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391. J-band variability of AGN
ID:
ivo://CDS.VizieR/J/A+A/555/A2
Title:
J-band variability of AGN
Short Name:
J/A+A/555/A2
Date:
21 Oct 2021
Publisher:
CDS
Description:
Spectral energy distribution and its variability are basic tools for understanding the physical processes operating in active galactic nuclei (AGN). In this paper we report the results of a one-year near infra red (NIR) and optical monitoring of a sample of 22 AGN known to be {gamma}-ray emitters, aimed at discovering correlations between optical and {gamma}-ray emission. We observed our objects with the Rapid Eye Mount (REM) telescope in J, H, K, and R bands nearly twice every month during their visibility window and derived light curves and spectral indexes. We also analyzed the {gamma}-ray data from the Fermi {gamma}-ray Space Telescope, making weekly averages.
392. Jet collimation in NGC 1052
ID:
ivo://CDS.VizieR/J/A+A/658/A119
Title:
Jet collimation in NGC 1052
Short Name:
J/A+A/658/A119
Date:
22 Feb 2022 14:52:38
Publisher:
CDS
Description:
With the increased sensitivity and resolution of radio interferometry the study of the collimation and acceleration region of jets in Active Galactic Nuclei(AGN) has come into focus within the last years. Whereas a large fraction of AGN jets reveal a change from parabolic to conical collimation around the Bondi radius, a small number of sources deviate from this standard picture, including the radio galaxy NGC1052. We study the jet width profile, which provides valuable information about the interplay between the central engine and accretion disk system and the collimation and acceleration zone of the jets. We observed the double-sided active galaxy NGC1052 at six frequencies with the VLBA in 2017 and at 22GHz with RadioAstron in 2016. These data are combined with archival 15, 22, and 43GHz multi-epoch VLBA observations. From ridge-line fitting we obtained width measurements along the jet and counter-jet which were fitted with broken power-laws. We find a break in the jet collimation profile at ~10^4^R_s_ (Schwarzschild radii). Downstream of the break the collimation is conical with a power-law index of 1.0-1.2 (cylindrical 0; parabolic 0.5; conical 1). The upstream power-law index of 0.36 for the approaching jet is neither cylindrical nor parabolic and for the receding jet with 0.16 close-to cylindrical. Both jets have an opening angle of ~30 degree at a distance of ~10^3R_S_ and are well collimated with an opening angle of <10 degrees downstream of the break. There are significant differences in the upstream collimation profile between approaching (Eastern) and receding (Western) jet. Absorption or scattering in the surrounding torus as well as an accretion wind may mimic a cylindrical profile. We need to increase the observing frequencies, which do not suffer from absorption to find the true jet collimation profile upstream of 10^4^R_s_.
393. Jet collimation in NGC 315
ID:
ivo://CDS.VizieR/J/A+A/647/A67
Title:
Jet collimation in NGC 315
Short Name:
J/A+A/647/A67
Date:
21 Oct 2021
Publisher:
CDS
Description:
The collimation of relativistic jets in galaxies is a poorly understood process. Detailed radio studies of the jet collimation region have been performed so far in a few individual objects, providing important constraints for jet formation models. However, the extent of the collimation zone as well as the nature of the external medium possibly confining the jet are still debated. In this article, we present a multifrequency and multiscale analysis of the radio galaxy NGC 315, including the use of mm-VLBI data up to 86GHz, aimed at revealing the evolution of the jet collimation profile. We then consider results from the literature to compare the jet expansion profile in a sample of 27 low-redshift sources, mainly comprising radio galaxies and BL Lacs, which were classified based on the accretion properties as low-excitation (LEG) and high-excitation (HEG) galaxies. We propose that the jet collimation in NGC 315 is completed on sub-parsec scales. A transition from a parabolic to conical jet shape is detected at z_t_=0.58+/-0.28-parsecs or ~5x10^3& Schwarzschild radii (Rs) from the central engine, a distance which is much smaller than the Bondi radius, rB~92pc, estimated based on X-ray data. The jet in this and in a few other LEG in our sample may be initially confined by a thick disk extending out to ~10^3^-10^4^R_{sun}_. A comparison between the mass-scaled jet expansion profiles of all sources indicates that jets in HEG are surrounded by thicker disk-launched sheaths and collimate on larger scales with respect to jets in LEG. These results suggest that disk winds play an important role in the jet collimation mechanism, particularly in high-luminosity sources. The impact of winds on the origin of the FRI and FRII dichotomy in radio galaxies is also discussed.
394. Jet kinematics of blazars at 43GHz with the VLBA
ID:
ivo://CDS.VizieR/J/ApJ/846/98
Title:
Jet kinematics of blazars at 43GHz with the VLBA
Short Name:
J/ApJ/846/98
Date:
21 Oct 2021
Publisher:
CDS
Description:
We analyze the parsec-scale jet kinematics from 2007 June to 2013 January of a sample of {gamma}-ray bright blazars monitored roughly monthly with the Very Long Baseline Array at 43GHz. In a total of 1929 images, we measure apparent speeds of 252 emission knots in 21 quasars, 12 BL Lacertae objects (BLLacs), and 3 radio galaxies, ranging from 0.02c to 78c; 21% of the knots are quasi-stationary. Approximately one-third of the moving knots execute non-ballistic motions, with the quasars exhibiting acceleration along the jet within 5pc (projected) of the core, and knots in BLLacs tending to decelerate near the core. Using the apparent speeds of the components and the timescales of variability from their light curves, we derive the physical parameters of 120 superluminal knots, including variability Doppler factors, Lorentz factors, and viewing angles. We estimate the half-opening angle of each jet based on the projected opening angle and scatter of intrinsic viewing angles of knots. We determine characteristic values of the physical parameters for each jet and active galactic nucleus class based on the range of values obtained for individual features. We calculate the intrinsic brightness temperatures of the cores, T_b,int_^core^, at all epochs, finding that the radio galaxies usually maintain equipartition conditions in the cores, while ~30% of T_b,int_^core^ measurements in the quasars and BLLacs deviate from equipartition values by a factor >10. This probably occurs during transient events connected with active states.
395. Jet power of blazars from the TGSS at 150MHz
ID:
ivo://CDS.VizieR/J/ApJ/861/97
Title:
Jet power of blazars from the TGSS at 150MHz
Short Name:
J/ApJ/861/97
Date:
21 Oct 2021
Publisher:
CDS
Description:
The composition and energy dissipation in jets are two of the fundamental questions of jet physics that are not fully understood. In this paper, we attempt to constrain the composition, magnetization, and radiative efficiency for blazars with the recently released low-frequency radio catalog of the TIFR GMRT Sky Survey at 150MHz. The jet power estimated from the low-frequency radio emission is much lower than that derived from spectral energy distribution fitting assuming one proton per electron. Assuming the jet power estimated from low-frequency radio emission is physical, the fraction of electron/positron pairs can be constrained with n_pairs_/n_p_~10. By comparing the power carried by the magnetic field and radiation with the jet power estimated from the low-frequency radio emission, we find both the relatively high magnetization parameter of {sigma}~0.5 and the radiative efficiency of {eta}~0.4 in the dissipation region of blazars. These results suggest that magnetic reconnection processes may play an important role in the energy dissipation of blazars. We also explore the connection between these three parameters (n_pairs_/n_p_, {sigma}, and {eta}) and the black hole mass, disk luminosity, and Eddington ratio. No significant correlation is found, except that {sigma} shows a possible correlation with disk luminosity.
396. Jet properties of {gamma}-ray-loud 3FGL AGNs
ID:
ivo://CDS.VizieR/J/ApJS/235/39
Title:
Jet properties of {gamma}-ray-loud 3FGL AGNs
Short Name:
J/ApJS/235/39
Date:
21 Oct 2021
Publisher:
CDS
Description:
Based on broadband spectral energy distributions (SEDs), we estimate the jet physical parameters of 1392 {gamma}-ray-loud active galactic nuclei (AGNs), the largest sample so far. The (SED) jet power and magnetization parameter are derived for these AGNs. Out of these sources, the accretion disk luminosity of 232 sources and (extended) kinetic jet powers of 159 sources are compiled from archived papers. We find the following. (1) Flat-spectrum radio quasars (FSRQs) and BL Lacs are well separated by {Gamma}=-0.127logL_{gamma}_+8.18 in the {gamma}-ray luminosity versus photon index plane with a success rate of 88.6%. (2) Most FSRQs present a (SED) jet power larger than the accretion power, which suggests that the relativistic jet-launching mechanism is dominated by the Blandford-Znajek process. This result confirms previous findings. (3) There is a significant anticorrelation between jet magnetization and a ratio of the (SED) jet power to the (extended) kinetic jet power, which, for the first time, provides supporting evidence for the jet energy transportation theory: a high- magnetization jet may more easily transport energy to a large scale than a low-magnetization jet.
397. JHK' imaging photometry of Seyfert 1. I.
ID:
ivo://CDS.VizieR/J/ApJS/141/23
Title:
JHK' imaging photometry of Seyfert 1. I.
Short Name:
J/ApJS/141/23
Date:
21 Oct 2021
Publisher:
CDS
Description:
Near-infrared JHK' imaging photometry was obtained of 331 AGNs consisting mainly of Seyfert 1 active galactic nuclei (AGNs) and quasars (QSOs). This sample was selected to cover a range of radio emission strength, redshift from z=0 to 1, and absolute B magnitude from M_B_=-29mag to -18mag. Among low-z AGNs with z<0.3, Seyfert 1-1.5 AGNs are distributed over a region from a location typical of "galaxies" to a location typical of "QSOs" in the two-color J-H to H-K' diagram, but Seyfert 1.8-2 AGNs are distributed around the location of "galaxies". Moreover, bright AGNs with respect to absolute B magnitude are distributed near the location of "QSOs," while faint AGNs are near the location of "galaxies". The distribution of such low-z AGNs in this diagram was found to have little dependence on their 6 cm radio flux. The near-infrared colors of the AGNs observed with an aperture of 7 pixels (7.49") are more QSO-like than those observed with larger apertures up to 15 pixels (16.1"). This aperture effect may be explained by contamination from the light of host galaxies within larger apertures. This effect is more prominent for less luminous AGNs.
398. JHK' imaging photometry of Seyfert 1. II.
ID:
ivo://CDS.VizieR/J/ApJS/141/31
Title:
JHK' imaging photometry of Seyfert 1. II.
Short Name:
J/ApJS/141/31
Date:
21 Oct 2021
Publisher:
CDS
Description:
Observations of 226 AGNs in the near-infrared J, H, and K' bands are presented along with the analysis of the observations for variability. Our sample consists mainly of Seyfert 1 AGNs and QSOs. About a quarter of the objects in each category are radio loud. The AGNs in the entire sample have the redshifts spanning the range from z=0 to 1, and the absolute magnitudes from M_B_=-29 to -18. All the objects were observed twice, and their variability was measured by differential photometry. A reduction method of differential photometry, optimized to the analysis of extended images, has been developed. The systematic error in variability arising from AGNs of highly extended images is estimated to be less than 0.01mag in each of the J, H, and K' bands. The systematic error arising from the flat-fielding is negligible for most AGNs, although it is more than 0.1mag for some particular cases. The overall average flat-fielding error is 0.03mag for the image pairs. We find that these systematic errors are superseded by statistical errors, and the overall average total systematic and statistical errors amounts to 0.05mag in the measured variability in each band.
399. 1.5Jy MOJAVE AGN sample and 3FGL data
ID:
ivo://CDS.VizieR/J/ApJ/810/L9
Title:
1.5Jy MOJAVE AGN sample and 3FGL data
Short Name:
J/ApJ/810/L9
Date:
21 Oct 2021
Publisher:
CDS
Description:
We use the complete MOJAVE 1.5Jy sample of active galactic nuclei (AGNs) to examine the gamma-ray detection statistics of the brightest radio-loud blazars in the northern sky. We find that 23% of these AGNs were not detected above 0.1GeV by the Fermi-LAT during the four-year 3FGL catalog period partly because of an instrumental selection effect and partly due to their lower Doppler boosting factors. Blazars with synchrotron peaks in their spectral energy distributions located below 10^13.4^Hz also tend to have high-energy peaks that lie below the 0.1GeV threshold of the LAT, and are thus less likely to be detected by Fermi. The non-detected AGNs in the 1.5Jy sample also have significantly lower 15GHz radio modulation indices and apparent jet speeds, indicating that they have lower than average Doppler factors. Since the effective amount of relativistic Doppler boosting is enhanced in gamma-rays (particularly in the case of external inverse-Compton scattering), this makes them less likely to appear in the 3FGL catalog. Based on their observed properties, we have identified several bright radio-selected blazars that are strong candidates for future detection by Fermi.
400. 1Jy northern AGN sample
ID:
ivo://CDS.VizieR/J/A+A/596/A106
Title:
1Jy northern AGN sample
Short Name:
J/A+A/596/A106
Date:
21 Oct 2021
Publisher:
CDS
Description:
Continuum spectra covering centimetre to submillimetre wavelengths are presented for a northern sample of 104 extragalactic radio sources, mainly active galactic nuclei, based on four-epoch Planck data. The nine Planck frequencies, from 30 to 857GHz, are complemented by a set of simultaneous ground-based radio observations between 1.1 and 37GHz. The single-survey Planck data confirm that the flattest high-frequency radio spectral indices are close to zero, indicating that the original accelerated electron energy spectrum is much harder than commonly thought, with power-law index around 1.5 instead of the canonical 2.5. The radio spectra peak at high frequencies and exhibit a variety of shapes. For a small set of low-z sources, we find a spectral upturn at high frequencies, indicating the presence of intrinsic cold dust. Variability can generally be approximated by achromatic variations, while sources with clear signatures of evolving shocks appear to be limited to the strongest outbursts.