies of three {gamma}-ray-emitting NLS1s: SDSS J211852.96-073227.5 with flaring {gamma}-ray radiation (Yang et al. 2018, Paliya et al. 2018) and SDSS J122222.55+041315.7 with the highest redshift by far (z~1) (Yao et al. 2015a), along with the prototype 1H 0323+342 (Zhou et al. 2007, Yao et al. 2015b). And we will discuss their multiwavelength properties and variability properties, including implications from high-energy observations in {gamma}-rays and X-rays, infrared and radio properties, and correlated variability between several wavebands.
We present measurement of the cut-off energy, a proxy for the temperature of the corona in the nuclear continuum of the Seyfert 1 galaxy 3C 120 using $sim$120 ks of observation from ${it NuSTAR}$. The quality broad band spectrum from 3$-$79 keV has enabled us to measure the Compton reflection component (R) and to constrain the temperature of the coronal plasma. Fitting one of the advanced Comptonization models, ${it compPS}$ to the observed broad band spectrum we derived the kinetic temperature of the electrons in the corona to be $kT_e = 25 pm 2$ keV with Compton ${it y}$ parameter of $y = 2.2 pm 0.1$ for a slab geometry and $kT_e = 26_{-0}^{+2}$ keV with a $y$ of $2.99_{-0.18}^{+2.99}$ assuming a spherical geometry. We noticed excess emission from $sim$10$-$35 keV arising due to Compton reflection and a broad Fe $Kalpha$ line at 6.43 keV with an equivalent width of 60 $pm$ 5 eV. The variations in count rates in the soft (3$-$10 keV) band is found to be more compared to the hard (10$-$79 keV) band with mean fractional variability amplitudes of 0.065$pm$0.002 and 0.052$pm$0.003 for the soft and hard bands respectively. 3C 120 is known to have a strong jet, however, our results indicate that it is either dormant or its contribution if any to the X-ray emission is negligible during the epoch of ${it NuSTAR}$ observation.
As part of an extensive study of the physical properties of active galactic nuclei (AGN) we report high spatial resolution near-IR integral-field spectroscopy of the narrow-line region (NLR) and coronal-line region (CLR) of seven Seyfert galaxies. These measurements elucidate for the first time the two-dimensional spatial distribution and kinematics of the recombination line Br{gamma} and high-ionization lines [Sivi], [Alix] and [Caviii] on scales <300 pc from the AGN. The observations reveal kinematic signatures of rotation and outflow in the NLR and CLR. The spatially resolved kinematics can be modeled as a combination of an outflow bicone and a rotating disk coincident with the molecular gas. High-excitation emission is seen in both components, suggesting it is leaking out of a clumpy torus. While NGC 1068 (Seyfert 2) is viewed nearly edge-on, intermediate-type Seyferts are viewed at intermediate angles, consistent with unified schemes. A correlation between the outflow velocity and the molecular gas mass in r<30 pc indicates that the accumulation of gas around the AGN increases the collimation and velocity of the outflow. The outflow rate is 2-3 orders of magnitude greater than the accretion rate, implying that the outflow is mass-loaded by the surrounding interstellar medium (ISM). In half of the observed AGN the kinetic power of the outflow is of the order of the power required by two-stage feedback models to be thermally coupled to the ISM and match the M-{sigma}* relation. In these objects the radio jet is clearly interacting with the ISM, indicative of a link between jet power and outflow power.
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 light curves to estimate the energy output. The dynamics of radio spectral energy distributions were examined to understand the mechanism causing the variability. All the sources display intensive variability that occurs at a pace faster than what is commonly seen in blazars. The flaring events show intensive spectral evolution indicative of shock evolution. The brightness temperatures and Doppler factors are moderate, implying a mildly relativistic jet. The computed jet powers show very energetic flows. The radio polarisation in one case clearly implies a quiescent jet underlying the recursive flaring activity. Despite the generally lower flux densities, the sources appear to show all typical characteristics seen in blazars that are powered by relativistic jets.
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