A5024093522- Astrophysics and Cosmic Phenomena
- Radio Astronomy Observations and Technology
- Gamma-ray bursts and supernovae
- Galaxies: Formation, Evolution, Phenomena
- Neutrino Physics Research
- Astrophysical Phenomena and Observations
- Astronomical Observations and Instrumentation
- Geophysics and Gravity Measurements
- Solar and Space Plasma Dynamics
- Particle Accelerators and Free-Electron Lasers
- Astronomy and Astrophysical Research
- Dark Matter and Cosmic Phenomena
- GNSS positioning and interference
- Pulsars and Gravitational Waves Research
- Gyrotron and Vacuum Electronics Research
- Ionosphere and magnetosphere dynamics
- Particle accelerators and beam dynamics
- Cosmology and Gravitation Theories
- Magnetic confinement fusion research
- Stellar, planetary, and galactic studies
- Particle physics theoretical and experimental studies
- Computational Physics and Python Applications
- Nuclear Physics and Applications
- Calibration and Measurement Techniques
- Astro and Planetary Science
Max Planck Institute for Radio Astronomy
2016-2025
Harvard University
2023-2025
Moscow Institute of Physics and Technology
2016-2024
Astro Space Center
2015-2024
P.N. Lebedev Physical Institute of the Russian Academy of Sciences
2014-2024
Institute for Nuclear Research
2024
Russian Academy of Sciences
2014-2024
Goddard Space Flight Center
2024
University of Maryland, College Park
2024
Harvard University Press
2024
We discuss the jet kinematics of a complete flux-density-limited sample 135 radio-loud active galactic nuclei (AGNs) resulting from 13 year program to investigate structure and evolution parsec-scale phenomena. Our analysis is based on new 2 cm Very Long Baseline Array (VLBA) images obtained between 2002 2007, but includes our previously published observations made at same wavelength, supplemented by VLBA archive data. In all, we have used 2424 spanning years 1994–2007 study determine...
ABSTRACT We describe the parsec-scale kinematics of 200 active galactic nucleus (AGN) jets based on 15 GHz Very Long Baseline Array (VLBA) data obtained between 1994 August 31 and 2011 May 1. present new VLBA images these 59 additional AGNs from MOJAVE 2 cm Survey programs. Nearly all 60 most heavily observed show significant changes in their innermost position angle over a 12–16 yr interval, ranging 10° to 150° sky, corresponding intrinsic variations ∼0. ° 5 ∼2°. The BL Lac smaller than...
We report the results of a 15 GHz (2 cm) multi-epoch VLBA program, begun in 1994 to study outflow radio jets ejected from quasars and active galaxies. The observed flow 208 distinct features measured 110 quasars, galaxies, BL Lac objects shows highly collimated relativistic motion with apparent transverse velocities typically between zero about 15c, tail extending up 34c. Within individual jets, different appear move similar characteristic velocity which may represent an underlying...
We present images from a long term program (MOJAVE: Monitoring of Jets in AGN with VLBA Experiments) to survey the structure and evolution parsec-scale jet phenomena associated bright radio-loud active galaxies northern sky. The observations consist 2424 15 GHz complete flux-density limited sample 135 above declination -20 degrees, spanning period 1994 August 2007 September. These data were acquired as part MOJAVE 2 cm Survey programs, archive. selection criteria are based on multi-epoch...
We have investigated a frequency-dependent shift in the absolute position of optically thick apparent origin parsec-scale jets ("core shift" effect) to probe physical conditions ultra-compact relativistic outflows AGN. used multi-frequency Very Long Baseline Array (VLBA) observations 191 sources carried out 12 epochs 2006 within MOJAVE program. The were performed at 8.1, 8.4, 12.1, and 15.4 GHz. implemented method determining core vector based on (i) image registration by two-dimensional...
We present 5321 mas-resolution total intensity and linear polarization maps of 437 active galactic nuclei (AGNs) obtained with the VLBA at 15 GHz as part MOJAVE survey, also from NRAO data archive. The former is a long-term program to study structure evolution powerful parsec-scale outflows associated AGNs. targeted AGNs are drawn several flux-limited radio γ-ray samples, all have correlated flux densities greater than ∼50 mJy GHz. Approximately 80% these sources detected by Fermi LAT...
We present 1625 new 15 GHz (2 cm) VLBA images of 295 jets associated with active galactic nuclei (AGNs) from the MOJAVE and 2 cm surveys, spanning observations between 1994 Aug 31 2013 20. For 274 AGNs at least 5 epochs, we have analyzed kinematics 961 individual bright features in their parsec-scale jets. A total 122 these not been previously by program. In case 451 jet that had 10 also examined for possible accelerations. At half well-sampled non-radial and/or accelerating trajectories,...
The Event Horizon Telescope (EHT) has led to the first images of a supermassive black hole, revealing central compact objects in elliptical galaxy M87 and Milky Way. Proposed upgrades this array through next-generation EHT (ngEHT) program would sharply improve angular resolution, dynamic range, temporal coverage existing observations. These improvements will uniquely enable wealth transformative new discoveries related hole science, extending from event-horizon-scale studies strong gravity...
We present the Black Hole Explorer (BHEX), a mission that will produce sharpest images in history of astronomy by extending submillimeter Very-Long-Baseline Interferometry (VLBI) to space. BHEX discover and measure bright narrow "photon ring" is predicted exist black holes, produced from light has orbited hole before escaping. This discovery expose universal features hole's spacetime are distinct complex astrophysics emitting plasma, allowing first direct measurements supermassive spin. In...
We have examined the compact structure in 250 flat-spectrum extragalactic radio sources using interferometric fringe visibilities obtained with Very Long Baseline Array (VLBA) at 15 GHz. With projected baselines out to 440 Mλ, we are able investigate source on typical angular scales as small 0.05 mas. This scale is similar resolution of VLBI Space Observatory Programme data longer a lower frequency and somewhat poorer accuracy. For 171 our sample, more than half total flux density seen by...
<i>Aims. <i/>We have investigated the differences in apparent opening angles between parsec-scale jets of active galactic nuclei (AGN) detected by <i>Fermi<i/> Large Area Telescope during its first three months operations and those non-LAT-detected AGN.<i>Methods. used 15.4 GHz VLBA observations sources from 2 cm MOJAVE program, a subset which comprises statistically complete flux density limited sample. We determined analyzing transverse jet profiles data image plane applying model fitting...
We investigate the dependence of gamma-ray brightness blazars on intrinsic properties their parsec-scale radio jets and implication for relativistic beaming. By combining apparent jet speeds derived from high-resolution VLBA images MOJAVE program with millimetre-wavelength flux density monitoring data Metsahovi Radio Observatory, we estimate Doppler factors, Lorentz viewing angles a sample 62 blazars. study trends in these quantities between sources which were detected gamma-rays by Fermi...
We have compared the radio emission from a sample of parsec-scale AGN jets as measured by VLBA at 15 GHz, with their associated gamma-ray properties that are reported in Fermi LAT 3-month bright source list. find our radio-selected photon flux correlates well quasi-simultaneously compact density. The LAT-detected complete generally higher densities, and cores brighter (i.e., brightness temperature) than non-detected objects. This suggests preferentially Doppler-boosting factors. In addition,...
Relations between the observed quantities for a beamed radio jet, which are apparent transverse speed and luminosity (βapp, L), intrinsic quantities, Lorentz factor (γ, L0), investigated. The inversion from measured to values is not unique, but approximate limits γ L0 can be found using probability arguments. Roughly half sources in flux density-limited, sample have value of close βapp. methods applied observations 119 AGN jets made with VLBA at 15 GHz during 1994-2002. results strongly...
We report new 2 cm VLBA images of the inner radio jet M87 showing a limb-brightened structure and unambiguous evidence for faint 3 mas long counterfeature which also appears limb brightened. Multiepoch observations seven separate features show typical speeds less than few percent speed light, despite highly asymmetric implications canonical relativistic beaming scenario. The observed morphology is consistent with two-stream spine-sheath velocity gradient across jet, as might be expected from...
We have conducted a multiwavelength survey of 42 radio loud narrow-1ine Seyfert 1 galaxies (RLNLS1s), selected by searching among all the known sources this type and omitting those with steep spectra. analyse data from frequencies to X-rays, supplement these information available online catalogues literature in order cover full electromagnetic spectrum. This is largest for source. detected 90% X-rays found 17% at γ rays. Extreme variability high energies was also found, down timescales as...
We present 15 GHz stacked VLBA images of 373 jets associated with active galactic nuclei (AGN) having at least five observing epochs within a 20 yr time interval 1994-2015 from the MOJAVE programme and/or its precursor, 2 cm Survey. These data are supplemented by 1.4 single-epoch observations 135 AGNs to probe larger scale jet structures. The typical geometry is found be close conical on scales hundreds thousands parsecs, while number galaxies show quasi-parabolic streamlines smaller scales....
The effect of a frequency dependent shift the VLBI core position (known as "core shift") was predicted more than three decades ago and has since been observed in few sources, but often within narrow range. This important astrophysical astrometric applications. To achieve broader understanding physics behind it, we conducted dedicated survey with NRAO's Very Long Baseline Array (VLBA). We used VLBA to image 20 pre-selected sources simultaneously at nine frequencies 1.4-15.4 GHz each measured...
Context. The apparent position of the "core" in a parsec-scale radio jet (a compact, bright emitting region at narrow end jet) depends on observing frequency, owing to synchrotron self-absorption and external absorption. While providing tool probing physical conditions vicinity core, this dependency poses problems for astrometric studies using compact sources.
We have obtained milliarcsecond-scale spectral index distributions for a sample of 190 extragalactic radio jets through the MOJAVE project. The sources were observed in 2006 at 8.1, 8.4, 12.1, and 15.4 GHz, we study four-frequency spectrum individual jet features. performed detailed simulations to effects image alignment (u,v)-plane coverage on maps verify our results. core indices are average flat, while is general steep with mean -1.04. A simple power-law fit often inadequate regions, as...
We report observations of Faraday rotation measures for a sample 191 extragalactic radio jets observed within the MOJAVE program. Multifrequency Very Long Baseline Array were carried out over 12 epochs in 2006 at four frequencies between 8 and 15 GHz. detect parsec-scale 149 sources find quasars to have larger on average than BL Lac objects. The median core are significantly higher jet components. This is especially true where we significant negative correlation magnitude measure...
Abstract We present the results of PSR π , a large astrometric project targeting radio pulsars using Very Long Baseline Array (VLBA). From our database 60 pulsars, we have obtained parallax-based distance measurements for all but 3, with parallax precision that is typically ∼45 μ as and approaches 10 in best cases. Our full sample doubles number reliable (≳5 σ ) model-independent constraint. Importantly, many newly measured are well outside solar neighborhood, so brings near-tenfold increase...
We present the first polarimetric space VLBI imaging observations at 22 GHz. BL Lacertae was observed in 2013 November 10 with RadioAstron mission, including a ground array of 15 radio telescopes. The instrumental polarization telescope is found to be within 9%, demonstrating capabilities Ground-space fringes were obtained up projected baseline distance 7.9 Earth's diameters length, allowing us image jet maximum angular resolution 21 $\mu$as, highest achieved date. find evidence for emission...