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491. MOJAVE. VI. Kinematic analysis of blazar jets
ID:
ivo://CDS.VizieR/J/AJ/138/1874
Title:
MOJAVE. VI. Kinematic analysis of blazar jets
Short Name:
J/AJ/138/1874
Date:
21 Oct 2021
Publisher:
CDS
Description:
We discuss the jet kinematics of a complete flux-density-limited sample of 135 radio-loud active galactic nuclei (AGNs) resulting from a 13 year program to investigate the structure and evolution of parsec-scale jet phenomena. Our analysis is based on new 2cm Very Long Baseline Array (VLBA) images obtained between 2002 and 2007, but includes our previously published observations made at the same wavelength, and is supplemented by VLBA archive data. In all, we have used 2424 images spanning the years 1994-2007 to study and determine the motions of 526 separate jet features in 127 jets.
492. MOJAVE. XII. Acceleration of blazar jets
ID:
ivo://CDS.VizieR/J/ApJ/798/134
Title:
MOJAVE. XII. Acceleration of blazar jets
Short Name:
J/ApJ/798/134
Date:
21 Oct 2021
Publisher:
CDS
Description:
We report on the acceleration properties of 329 features in 95 blazar jets from the MOJAVE Very Long Baseline Array program. Nearly half the features and three-quarters of the jets show significant changes in speed and/or direction. In general, apparent speed changes are distinctly larger than changes in direction, indicating that changes in the Lorentz factors of jet features dominate the observed speed changes rather than bends along the line of sight. Observed accelerations tend to increase the speed of features near the jet base, <~10-20pc projected, and decrease their speed at longer distances. The range of apparent speeds at a fixed distance in an individual jet can span a factor of a few, indicating that shock properties and geometry may influence the apparent motions; however, we suggest that the broad trend of jet features increasing their speed near the origin is due to an overall acceleration of the jet flow out to deprojected distances of the order of 10^2^pc, beyond which the flow begins to decelerate or remains nearly constant in speed. We estimate intrinsic rates of change of the Lorentz factors in the galaxy frame of the order of {sdot}{Gamma}/{Gamma}~=10^-3^ to 10^-2^/yr, which can lead to total Lorentz factor changes of a factor of a few on the length scales observed here. Finally, we also find evidence for jet collimation at projected distances of <~10pc in the form of the non-radial motion and bending accelerations that tend to better align features with the inner jet.
493. MOJAVE. XIII. New 15GHz observations on 1994-2013
ID:
ivo://CDS.VizieR/J/AJ/152/12
Title:
MOJAVE. XIII. New 15GHz observations on 1994-2013
Short Name:
J/AJ/152/12
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present 1625 new 15GHz (2cm) VLBA images of 295 jets associated with active galactic nuclei (AGNs) from the MOJAVE and 2cm VLBA surveys, spanning observations between 1994 August 31 and 2013 August 20. For 274 AGNs with at least 5 VLBA epochs, we have analyzed the kinematics of 961 individual bright features in their parsec-scale jets. A total of 122 of these jets have not been previously analyzed by the MOJAVE program. In the case of 451 jet features that had at least 10 epochs, we also examined their kinematics for possible accelerations. At least half of the well-sampled features have non-radial and/or accelerating trajectories, indicating that non-ballistic motion is common in AGN jets. Since it is impossible to extrapolate any accelerations that occurred before our monitoring period, we could only determine reliable ejection dates for ~24% of those features that had significant proper motions. The distribution of maximum apparent jet speeds in all 295 AGNs measured by our program to date is peaked below 5c , with very few jets with apparent speeds above 30c . The fastest speed in our survey is ~50c , measured in the jet of the quasar PKS0805-07, and is indicative of a maximum jet Lorentz factor of ~50 in the parent population. An envelope in the maximum jet speed versus redshift distribution of our sample provides additional evidence of this upper limit to the speeds of radio-emitting regions in parsec-scale AGN jets. The Fermi-LAT-detected gamma-ray AGNs in our sample have, on average, higher jet speeds than non-LAT-detected AGNs, indicating a strong correlation between parsec-scale jet speed and the gamma-ray Doppler boosting factor. We have identified 11 moderate-redshift (z<0.35) AGNs with fast apparent speeds (>10c) that are strong candidates for future TeV gamma-ray detection. Of the five gamma-ray loud narrow-lined Seyfert I AGNs in our sample, three show highly superluminal jet motions, while the others have sub-luminal speeds. This indicates that some narrow-lined Seyfert I AGNs possess powerful jets with Lorentz factors in excess of 10, and viewing angles less than 10{deg}, consistent with those of typical BL Lac objects and flat-spectrum radio quasars.
494. MOJAVE. XI. Spectral distributions
ID:
ivo://CDS.VizieR/J/AJ/147/143
Title:
MOJAVE. XI. Spectral distributions
Short Name:
J/AJ/147/143
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have obtained milliarcsecond-scale spectral index distributions for a sample of 190 extragalactic radio jets through the Monitoring of Jets in Active Galactic Nuclei with the VLBA Experiments (MOJAVE) project. The sources were observed in 2006 at 8.1, 8.4, 12.1, and 15.4GHz, and we have determined spectral index maps between 8.1 and 15.4GHz to study the four-frequency spectrum in individual jet features. We have performed detailed simulations to study the effects of image alignment and (u, v)-plane coverage on the spectral index maps to verify our results. We use the spectral index maps to study the spectral index evolution along the jet and determine the spectral distributions in different locations of the jets. The core spectral indices are on average flat with a mean value of +0.22+/-0.03 for the sample, while the jet spectrum is in general steep with a mean index of -1.04+/-0.03. A simple power-law fit is often inadequate for the core regions, as expected if the cores are partially self-absorbed. The overall jet spectrum steepens at a rate of about -0.001 to -0.004 per deprojected parsec when moving further out from the core with flat spectrum radio quasars having significantly steeper spectra (mean -1.09+/-0.04) than the BL Lac objects (mean -0.80+/-0.05). However, the spectrum in both types of objects flattens on average by ~0.2 at the locations of the jet components indicating particle acceleration or density enhancements along the jet. The mean spectral index at the component locations of -0.81+/-0.02 corresponds to a power-law index of ~2.6 for the electron energy distribution. We find a significant trend that jet components with linear polarization parallel to the jet (magnetic field perpendicular to the jet) have flatter spectra, as expected for transverse shocks. Compared to quasars, BL Lacs have more jet components with perpendicular magnetic field alignment, which may explain their generally flatter spectra. The overall steepening of the spectra with distance can be explained with radiative losses if the jets are collimating or with the evolution of the high-energy cutoff in the electron spectrum if the jets are conical. This interpretation is supported by a significant correlation with the age of the component and the spectral index, with older components having steeper spectra.
495. MOJAVE. X. Parsec-scale kinematics of AGNs
ID:
ivo://CDS.VizieR/J/AJ/146/120
Title:
MOJAVE. X. Parsec-scale kinematics of AGNs
Short Name:
J/AJ/146/120
Date:
21 Oct 2021
Publisher:
CDS
Description:
We describe the parsec-scale kinematics of 200 active galactic nucleus (AGN) jets based on 15GHz Very Long Baseline Array (VLBA) data obtained between 1994 August 31 and 2011 May 1. We present new VLBA 15 GHz images of these and 59 additional AGNs from the MOJAVE and 2cm Survey programs. Nearly all of the 60 most heavily observed jets show significant changes in their innermost position angle over a 12-16yr interval, ranging from 10{deg} to 150{deg} on the sky, corresponding to intrinsic variations of ~0.5{deg} to ~2{deg}. The BL Lac jets show smaller variations than quasars. Roughly half of the heavily observed jets show systematic position angle trends with time, and 20 show indications of oscillatory behavior. The time spans of the data sets are too short compared to the fitted periods (5-12yr), however, to reliably establish periodicity. The rapid changes and large jumps in position angle seen in many cases suggest that the superluminal AGN jet features occupy only a portion of the entire jet cross section and may be energized portions of thin instability structures within the jet. We have derived vector proper motions for 887 moving features in 200 jets having at least five VLBA epochs. For 557 well-sampled features, there are sufficient data to additionally study possible accelerations. We find that the moving features are generally non-ballistic, with 70% of the well-sampled features showing either significant accelerations or non-radial motions. Inward motions are rare (2% of all features), are slow (<0.1mas/yr), are more prevalent in BL Lac jets, and are typically found within 1mas of the unresolved core feature. There is a general trend of increasing apparent speed with distance down the jet for both radio galaxies and BL Lac objects. In most jets, the speeds of the features cluster around a characteristic value, yet there is a considerable dispersion in the distribution. Orientation variations within the jet cannot fully account for the dispersion, implying that the features have a range of Lorentz factor and/or pattern speed. Very slow pattern speed features are rare, comprising only 4% of the sample, and are more prevalent in radio galaxy and BL Lac jets. We confirm a previously reported upper envelope to the distribution of speed versus beamed luminosity for moving jet features. Below 10^26^W/Hz there is a fall-off in maximum speed with decreasing 15GHz radio luminosity. The general shape of the envelope implies that the most intrinsically powerful AGN jets have a wide range of Lorentz factors up to ~40, while intrinsically weak jets are only mildly relativistic.
496. MOJAVE. XVII. Parsec-scale jet kinematics of AGNs
ID:
ivo://CDS.VizieR/J/ApJ/874/43
Title:
MOJAVE. XVII. Parsec-scale jet kinematics of AGNs
Short Name:
J/ApJ/874/43
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present results from a parsec-scale jet kinematics study of 409 bright radio-loud active galactic nuclei (AGNs) based on 15GHz Very Long Baseline Array (VLBA) data obtained between 1994 August 31 and 2016 December 26 as part of the 2cm VLBA survey and Monitoring Of Jets in Active galactic nuclei with VLBA Experiments (MOJAVE) programs. We tracked 1744 individual bright features in 382 jets over at least 5 epochs. A majority (59%) of the best-sampled jet features showed evidence of accelerated motion at the >3{sigma} level. Although most features within a jet typically have speeds within ~40% of a characteristic median value, we identified 55 features in 42 jets that had unusually slow pattern speeds, nearly all of which lie within 4pc (100pc deprojected) of the core feature. Our results, combined with other speeds from the literature, indicate a strong correlation between apparent jet speed and synchrotron peak frequency, with the highest jet speeds being found only in low-peaked AGNs. Using Monte Carlo simulations, we find best-fit parent population parameters for a complete sample of 174 quasars above 1.5Jy at 15GHz. Acceptable fits are found with a jet population that has a simple unbeamed power-law luminosity function incorporating pure luminosity evolution and a power-law Lorentz factor distribution ranging from 1.25 to 50 with slope -1.4+/-0.2. The parent jets of the brightest radio quasars have a space density of 261+/-19Gpc^-3^ and unbeamed 15GHz luminosities above ~10^24.5^W/Hz, consistent with FRII class radio galaxies.
497. MOJAVE. XVI: parsec-scale AGN jet cores at 15GHz
ID:
ivo://CDS.VizieR/J/ApJ/862/151
Title:
MOJAVE. XVI: parsec-scale AGN jet cores at 15GHz
Short Name:
J/ApJ/862/151
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present an analysis of the core linear polarization properties of 387 parsec-scale active galactic nuclei (AGNs) jets. Using 15GHz VLBA data, we revisit the conclusions of the first paper in this series with multiepoch measurements and more detailed analysis of a larger AGN sample that spans a broader range of synchrotron peak frequencies. Each AGN has been observed for at least five epochs between 1996 and 2017. We find that BL Lac objects have core electric vector position angles (EVPAs) that tend toward alignment with the local jet direction; compared to flat spectrum radio quasars, their EVPAs are also less variable over time. The AGN cores that are most fractionally polarized and least variable in polarization have EVPAs that are closely aligned with the local jet direction; they also have low variability in EVPA. These results support the popular model of a standing transverse shock at the base of the jet that collimates the jet magnetic field perpendicular to the jet direction, increasing the fractional polarization and leading to greater polarization stability over time. High-synchrotron-peaked BL Lac objects form a low luminosity, low fractional polarization population. The five narrow line Seyfert 1 galaxies in our sample have low fractional polarization and large EVPA-jet misalignments. Although AGNs detected at {gamma}-rays are thought to be more Doppler boosted than nondetected AGNs, we find no significant differences in fractional polarization based on detection by Fermi-LAT; the {gamma}-loud AGNs are, however, more variable in core EVPAs.
498. MOJAVE XV. VLBA 15GHz obs. of AGN jets 1996-2016
ID:
ivo://CDS.VizieR/J/ApJS/234/12
Title:
MOJAVE XV. VLBA 15GHz obs. of AGN jets 1996-2016
Short Name:
J/ApJS/234/12
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present 5321 mas-resolution total intensity and linear polarization maps of 437 active galactic nuclei (AGNs) obtained with the VLBA at 15GHz as part of the MOJAVE survey, and also from the NRAO data archive. The former is a long-term program to study the structure and evolution of powerful parsec-scale outflows associated with AGNs. The targeted AGNs are drawn from several flux-limited radio and {gamma}-ray samples, and all have correlated VLBA flux densities greater than ~50mJy at 15GHz. Approximately 80% of these AGNs are associated with {gamma}-ray sources detected by the Fermi LAT instrument. The vast majority were observed with the VLBA on 5-15 occasions between 1996 January 19 and 2016 December 26, at intervals ranging from a month to several years, with the most typical sampling interval being six months. A detailed analysis of the linear and circular polarization evolutions of these AGN jets is presented in the other papers in this series.
499. Monitoring AGNs with H{beta} Asymmetry (MAHA). I.
ID:
ivo://CDS.VizieR/J/ApJ/869/142
Title:
Monitoring AGNs with H{beta} Asymmetry (MAHA). I.
Short Name:
J/ApJ/869/142
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have started a long-term reverberation mapping (RM) project using the Wyoming Infrared Observatory 2.3m telescope titled "Monitoring AGNs with H{beta} Asymmetry" (MAHA). The motivations of the project are to explore the geometry and kinematics of the gas responsible for complex H{beta} emission-line profiles, ideally leading to an understanding of the structures and origins of the broad-line region (BLR). Furthermore, such a project provides the opportunity to search for evidence of close binary supermassive black holes. We describe MAHA and report initial results from our first campaign, from 2016 December to 2017 May, highlighting velocity-resolved time lags for four active galactic nuclei (AGNs) with asymmetric H{beta} lines. We find that 3C120, Ark120, and Mrk6 display complex features different from the simple signatures expected for pure outflow, inflow, or a Keplerian disk. While three of the objects have been previously reverberation mapped, including velocity-resolved time lags in the cases of 3C120 and Mrk6, we report a time lag and corresponding black hole mass measurement for SBS1518+593 for the first time. Furthermore, SBS1518+593, the least asymmetric of the four, does show velocity-resolved time lags characteristic of a Keplerian disk or virialized motion more generally. Also, the velocity-resolved time lags of 3C120 have significantly changed since previously observed, indicating an evolution of its BLR structure. Future analyses of the data for these objects and others in MAHA will explore the full diversity of H{beta} lines and the physics of AGN BLRs.
500. Morphologies of selected AGN
ID:
ivo://CDS.VizieR/J/AJ/140/533
Title:
Morphologies of selected AGN
Short Name:
J/AJ/140/533
Date:
21 Oct 2021
Publisher:
CDS
Description:
We investigate the optical morphologies of candidate active galaxies identified at radio, X-ray, and mid-infrared wavelengths. We use the Advanced Camera for Surveys General Catalog (ACS-GC) to identify 372, 1360, and 1238 active galactic nucleus (AGN) host galaxies from Very Large Array, XMM-Newton, and Spitzer Space Telescope observations of the COSMOS field, respectively. We investigate both quantitative (GALFIT) and qualitative (visual) morphologies of these AGN host galaxies, split by brightness in their selection band.